BIOLOGY FORM 5-COMPARATIVE STUDIES OF NATURAL GROUPS
BIOLOGY FORM 5-COMPARATIVE STUDIES OF NATURAL GROUPS
Viruses: -are simple structures with genetic material in the centre and surrounded by capsomere.
- Are obligate or compulsory parasites as they can only carry out metabolic activities inside organisms.
- Parasites are any organisms living in or on another organism deriving nutrients from the host and depending on the host for its life processes and retain only a few of them such as reproduction.
- Viruses are a cellular nucleic particles coated with a protein coat.
Generalized section of a capsomere – processing virus.
- STRUCTURE: They have very simple structure consisting of the following.
- CORE: the genetic material rather DNA or RNA maybe single structure or dabble stranded.
- CAPSID: a protective coat of protein surrounding the core
- NUCLEOCAPSID: the combined structure formed by the core and capsid.
- ENVELOPE: a few viruses such as HIV and influenza have an addition lipoprotein layer as around the capsid derived from the cell surface membrane of the host cell
- CAPSOMERES: capsids are often built up of identical repeating subunits called capsomeres.
- They posses both living and non living characteristics therefore they are a border line case between living and non living.
- Viruses are very small organisms ranging in size from 20-300nm. They cannot be seen by the light microscope and on the average they are about 50 times smaller than bacteria indicating that they pass though fitter which retain bacteria.
- They are cellular i.e. they consist of nucleic acid either DNA or RNA surrounded by a protein coat called capsid. These fragments of genetic material are neither nucleus nor cytoplasm it is only the DNA or RNA which form the central core. The fully assembled infected particle is called vision.
- Viruses are obligate parasites / endo parasites and can only reproduce inside the living host.
- They are highly specific to the host, sometimes to the host tissue, and to the cell. Virus will recognize and infect only a certain type of cells.
- Viruses do not have a mechanism for producing energy for themselves and therefore all the enzymes for protein synthesis and the ribosome come from the host cells.
- Viruses can be crystallized i.e. they show no life process when outside the cell; however the crystals retain the effective capacity as if they are in appropriate hosts.
- Viruses rely on passive dispersal or a vector to move them from one host to another because they don’t have any locomotive structures.
- Viruses are metabolically / biologically inert. They cannot carry out any life process such as respiration, reproduction / protein synthesis
- They either contain DNA or RNA but not both.
- Viruses have to symmetries either helical or isometric.
- Virus are classified as either
- DNA viruses
- RNA viruses (In core)
Can be classified according to the host e.g. bacteriophage only infect bacteria and animal virus only infect animals.
Most of animal viruses are DNA viruses and plants viruses are RNA viruses.
STRUCTURE OF TO BACTERIOPHAGE
STRUCTURE OF A TOBACCO MOSAIC VIRUS
Events of viral replication.
Problem of classifying viruses
- They are very simple in structure being compared of nuclei acid (DNA or RNA) and protein
- They seem to be more related to their host one another
- They usually undergo mutation.
- They are a border line case i.e. they posses both living and non living characteristics.
|LIVING CHARACTERISTICS||NON LIVING CHARACTERISTIC|
ECONOMIC IMPORTANCES OF VIRUSES
Demerits of viruses
- Causes diseases to animals. Man incurs a great loss due to reproduction or death of animals e.g. foot and mouth disease in cattle, Rift valley in cattle new castle in poultry.
- Causes diseasesto plants leading to great losses for example maize strake, cassava mosaic, tobacco mosaic
- Cause disease to humans leading to depopulation and loss of man power eg HIV causes AIDS.
- Increases cost of living when you consider the cost of prevention or treatment of viral diseases.
Merits of viruses
- Used in research purposes this leads to development of drugs and research of the behavior or characteristics of other organisms.
- Useful in biological control of other pests like harmful which attack plants and animals.
- Some are used in developing vaccines which are useful in preventing diseases e.g. polio, measles.
- LIFE CYCLE OF RETROVIRUS HIV
- AIDS is caused by HIV or Human immunodeficiency viruses. If belongs to a group RNA viruses known a retroviruses.
- This name comes from the fact that these viruses can convert their RNA back into a DNA copy using an enzyme known as reverse transcriptase. Normally a section of DNA (gene) is copied to make RNA a process called transcription.
- Making DNA from RNA is therefore reverse transcription and the enzyme is called reverse transcriptase (this enzyme has proved extremely useful in genetic engineering )
KINGDOM PROKARYOTAE / MONERA
- They are unicellular, prokaryotic and microscopic organisms (can only be seen with a microscope).
- Their cell wall is made up of murein (proteins and polysaccharides)
- The genetic material i.e. circular DNA is not enclosed by nuclear membrane and lies freely in cytoplasm (Nucleoid) and therefore they are not true cells. They also do not have membrane bound organelles
- Their ribosome’s are 70’s and smaller in size.
- There is no spindle formation during cell division and therefore reproduce mainly a sexually by binary fission and in some few species they reproduce by conjugation through Pilli.
- Some have ability to fix the atmospheric nitrogen to nitrides and nitrates which are then used by plants.
- Some can form spores in aqueous conditions and thus can survive extreme temperature and drought.
- They have mesosomes for respiration and associated with DNA which helps in cell division and helps in formation of new cells.
Generalized Structure of Bacterium
CLASSIFICATION OF BACTERIA ON BASIS OF MORPHOLOGY (SHAPE)
1. COCCI (singular coccus)-they are spherical in shape
Staphylococci (like a bunch of grapes.)
- E.g. Staphylococcus aureus lives in nasal passages: different stains cause boils pneumonia food poisoning and other diseases.
e.g. many streptococcus spp; same infect upper respiratory tract and cause disease e.g. s. pyogenes causes scarlet fever and sore throats; s. thermophilus gives yoghurt its creamy flavour ; s.lactis.
The pneumococci (diplococcus pneumonia) are the only capsule members causing pneumonia.
2. BACILLI (sing bacillus) rod shaped.
Single rods e.g. Escherichia coli, common gut-living symbiont; lactobacillus, salmonella typhi causes typhoid fever.
Rods in chains
E.g. Azotobacter, a nitrogen fixing bacteria; bacillus anthracis cause anthrax.
- bacilli with endospores (showing) various positions, shapes and sizes of spores)
Oval spore central not swollen e.g. bacillus anthracis, causes anthrax. Terminal swollen e.g. clostridium tetani, causes tetanus.
Sub terminal swollen e.g. clostridium botulinum (spores may also be central) causes botulism.
3. SPIRILLA (sing spirillum) spiral – shaped.
Helical rod with single flagellum e.g. spirillum
NB; body of spirochetes is similar in form but locomotion differs e.g. Treponema pallidum causes syphilis.
4. VIBRIOS comma – shaped
E.g. vibrio cholerae causes cholera, single flagellum.
CLASSIFICATION OF BACTERIA ON BASIS OF STAINING PROPERTIES.
- Bacteria differ from each other in the nature of their cell walls. There are two types: gram positive and Gram negative and this is so basing on the staining properties.
- Gram positive have thick walls and murein is filled with polysaccharide and protein. They are most susceptible to antibiotics and lysozyme than gram negative ones.
- Lysozyme digest the polysaccharide of murein and puncture it causing osmotic sucking and bursting (anti – bacterial enzyme)
- Examples of gram positive bacteria are Lactobacillus.
- Gram negative bacteria have a rather thin cell wall and the murein is located on the outside with a thin, smooth, membrane like layer of lipids and polysaccharides.
- The layer protects them from lysozyme and the most of them are not very susceptible to antibiotics. Examples of gram negative bacteria are Escherichia coli.
REPRODUCTION IN BACTERIA
Bacteria reproduce asexually by binary fission, which is by division into two identical daughter cells. The cell division is there by replication of DNA and while this is being copied it may be attached to the new cross wall between the daughter cells wall material. The generation time for bacteria is very fast which may be on the average of 20 minutes.
ECONOMIC IMPORTANCE OF BACTERIA
Beneficial effects of Bacteria
- Bacteria are used in biotechnology.
- Biotechnology is the application of organisms biological system /biological processes to the manufacturing and servicing industries for benefit of humans.
- They are used in manufacturing processes e.g. leather; retting flex to make linen and making soap powder.
- They are source of antibiotics e.g. streptomycin from genus streptomyces, Gramicidin from bacillus breves’.
- They are used in food production e.g. manufacturing of yoghurt, cheese, vinegar, coffee and tea.
- Cheddar cheese is produced from lactobacillus species. Yoghurt is produced from streptococcus thermophilus.
- They are used in production of single cell protein (SCP) e.g. pruteen is used in animal feeds.
- They are used in sewage treatment most of them are saprophytic bacteria.
- They cause breakdown of plant and animal remains therefore they are decomposers thus bring about recycling of essential nutrients such as carbon, nitrogen, phosphorus and sculpture E.g. Azotobacter, Rhizobium.
- They are used in nutrient and biogeochemical cycle e.g. Nitrogen fixation. They are the only organisms which can fix nitrogen e.g. nitrosomonas and Nitrobacter.
- Their form symbiotic relationships with other orgasms e.g. cellulose digesting bacteria in the gut of herbivores.
- Are used in biological research and genetic engineering and this is important in development of vaccines and in synthesis of growth hormones e.g. somatotrophin to treat dwarfism production of insulin to treat diabetes.
- They are used in biological control of pests e.g. caterpillar.
- They can be used as biological weapons e.g. anthrax.
Harmful effects of bacteria.
- Bacteria are pathogens. Some are extra-cellular parasites while others are intra-cellular. Symptoms of the disease are often caused by the toxins they produce. Some infect plant e.g. Agro bacterium fumefaciens causing crown galls, fruit trees and erwinia amylovorum causing fire blight of apples and pears.
- Others infect animals and humans i.e. cholera caused by vibrio Cholerae, typhoid by salmonella typhi, tetanus caused by clostridium tetani.
- They cause decay of vegetables, food crops; fruits making storage are very expensive.
- The denitrifying bacterium (Thiobacillus) reduces soil fertility by converting nitrates and nitrides to atmospheric nitrogen which cannot be utilized by plants.
They are unicellular, eukaryotes and microscopic (a few). Their classification is based on the locomotary organ is present, and then the organ/organelle is used to classify the organism into smaller groups. E.g. flagella under the phylum flagellate pseudopodia under the phylum rhizopoda.
- They have different modes of nutrition some are photosynthetic i.e. algae, some are lutentrophic e.g. amoeba, and some are parasitic e.g. phylum oomycota phytophtera infestans.
- They can inhibit different environmental conditions e.g. some are terrestrial like slime moulds and oomyocta while some are aquatic e.g. algae (fresh water and marine).
- They form a link between eukaryotes and prokaryotes e.g. mitochondria and chloroplast contain DNA resembling that of prokaryotes.
E.g. Amoeba proteus, Entamoeba histolytica.
- Unicellular eukaryotes.
- The locomotary organelle is the pseudopodia.
- They exhibit both sexual reproduction by conjugation and asexual reproduction by binary fission and multiple fission speculation.
