BIO 102 GENERAL BIOLOGY-2.pptx

GENERAL BIOLOGY II BIO 102 GENERALIZE SURVEY OF PLANTS AND ANIMAL KINGDOM  Classifications of Living Organisms Aristotle (384-322 BC) a Greek philosopher, was the first to make an attempt to classify living organisms. The present method of classifying and naming living or...

GENERAL BIOLOGY II BIO 102 GENERALIZE SURVEY OF PLANTS AND ANIMAL KINGDOM  Classifications of Living Organisms Aristotle (384-322 BC) a Greek philosopher, was the first to make an attempt to classify living organisms. The present method of classifying and naming living organisms is based on the work of Linnaeus (1707-1778), a Swedish naturalist. The study of the general principle of classification is known as taxonomy or systematic. Hierarchy of Living Organisms Kingdom has the largest group of organisms. Each kingdom is split into smaller groups, and these groups into even smaller groups and so on. The arrangement of living organisms in this hierarchy from the highest to the lowest is as follows: Kingdom Phylum or Division (Plants) Class Order Genus Species  As we go down the variety of organisms decreases. The kingdom has the largest variety of organisms. They have certain important features in common but show many differences. The species is the smallest unit of Classification. They are identical in general appearance. They can mate with one another and produce fertile offspring. Organisms within a species are very closely related  Binomial Nomenclature This is the use of a standard system to name living organisms, though we are familiar with common names of living organisms such as Mango, Goat, Pawpaw, Lion etc. In Binomial Nomenclature, each kind of organisms is given two names: the first name is the genus to which the organism belongs and the second been the species to which it belongs. On the genius name begins with an initial capital letter, Hence the scientific name of Pawpaw is Carica Papaya, Lizard – Agama agama. The names are written in italics or underlined separately.  Kingdoms All living organism were placed into two kingdoms by Linnaeus. The Kingdom was plants and animals. This is known as two – kingdom classification. In this classification, many one-celled organisms could not fit in properly; it failed to establish clear-cut distinction between plants and animals. It also could not indicate correct relations among organisms.  So, in 1969, Whittaker proposed the five- kingdom classification which is generally used at present. The classifications are: Moneras Protists Fungi Plantae and Animalia  The Kingdom Monera contains the prokaryotes – Which are the very simple –celled organisms that has no true nuclei. The eukaryotes- which cells are highly organized with definite or true nuclei are classified into the four  Kingdom Monera (Prokaryotes) Single- Celled organisms, motile or non-motile, microscopic. Simple – Celled Structure with no definite nucleus. Examples includes Bacteria, Blue- green algae, actinomycetes  Kingdom Protista (Eukaryotes) Single –Celled, motile or non-motile. Organisms are much larger than the monerans. Complex Cell Structure with a definite nucleus. Examples includes: Chlamydomonas, Amoeba Kingdom Fungi (Eukaryotes) Non-motile organisms usually of thread- like structure or hyphae. Plant- like but cannot carry out photosynthesis due to absence of chlorophyll, obtain food through surface from living or non living organism source by absorption, reproduction could be by asexual or sexual or sexual spores. Examples includes: moulds, Mushrooms, shine moulds, yeasts.  Kingdom Plantae Many-celled, non-motile, contain Chlorophyll that enables them make their own food by Photosynthesis. Plants have indeterminate growth. Examples includes: Mosses, Ferns, Pines, Seed Plants (yam, bean, and plants).  Kingdom Plantae Plants can readily be understood in the context of their autotrophic mode of nutrition. They simply transform light energy into chemical energy by anchoring firmly in one place with a maximum surface area to capture sunlight. Plants use the cheapest material around, water and carbohydrate to generate size. Because plants are immobile, they are extremely responsive to environmental cues and have their life cycle in perfect synchrony with the seasons.  Plants have a unique mode of development. This involves giving by meristems at their tips. They also have remarkable power of regeneration. Any single plant cell can regenerate an entire plant with its cell types. The cells have cellulose cell wall.  The plant kingdom is mainly classified into: Thallophytes (Alga) Bryophytes Pteridophytes Gymnosperms Angiosperms Tracheophytes (Pteridophytes, Gymnosperm and Angiosperm) The tracheophytes are known as vascular plants. This is because they have vessels or vascular tissues for conducting water and food. They are the largest group of plants which includes the seed plants (flowering plants) as well as some spore-bearing, non flowering plants like ferns.  Pteridophytes, A pteridophyte is a vascular plant (with xylem and phloem) that reproduces by means of spores. Because pteridophytes produce neither flowers nor seeds, they are sometimes referred to as " cryptogams", meaning that their means of reproduction is hidden E.g fern in forest  Gymnosperm The gymnosperms 'revealed seeds') are a group of seed-producing plants that includes conifers, cycads, Ginkgo,and gnetophytes, forming the clade Gymnospermae. The term gymnosperm comes from the composite word in Greek: 'naked' and seed'), literally meaning 'naked seeds'. The name is based on the unenclosed condition of their seeds (called ovules in their unfertilized state). E.g. conifers, cycade, ginkgo biloba, pine tree Gymnosperm  Angiosperm Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae commonly called angiosperms. They include all forbs (flowering plants without a woody stem), grasses and grass-like plants, a vast majority of broad-leaved trees, shrubs and vines, and most aquatic plants. The term "angiosperm" is derived from the Greek words ('container, vessel') and8 ('seed'), meaning that the seeds are enclosed within a fruit. They are by far the most diverse group of land plants with 64 orders, 416 families, approximately 13,000 known genera and 300,000 known species. Angiosperms were formerly called Magnoliophyta (/ mæɡˌnoʊliˈɒfətə, -əˈfaɪtə/). Flowering plants  Evaluation 1. Differentiate between Bryophytes and Tracheophytes 2. Why are invertebrates grouped under the kingdom Animalia  Evaluation 2 Give an example(s) of the following alga types: 1. Green Algae 2. Brown Algae 3. Golden – Brown Algae 4. Yellow-green Algae  Monocotyledonous Root The anatomy of the monocot root is similar to the dicot root in many respects. It has epidermis, cortex, endodermis, pericycle, vascular bundles and pith. As compared to the dicot root which have fewer xylem bundles, there are usually more than six (polyarch) xylem bundles in the monocot root. Pith is large and well developed. Monocotyledonous roots do not undergo any secondary growth.  Dicotyledonous Stem The transverse section of a typical young dicotyledonous stem shows that the epidermis is the outermost protective layer of the stem Covered with a thin layer of cuticle, it may bear trichomes and a few stomata.  