- Some secret slime coats, tests, shells, other posses no specific outer covering.
Structure of entamoeba histolytica.
- They have a defined /conspicuous cytoplasm – plasma gel in the plasmasol.
- Stored in cytoplasm are food vacuoles.
- There is an elaborate spherical nucleus with chromatin blocks and karysome this referring to the nature, the number, the type of chromosomes .chromatins are the chromosome in the stages of development.
- They exist in two body forms i.e. small and large. By some mechanism not known, the smaller form transforms into the larger form, which are similar in structure.
- The locomotary organelle is a single pseudopodium.
- The outer covering is all bound by a single plasma membrane/ cell membrane.
- Food vacuole of smaller one contains bacteria at different stages of digestion.
- The food vacuole of larger one contains the digested gut epithelial cells of red blood cells at different stages of digestion.
Diagram of entamoeba histolytica (See chandy’s Biology for class XI page 198 fig 5.6)
Adaptations of Entamoeba to its mode of life.
The adaptations can be divided into three major parts,
- Structural adaptation.
- Physiological adaptation/modification.
- Reproductive adaptation.
- There is only one pseudopodium since it does not need to move from place to place as the free living amoeba as it has most of the requirements in its environment.
- There is no contractile vacuole indicating that cytoplasmic contents of entamoeba are isotonic to the most environments.
- Isotonic-having a concentration such that it neither gains no loses water by osmosis.
- They can vary/change the diet from bacteria to animal cells and produce the necessary enzymes for digestion.
- They can live in conditions where oxygen content is very low, however when they puncture a capillary and ingest a red blood cell (as they live on epithelial), they can respire aerobically.
- They require little amount of energy as movement is limited
- Like all parasites, entamoeba produces a larger number of off springs so that they survive the hazards of the environment as they move from one host to another.
- They reproduce asexually by binary fission and large numbers of cysts are produced each giving rise to 8 daughter amoebulae.
- The cysts are viable under variable environmental conditions and can survive in alternative hosts thus increasing the chance of survival.
NB; Entamoeba histolytic causes amoeba dysentery which is characterized by adnominal pains, nausea, vomiting and fever.
Under severe attacks, ulceration develops and blood is released into the intestine and out of the body through frequent motion which contains blood and mucus.
The parasite (i.e. Entamoeba) can affect the kidney, the liver and the brain.
- They posses flagellum at some stages of their life cycle.
- They possess chromatophores (colored pigments)
- They have a definite shape and have pellicle which surrounds the body and maintains the shape.
- They reproduce asexually by binary fission
- They have variety modes of life
Adaptation to parasitic mode of life
- They have no contractile vacuole and no gullet as they are living in constant internal environment i.e. the blood.
- The undulating membrane increases surface area to volume ratio for absorption (no gullet). In Some cases it is for locomotion incase of high viscosity.
- Being pointed at both ends, passage through the capillary is easier.
- There are small flagella as they are parasites and locomotion is limited.
- The body fluids are isotonic to the blood plasma hence they do not need to regulate their mechanisms.
- Being parasites they require less thus have a few mitochondria for release of energy.
- Large surface area to volume ratio helps in excretion, nutrition and efficient gaseous exchange as all this is through diffusion.
- Binary fission occurs rapidly even under host high resistance mechanism
- The spleen and the lung cells contain the resting forms of the parasite. Leshmenia form of the parasite which can remain alive even when the parasites (slender form) in the general circulation are eliminated.
- The multiplication of the parasites up to infective stage in the tsetse fly serves as a good reservoir/storage.
Diagram of Trypanosome gambiense; slender form
- They are aquatic i.e. some are fresh water, some are marine and some species live in moist soil. Most members of the phylum have chloroplast and thus carry out autotrophic mode of nutrition though a few members are colorless and live in rectum of frogs.
- All members posses flagella as a locomotory organelle and there for are active swimmers.
- Member of the phylum have pellicle which maintains the shape of the body although they can change their shape as they move about i.e. Euglenoic movement.
- All have myonemes (sort of muscles) which are contractile.
- They store carbohydrate in form of paramylum. Paramylum gives a negative test with iodine.
- They possess vacuoles and gullet.
- They are sensitive to light i.e. they have photoreceptors stigmas.
- They chiefly respire aerobically and a few species living in the rectum of frogs can respire anaerobically.
- Under unfavorable condition they can form cyst which is tough and made of cellulose.
Characteristics of euglena which makes it a plant.
- They posses chloroplast with chlorophyll A and B therefore they are autotrophic.
- They have the ability to utilize nitrates and ammonia for nitrogen requirements i.e. use of nitrates to make their proteins.
- Possess paranoids which are the form of stored protein.
- Storage of carbohydrates in form of paramyium.
- Presence of contractile vacuole.
Characteristics of euglena which makes it an animal.
- Presence for pellicles for support in the body.
- Possess flagella which enable it to move actively (euglenoid movement).
- They utilize amino acids and polypeptides as source of nitrogen.
- Ability to form cysts during unfavorable conditions.
- Possess myonemes which are contractile like muscles.
- Possess gullets, sphincter.
- Have a reservoir.
- Possess eye spot and stigma as photoreceptor organelle.
Diagram of euglena
Adaptations of euglena to its mode of life.
- The body shape is elongated and oriented in such a way that allows them to be active swimmers.
- The fresh water species possess contractile vacuole which excrete excess water .The marine species do not have contractile vacuole.
- They possess chloroplast for photosynthesis i.e. autotrophic nutrition. But when the conditions are not favourable e.g. in the absence of light they feed saprophically.
- Possess flagella for locomotion.
- They are mostly aquatic i.e. fresh water a few are marine and the other few are terrestrial.
- They contain / possess chlorophyll A and B and thus can photosynthesize (autotrophic nutrition).
- They have cell wall made of cellulose.
- They store carbohydrate in form of starch and posses vacuole.
- They have different body forms and range in size i.e. some are unicellular e.g. Clymadomonas, some are filamentous (spirogyra) and others live in groups.
- They reproduce asexually by fragmentation and sexually by conjugation.
- They are eukaryotes.
Structure of spirogyra.
Adaptation to mode of life.
- have chloroplast with chlorophyll A and B and thus can photosynthesize
- posses contractile vacuole for osmoregulation i.e. remove excess water
- Presence of mucilage covering for protection i.e. prevents growth of micro- organisms on the cells such as epiphytes. Epiphytes are plant parasites.
- They can undergo vegetative propagation and therefore have high rate of reproduction.
- They are facultative parasites growing within plant tissues i.e. within the host; the mycelium is intercellular with the haustoria.
- The body is mycelium i.e. thread like structures with no septor (non septate).
- Have cell wall made of cellulose with deposits of fat substance, peptic materials and impregnated with chitin.
- They reproduce sexually and asexually and under unfavorable conditions conidia forms which develops into mycelium.
Adaptations to mode of life.
- Have extensively branching haustoria which penetrates into mesophyll cells or other tissues.
- They produce enzymes i.e. pectinases and cellulases which destroy the host cells.
- They are non septate with thin walls thus easy absorption of food materials into their bodies. (The walls are permeable).
- The sporangium hanging on the long sporangiophore makes it easy for the spores to be spread by water current/wind for other plants. By being on the lower part of the leaf they are easily protected from dehydration.
- They have high reproductive rate i.e. produce many spores asexually and rapidly also when conditions are not favorable they can still undergo asexual reproduction by formation of conidia.
- The spores can remain dormant for a long period (more than one year) thus increases it chances of survivals.
- The zoospores can penetrate through different parts of the plant like stomata in the leaves, lenticels in stem, epidermis or wounds.
Phytophthora infestans growing in a diseased potato leaf with sporangiophores emerging from the underside of the leaf.
E.g. Plasmodium malariae.
- Most of them are obligate parasites and so most of them their life processes are taken up by the host e.g. they have no means of locomotion such as cilia, flagella and no excretory organelle.
- Reproduce asexually by spore formation.
- They have a definite shape maintained by presence of pellicle.
Species: P. vivax, P. malariae, P. falciparum.
All the species cause malaria (meaning bad air in)
Structure of plasmodium.
- They are oval or spindle in shape or can even be called sickle with the small amount of cytoplasm with the nucleus occupying a large area in the center. The body shape is maintained by the presence of pellicle.
N.B; P.falciparum is most dangerous of all species that it attacks the liver.
LIFE CYCLE OF PLASMODIUM.
- Sickle cell sporozoites 2um long enter the blood stream of man with saliva of female anopheles mosquito when it pierces the skin.
- They remain in the blood stream for an hour and then enter in the liver.
- They feed on liver cells (glucagon and fat) and form meront (schizont)
- They then divide mitotically and repeatedly to form nuclei which are surrounded in cytoplasm to form merozoites / schizozoites.
- Liver cells burst and release the merozoites/schizozoites.
- The merozoites enter the blood, others re-enter the liver cells (pre-erythrocytes cycle) which takes 8-10 days.
- Inside the RBC’s the schizozoites feed and grow to become amoeboid in shape.
- A vacuole appears on the central region and pushes the nucleus to the sides forming ring structure (detected in blood when examined under microscope) growth and multiple division form the schizozoites, some excretory granules are formed from cytoplasm of RBC; as it bursts and open the schizozoites and excretory granules/ organelle are released to the plasma some schizozoites re- enter the RBC (erythrocytes cycles).
- The toxic effect takes about 48 hours (process) which causes a characteristic malaria fever.
- Some schizozoites stop dividing and grow to form gametocytes.
- Female gametocytes have a small nucleus and cytoplasm is rich in food materials and granulated.
- The male gametocyte has a large nucleus with clear cytoplasm.
- If the gametocytes are ingested by a female anopheles mosquito they develop into male and female gametes which unite and form a zygote (i.e. male gamete penetrates through the female gamete through papillae).
- From the zygote, multi nuclei structures called sporocysts develop which within a few days divide into thousands of tiny spindle shaped cells called sporozoites which migrate to the mosquito’s salivary gland.
- When the mosquito bites another victim the cycle begins
Adaptation to modes of life
- Having a spindle/ sickle structure, they can easily penetrate the liver cells and RBC thus making it easier for them to re infect both liver cells and RBC’s thus increasing chance of survival.
- The zygote may develop a cyst.
- Have well developed chemo tactic responses which enable it to detect different tissues/organs in the host’s body e.g. sporozoites remain in the general circulation for one hour and migrate to the liver.
- In the mosquito’s body mature sporozoites reside in the mosquitoes salivary gland
- They are resistant (highly) to hosts (i.e. humans and mosquitoes) anti bodies and toxins and gametocytes are not digested in the salivary gland by mosquitoes.
- The plasmodium is an obligate parasite confined to the hosts thus increases their chances of survival.
- They can live / tolerate low oxygen content as they are parasites they need very little energy because all processes are performed by the host except reproduction.
- They are adjusted to different osmotic conditions in the hosts i.e. mosquito and human beings and thus increase chance of survival.
- They have a high reproductive rate and this increases their chance of survival.
Effects on the host
- Plasmodium vivax causes tertian fever, recurring at 3days intervals and is at least with survival.
- Plasmodium malariae causes quartan fever recurring at 4days interval
- Plasmodium falciprum causes maligent quotidian malaria being most lethal with a continuous fever.
- The incubation period is 8 – 10 days. This is when the parasites are in the liver, over 8- 10 days malaria fever begins characterized by cold, hot and sweating increases i.e. shivering occurs and the patient feels cold, temperature rises followed by sweating. The patient then shows recovery signs except for some weaknesses. But each fresh attack has an increasing debilitating effect.
- Have rigid cell walls made of chitin (polysaccharide rich in nitrogen).
- The body is mycelium with thread like structure (hyphae). The hyphae can be septate or aseptate/coenocytic (no cross walls).the hyphae may be septate and multi nucleiate or uni nucleiate.
- They have heterotrophic mode of nutrition as they lack chloroplast. Some are holozoic e.g. micorhiza, some are saprophytic e.g. moulds/mucor species, some are parasitic like Candida species, epidemophyta (causes athletes foot), microsporum (causes ring worm).
- They store carbohydrate in form of glycogen.
- They have centrioles.
- They reproduce asexually by formation of spores and sexually by forming gametongia.
- They are non- motile/sessile.
- They grow on dead decaying organic matter some grow in terrestrial environment rich in organic matter and some grow in sugar solutions.
CLASSIFICATION OF FUNGI
- Zygomycota e.g. mucor species, rhizopus.
- Ascomycota e.g. saccharomyces.
- Basidiomycota e.g. Agaricus.
The body is mycelium with non septatic/coenocytic hyphi.
They reproduce asexually and sexually by zygospore formation also asexually by forming the sporangia.
Adaptations to its mode of life.
- Have branched rhizoids/ hyphae which secrets enzymes for extra-cellular digestion.
- The walls of the rhizoids are permeable thus are used for absorption of the digested food and they are also for attachment.
- The hyphae are aseptate for easy passage of the absorbed food.
- They have a high reproductive rate i.e. they produce large number of spores both sexually and asexually thus increases chances of survival.
- The sporangium are highly raised by the sporangiophore so that the spores can be easily be blown by the air current when the sporangium ruptures.
- The sporangium has collumela which changes its shape from Spherical to platform like when sporangium ruptures for easy dispersion of spores.
- The spores are light enough to be blown by wind and can remain dormant for a long period and are yet viable.
E.g. Agaricus campestris [mushroom]
- The hyphae are septate and compacted /fused .This makes the basidiomycota to be more advanced compared to other phylum
- They reproduce sexually by basidiospores and asexual reproduction is not common.
- They live on dead decaying organic matter /damp soils rich in organic matter
- They are saprophytes i.e. digestion is extra cellular.
Adaptation to mode of life.
- Have rhizomorphs for anchorage and act as perenating organ for vegetative propagation.
- The rhizomorphs produce a variety of hydrolytic enzyme for extra cellular digestion as they are saprophytic .The walls are permeable to digested nutrients and water thus serving as an absorbing organelle.
- The stipe also raises the pileus/cap well above the ground for easy dispersal of spores by the wind.
- The cap protects the gills inside which the spores are protected.
- They produce large number of basidiospores thus increasing chances of survival.
- Genus sacchromyces cerevisine (yeast).
- Genus penicillium notatum (penicillium).
- Genus Aspergillus campestral.
The Phylum consists of members which are of great economic importance.
- They have septate hyphae and some are unicellular.
- They reproduce sexually by ascospores (from the fruiting body ascus.) and asexually by conidiophores.
- They are terrestrial growing on rich soils or on sugary solutions (i.e. nectars of flowers, fruits, juices, slim wax from the trees).
- They are saprotrophs.
Structure of yeast
- They are unicellular organisms.
- They reproduce asexually by budding.
Adaptation to its mode of life.
- They are anaerobic and they live in low oxygen content.
- They have a high rate/a fast rate of reproduction by budding (asexual) when conditions are unfavorable they conjugate.
- They are saprophytic producing enzymes for extra-cellular digestion.
Differences between plants and fungi (Animal characteristics)
|Carbohydrate stored in form of glycogen.||Carbohydrates stored in form of starch.|
|They are heterotrophic i.e. Saprophytic parasitic mutualistic thus have no chlorophyll and thus cannot photosynthesis.||They are autotrophic posses chlorophyll and can photosynthesize.|
|They possess centrioles
The cell wall is made of chitin
|They do not posses centrioles
The cell wall is made of cellulose
|They have thallus body i.e. Not differentiated into roots, stems and leaves.||They have a well developed and differentiated body.|
ECONOMIC IMPORTANCE OF FUNGI
- Source of food (direct source) e.g. Agaricus species i.e. mushroom, aspergillus.
- Are decomposers i.e. bringing about the decaying of organic matter hence nutrient recycling e.g. rhizopus or mucor, moulds.
- Source of antibiotics e.g. penicillium notatum produces penicillium, p.griscofulvum produces griseofulvin, Aspergillus fumigatus produces fumagillin.
- Used in production of phyto hormones e.g. gibberellins from fungi gibberella
- Used in extraction of vitamins e.g. B-complex from yeast
- They are used in food industry and alcohol production particular in baking e.g.yeast in making of bread, fermentation in alcohol/liquor production e.g. yeast, citric acid production by Aspergillus lactic acid by rhizopus species.
- Sewage treatment (including decomposers) e.g. moulds or rhizopus.
- The toxication of cyanide especially in cassava e.g. moulds.
- They are used in biological control fungi such as Chinese caterpillar fungus which parasite insects can be extremely important for controlling insects/ pests or crops. The spores of fungi are spread on the crop and control the beetles, leaf hoppers and citrus rust mites.
- Used in genetic engineering and biological research e.g. neurosporal spps.
- Involved in production of single cell protein.
- Involved in micorhiza and plant growth vitally importance for the growth of plants including crops through development of micorhiza association. Micorhiza is a combination of fungi and flowering trees. About 50-90 percent of flowering plants have a symbiotic relationship with fungi. There are two types of micorhiza, endomicorhiza and ectomicorhiza. Endomicorhiza is a very common variety i.e. characteristics of most crop species endomicorhiza are unicellular fungi living inside the outer root cells of plant.
Ectomicorhiza is a less common variety and is a characteristic of ferns and trees only.
- Generally advantage –micorhiza develops when hyphae densely the root hair and penetrate the root cells.
- They are poisonous e.g. some agarics species. Amanita species cause death to humans.
- They cause diseases to humans e.g. Athletes foot by epidemophyton species, worm by Candida species and thrush by Candida species.
- They cause diseases and damage to crop plants during growth e.g. puccinia species causes rust on leather materials, grains and seeds. They also spoil cooked food e.g. moulds on bread.
- They cause damage to woods on both living and stored timber e.g. bracket fungi.
- There are many variations of the kingdom and they all possess chlorophyll A and B thus capable of photosynthesizing i.e. convert sunlight energy into chemical energy and thus are producers of ecosystem.
- They have well developed vegetative bodies and are sometimes differentiated into roots, stems and leaves and also reproductive bodies.
- They are sessile/ limited locomotion which show curvature movements.
- Plants have cellulose cell walls.
- They have prominent large vacuoles in their cells and store carbohydrate in form of starch.
- They are multi-cellular organisms with apical growth and localized growth with indefinite number of parts.
- Their life cycle involves alteration of generation which is more prominent in the lower plants.
CLASSIFICATION OF KINGDOM PLANTAE.
- Bryophyta e.g. musci e.g. funaria
- Filicinophyta (pteridophyta) e.g. dryopteris filix
- Coniferophyta e.g. pine (pinus sylivestris).
- Angiospermophyta. E.g. (flowering plants) class; monocotyledonae, dicotledonae.
- They have vegetative bodies with no vascular tissues.
- They are terrestrial living in moist, shady organic rich soils.
- The body is thallus or differentiated into simple stems and simple leaves.
- The plants (gametophyte) have rhizoids for anchorage and there are no true roots, stems and leaves while the sporophyte is attached and is partially dependant on the gametophyte for nutrition.
- They show alteration of generation. This is the occurrence of the phages in the cycle of the organism (plant) whereby a haploid gametophyte producing gametes (sexual phase) alternates with a diploid sporophyte producing spores (asexual phase). In the lower plants i.e. bryophyte the gametophyte phase is dominant over the sporophyte phase. Thus the sporophyte is attached to and semi dependant on gametophyte for its nutrition.
Adaptations of funaria to its autotrophic mode of life
- They have chlorophyll (gametophyte is green and the sporophyte) thus can photosynthesize therefore autotrophic mode of nutrition. The gametophyte also has multicellular rhizoids for absorption of water and mineral salts. Also anchores the plant to the soil.
- The reproductive structures i.e. antheridia and archegonia are protected by sterile hair.
- They show alteration of generation in their life cycle so that when one generation is weak it can depend on another one e.g. the sporophyte depends on gametophyte for nutrition and support.
- The plant can exploit both sexual and asexual reproduction
- The capsule of the sporophyte posses peristome and annuls cells which aid in dispersal of the spores. It also has an operculum which acts as a lid covering the capsule.
- The archegonia neck canal cells produce sugary solutions for a chemo tactic response to guide the anthrezoids into the ovum this increases the chances of fertilization.
- The sperms have flagella which aid in swimming through the water to the archegonia.
- The seta serves as upward means of transport of nutrients and water to the capsule.
- Seta is also raised well above the gametophyte so aiding the dispersal of spores by wind. The spores are light and produced by antheridia and are large in number increasing chances of survival.
- The gametes produced by antheridia are in large number thus increasing chances of fertilization.
- Sporophyte has a well developed vegetative body with extensive adventitious roots, underground stem, rhizomes, and large leaves (the fronds)
- The leaves are called fronds because they are relatively larger than the stem and roots.
- The young leaves show circinate fashion.
- The sporophyte has a well developed vascular tissue primitive (siphonostele) hence the xylem contains tracheids with no vessels and the phloem has no companion cells.
- The spores are found underneath the leaves in cluster forming the sori.
- They also show alternation of generation with the sporophyte being dominant and gametophyte (pro thallus) short lived. Both Sporophyte and Gametophyte are independent.
Description of dryopteris filix(fern)
- It is a well developed plant with adventitious roots and stem is a rhizome.
- The leaves are relatively large compared to the other parts and are called fronds.
- The young leaves are rolled with circinate fashions which grow into a frond.
- A fronds consist of the rachis which is sub divided to pinna which in turn holds the pinnule.
- The rachis possess ramenta (brown scales) for protection.
- The fronds have spores underneath which are born in clusters called sori and the spores
- The gametophyte is a thin heart shaped pro-thallus which lacks cuticle therefore requires moist conditions to prevent them from drying out. The prothallus possess both the male antheridia which is attached near the rhizoids and the female archegonia which is attached near the notch. The gametes are produced and fertilization occurs giving rise to zygote which develops into sporophyte generation.