Algae or Thallophyta Objectives Algal Morphology Characteristic Forms of Algae Classification of Algae Spirogyra Structure of a spirogyra Ecological Adaptation  Introduction In this unit we shall be looking at the first classification of the plant kingdom, which is the Algae. Algae show great diversity in size and structure. They are unicellular, Colonical, filamentous and thalloid in form. Some are microscopic, while others are very big in size. They do not form complex organs or tissues. The study of their ultra structure under electron microscope shows that blue-green algae have prokaryotic type of cell like that of bacteria while all other algae are eukaryotes  Algal Morphology Morphologically, algae can be distinguished as unicellular, colonial, filamentous, heterotrichus, thalloid and polysiphoid forms. Examples of each of these types of algae are given below.  Various Forms of Algae 1. Unicellular Algae: Example Anacystis, Microcystis 2. Colonial Algae Microcystic, Volvox 3. Filamentions Algae Nostoc} blue-green algae; Ulothrix, Oedogonium 4. Heterotrichous Algae Draparnaldiopsis, Coleochaete, Ectocarpus 5. Thalloid Ulva, Fucus} Brown algae 6. Polysiphonoid Polysiphonia (Red algae)  Characteristics of Algae They are simple plants without roots, stems and leaves. They have Chlorophyll. Some have blue, yellow, brown and red pigments with the chlorophyll. Majority are uni-cellular while few are multicellular. Some, such as sea weeds are large. They are mainly aquatic, with a few on damp soils and shady places examples are spirogyra, anabaena and Sargassum The cell wall of algae is composed of a true cellulose. Reserve carbohydrates are usually starch and not glycogen as in fungi.  Classification of algae 1. Cyanophyta (prokaryotic algae) or blue-green algae eg. Including Nostoc, An abaena, Oscillatoria. 2. Chlorophyta (algae) eg. Chlamydomonas, Spirogyra, Chlorella 3. Phaeophyta (brown algae) eg. Fucus, Sargassum, laminaria. 4. Xantophyta (yellow –green algae) eg. Vaucheria, Botrydium 5. Chrysophyta (Golden-Brown algae) eg. Synura, Mallomonas, Chromalina. 6. Euglenophyta (Euglenoids) eg. Euglena, Trachelommas. 7. Dinophyta (Dinoflagellates) e.g. Ceratium, Peridinum. 8. Crytophyta(Crytomanads) e.g. Crytomones, Chroomonas. 9. Bucillariophyta (Diatoms) eg. Diatoma, fragilaria.  Spirogyra Spirogyra a green algae belongs to the family Chlorophyceae and the order conjulaes or Zygnematales. It is a cosmopolitan plant which forms a tangled mass of filaments floratiny on stagnant fresh water, especially in ponds, ditches, springs and streams. Some species grow in running water. Such species produce a short unicellular organ of attachment, called hapteron, for anchorage on Sea weeds.  Spirogyra is commonly found as bright green masses of thread-like or filamentous structures on the surfaces of waters, and is often referred to as a “Pond Scum”.  Structure of a Spirogyra Mature filament is unbranched and consists of single row of identical cylindrical cells joined end to end. Cell wall is made of Cellulose and pectin External cell wall is covered by mucilage, making it shinny. Cyloplasm is a thin layer with spiral bands of chloroplast. Nucleus is suspended at the centre by strands of Cytoplasm. Chloroplast contains small nodular protoplasmic bodies called the pyrenoids. Starch grains are deposited around each pyrenoid.  Algae range from Unicellar (microscopic) to large (macroscopic) thalloid forms growing in variety of habitats almost all over the surface of earth. Wherever there is water, a little moisture or water vapours, and light, however feeble, Algae are sure to appear as green, yellow or brown patch. When several types of algae grow together under similar natural conditions we call them communities. The composition of a community is determines by the physical and chemical nature of the habitat. In many cases, the algal community indicates to us about the nature of the habitat, whether, it is rich or poor in nutrients or polluted etc., in other words it serves as an ecological indicator.  Aquatic Algae Most of the algae grow in water; however, there are also sub-aerial algae. Depending on the concentration of salts there are various kinds of water bodies, such as fresh water brackish water, sea water, brine-salt lakes and salt pans. There habitats nowadays may contain many types of pollutants, like excessive organic metal, heavy metals, pesticides, industrial effluents which are produced and dumped into them by man. This greatly affects algae and other organisms present in the water.  Fresh Water Habitats Fresh water habitats comprise of rivers, mountains streams, lakes and temporary rainwater puddles. Examples of Algae find here include green algae like oedogonium, diatoms, desmids, etc. In slow flowing rivers with rocky shores, one may find many filamentous algae like spirogyra, oedogonium. The surface of submerged rocks also shows epiphytic algae like desmids and Cyanobacteria.  Marine Habitats Sea inhabits largest number of algae collectively known as seaweed. Seacoast is periodically flooded and exposed to sun because of the feeds. The area between the high tide and low tide level is known as intertidal zone. The seaweed that grows in the intertidal zone face alternate drying and wetting. They are also firmily attached to the underlying rocks by means of hold fasts. At times they may get detached and found flowing in the open sea as in the case of Sargasso sea. Example of seaweed include Sargassum wightii (brown algae), Turbinaria, gracilaria edulis  Special Attributes Algae are also found in special habitats where environmental conditions are in extreme such as Brines and salt lakes where cyano bacteria (Anabaeria) and Unicellulal green alga Dunaliella can be found; Thermal Regions (not water) thermal springs with temperatures ranging from 40º to 70 ºc) inhabit alga like oscillareria, Mastigocladus and Cyanobacteria; Polar Regions (extremely cold climate conditions) where Nostoc, oscillatoria, can be found.  Soil and Subaerial Algae Surface layers of soils provide a favourable substratum when wet for the growth of several types of algas. Terrestrial algae such anabaena, play a major role as primary colonizers on newly exposed areas. Subaerial algae obtain their water from the moisture in air and grow if moisture is available. They are capable of enduring drought like the soil algae. One can see dark brown patches, sometimes with a velvelty carpet like cushions covering extensively the exposed surfaces of buildings, walls, finances, asbestos, roofs, rock surfaces and also tree trunks.  Evaluation Give an example(s) of the following alga types: 1. Green Algae 2. Brown Algae 3. Golden – Brown Algae 4. Yellow-green Algae  Evaluation Outline the general characteristic features of named Algae 2. Describe the structure of filamentous Algae  BRYOPHYTES During the course of evolution, a change from aquatic habitat to terrestrial habitat occurred and the only primitive land plants evolved. These are known as bryophytes. Although bryophytes colonize terrestrial habitats but they are still dependent on water for completion of their life cycle. They produce motile male gametes which require a thin film of water for their motility to reach the non-motile female gamete to accomplish fertilization.  