External features of sporophyte generation of dryopteris filix mas (the male fern)
ADAPTATION OF FERN TO MODE OF LIFE
- The sporophyte is well developed with roots for anchorage and for absorption of water and mineral salts.
- Have stems for support and leaves with rachis for upward transport of water and mineral salts.
- They also possess chlorophyll thus can photosynthesize.
- The roots also serve as parenting organ for vegetative propagation.
- The rachis and young leaves possess ramenta for protection from mechanical injury and desiccation.
- They possess cuticle on their leaves to prevent excessive loss of water through transpiration.
- They have mechanical tissue (scterenchyma and collenchyma) for support a conducting tissue (phloem and xylem) for transport.
- The sori are found on the underside of the leaf, this prevents them from direct sunlight thus desiccation. The sori in turn are protected by inducium.
- The leaves are large in size to increase area for absorption of sun light.
- The sporangium has mechanism for dispersing the spores due to the presence of annulus cells and stadium cells.
Importance of dry and wet conditions in the life cycle of mosses and dryopteris.
- The stem is underground and can survive unfavorable conditions such as drought.
- The gametophyte and sporophyte are independent of each other and each can photosynthesize.
- The archegonia produce solutions which attract the anthrezoids chemotactically.
- The anthrezoids have flagella which can help them to swim to the archegonia.
- Required for dispersal of spores by the wind.
- Required for drying and rupturing of the capsule.
- The gametes develop in protective structures, the antheridia and archegonia in dry conditions.
COMPARISON OF MOSSES AND DRYOPTERIS.
- Fertilization requires wet conditions because the flagellated anthrezoids have to swim through water to the archegonia.
- They both show alternation of generation with the gametophyte alternating with the sporophyte.
- They all produce spores which require dry conditions for dispersal.
- They both have archegonia and antheridia as reproductive structures.
- Meiosis occurs during spore formation in the spore mother cells contained in the capsule
- They have stomata for gaseous exchange
- The gametophyte has rhizoids for anchorage and absorption.
- The leaves are needle –like covered with a waxy cuticle and have sunken stomata.
- The tree is the sporophyte generation and is heterosporous. In spring male and female cones are produced on the same tree. The male cones are rounded and found in clusters behind the apical buds at the bases of new shoots. They develop in the area of scale leaves in place of dwarf shoots. Female cones arise in the axis of scales i.e. at the tip of new strong shoots at some distance from male cones and in a more clustered arrangement. Both cones consist of spirally arranged, closely packed around a central axis.
- pollination in vallisneria (Tape grass)
Adaptations of pinus to its mode of life.
- The sporophyte is differentiated into roots which are well developed and grow deep into the soil for anchorage and absorption of underground water.
- The stem is reddish brown in colour and covered by scaly leaves to prevent water loss through transpiration.
- The leaves are needle like to minimize loss of water (as surface area is reduced).
- The leaves are evergreen for photosynthesis.
- The stomata are sunken which reduce water loss through transpiration.
- The leaves have hypodermis below the epidermis which prevent further desiccation.
- They have the conducting tissue, the xylem and phloem, for upward movement of water and mineral salts (xylem) and transport of food (phloem).
- They have developed mechanical tissues (woody stem) i.e. sclerenchyma and collenchyma) which provide mechanical support as the plant has to grow into tall trees.
- The microspores and megaspores have scales which prevent them from water loss.
- The presence of air sacs in the microspores facilitates wind dispersal thus conifers do not need water for fertilization since male gametes are blown by wind to reach the female gametes.
- The microspores develop a resistant wall for protection and they are small and light to be blown by wind.
- They produce a large number of seeds in the cones to increase chance of survival.
- Formation of resin canals that resist entry of fungi and other pathogens when the plant is injured. The resin normally covers up the injured part and the seed bearing habit enables the plant to survive during adverse conditions (unfavorable conditions ) as the seeds are protected by the seed coat.
- The stored food in the seed can be used by developing embryo during germination.
They are common land plants with approximately 335,000 species. ¾ of them are dicots and ¼ of them are monocots. They live in all types of habitats. Some are terrestrial while others are aquatic (fresh water or marine).
They show diversity in morphology from simple grass with no cambium to trees such as baobab tree with cambium which allows development of girth.
- The sporophyte is well differentiated into roots for anchorage and absorption of water and mineral salts, stem for support and transport and leaves for photosynthesis (i.e. they have chloroplast).
- They show alternation of generation with the sporophyte being dominant over the gametophyte, i.e. the gametophyte is reduced.
- Have well developed vascular tissues which consist of xylem with tracheids and vessels for transport of water and mineral salts and support and the phloem has got companion cells and sieve elements.
- They are heterosporous (microspore/pollen grain and megaspore/embryo)
- Fertilization does not depend on water because the male gamete is connected to the ovum by the pollen tube formed by germination of pollen grain when it lands on the stigma of the same species.
- They provide flowers in which megaspores and microspores develop.
- They undergo double fertilization. After fertilization, ovary develops into fruit and the ovules into seeds which are enclosed in the ovary.
- Xylem contains vessels and tracheids and phloem has sieve tubes and companion cells.
The angiosperms are divided into two major groups;
MAJOR DIFFERENCES BETWEEN MONOCOTYLEDONS AND DICOTYLEDONS.
|Class monocotylenae||Class dicotyledonae|
The structure and function of flowers
Flowers are reproductive structures in flowering plants (angiosperms) whose evolutionary origin are unclear but sometimes regarded as collection of highly specialized leaves. The flowers are commonly referred to simply as organs of sexual reproduction.
Parts of Flower
They are arranged in spiral form in few primitive flowers or in whorls around the upper parts (receptacle) of a flower stalk (pedicel). Some flowers are found as a collection of flowers borne on the same stalk (inflorescence)
- Receptacle– Is the end of the flower stalk (pedicel) from which the perianth, gynaecium, and androecium arises.
- Perianth– Consists of two whorls of leaf like segments. The whorls are similar in monocoty but different in dicot. The outer whorl is called sepal (Calyx) and inner whorl is petal (corolla)
- Calyx– Is the collection of sepals, they are usually green and leaf like structures that encloses and protect the flower buds.
- Corolla– Is a collection of petals. In insects pollinated flowers the petals are usually large and brightly coloured to attract insects.
- Androecium– is a collection of stamens forming the male reproductive organ of the flower. This consist of anther and filaments, in anther pollen grain are made. Filaments rises water to the anther.
- Genaecium (Pistil) is the collection carpels forming the female reproductive organs of the flower. This consists of stigma, style and ovary. Stigma receive pollen grain during pollination, style holds in position stigma and ovary contains one or more ovules.
Generalized structure of flower
Symmetry of flowers
If the flower parts are arranged in radial symmetry around the receptacle, the flower is said to be regular or actinomorphic e.g. bluebell.
If the flower shows bilateral symmetry only, it is said to be irregular or zygomorphic e.g. pea.
Is the presentation of floral parts of the flower by using symbols.
In floral formulae the following terms are used to describe the following terms are used to describe various parts of the flower.
A. Symmetry of the flower
B. Sex of the Flower
Diecious flower – The flower with separate male and female parts
Momoecious flower- The flower with both male and female parts both on the same flower
C. Flower recepatacle
Pedicelate flower – Is the type of flower with pedicale or flower stalk
Sessile flower – Is the type of flower without pedicel or flower stalk
N.B. This is not seen in floral formulae but appears in floral diagrams.
Consists of two whorls of the flower which is
K- Calyx followed by the number of sepals. If sepals are free K5 and if sepals are fused K(5)
C- Corolla followed by number of petals. If the petals are free C5 and if sepals are fused C(5).
Male parts of the Flower
A – Androecium followed by followed by the number of pollen grains e.g. A5 if fused. A∞ if the number of pollen grains exceed 16.
Female part of the flower
G – Gynaecium followed by the number of carpels eg G1 is free , G(2) if fused. The position of ovary with respect to receptacle
Hypogenous flower/ Inferior ovary
A flower in which ovary is placed highest on the thalamus and the other floral structure underneath.
For the example
Diagram of hypogenous
A flower in which ovary is at the same plane as other floral structure.
For example G2
A flower in which ovary is placed lower to other floral structure on the thalamus
Also flower have first leaf which is known as bracteates; a flower with bract. Ebracteate a flower without a bract.
Symbols of Floral formulae
Br Bracteate flower
Ebr Ebracteate flower
C Corolla or
G Gynoecium or
Examples of Floral frolar formulae
- Garden pea Pisum satirum
- Hibiscus flower
BIOLOGY FORM 5-COMPARATIVE STUDIES OF NATURAL GROUPS
This is the representation of flower parts by using concentric cycles to present various parts of the flower.
- The outer cycle represents the first whorl of the flower which calyx/ sepals
- The second cycle represents the corolla or petals
- The 3rd represents androecium
- The 4th part represent gynaecium
- In floral diagram the gynaecium also show the ovary with placentation.
The ovary consists of ovary wall called locule. The ovules are situated on the inner or adaxial (ventral) forms a placenta. In carpel the placenta occurs close to the margin.
The placenta is natural in nature. The placenta occurs close to the margin.
This occurs when carpels are folded, the ovary is multilocular and placenta occurs at the centre of the ovary where margin of the carpel meets.
This occurs when carpels partitious of the ovary disappears.
This occurs when the carpels are joined margin to margin and the placentas are found to be situated on the ovary walls.
Diagrams of the placentation
Example of floral diagram
Frolar diagram of hibiscus flower
Animals are quite distinct from members of the other kingdoms. Unlike prokaryotes and proticts animals are multicellular. In fact some of the largest animals have trillions of cells. Unlike plants animals are heterotrophs.
Characteristics of the kingdom:
- Animals are multicecullar eukaryotes with a high level of tissue diffentiation and specialized body organs.
- They have cells which have no cell walls.
- They have no chlorophy therefore have hetetrophic nutrition. They cannot manufacture their own food and instead must ingest it and braek it down metabolically for its energy content.
- They can move about at some point in their life cycle – usually through the entire cycle –to search for food and mates and to avoid danger.
- They are diploid, and their mode of reproduction is sexual, because each individual grows and changes from organs ,it passes through various distant stages of development .
- They are radial or bilaterally symmetrical.
- Some they have diploblastic or triploblastic.
- Some they have exoskeleton.
- Some are pseudo coelom (coelom and acoelom).
Classification of kingdom Animals
- Phyllum Platyhelminthes eg fasciola /Taenia
- Phyllum Aschelminthes (Nematoda) eg ascans roundworms)
- Phyllum Annelida eg earthworms
- Phyllum Arthropoda e.g. cockroach, locus, millipede.
- Phyllum chordate.
PHYLLUM PLATYHELMINTHES: eg fasciola/taenia
This is a group of animals commonly known as flat worms. They are also called solid worms or acoelomates because they have no coelom .The only internal space consists of the digestive cavity.
- They are ribbon shaped animals with soft bodies.
- They are dorso – ventrally flattened from top to bottom.
- They are triploblastic – ie their bodies are made of the three layers (Ectoderm, mesoderm and Endoderm.)
- They have no coelom.
- They cinsist excretory structure called flame cells.
- The members may be free living, ecto or endoparasites.
- They are bilateral symmetrical.
- They have soft ciliated epidemic or cuticle with suckers and hooks for attachment (Trematoda and cestoda).
- They have muscles well developed from mesoderm.
- They have well developed nervous system consisting of two lateral cerebral ganglia joined by a nerve ring and two main longitudinal nerve cords which give off numerous branches.
- They are hermaphrodite.
- Their life cycle involve at least two host. The intermediate host being an invertebrate
- The gut when present has a single aperture mouth.
- They show cephalization a condition in which sense organs and nervers systems that serve as a brain in a definite head region of the organism. Nervous system – serve as a brain. Sense organ specialized in sense light, chemicals and pressure.
Found in marine and fresh water.
Three classes of Platyhelminthes
- Turbellania eg planaria – which are mostly free living and a few and salty water and in moist soil. Planaria is found in spring lakes ponds etc.
- Trematoda (flukes) eg fasciolas peg fasciola hepatics – these are parastties the tropical liver fluke of cattle, sheep and sometimes infect man.
- Cestoda eg Taeria sp (eg taenia sagnata). These are parasitics of the beef, pork etc.
Class trematoda (the flukes)
- The body surface is not ciliated, the body is flat and leaf like but in few case cylindrical eg blood flukes –ie schistosoma Manson causing bilharzia.
- The possess digestive system (gut)
- Mostly endoparasitic flukes of vertebrates with sexual and asexual reproduction.
- They are hermaphrodite.
- The life cycle involves at least two host, vertebrate and invertebrate.
- They have suckers, ventral and oral for attachment to the host.
- The members are Ector and endo parasites living
- Example: fasciola hepatica, the liver fluke belongs to this class. It is a parasite of sheep and other mammals.
The adult fluke has a flattened oval shaped in the anterior region, there is a triangular projection at the apex of which lies the mouth, surrounded by the oral sucker and between the two sucker, there is a shallow depression the general atrium .
At the posterior and there a minute terminal excretory pore.
The animal feeds in the liver on the blood and cell which are ingested by the pumping action of the phyranx digestion and absorption takes place in the caeca and ingestion is through the mouth
The reproduction system:
The liver flukes is hermaphrodite and the reproductive organs are complex.
They have also development complex life history invading more than one host. The host harbouring the sexual stage are know as the final host and the host with the other stage are known as intermediate host.
Cross fertilization in liver flakes has been observed though self fertilization is also possible.
The life cycle involves three oval stages the eggs pass out at the genital atrium and are carried into duodenum by the bile where the eggs leave the Liver tissue of enter the blood circulatory system and make their way into the alimentary canal. When they leave the body of the host the egg emerge with faces of the herbivorous and their development is completed if the are deposited in water because egg pass out while the embryo has not yet developed.
When the eggs in the faeces deposited in water hatch out into a ciliated larva called miracidium.
The miracidiu, swims actively to the suitable host and attracted to a fresh water snail of the genera limnaea truncatula. It enters the snails body through boring of the skin by proteoltytic enzymes secreted by penetration gland.
Before the ciliated larvae enter the snail it develops structure which can bore into the body of snail. This larva consist of ciliated cells one of which bears two pigmented eye sports and excretory system.
In the snail it normally stays in the digestive gland.
It loses its cilia and changes into a sphere shape known as sporocyst.
Life cycle of the live fluke.
The laver that liberated into the body of the snail through ruptures of the sporocyst, called redial.
Each redial has a cylindrical central portion with two tapering ends, a muscular pharynx leading to the gut, flame cells, Circular and longitudinal muscles they also have germinal cells which give rise to more redial. This stage consists of active larvae which can move about in the snail body.
The germinal cells of the redial give rise to cercaria larvae. This larva has a rounded body provided with a tail. It contains two suckers (oral of ventral) and the excretory system. When mature, they leave the snail through the pulmonary aperture of the snail and enter the water, encyst on vegetation or may be taken by a sheep when drinking water or eating the grass.
The cyst is small transparent objet with a yellow or browns tint. In the herbivorous the cyst wall is digested by the gastric juices. The metacercariae pass-through the gut wall and coelom, reaches the liver.
The young liver flukes lies in the tissue of the lived and later in seven weeks they reach the bile duct.
Miracidium develops into a sporocys ——-> rediae ——- a cercariae.
Write down the effect of liver fluke on the host?
Adaptations of the flukes to parasitism:
- Production of large numbers of eggs followed by polyembrypny of each larva ensure survival and overcomes the great mortality rate during the course of the parasits to find the proper host.
- Presence of secondary host enswer survival and production of more individuals by polymbry ony before primary host is reached.
- Possession of anti – enzymes which make the parasite not to be effected in digestive enzymes of both hosts.
- Possession of suckers for attachments to the host and spines below the outicle prevent them from being washed away when bile or blood flows.
- Hermalphroditism ensures fertilization and where sexes are separated male and female are always in close association.
Class cestoda (taenia sp / tapeworms )
- The body is made up of separate but identical segments called progolottis. The progolotids are joined in series to the head to wards the posterior end.
- The body surface is not ciliated
- They have no digestive system.
- They have scolex at the anterior end which is attached to the host by hooks of snckers.
- They show strobilization, a process where proglohids are constantly budded off.
- They have a thin cuticle protect them from the hosts digestive enzymes. However it allows food such as glucose and amino acids to n be absorbed from the intestive of the host.
- Each proglotid (segment) consist reproductive organs. (i.e they are hermaphrodite) self fertilization within one segment can occur.
Adaptation to Parasitism:
- The taenia /Tapeworm has developed hooks e suckers for firm attachment to the intestine surface of the host intestine.
- It is ribbon – like (highly flattened) so that it cannot be remove easily.
- They produce anti –enzyme which prevents the effect of hosts digestive enzymes.
- Surface prevent them to be digested by enzymes host.
- They secret a layer of mucus on the body surface to prevent to be digested.
- The problem of finding a new host;
Each proglottids is sexually comlete being hermaphrodite , -this ensures fertilization of the egg, they are highly developed organism to the level of each proglottid being sexually sufficient in having both sexes.
- Production of large numbers of egg to overcome the high death rate and loss of the ears.
- Production of encysted eggs a larva to overcome adverse condictions.
PHYLLUM ASCHELMININTHES (Nematode eg Roundworms –Ascaris ).
- The body is round ,slender ,tapering at both ends.
- They are bilateral symmetry and cephalization .
- Unsegment worms.
- The body is triploblastic and possess an unlined body cavity called psendocoelom (false body cavity).
Psendocoelom – acoelom which is not a true coelom because does not occur within the mesoderm but it is between mesoderm’s is not endoderm’s . Also the cavity is not lined by an epithelial peritoneum.
- Body is covered with tough cuticle .
- Have a complete digestine tract with an anterior mouth and a posterior anus.
- They have only longitudinal muscles which give flexing motion.
- They possess separate sexes female larges than male – no asexual reproduction.
Free living in soil or water or parasite of man, demostic animals and plants.]Example of parasitic
- Ascaris lumbricoides –Intestinal roundworm in man.
- Aricylostoma duodenale –Hookworm in mam intestine .
- Wchereria bancrotti – cause elephantiasis
- Live in blood a hymph.
- Melodogyne –cause galls on the roots of tomato plants leading to wilting a poor growth.
Fig: Ascaris Lumbricoides.
They are white or yellow to pinking, cylindrical worms, non segmented, tepering at both ends. At the anterior end there is a muscular sectorial pharynx which leads to a straight alimentary canal.
There is a false body cavity (pseudocoeom) and a brain but no circulatory system and no definite nerve cord.
The parasites copulate in the hosts intestine and the unripe fertilized eggs with a farces in large numbers into the soil.
Alarva developed in the eggs after 3-4 weeks under warms, moist shady condition. In drought or cold condition s the eggs lie dormant for three or more years.
When eaten the embrocated eggs hatch in the ileum into a small motile larva which burrow and penetrate the mucosa lining and aculeate round the body through the veins or lymph vessels to the lungs ,where they mouth and groove in size pass up the air passage to the pharynx.
Coughed and swallowed again to the esophagus, stomach then to the intestine.
In the ileum they mature as they feed on partially digested food .Fertilization taken place and eggs are passes out in two month after infection of the eggs.
Pathogenicity (effects on the host)
- Mainly abdominal pain.
- Small hemorrhage of lung cause by burrowing of many larver .
- Borrowing of many larvae through the liver a lungs cause inflammation of these organs and symptoms like pneumonia in lung inflammation.
- Worms laver may migrate to other organ e.g. kidneys, brain ect a cause inflamition serious illiross or death of the host
- Proper disposal of human faeces
- Proper washing of hands after siol handling any food.
- Vegetable eaten in raw must be well washed.
- Keep short finger nail.
Adaptation of the parasite
- Lays abundant number of eggs to overcome a great loss in the long life history.
- Lays tough shelled egg so that they can withstand adverse condition.
- Laying unripe eggs so that they can develop outside the host and give sample time to be taken by the host.
- Possession of tough cuticle and antienzymes resistant to hosts enzymes digestions.
Annelids Arthropods and chordates tare called Coelomate Animals due to the possession of a true coelom.
Coelom is the main fluid filled, body cavity of many triploblastic animals occurring in the mesoderm in which the gut is suspended, and lined by a thin layer of epithelial cells known as the peritoneum.
The fluid filled coelom provides some advantage to the animals.
- This space within the body cavity, the reproduction and digestive organ can evolve more complex shapes and functions. i.e. it provided large cavity in which organ can develop and function freely visceral organ are such as the heart, lungs, liver, kidneys gonads etc.
- In this fluid filled chamber, the gut tube and other organ are cushioned and thus provide better protector.
- Since, this liquid cannot be compressed, the pseudo coelom or true coelom when present can act as a hydrostatic skeleton /water skeleton providing support and rigidity for the soft animals e.g. earthworm which allow the locomotion by whipping movement .This is because the fluid cavity can change its shape without change in volume.
- The activities of a suspended gut can take place undisturbed by the activity or inactivity of the animal’s outer body wall. i.e. The coelom which separates the gut from the rest of the body wall enables the gut to move independently of the body as a whole .And thus food can pass along the gut by peristalsis while the animals is otherwise quiescent .
The term Annelid means tiny rings and refers to the external segments visible on members of the phylum.
- They are triploblastic and coelomate animals.
- They are bilaterally symmetrical there similar segments. Each segment or metalmark contains a number of eg portion of the body wall, gut, coelom,nerve,pair of chaetae (bristle /setae pair of nephritis, and segmental blood vessels.
... But the segment, in metameric do not function as independent unit but are coordinated as integral parts of the body.
- Body wall and digestive track both with layers of circular and longitudinal muscles and each segment is separated from the next by an internal partition or septa (singular septum).