General Characteristics of Bryophytes Bryophytes lack roots and do not have vascular system. Some mosses have a primitive system of tubes that conduct water and food – conducting tubes are called leptoids. A single plant is very small, hardly a few cm in size. It seldom grows large because of lack of supporting tissues. Bryophytes show two distinct and well defined phases of life cycle, sexual and asexual which follow each other. T he gametophyte is haploid and produces gametes. The Sporophytes is diploid and produces spore. The haploid generation alternates with diploid genetic known as Alternation of generation. The gametophyte may be thalloid or has an axis differential into stem- like and leaf-like structures which have xylem and phloem. The gametophyte is green, photosynthetic and nutritionally independent, and anchors to the soil by unicellular or multicellular filaments called rhizoids.  Rhizoids appear like roots but they lack vascular tissues  Morphology of Bryophytes Bryophyte is mostly divided into liverworts and mosses.  Liverworts Gametophytes usually are close to the ground. There are 2 forms of liverworts namely; thalloid liverworts (gametophyte) and is dorsi-ventral, with upper and lower surfaces. Leafy liverworts (differentiated into leaf-like and stem-like structures). Leaves of liverworts are without midribs. Grows on moist ground or rocks that are also wet. (can be found in muddy areas. Examples include Marchantia and Riccia  Mosses This is the largest class of Bryophytes. They are divided into three subclasses: Sphagnidae (Reat mosses) Andreaide rock mosses) and Bryidae (true mosses). Example includes funaria  BRYOPHYTE summary 1. Bryophytes are simple non-vascular land plants and it is believe that they evolved from green algae because of several common characteristics. 2. Bryophytes shows two distinct and well defined phase of life cycle ie. The gametophyte phase and the sporophyte phase. The gametophyte produces the gamete while the sporophyte produces the spore. 3. The challenges of land environment for a plant are fixation to the ground conduction of water and dispersal of sperms and spores. Bryophytes take care of there by developing land adaptations such as epidermis, cuticles, stomata, air spores, rhizoids, etc. 4. Liverworts (Marchantia) and Mosses (Funaria) are example of Bryophytes.  Pteridophyte General Characteristics of Pteridophytes i. Pteridophytes have two distinct phases in the life cycle. These are Gametophyte and Sporophytes which follow each other in regular succession. The two generations look different.  Xtics of Pteridophytes cont’d ii. The sporophyte is the dominant generation, independent of the gametophyte; it possesses a vascular system and it is in a different habitat. iii. Pteridophytes exhibit a great variation in form, size and structure. iv. Most are herbaceous except a few woody tree ferns. v. They may be dorsi-ventral or radial in symmetry. vi. They have dichotomously or laterally branched stems that bear megaphyllous leaves. vii. Roots are generally adventitious, the primary embryonic root being short-lived. viii. Spores are produced in special structures called the sporangia that are invariably subtended by life-like appendages known as sporophylls. ix. In most cases, the sporangia are compacted to form distinct spore producing regions called the strobile. The sporangia in some cases, may be produced within specialized structures called the sporocarp. x. The leaves of a fern plant is called frond. xi. Pteridophytes, in general, are homophonous i.e. they produce only one-type of spores. However, a few species produce two types of spores (micro- spores and megaspores). xii. They form green, dorsiventrally differential, thallose gametophytes with sex organs restricted to the ventral surface. xiii. The female reproductive structure is archegonium and the male reproductive structure is antheridium.  Relationship of Pteridophytes with Other Groups Pteridophytes and Bryophytes: Similarities 1. Liverworts and Pteridophytes show similarity in vegetative structure of gametophytes. 2. Their female and male reproductive structures are archegonium and antheridium, respectively. 3. The opening of the mature sexual reproductive organs and the subsequent fertilizations are condition by the presence of water in liquid salt. ie both require water for fertilization. 4. They usually show a distinct and clearly defined heteromorphic alternative of generations and the two generations follow each other in regular succession. 5. The spores arise in the same manner in both groups. 6. Development of embryo occurs in the archegonium. 7. The young sporophyte or embryo is partially parasitic upon the gametophyte.  Difference 1. In Pteridophytes, the sporophyte is independent at maturity and is the dominant phase of life cycle instead of gametophyte as in bryophytes. 2. The Sporophyte has true roots, stems, and leaves and well developed conducting tissues-xylem and phloem, which are absent in bryophytes. 3. Some of the Pteridophyte is heterosporous but all the bryophytes are homosporous.  Pteridophytes and Flowering Plants In Pteridophytes, plant body is not divided into root and shoots system, in flowering plants, plant body differentiated into distinct root and shoot system. Vascular bundles are less developed in Pteridophytes, (tracheids) Flowering plants has well developed vascular bundles (xylem and phloem). There is no pollen grain, pollen tube; in Pteridophytes following plant has pollen grain. Pteridophytes have no seeds (but sori) while flowering plants produce seeds with cotyledons or endosperms.  Morphology of a Pteridophyte– Pteris vittata Pteris is a widely distributed genus with about 250 species. It grows abundantly in cool, damp and shady places in tropical and subtropical regions of the world. Pteris Vittata is a low level fern which brings out new leaves throughout the year. It is very common along mountain walls and grows up to 1200 metres above sea level.  All the species of pteris are terrestrial, perennial herbs with either creeping or semi erect rhizome covered by scales. Roots arise either from the lower surface or all over the surface of rhizome. Leaves are compound in most species, but a few have simple leaves eg. Pteris cretica. The stalk of leaf continues as rachis and bears leaflets called pinnae. In Pteris vittata, the pinnae present near the base are tips are smaller than those in the middle. Condition for Adaptation Sporophyte shows greater degree of complexity in structural organization. It is organized into stem, root and leaves. The Vascular tissues (xylem and Phloem) are developed only in the sporophyte. The aerial parts are covered with a layer of cuticle. On the Epidermis, there are stomata for the exchange of gases. These anatomical complexities of the sporophyte of Pteridophytes helped in inhabiting a much wider range of environmental condition than the gametophyte could do.  Alternation of Generation Heteromorphy ---alternation of distinct generation Haploid gametophyte –1n set of chromosome Diploid sporophyte– 2n set of chromosome Gametophyte produce sperm and egg Sporophyte produce spores  Evaluation Outline the relationship between Pteridophytes and Bryophytes in respect to their similarities and Differences. SEED PLANTS (GYMNOSPERM AND ANGIOSPERM) Seed plants are seed producing vascular plants. They are also called Spermatophyte. They have well developed roots, stems and leaves. The seeds containing the embryo develops from a fertilize egg of a very small gametophyte which is completely dependent on the sporophytes, the plant form we see around us. The efficient seed dispersal of seed plants account for their continued existence and widespread occurrence. The fertilization of the egg is by the male gamete which is brought by pollination, followed by the growth of the pollen tube which carries the male gamete to the egg. Water is not needed in this process, hence the seed plants are true land plants. In this unit, we shall be looking at the seed plants: Gymnosperm and Angiosperms.  OBJECTIVES By the end of this unit, you should be able to: list out general characteristics of seed plants outline the specific characteristics features of gymnosperms and angiosperms highlight morphological characteristic of a named gymnosperm and angiosperm classify gymnosperms and angiosperm highlight the terrestrial (ecological) of seed plants. General Characteristics of Seed Plants They are terrestrially adapted i.e they are land plants. The gametophytes of seed plants become more reduced and dependent on the sporophytes. They produce two types of spores (Megaspores and Microspores) ie. they are heterospores. They undergo pollination which replaces swimming as the mechanism for delivering sperm to egg. They produce seed.  Gymnosperms Classification Gymnosperms are generally classified into four divisions. These are - Coniferophyta - the conifers - Cycadeophyta - Cycads - Ginkophyta - ginko - Gnetophyta - gnetae.  Conifers Among the gymnospems, the conifers are the most important. They have the following characteristics: They are cone bearing plants with vascular tissue. All are woody plants; the great majority been trees with just a few shrubs. Species can be found growing naturally in almost all parts of the world. They are frequently dominating plants in their habitats. They are of immense value, primarily for timber and paper production. The wood of conifers is known as softwood. Examples are: Cedars, Cypresses, Pines, Redwoods etc. External Morphology of Conifers All are wood plants, and most are trees. Majority has a monopocal growth (ie. a single, straight trunk with side branches) with optical dominance. Size varies from less than a metre, to over 100 meters. They are the world largest, tallest and oldest living things. Ecological Adaptation of Conifer The have distinctly scented pesin, which is secreted to protect the tree against insect infestation and fungal infection of woods. They maintain high rates of photosynthesis at relatively low temperature. Their needles (leaves) have thick warty coatings and sunken stomatas which prevent excessive loss. The sapwood column is large and acts as a short-term reservoir that supplies water to foliage during drought periods.  Angiosperms The angiosperms are also known as flowering plants. They occupy every habitat on earth except extreme environments. They live as epiphytes (i.e living on other plants); as floating and rooted aquatics in both fresh water and Marine habitats, and as terrestrial plants that vary tremendously in size, longevity and overall form. They can be small herbs, parasitic plants, shrubs, vines or giant trees. They are also sources for other important resources such as medicine and timber.  Classification Angiosperm are generally classified into two (2). These are: Monocotyledons (Monocots) Dicotyledons (Dicots).  General features of Angiosperms They could be photoautotroph, Saprobes or parasitic. Mostly pollinated by insects, birds, and other animals, while some are by wind They have vessels (xylem and phloem). The monocots include lilies, grasses, corn, wheat, palms, while the dicots include roses, maples, oaks, peas, and beans. Angiosperms posses certain external features that remarkably distinguish them from other seed plants. This feature includes: 1. Flowers They have modified leaves Has sepals – usually green Petals –brightly colored and insect pollinated Petals –drab – wind pollinated Has carpels – female reproductive organ. Has stamen- male reproductive organ.  2. Fruits It protects documents seeds. They have mature ovary. Simple fruit has single ovary flower (e.g. Pea pod, apple) Aggregate fruit – produce from separate flowers (e.g pineapple) Modifications for dispersal includes: attractive food, dispersal by wind, burns.  Terrestrial Adaptation of Vascular Plant (Seed Plants) Possession of cuticle They do not need immediate aquatic habitat. Roots have no cuticle. They are woody materials made of Cellulose and lignin. Possession of vascular tissues (Xylem and Phloem).  Evaluation 1. Outline how conifers are terrestrially adapted. 2. What are the distinguishing features of a flowering plant?  ANIMAL KINGDOM (INVERTEBRATES AND VERTEBRATES) outline the general characteristics of invertebrates differentiate between invertebrates and vertebrates outline the features of protozoas highlight the morphological structure of a protozoa explain different ecological adaptation of a protozoa based on its external morphology.  General Characteristics of Invertebrates The Invertebrates animals abound in number very greatly, about 95 percent of the identified and described species of living species of animals are invertebrates. They vary in size, some are microscopic e.g. Protozoans, while others are enormously large, e.g. some giant cephalopods. Their shape is variable and they show different kinds of symmetry but considerable number is Asymmetrical as well. Except protozoa other invertebrate phyla shows multicellularity. They show different grades of body-organization;  They integument of invertebrates is simple. The gut may be entirely absent, or partially formed or fully formed. However, if present, it is always dorsal in position. Likewise, if heart is present, it is always dorsal in position. The nerve cord is ventral in position and solid in organization. Circulatory system, if present in invertebrates, may be open type, or closed type or combination of both. They show diversified excretory mechanisms, some takes place by general body surface, or by specialized cells as flame cells or structure like nephridiaa, Malphighian tubules, green glands, kidneys. Etc.  They undergo different methods of reproduction such as fission, conjugation, parthenogenesis and gametic fusion. All invertebrate animals are cold- blooded.  Difference between Invertebrates and Vertebrates invertebrate vertebrates May have non-living There is always an endoskeleton, exoskeleton made of living tissues like cartilage and bones. The respiratory organs usually The respiratory organs develop in develop from the ectoderm. relation to the wall of the pharynx and consist of gills or lungs, but gill clefts are present in the embryo of all vertebrates The circulatory system is The Circulatory system is a closed usually not closed. system with arteries, veins and capillaries. Respiratory pigment Haemoglobin is contained in the haemoglobin, if present, is red blood corpuscles. dissolved in plasma. Eyes develop from the skin Eyes develop as outgrowths and of the not from the brain. Compound brain compound eyes are eyes are often present. never found. Reproduction sexual or asexual Reproduction is only sexual  Phylum Protozoa The term Protozoa refers to Unicellular animals of the microscopic size. They from the simplest of all the groups in the animals’ kingdom. The name protozoa means “first animals” and has been derived from two Greek words, PROTOS, meaning first and zoon, meaning animal. They are looked upon as the most primitive form of life, appearing first in the evolutionary history. Structurally a protozoan is a one-called animal comparable with one cell or a METAZOAN but functionally it is an entire