- Excretory system typically of one pair of nephritis per segment each removing excess water and blood stream by means of ciliated funnel and excretes them through a pore.
- They have closed circulatory system of longitudinal blood vessels with lateral branches in each segment.
The contraction of several heart or muscular vessels, pumps the blood continuously through the closed circuit.
- Their sexes may or may not be separated. Eg –earthworm –hermaphrodite. Marine worm – shed sperm a eggs into seawater, where the gamete unite a develop.
- Their body covered by thin moist cuticle.
- Respiration is body by epidermis
- They have nervous system with pair of celebral ganglion (brain) and connective to a double mid ventral nerve cord extending length of the body with a gangling and pairs of lateral nerves in each segment. i.e. –each segment contains dusters of nerve cell connected to the brain by nerve cords.
Classification of phylum Annelid
Polychaetae – marine worms
They are marine worms characterized bt the presence of large no of bristles chaetae eg nareis. Aquatic being free swimming in water or burrow in the mud or sand
OLIGACHAETA eg earthworms
They have few number of chaetae eg lumbricus terrestris
In damp soil fresh water
Hirudinea – the leeches
These are ectoparasites commonly knowns as leaches. They are highly specialized and have lost mmost of structure typically of the phylum. Eg.- chaetae are not present Few segments present Example Hirudo meducinallis
This is a group of terrestrial earth worms and resh water species eg. Lumbricus terrestris
- They are bilaterally symmetrical
- They show cephalization ie have head where the nerve ganglion are located
- They possess true coelom lined within mesoderm
- The body wall is concerned with a protecture cuticle.
- They have longitudinal muscles that can shorten the worm and circular lengthem it.
- They are hermaphrodite
- They have no participodia (side feet) function in movement and gas exchange.
- Obtain a grip on the substratime during crawling. There is a thickened region called clitellum used to secrete a cocoon which eggs pair.
- Every segment has four pair chaetae
- Have thickened muscular blood vessels in the auterior regions act as a pums (heart) help to move the blood in the body,
The body of an earth worm consisting of about 150 segments growth to about 25cm long. This animals is slender with a terminal mouth at the anterior and anus posterior.
Anteriorly is the mouth which over hung by the prostomium that is not a true segment the lower border of the mouth is know as peristomium
With the exception of the first segment has four chaeta/setae from segment 32-37 is a thickened region called the clitellum which secretes materials forming cocoon which contain eggs.
Excretory opening except on the 2nd and 3rd segment and the last each segment bears a Nephridiopore infront of chaete.
Reproduction – opening are separated the openings of the sperm thecae with seminal fluid is into these the seminal fluid from the other worm ventrally on segment are two very small slits which are the opening of the oviducts (female openings) and on segment 15 are two prominent open logs of the vasa deferential (male openings)
Adaptations of earthworm
- Their tapered end shape is ideal for burrowing and the chaetae of each segment used to griping the ground when the animals move
- Due to lack of an enzyme of digesting cellulose the efficient grinding apparatus in the gizzard is well suited to break up plant tissues.
- The secretion of mucous by the worm skin serves to bind the walls during burrowing.
- The ability of the worm to thrust the earth aside when it I looses or to consume it when it is tightly packed ensure sufficiently under both types of soil conditions.
- The formation of cocoon ensure efficient provision offspring during unfavaurable condition.
- They are eating soil containing dead and decaying plant endless food matter so ensures an endless food supply (ommirous).
ECONOMIC IMPORTANCE OF THE EARTH WORM
- Their burrows provide nature drainage channels and improving soil aeration
- They increase the depth of topsoil by burrowing into subsoil and bringing it to the surface. The topsoil produced by worms is neutral thus tends to reduce both acidity and alikalimity in soil
- Improve soil fertility.
- The ability of swallowing soils and the letting it pass through the length of the worms out through the anus such soil is rich in minerals eg nitrogen and phosphorous since it is mixed with vegetable matter.Texture formation
- The constant passage of soil through the gut reduce the particles to a fine state of division which provide an ideal medium for germinating of seeds
- Used as baint by fishermen
- Food for fish
Arthropods are the most successful of all animals. About two third of all named species on earth are arthropods.
General characteristics of the phylum
- The epiderma is covered by a hard chitinous cuticle that make the body covering water proof
- They have exoskeleton or external skeleton that surround the animals and provides strong support as well as rigid levers.
- They are bilaterail symmetry
- They undergo moulting lecdysis process by costing off exoskeleton during development growth.
- Their body show metamerically segmented ie formation of segment which are more less similar.
- The segmented body is regionally differentiated into regions/sections such as the head thorax and abdomen.
This tendency of the body being differentiated into distinct regions is knowns as Tagmatization. E.g. at the head read regions grew other appendages.
Mouthparts that allow chewing sucking.
Antennae that for sens
- They have efficient respiratory organs provie a large surface areas for collecting oxygen and releasing co2 quickly which allo them to metabolize by generating enough energy move rapidly. E.g insects have traclea branching networks od hiollow air passages spiders
Spider of relative have book lungs chamber with leaflike plates for exchanging gases
Aquatic arthropods have gills flat tissues plates that act as gas exchange surfaces.
- Organs of special sensea are typically present. Eg. Special compound eyes which consists facets and simple eyes capable for color vision and can detect the sli0ghtest movements of prey or predactors
- Their circulatory system is open with few vessels that blood flows through cavities between the internal organs and not through closed vessels.
- The coelom is greatly reduced the perivisceral cavity being the haemocoel
- Excretory structute which eliminate metabolic waste products is by malpighian tubeles that extend from the digestive track into the blood.
- They are triplobastics
- Sexes are separated.
Five main clases of arthropods
- They posses two body divisions
- Cephalothoraxes (the tendency of the head fused with thorax ) and the abdomen
- Have carapase or an exoskeleton hardened with calcium salts that act as protective shell.
- Have two pairs of antennas
- The respiratory structure are gills
- They are equatic
Example – crab
– cray fish
- There is a district head but the trunk has no obvious divided into thorax and abdomen
- Have one pair of antennae
- Have one pair of legs on each body segment
- They are all carnivorous and feed mainly on insects worms etc
- The first trunk segment have appendages that modified into a pairs of poison fangs
- They are terrestrial animals which lives in moist places in soil under stone etc.
Example – centipede
- They are slow moving counterparts to centipede
- They have two pair of legs per segment
- They are round, not flattened body.
- Their bodies consists of haed region followed by numerous segments.
- Most millipede are herbivoures.
- Have one pair of antennae.
- They have no antennae
- The bodt is divided into two region a cephalothorax (prosoma) and abdomen (opisithosoma)
- Have six pairs of appendages born on the prosoma
- one pair of chelicerae or poison fangas
- used for killing prey or self defense
- one pair of pedipalps that inject poison
- foue pairs of walking legs
- Respiration pairs of walking legs.
- Most members are terrestrial
- Most are carnivorous except the mites which are herbivores
Example – spider
- The body is divided into three main regions head thorax and abdomen
- Have one pair of antennas born on the head
- Have three pairs of walking legs born on the thorax
- Have on or two pairs of wings or may not present
- Have one pair of common eyes
- The respiratory system is a yacheal system with segmentary spieacles arranged
- Metamorphosis occur during development ie period of rapid transformation of larva to adult or morphological changes animal such as insect
Examples – Locust
– cockroach (preriplanet ariericana)
The adaptive features of the arthropods
- Possession of cuticle
Have wax which restricts water loss from the body surfaces
It forms rigid wings which makes easily fly of the isects.
Also cuticle protect the arthropods from predators since predators found difficult because of hardened exoskeleton
- From invasion by parasite
- From physical environmental (mechanical injury)
- From chemicals such as insecticides
- From abrasion such as insecticides
- From abrasion by the food since the gut lined by cuticle.
- The mouth parts show adaptive radiation
Their mouth parts modified and specialized according their feeing habits.
The arachnida do not ingest solid food, so they poor salivd containing protease over their prey p suck up the fluid eg spiders of scorpion
- Presence of sill spinning organs called spinnerets which form we spinning used for trapping insects eg spider.
- Possession of sensory organs.
- Most have antennae capable of detecting slightest movements, sounds or chemicals
- Compound eyes
- Possession of molting (ecdysis) process during development this remove the hard cover and become soft which allow growth
- The flattened shape of the body enable them to insinuate themselves into small cracks crevices where they are almost inaccessible. Eg cockproach, centipede.
- Deposition of there are aggs in small crevices ensure a considerable measure of safety for the eggs with the further protection of the tough coat
- They used claws of the peripalps to crush their prey eg scorpion
The biological success of insects
As terrestrial animals prevent against desiccation and other danger to all land animals. Thus it limits size but then solved these problems by undergoing their ecdyses during larva stages usually protected against desiccation and other dangerous to all land animals.
Thus it limits size but then solved these problems by undergoing their ecdyses during against desiccation and by ceasing growth after metamorphosis – support the body
This is the tendence of the body segments being differentiated into districts regions such as head thorax and abdomen and each one specialized in function. Example – hedd consist mouth pairs
Compound eye antennae and each part specialized in function eg mouth parts for feeding cpd eye for sighting Anterna for sensitivity.
The high rate of reproduction
Rapid increase the number of individuals ensured high rate of be able to colonize rapidly a new territory.
The economic importance of arthropods
Beneficial insects Harmful
- Act as pollinators eg bees butter flies ect.
- Pests of crops eg locust cause a great damage within a short period
- Pests of stored food eg beetle
- production of honey eg. Honey bees
- production of wax used in polishes candles etc eg bees wax
- Production of silk.
- Some insects destroy things at home such as furniture and clothes eg. Ants cockroach
- Food for human and demestics animals eg locust honey produced by honey bees crabs drawn
Vectors of disease
Some insects transimit serious diseases for example malaria sleeping sickness yellow fever of eleplantiasis etc. Eg mosquito housefly
Biological control insects have been used in a number of cases to control damaging pests I certain cases isects have been very effective as a predators or parasite to reduce the number of a pests. Eg wasps ground beetle their lark eat insects that feed on and damage citrus fruits other trees.
Some arthropods cause painfully to human when defending them selves. Eg scorpion certipende bees.
The notochord (chorda dorsalis) of specialized vacuolated cells
This is a stiff but flexible rod situated dorsal to the gut flexible rod situated dorsal to the gut ventral to the nerve cord (cns)
Is the first axial structure bid down in the embryo
It has skeletal function eg muscle attachment and is a skeletal rod serves in supportive functional Extends from the head to during development replaced by the vertebral column.
Visceral clefts (pharyngeal gill slits or branchial clefts) these are paire series of openings (perforations) one the kiteral sides of pharynx.
In the simple (primitive charclates eg cephalochordate urochordata inotachord in the head region ) tail choidata) the pharynx is a sieve live structure with numerous slits used to strain food particles from the water (folter feeding)
In certebrates the number of slitts is greatly reduced and they may be modified for different purpose example.
- In aquatic- fish larval amphibians their walls are lined with feathery gills used for gas exchange.