organisms, physiologically balanced and performs all the essential process of an animal, hence protozoans are called acellular or non-cellular organisms. Distinguishing Features of the Phylum Protozoa i. The mode of life could be free-living or parasitic. ii. The presence of moisture in their environment is an essential condition for their mode of life. iii. Locomotry organs are finger – like Pseudopodia or whip-like Flagella or hair-like Cilia or absent. Meganucleus) eg. Paramecium iv. Nutrition may be holozoic (animal- like), holophytic (Plant-like), Sapro- phylic or parasitic. v. Respiration occurs through general surface of the body. vi. Excretion occurs through general surface or through contractile vacumes which also serve for Osmo-regution. vii. Reproduction takes place asexually by binary or multiple fission and budding, and sexually by conjugation of the adults or female gametes. viii. Encystement commonly occurs to  Classification of Protozoan The classification of the Phylum Protozoa is based on locomotory Structure. The Phylum Protozoa is divided into sub-phyla; i. Plasmodrome; Members have Pseudopodia (false feet) or flagella or no locomotory structure eg. Amoeba, Euglenas. ii. Ciliophora: Members have cilia and more than one nucleus of which one is large (Meganucleus) eg. Paramecium.)  Morphological Structure of Amoeba Amoeba, a member of class Sarcodine is the common example of the simplest animal life and is usually universally studied as an: Introduction to the Phylum Protozoa. The most common species is Amoeba proteus. It measures about 0.25 to 0.60mm in size and is difficult to see without the aid of a microscope.  Under the microscope, it appears as a minute slate – coloured shining, irregular mass of a gelatin-like substance with study moving fine particles. It has an irregular shape due to the fact that protrusions of its own substance and formed at its surface in different directions – the Pseudopodia and they are constantly changing in shape in them achieve animal by the protoplasm. It consists of a very- thing elastic external plasma membrane or plasmallema  Habitat The common Amoeba Proteus may be collected from a variety of places where condition of water, temperature and organic food are favourable such as debris from watering troughs, bottom of ponds, pools, drains, ditches, abandoned tanning pits and wherever there is abundant aquatic vegetation.  Locomotion Pseudopodia are associated with ingestion of food and Locomotion- During Locomotion, it form one or more blunt finger-shaped processes or pseudopodia which continue to grow more and more by the flow of the protoplasm which is obviously withdrawn from somewhere else and, therefore, if the formation of the Pseudopodium is mainly in onedirection, the amoeba must change in position and it is in this way that locomotion is effected.  Irritability This has a particular reference to the pseudopodia. If a pseudopodium, an extension, should come in contact with a foreign body, such as a grain of sand, it is retracted and a new one is pushed out in a changed direction. This implies that the generated Protoplasm of amoeba has the power to perceived nervous messages or stimuli over the whole of its surface, since at whatever point the pseudopodium is extended it will react to this reaction.  Food and Feeding The aquatic environment of amoeba has tiny particles of various organic substances, suitable for food. This includes unicelluar plants, particular bacteria and diatoms, tiny filaments of algae, various protozoan species together with organic debris of many kinds. It is holozoic in nutrition,  Egestion There is no specialized organelle in amoeba for throwing out the indigestible material. It leaves the animal through a temporary opening in the ectoplasm at the rear of the animal. The plasmallema ruptures at this point of contact with the vacuole and the feaces are egested or the animal flows away. New plasmalemma is formed at the ruptured area to stop the outflow of endoplasm. Respiration The process whereby the Carbondioxide leaving the protoplasm is exchange for oxygen entering it, is known as Respiration. In amoeba this exchange is carried on mainly through the general surface of the body. The water in which amoeba lives must contain dissolved oxygen in order that this diffusion may go on.  Osmo Regulation Osmo regulation refers to the regulation of water content. The contractile vacuole is responsible for this function. The contractile vacuole is a clear space. It contains a fluid less dense than the surrounding protoplasm. At more or less regular intervals, it suddenly collapses, its walls having contracted, force out the fluid contents which is known to contain traces of urea and Carbon dioxide but mostly water. Reproduction Reproduction is asexual and is by the methods of: i. Binary Fission ii Sporulation iii. Encystment  Summary Protozoans forms the simplest of all the groups in the kingdom Protozoans are called acellular or non-celluar organisms. Protozoans mode of life could be free-living or parasitic The Classification of the Phylum Protozoan is based on Locomotory structure. Amoeba and Paramecium are examples of the phylum protozoa. As a form of adaptation, the pseudopodia are associated with ingestion of food and locomotion. The contractile vacuole is responsible for the regulation of water content in protozoans.  Evaluation 1. Draw an annotated diagram of a named Protozoa. 2. Outline the distinguishing features of a protozoon from other groups of animals.  PHYLUM PORIFERA OBJECTIVES At the end of this Unit, you should be able to: out line the distinguishing features of poriferas draw the external features of a named porifera classify the phylum porifera outline the structure and ecological adaptation of porifera  Introduction in this unit, you shall be looking at the phylum porifera. The members of phylum Porifera are very interesting and are found widely distributed in both fresh and salt water. They vary considerably in size and shape; some reach a size of 80cm to 2 metres in diameter while others form a thin incrustation on rocks, sponges as porifera are also called, has a very large number of microscopic pores on the surface of their body through which water passes constantly in from this stream of water, the sponges are able to strains out the microscopic organisms, which are used as food. Because of the presence of million of “pores”, this Phylum of animals has been called Porifera or Pore bearers.  Distinguishing Features of Phylum Porifera From the point of view of structure of multicellular animals, the poriferas also known as sponges are the simplest and the most primitive. The main distinguishing characters of the Phylum, which is also known as Parozoa are as follows: i. They are asymmetrical ii. Well developed tissues and organs are not present. iii. Digestive system is absent and digestion of food is intracellular. iv. The body wall surrounding the central cavity is only two layers the outer layer known as the dermal layer and the inner layer as the gastral layer. v. The gastral layer contains flagellated collared cells or choanocytes. vi. They do not have respiratory and excretory organs. Nerve cells are also absent. The pores or Ostia opening into the gastral cavity are surrounded by contractile cells. vii. The entire outer surface of the body shows the presence of large number of Ostia through which a  Classification of Poriferas The different kinds of spicules in the wall of Poriferas are used in Classification. Therefore Porifera is divided into the following classes: i. CALCAREA OR CALCISPONGIAE eg. Leucosolenia, Scypha, Grantia, etc. ii. HEXACTINELLIDA e.g. Euplectella, Hyalonema iii. DEMOSPONGIA eg. Spondilla, Spongia Leucosolenia (A Simple Coconial Sponge) Phylum - Porifera Class - Callerea Order - Homocoela Genus - Leucosolenia  External Organizations Leucosolenia is whitish or Yellow in colour. Consists of a cluster of vase-shaped individuals All individuals are connected to common horizontal branches with their base. The individuals are free above and open to exterior by a large opening called osculum, present at their tip. Osculum is surrounded by an oscular fringed which is composed of a circlet of monaxim catcareous spicules. Each individual cylinder has many pores, called Ostia, in the surface and it may attain a height of about 25cm.  