- While in reptiles buids and mammals they occur only during embryonic development and in the adult from they disappear except the first which become the Eustachian tube.
The dorsal Hollow nerve coord above the notochord part from the brai case (cianium) skill) and posterior part by vertebral column.
Direction of blood flow in the main vessels
They have closed blood system in which blood flow in a special blood vessels.
The blood flows forward toward the heart ventrally and ack ward away from the heart dorsal to the gut.
The directions of blood flow in chordates are in shart contrast with those found in non chardate eg Annects
The blood flo-w is forward in the dorsal vessed downward around the gut in the hearts backward in theventral vessel.
The position of the heart.
In the higher chordates it becomes folded and divided into chambers it is always situated vetrally bellow the gut while in non- chordates it lies dorsally above the gut.
They are bilaterally symmetrical
Limbs formed from more than one segment
Their limbs are outgrowth of the body containing tissive derised from both ectoderm and mesoderm.
Post anal segment tail (true tail
- Only found in the chordates
- In higher chordates it has often seven adapted to other uses
Eg – crocodiles as weapon
– many animals for flicking insets
– lizards store food
While in many chordates it is vestigical or absent in the adult
The body division into head neck trunk and fail
No more than two pairs of limbs or any locomotive structures E.g. fins limbs aims
- Pisces eg fish
- Amphibian eg topid, frogs
- Reptiria eg lizards snakes, tortoise, crocodiles
- Eves eg birds
- Mammalian eg man whalesco.rat/mouse
- They are aquatic
- Paired limbs – fins pectoral and pelvic
- Visceral cefts persist in adult stage as respiratory well developed
- There is an exoskeleton of placoid
- No middle or external ear
- Eggs are laid in water ie fertilization is external or internal
- Chondrichthyes (cartilageous fish) eg dogfish
- Osteichyes (bony fish) eg Tilapia
- Sub-classs osteichthyes eg Tilapia
- The body is streamlined shape
- The mouth is terminal and horny operaculum
- Eyelicls absent
- They are heaver than cartilaginous fish because bones are denser.
- They posse swim badder a sac filled with air which allows the fish to suspendes at any depth in the water.
- The body is covered with scales called ganoid scales which are over/aping bony plates, sometimes spiny along the edges which provide some protection for the fish.
- They have a highly developed lateral line system which enables fish to detect changes of water pressure and thus the movement’s of predactors prey and others objects in the water.
- Have tail called homocercal the lobes are more or less equal
- They are aquatic exchange of gas is by gills.
- They are oviparous they lay eggs (external fertilization) they are poikilo thermic
- Have fins –pectorial pelvic
In fresh water of salty water
External features of Bony fish eg Tilapia
Body is divided into 3 regions
These given it a streamlined shape which allows it to move smoothly through the water. This are flattened laterally tapering at ends
Exoskeleton is made up of bony scales. This fish is covered with thin scales which overlap one another so that the free endes points backwards. It protected the animals but still allows it to move.
Head – is covered by plates of scales tapes towards the mouth
Function – offering the least resistance as has-a pair of nostril inside which ire the olfactory organs found on the top of the head, anterior to the eyes.
Ear – no external ears.
Organ for balance in addition to receiving vibrations carried by bones of the skull.
Pupils are big admit much light
Operculum (gift cover)- covered five pairs of gill slits found either side of the bo dy in the neck region.
Trunk – have fins of two types
- Paired lateral fins
- Unpaired median fins.
Paired fins are – pectoral (fore limbs)
– pelvic (h ind limbs )
Unpaired and are – dorsal
– anal (tail or caudal)
Functions of the fins
Dorsal and anal fins present the body from rolling side ways hence they help to stabilize the body also prevent unstable movement
- Control the direction
- Keeps the fish upright
The paired fins (pectoral pelvic)
- Steering and balancing the fish
- Help the fish to change its direction
- Control upward and downward movements
- As me brakes when they extend rapidly at right angels to the body stop the beat against the water they cause the slow forward or backward movement.
Function of scales:
Scales are known as dermal scales each other in which case when the fish is moving it offers less resistance or reduce fraction (can easily pass) through the water. They proved protection.
Function of lateral line:
To detect vibrations in water
Function of swim bladder
An air sac found below the backbone in some fish it is connected to the fish hence of fish can float
Floating – used the volume of gas in the swim bladder must be sinking the volume of gas must be decresed.
Class chondrichthyes: (cartilaginous fish) e.g. dog fish.
- Is a marine fish with cartilaginous endoskeleton?
- The body is streamlined.
- They are thicker at the center and pointed at the ends.
- Have narrow eyes without eyelids.
- The mouth is transverse and crescentric.
- Nostrils are present.
- Their tail are heterocercal, the two lobes of the tail is unequal.
- The skin is covered with small pointed abnormal identical (placid scales) similar in structure to the teeth.
Adaptation of fish to aquatic life:
- The body is streamlined to facilitate passage through the water.
- Gill respiratory organ which enable the fish to utilize oxygen dissolved in water , gill slits outlets of water during breathing .
- Lateral lines detects disturbance in water and the fish is easily made aware of any approaching danger (strong current or enemy).
- The various types of fins which their overall function it to control the stability and direction of fish.
- The body is provided with a powerfully muscular, tail and forms a strong propulsive organ and this combined with a smoothly streamlined body enable locomotion’s in water swimming.
- Eyes are covered with a transparent skin which present H20 from the entering the eye.
- Sharp scales – for protection from predators an addition of little resistance to forward motion.
- Also scale provides a protective exoskeleton.
Economic importance of fish:
- Food for man -provide the first class protein hence food value
- Fish supply many useful products. Examples;
- Cod liver oil – one of the best sources of vitamin A &D.
- Fish oil is used in manufacture of certain paints.
- Provide food for animals e.g. cat, dogs etc.
- Glue is made and bones of fish scales of certain fish.
- Also fish is a food for other aquatic animals and this is the ecological significant to the aquatic system.
(In food chain web).
This is a class of animals which spend part of their life in water and part of it on land, Hence the term amphibian.
- This group of animals are between fish and reptiles. Conquest of land necessity taste evolution of certain features which could adapt them to a dry hobbit. e.g frog.
- They adapt both aquatic a terrestrial.
- Have two pairs of limbs for swimming a jumping.
- The head is compressed if a very short neck separates the head to trunk.
- Young amphibians breathe by means of gills but the adult ones breath by lung except salamanders.
- Development is by metamorphosis eg frog…
- They are terrestrial but still depend on moist environment because of the constant loss of water through the skin.
- Some of amphibian’s possess tails e.g. salamanders a newts.
- Found in the order caudate of no tails e.g. frog toad in order Anura.
- Some they are legless scale e.g. caecilian in order gymnophionia .
- Circulatory system was modified so that lungs of skin could be supplied with the blood place through their moist, glandular skin and liming of regenerating most parts e.g. salamanders.
- They pay eggs in water moist places because eggs lack shells membranes that can retain water therefore the eggs can out rapidly.
- Fertilization is externally .
- They are poikilothermic.
- Heart have 3 chambered, 2 articles of 1 ventricle.
- Some amphibians eg Toad, frog have ability of changing the colour of their skin from light to dark.
- This change is controlled by the hormones inter
- Median secreted by the intermediate lobe of the pituitary glands.
- Some frog’s toads secrete poisons substance which serves as a means of protection for animals which act as predators.
- Have unitary bladder called all antic bladder used for preservation of water absorbed from blood vessels during dry period or miner nation.
- Young are period herbivorous while adult are carnimonors except salamanders.
Found in grass near water in damp. e.g. frog, toad ram temporalis
The body is divided into
- no neck a fail
- The body usually green with black or dark brown patches of some tints of yellow.
- They are flattened dorsally ventrally
- The head tapers in front a is bluntly rounded.
- Have wide amount in the terminal
- Have pair of nostril for respiration
- Two spherical eyes c are large and protruding, lie almost dorsally but face laterally.
- Eyelids are poorly developed.
- Upper stiff an immovable.
- Lower represent a instating membrane that is transparent, can move upward over the eyeball, to keep it moist in the cur and as a protection when was under water.
- Behind each eye have flat eardrum or tympanic membrane that receive sound waves in the air or water.
- Widens laterally them tapers btn the hind limbs to end at cloaca, c form the anus, discharge undigested food water of urine.
- Ventrally – thoracic reign is firm while abdominal is soft.
- The front limbs are short shout a have four digits.
- It supports the front of the body in the ground a the resting position
- The land limbs are long, muscular folded two three progress .
- The skin is soft, moist a slippery to the touch.
Function of the body walls (the skin).
- Protection by – slippery a poisonous substance which render the animals unpalatable to larger carnivorous.
- Sensory organs – sensitivity is located in various types of sense organ which are stimulated by organ and by temperature changes.
- Respiratory – The moist surface with the thin skin and excellent blood supply make the body wall a very important respiratory organ.
- Excretory – The presence of seculars glands which secret mucus, keeps the skin moist thus enabling absorption of 02 and elimination of CO2.
- Adaptations:1. Camouflage. Pattern of the pigment patches breaks up the shape and act as camouflage in the grass or in the water. E.g. Ability to change color blends it to its background.
- Limbs of girdles modified for jumping and swimming.
- Swift movement of tongue aids in catching prey , and teem with their sharp backward points render escape of large prey.
- Protruding eye give a wide field of view and has an accessory function in assisting swallowing.
- Hibernations, reduce metabolism enables survival when there is no food available and food is stored in special organ eg hiver, store glycogen a facts, allantois bladder stored water.
- Production of large number of offspring and protection of the embryo in felly ensures survival.
Reptilian is air breathing animals and were the earliest vertebrates to become well adapted to life on land.
Members of this class together with bird and mammals are called amniotic since
- They bear young ones dive (full developed)
- They bear shelled eggs on land.
- Complicated mode of development.
- They lay soft shelled eggs called amniotic egg which protects the embryo from drying out, nourishes it, and enable it to develop outside the water. The term amniotic comes from the word animus which is the membrane containing fluid in the which the embryo lies and another membrane allantois visualize contain blood vessels and also possess egg yolk, which contain noonisgment for long period .
- They have long tail and two pairs of walking legs except snakes, used for clawling a wringgling along using to tail.
- Frtilization is said to be internally .
- Have fawns contain teeth set in sockets and all of the same shape (Homodentel teeths)
- They are poikilothermic
- Have major nitrogenous waste products called uric acid.
- Breathing by using lungs.
- They don’t have a diaphragm.
- They are aquatic or terrestrial.
External features: e.g. lizard.
- They are covered by scales and shed several times a year when the animals mount.
- They lay small eggs
- Have two pairs of limbs fore limbs a hinds limbs both have 5 digits with claws.
The body divided into
- Is pyramid in shape – slightly depressed
- Opening the external nostrils.
- The eyes have lower upper opaque movable eyelids.
- Have tympanic membranes which are more sunk compared with those of the frog.
- Elongated strongly convex dorsally.
- There is a cloaca aperture at the root the tail on the ventral surface.