Ecological Adaptation Habit and Habitat Leucosolenia is a small, delicate branching, colonial marine spronge. It is worldwide in distribution and found attached to stones and rocks of sea-shore water. For its life activities, it depends entirely on water. Structural Adaptation of Leucosolenia  Structural Adaptation of Leucosolenia The body wall of leusolenia is very thin and unfolded consisting of two Layer (choanodern). These layers are separated by gelatinous layers of Mesoglea or Mensenchyme. The dermal layer is a protective layer. The constant movement of their flagella, situated in the gastral layer, set in continuous water current in one direction. The Mesoglea contains types of cells which together form the Mesenchyme. The amoebocytes. Which are the most important cells in the mesenchyme performs the following functions: They take food from the choanocytes and supply it to the other cells,  They carry on intracellular digestion of food and also help in the storage. They carry on transport of waste matter. They form scleroblasts which produce spicules or sponging fibre. These form the endoskeleton. They also function as germ cells. Sensitivity Although the sponge has no nervous system but still they show response to contact, chemicals, light and heat. Reproduction The sponges carry in reproduction by the following method: 1. Regeneration 2. Asexual reproduction 3. Sexual reproduction  Canal system in sponges The passages through which water travels from outside the body to the interior of the body and then outside again, form the canal systems in sponges. The canal system is advantageous as follows; It brings a constant supply of water The continuous current of water passing through a sponge furnishes an ample supply of oxygen for all the cells. The continuous current water passing through a sponge carries away carbon dioxide and waste nitrogenous substances. The water which leaves a sponge has been filtered off much of its food and oxygen and is loaded with poisonous waste resulting from metabolism.  Summary Spronges are aquatic invertebrate. They are asymmetrical. Leucosolenia is an example of sponges. Leucosolenia consist of a cluster of vase- shaped individuals. Their dermal layer is a protective. They depend on water for their life activities which includes: supply of food, oxygen and disposal of water materials.  Evaluation 1. Draw the external features of a named porifera. 2. What are the features that adapt the porifera to its environment?  PHYLUM COELENTERATA(Cnidaria) classify the phylum coelenterate outline the characteristic features of coelenterates mention the various classes of coelenterates with examples make a labeled diagram of a named coelenterate- hydra describe the external features of hydra outline the adaptive features of hydra.  Introduction You have already seen in the last unit above, how sponges- phylum Porifera is organized. We shall now look at the phylum coelenterata. The coelenterates include more than 9000 living species, all aquatic, mostly marine but also some fresh water forms. They are a successful group of animals, though of great structural and functional simplicity among metazoans. Examples include jelly fishes, sea anemones, corals, hydra etc  Characteristic Features of Coelenterates All are aquatic animals They are radially or bilaterally symmetrical They diploblastic, with an epidermis and a gastrodermis, and a less cellular or non- cellular, gelatinous mesoglea in between They have no coelom, or separate excretory or respiratory system Two individual forms of coelenterate exist: polyps and medusa  Forms of Coelenterate There are two forms of individuals in Coelenterates. These forms are: Polyp Medusa  Polyp Polyp is tubular, the oral end being free carrying a whorl of tentacles, and the aboral end attached to the sub stratum by the basal disc. The polyp is the sedentary, benthic form  Medusa The Medusa is the free swimming umbrella-like pelagic form, with mouth at the end of the manubrium on the subumbrellar side.  Classification of Phylum Coelenterata (Cnidaria) Depending mainly upon whether polyp or medusa is the dominant form in the life cycle, coelenterates are divided into four classes: Hydrozoa Scyphozoan Cubozoa Anthozoa  Class Hydrozoa They may be solitary or colonial forms There are asexual polyps and sexual medusae, though one type may be suppressed Animals may be either fresh water or marine Examples include Hydra and Obelia  Class Scyphozoa They are solitary medusa Polyp stage reduced or absent Medusae do not have velum All are marine Aurelia is a typical example of this class Class Cubozoa They are solitary medusoid forms They have reduced polyp stage Medusa is square in cross section All are marine animals Example include Carybdea Class Anthozoa All are polyps They are solitary or colonial Gonads are gastrodermal All are marine Example include sea anemone  External Features of Hydra Body resembles a narrow elastic tube, closed at one end and open at the other The closed end of hydra is known as the foot or the basal disc refered to as the aboral end Has a conical process, the Hypostome or the Oral Cone in the centre of which is situated an irregular or star shaped mouth Has slender contractile and hollow tentacles between 6-10 in numbers Body may attain a length of 20mm or more when fully extended Usually have small hydras known as buds attached to them when food supply is in abundance  Adaptive Features of Hydra Foots secretes a sticky substance for Anchorage and Lcoomotion Interstitial cells which is chief agent in regeneration, repairs, budding and reconstructing tissues in growth Nematoblast helps in defence Hydra usually remains attached by its basal disc or foot to objects under water The movement of hydra are for: the capture of the prey; response to stimuli; locomotion Swimming is facilitated by the wave-like movement of the tentacles Hydra is a Carnivorous animal Egestion is through the mouth  Summary Coelenterates are all aquatic in nature They are radially symmetrical Coelenterates also known as Cnidaria is classified into four: hydrozoa, Scyphozoa, Cubozoa , and Anthozoa Hydra, a typical example of the Coelenterates belong to the class Hydrozoa  Evaluation With the aid of a labeled diagram, describe the external features of Hydra. Outline the characteristic features of the phylum Cnidaria  Platyhelminthes Kosi has been experiencing some symptoms for now. These include; abdominal pain, loss of appetite, upset stomach, nausea, weight loss, fatique, weakness. He