- Skin –periodical the outer layer disintegrates into fragments interact of being shelled off as in many snakes.
Adaptation of Reptiles: e.g. Lizard.
- Possessions of dry scale skin is practically impermeable thus prevent water loss.
- Posses lungs for respiration – breathing is coordinated with movement of muscles a ribs.
- Reabsorption of water in kidney of rectum is efficient thus reptiles excrete uric acid and the faces in semisolid form.
- Soft shelled eggs provided protection but porous allow aeration.
- Herb nation during adverse condition allow them to continue in surviving.
- Ability to regenerate i.e. their tail may cut off when attached but latest regenerates.
- Body shape (long narrow body) and color help to give it camouflage. E.g for moving into holes or underneath vegetation.
- Improvements of necessary sense organs e.g. eyes, ears, noses.
- Their brain is more developed than that of amphibians. E.g development of cerebral cortex.
- The neck enable the lizard to move so it can catch the prey without moving the the body,
- Development of limbs for running.
- Cleidoic development renders the embryo independent of aquatic surrounding because the embryo develops in a ware medium within the egg shell.
- Since the sperm could not penetrate the egg shell for fertilization, must occur wthin the body of female before the shell is added.
Advantages of Reptilians over the Amphibians
- Possession of dry scaly body covertly adapted to life away from water.
- Limbs suits for rapid locomotion
- Further separation of the oxygenated and deoxygenated blood in the heart, due to their which are imperfectly i.e. have 4 chambered =2 auricles and a partly divided of vertricle.
- Eggs suits for development on land with membranes and shells to protect the embryo.
- The are warm – blooded and have a four chambers heart is 2 auricles of 2 ventricles.
- Possession of dermal milk glands, the mammary glands which produce milk for feeding their young’s.
- Most of mammals are at least partially covered by heiry called fur except the whale and porposes, have virtually no hail at all.
Function of fur:
- Temperature regulation acting as insulator
- May also be tactile (sensory of function)
- Protective in function
- They have external ears with a soft flap called the pinna, which used to collects some waves that entering the ear.
- Mammals are heterodyne.
They made up different kind of teeth in the cavity eg incisors, molars, premolars and canine, according their feeding habit.
- Have specialized limbs with bones elongated shortened or broadened, depending on the animals particular locomotors or food gathering needs
Eg antelope have strong slender bones that ailon swift running.
- Majority have a special reproductive structure the placenta, that supports the growth of the embryo to a fairly complete stage of development before birth.
Eg sub-class eutherian.
- Possession of a muscular cliaphram
- Separate the thoracic cavity from the abdominal cavity.
- Importance for efficient breathing mechanism.
- They are viviparity – fertilization is internally, and produce their young ones alive.
- They have highly developed nervous systems and senses smell and hearing in most mammals of sight in a few.
- They provide parental care not only on suckle their young, but depending on the species to guard the new generation fiercely and teach their survives skills.
- Some have dermal glands
Eg. Sweat glands – sweat
Secretion for temp regulation.
- Sebaceous glands – hair secrete sebum a substance of lubricates hair is bactenocidal in nature.
External feature: eg rat / mouse
They body divided into
- Varies in colour from nearly black to pale grey brown.
- They body covered by ur consisting of short few hairs set closely enough form a thick pile
- Have long scaly tail.
- Head is avoid in shape, tapering in the front, where the mouth is small and terminal – bounded by soft upper a lower lips.
- Upper lip exposed large incisor teeth for chiseling action.
- Have pair of nostril.
- Towards to dorsal surface, are the large eyes with movable upper of lower lids.
- At the inner corners of the eyes there are nictacting membranes which can be moved across the eyes to wash it.
- Have long, stiff sensitive hairs called vibrissae, at the side of the mouth nostrils of the around the eyes.
- Sensitive to touch of dark ross of the barrow.
- Have ear with long flexible plena.
- Although wades from the neck, divided into thorax of abdomen by diagram partition.
- Ventrally, the thorax is firm b’se of the sternum of rips while the abdomen is soft.
- On the ventral surface, in the female there are six pairs of mammary glands bear the teats – three on the thorax or three on the abdomen.
- Beneath the tail is the anus of ventral to it is the urinogenital opening.
- On the old male, there is a perineal glands fond between the anus of urinogenital opening (hairless) patch of skin – gives an oclour characteristic.
- The male opening is born on a projection, the penis, which bears a retractable sheath called prepuce. At the sides of the Panis are the tastes contained in the scrotal sacs.
- The female opening is longitudinal slit the vulva which bears a vestigial penis called the clitons on the ventral side. The tail is short and usually bent upward.
The front limbs are shorter than hind limbs, and both bears five digits ending with sharp claws, modified for jumping.
Function of mammalian skin: (body wall)
The body wall (skin) provides protection from various hazards: it is an excretory regulation and sensitivity.
- Physical protection from damage is provided by stratum corneum and fur, while the colour gives some measure of camouflage.
- Insulation. The hair traps a layer of air near the body surface and this acts as an insulating layer, preventing excessive loss of heat as as well as thickness of the adipose tissue.
- Excretory organ. The sweet is to some extent an excretory. It consists of water, dissolved salts (Na &Ch) a small quality of urea Co2, where is passed from the capillaries into the cells of the tubules and secreted by them. Generally the sweat is evaporated, but in condition of high temperature or great muscular activity, it may run off the body as fluid.
- Sensitivity. Nerve ending in the skin are sensitive to a variety of stimuli which are commonly grouped together under the sense of touch. There are endings sensitive to mechanical contact, others for pain and others for high and low temperatures.
- Regulation of heat loss. The greatest quantity of heat is lost by evaporation of sweat from the surface.
There fore regulation of the amount of sweat will mean regulation of heat loss. It is accomplished by control of the surface blood vessels including those which supply the sweat glands.
Adaptation of mammals eg rat / mouse
- The great length of the gut enables maximum absorption.
- Viv parity entails internal fertilization of provision for attachment of the embryo by placenta, through which it receives all necessary supplies.
- In the reproductive organs, the mechanism of internal fertilization is present of coordinated to occur at the heat periods (at the right time)
- Possession of placenta which provides an ideal means of exchange between the mother’s and embryo’s blood with the necessary safeguard against dangerous materials.
- Parental care. The birth process and lactation at the correct period, show further adaptation for care of the young until they are able to fend for themselves.
- Possession of nictation membrane which protect the eye in duty condition by washing it.
- `presence of vibrissae for gauge the width of the burrow in its darkest depths.
- Possession of natural colour for camouflage from predators.
- Possession of great efficiency in respiratory and circulatory systems and the structure of the skin is admirable adapted to control heat loss.
- Possession of large Iscor teeth in the upper lip for chiseling action of presence of ear or pinna used to reflect sound waves into the canal of determine the direction of the sound.
Discuss the economic importance of the phylum Chordata.
Class Aves eg pigeon.
This a group of homoeothermic, terrestrial vertebrates which have features. They are highly specialized vertebrates which fly almost every part to their organization, are modified to serve aerial life.
- They are homoeothermic, their body temperature is between 40 -42 c provided by effective insulation of smooth features.
- They are covered with features which act as an epidermal exoskeleton which provide effective insulation as they maintain a higher body temperature than do most other animals.
- The fore limbs modified to wings, which provided with large feathers, to give the power of fighting.
- The sternum and pectoral girdles are modified and save as origin of powerful muscles of wings. ie. They have lightweight, hollow bones and a breast bone or sternum, enlarged into a blade – shaped anchor for the powerful pectoral muscle that raise and lower the wings.
- The pelvis girdles and hind limbs are modified to support the entire coat of the body on the ground.
- Have efficient respiratory system that have a series of connected lungs and air sacs that exchange oxygen of CO2 in an efficient one way flow.
- Absence of teem, eyes are efficient to enhance vision.
- Have beak formed in the upper of lower flaws covered by horny sheath.
- Laying tough egg shelled which are internally fertilized.
- The skin is loose of dry worn-out sweat gland.
- Have scaly feet of no urinary bladder.
- Small rounded with prominent beak covered with a horny sheath.
- The eyes are large with an upper of lower eyelid, and transparent
- Long mobile neck
- Covered by feather – directed forwards and overlap the true tail.
- The domestic pigeon loose heat by painting and have many air spaces in their lungs of evaporation, of moisture occurs from the tongue of epithelia surface of the buccal cavity.
- They have nervous system which is responsible for the regulation of heat loss.
Know as wings bear large quill feathers, divided into three (3) regions
- Hind which is close bound by skin with only 3 digits
– Divided into 3 regions
(i) Thigh (ii) shark (iii) foot.
The body wall:
- Has an outer epidermis of an inner dermis.
- Feather are out growths from the epidermis.
- Includes feathers consisting of protective horny scales.
- The scales cover the torso-meta tarsus and the four digits of the foot.
- Each digits terminals into a claw which is also a horny product of the epidermis.
Types of feathers:
Basically 3 types:
- Quill features
- Found in wings also known as flight wings also known as flight wings, they are large. Strongly joined to the body wall.
- Restricted to the wings of tail.
- Contour feathers
- Cover the body smooth hairs fills the gaps between the quill feathers.
- They have bulbs which are not strongly joined can be separated easily
- Structurally they are smiler to quill feathers but they are smaller than quill.
- Main suppose of contour feathers insulation against heat loss.
- Down feather (filo plumes)
- Are stumpy hair like structures beneath the contour feather their bulbs do no interlock
- Are the only feather of a newly hatched birds later on replaced by quill of contour as the bird growths
Function of feathers:
- For insulation against heat loss especially contour feathers.
- Importance in flight esp. quall feathers
- Defense of offence features especially the wings in some birds can be used for fighting.
Adaptation feature of Aves
1) Connection with flight:
- The skeleton is modified for accommodating a large flight muscles and hollow bones (field with air instead of narrow) to reduce body weight.
- Feathers designed for flight of the fore limbs provide large surfaces area by feathers off small wing area as well as tail that stabilize the bird braking and landing.
- Have an efficient respiratory system supplied by the large air sacs.
- Have got excellent sense of vision
- Very good muscular coordination eg the extension of the sternum (breastbone) for the attachment of the pectoral muscles.
- High body temp:- allow high metabolic rates, which in turn fuels the activities of the flight and leg muscles.
- The body modified into streamlined that makes easily to pass trough air.
2) Cleidoic development:
- Provide large shelled eggs with large yolk amniotic.
- Possess embryonic membranes
- yolk sac
- amnion – amniotic fluid – most prevention from mechanical injury.
- allantois – ventral outgrowth of the gut functions as an embryonic bladder, store waste products since the duct of the kidney lead to it.
- chorion – respiration – it expends of come to lie next or close to egg to shell, also s
Supplied with blood vessels hence functions as an embryonic lungs.
- Form waste products c are insoluble thus require small space for storage.
- Reduction in the ovaries esp. oviduct.
3) Homoeothermic condition:
- Have high metabolic rate which account for high body temp.
- The body is covered by feathers which prevent heat loss – through insulation.
- They lack sweat glands hence prevent heat evaporation.