for test only to find out the has tapeworm in his intestine. The tapeworm belong the group/phylum platyhelminthes Platy means flat while helminthes means worms  Platyhelmeinthes are dorsiventrally flattened, dorsi means top while ventral means bottom i.e from top to bottom is flat. Many of them are endoparasites e.g. tapeworm while some are free living organism in water e.g. planaria Adaptive features to the human or animal gut thru the hooks, it has suckers around for sucking nutrients form the host as endoparasites  Example liver fluke, tapeworm, hookworms, Excretory system has the flame cell for excretion. Flame cell for osmoregulations, the cillia of the flame cell beat to draw water and nutrients into the body of the organism which goes out through tubule salt water balance is osmoregulation and getting rid of  Reproduction in flatworms, they are hermaphrodites and fertilization occours internally, once they are fertilized the animal lays the eggs outside. The egg grows into larva, the larva stage can survive in the intestine of pigs, cow and humans and finally grow in adult tapeworm Some multiply by regeneration where a single flatworms breaks into fragment parts which each regenerate into adult flatworms. Fasciola hepatica, schitosoma haematobium Cestoda e.g. tapeworm  PHYLUM PLATYHELMINTHES OBJECTIVES At the end of this unit, you should be able to: outline the characteristic features of platyhelminthes classify the phylum platyhelminthes draw and outline the external feature of a named platyhelminthes outline the habitat of liver fluke outline the adaptive feature of platyhelminthes.  Introduction we have just studied diploblastic animals i.e. (coelentrates) animal where body is made up of only germ layers – the ectoderm and endoderm in the last class. Now we shall proceed to study triploblastic animals which apart from the ectoderm and endoderm, has third germ layer known as the mesoderm. The first phylum among the triploblastic animals is the phylum playthelminthes. These animals range in size from less than a millimeter to a few metres in tapeworms. They include free-living and parasitic species. May live on land but some are fresh- water or marine, crawling in weeds and sediments.  General Characteristic Features of the Phylum Platyhelminthes They are bilaterally symmetrical Their body are dorsiventrally flattened; known as flatworms Triploblastic animals – made up of three body layers They lack body cavity hence called Acoelomate They have complete reproductive organs Digestive system is absent in some; and when present has only the mouth but no anus Nervous system are ladder-like, with simple sense organs They have no respiratory, circulatory or skeletal system They have a proto-nephridial type of excretory system. Classification of Platyheminthes The phylum platyhelminthes is classified into three main classes. These are; Turbellaria Trematoda Cestoda  i. Turbellaria: mostly free-living and aquatic, with soft bodies and leaf like in form. They have body covered with cilias, some are terrestrial and confined to humid areas and with only one opening to the gut. Examples include planaria, etc. ii. Trematoda: They are parasitic; lacking cilia; cuticle covering leaf like body with one or more suckers. Examples include  iii. Cestoda: They are endoparasites (internal parasites), having no gut (digestive) system. There are parasites in the digestive tracts of various vertebrates. They are Ribbon – like in form made up of many segments (proglottids) with an anterior scolex carrying suckers and hooks to hest tissues. When mature, each prolothic has a complete set of reproductive organs of both sexes. Examples are the Tapeworms like Taenia solium, Taenia saginata etc. Fasciola Hepatica (Sheep Liver– Fluke) Fasciola hepatica is an example of trematode parasite. It requires two hosts to complete its life-cycle – a vertebrate as the primary hurt, and an invertebrate animal as the secondary host. The vertebrates may be man, sheep, cow etc through their faeces transferred to secondary host (invertebrate) snails.  External Morphology Body is soft and Pinkish – brown in colour Elongated and dorso – ventrally flattened (leaf- like) Appear to be oval in shape, measuring 1.8 – 3 cm in length and 0.4 – 1.5 cm in width. Broad and rounded at the anterior end of the body; and bluntly pointed at the posterior end. The anterior sucker acts as a anchotorial organ for adhesion and ingestion. Has a muscular bowel – like ventral or posterior sucker which is for adhesion only Body has a minute gonopore or genital aperture mid-ventrally which is little in fruit of the posterior sucker. Anus is absent.  Habitat The adult Fasciola hepatica lives in the liver and bile ducts of the primary host which is the sheep but it may occur in some other vertebrates such as goat, dog ox deer, rabbit, elephant, man etc. A primary hostt may harbour up to 200 adults of liver fluke in its liver which subequently may stop to function. causing liver disease. The immature life-stages of the fluke occur in a mollusc (snails), Limnea truncatula, which is a secondary or intermediate host. The liver-fluke is world-wide in distribution in sheep and cattle raising areas the infection of this fluke is also formed in man.  Structural Adaptation The body-wall of the liver fluke is composed of only cuticle (and musculature) which covers the body as a thick and tough layer, proving protection to the fluke against chemicals of the host. Digestive System: it sucks blood, lymph etc. as food in its alimentary canal due to suctorial pharynx. The interlinary caecal distribute them to different parts of the body.  Excretory System: It has protonephridia type of excretory system, which is composed of large number of excretory cells called flame cell. The excretory substances collected in the human gut of the flame cell are pushed into excretory capillaries and tubules due to vibration of cilia of the flame cells.  Respiratory System: It respires by general body surface. Reproduction System: It is a hermaphrodite. The male and female reproductive organs are present in the same individual and regeneration  Parasitic Adaptation Since they live well protected, with their hunger well satisfied without any need for change of position, there is no need of locomotory organ. Attaches themselves to the gut wall or bile ducts by means of suckers and hooks or suckers alone. In the digestive system of the host, they can absorb the digested food through their soft skin Sense organs are absent without any inconvenience as they live in perpetual darkness Secretes certain anti-enzymes which counteract or neutralizes the digestive juices of the host in order to prevent being digested The intestinal parasites stimulate the intestinal wall of the host to produce enormous amount of mucus which covers the thick cuticle of the parasite with a protective envelope.  The osmotic pressure of the parasite’s body fluids is nearly the same as that of the host, if not, the resulting exchange of water would set up serious disturbances Their reproductive organs are enormously developed. Eggs are provided with thick shells and remain viable for a long time They are hermaphrodite, ensuring that eggs and sperms reproduced in one and the same individual Paedogenesis or multiplication by the larval form by asexual means – this improves their chance of survival  Phylum Annelida Annedlida means little rings They have segmented bodies They have so much benefits on agriculture as they contribute to soil fertility They have chaete for movt They are carnivorous and hermaphrodites  arthropoda Arthropod means jointed appendages/feet They have 3 body segments, head, thorax and abdomen Have exoskeleton 4 classess 1. cheliceriformes e.g. scorpions 2. Cephalothorax (cephalo means head and thorax) e.g spider, 3. myriapoda (many feet) eg. Millipede and centipedes 300 legs 4. hexapoda means 6 feet. Eg. Beetle 5. Crustacea e.g crab, crayfish, binnacles, 80% of all animals on earth are anthropods. There are more species of insects than all animals combined on earth. The most abundant animal on earth  Insects are the basic factor in plant pollination They develop metamorphosis, complete/partial metamorphosis, egg ---larva pupa ---adult  PHYLUM ANNELIDA OBJECTIVES After studying this unit, you should be able to: outline the characters of the phylum annelida name the classes under the phylum annelida highlight the external features of a named annelids show diagrammatically the external morphology of a named annelid outline the adaptation of a named annelid to its environment.  Introduction We shall be looking at the first Coelomate Phylum, that is, the Phylum Annelida (Coelomate Implies animals with a cavity lined by an epithelium of cells derived from the embryonic mesoderm). Annelids have elongated body divided externally into a number of rings which represent a division of the internal parts into a series of segments. Examples include Earthworms, Neanthes, Leeches, etc.  Characteristic Features of the Phylum Annelida They are mostly aquatic, some are terrestrial. Some are sedentary or free living, and some are ectoparasites. The body is vermiform, bilaterally symmetrical, and metamerically segmented. Vermiform describes something shaped like a worm. They have straight tube alimentary canal, and undergo extra-cellular digestion. Has segmentally arranged Locomotory organs, repeated groups of chitinous setae or chaetae. Leaches have no setae.  Chitinous Setae are locomotory organs of annelids which are present on parapodia. Locomotory structure in annelids is epidermal chitinous Setae or bristles, which are present on parapodia. Parapodia is a pair of fleshy, lateral paddle-like outgrowth which bear long setae for movt  Respiration is generally through body surface or through a special projection of parapods. Has well developed closed type blood vascular system. Possesses Nephridia which is the excretory organs. Nervous system consists of paired cerebral ganglia or brain, a double ventral nerve cord bearing segmental ganglia. Gonads develop from the coelomic epithelium. Sex may be separate or united, and development may be direct or indirect.  Classification of Phylum Annelida The Phylum Annelids is generally divided into three classes. These are: 1. Polychaeta 2. Oligochaeta 3. Hirundea  1. Polychaeta: Mostly marine forms, distinct head with eyes and tentacles, segmental with laterial projection of the body wall known as parapodia, do not have clitellum. Sexes are separate. Have no distinct or permanent sex organs. Many forms reproduce asexually by budding. Example, lugworms, clam worms, bristleworms, fire worms,  2. Oligochaeta: Lives in soil, or in fresh water, body is conspicuously segmented but no distinct head; parapodia absent; they are hermaphrodites; has more complicated reproductive system with compact ovaries and testes but fewer in number clitellum is present ; no larva, and development is direct. Example is Earthworm.  3. Hirundea Has fixed body segments numbering 34; some group may have only 31 or 17 segments; Anterior and posterior sucker present, Clitellum is present, no parapodia or setae. They are hermaphrodites, has direct development; may be terrestrial fresh water or Marine. Examples are Leeches. Earthworm (External Features) - Body is elongated nearly cylindrical and tapering at both the ends. - Mature Earthworm measures 150mm in length and 3-5 mm in width. - It is rich brown in colour, the dorsal surface darker than the ventral. - The metameric organization of the body is clearly indicated on the outside by the circular groves corresponding to body segments or metameres.  - The first segment where the mouth is situated is called peristonium. - The preistomium projects forward a small sensory tube at the dorsal side which is known as Prostomium. - In a mature worm there is the Clitellum lying about 20mm behind the anterior extremity, plays an important part in its reproduction. - About the middle of each segment is a ring of Chitinous structures called Setae - The first, the last and the three segments of the clitellar regions are without setae. - A single female generative or oviduct aperture is present on the 14th segment in level with the surface of the Clitellum, seen as a light coloured patch.  - The paired male generative or spermiducal apertures lie on the ventral surface of the 18th segment. - The genital or copulatory papillae are in the 17th and 18th segments.  STRUCTURAL ADAPTATION - The body wall forms a protective covering for all the enclosed internal parts. - The mucus in the epidermis underlying the body wall keeps the skin of the earthworm slimy and clean and does not carry any foreign germs to settle in it. - The body wall serves as the only organ of respiration because of its thin pervious and highly vascularised nature. - The skin serves as an efficient receptor organ. - Mucus act as a cement for plastering the walls of the burrow. - The setae aid in locomotion. - The earthworm feeds in decaying leaves and humus present in the soil. - The Earthworm excretes waste products with the aid of an organ known as Nephridia.  HABITS AND HABITAT Earthworms are found is nearly all parts of the world, Even in mountains up to a height of about 3,000 metres. They eat their way through the ground and form burrows which they inhabit. They form burrows by merely pushing in the body especially in soft soil their habit of swallowing soil also aids in the making of burrows especially in the compact soil. Soil containing organic matter is digested and absorbed as food and the residual soil is ejected in a form known as CASTING Earthworms exude a liquid which is antiseptic and protects the worm from any harmful bacterial that may be present in the soil or settle down on the body of the animal.  Burrows of the earthworm are usually 30- 60cm deep and may be partly lined with dead leaves. At the bottom of burrows, there is an enlargement where the worm can turn round and on top, the creature sometimes draws over the opening of some small pebbles for the purpose of keeping out water and enemies like centipede.  Summary Annelids have elongated body divided externally into a number of rings which represents a division of the internal parts into a series of segment Annelids are mostly aquatic, some are sedentary or free living, while some are ectoparasites Annelids are generally divided into three classes: Polychaeta, Oligochaeta, and Hirundea Earthworm is a typical example of an annelid  Evaluation Make a large labeled diagram of the external features of an earthworm Enumerate some major difference between Annelida and Nematoda  PHYLUM MOLLUSCA OBJECTIVES By the end of this unit, you should be able to: list out the characteristic features of phylum mollusca list the various classes of the phylum mollusca with examples describe the external features of a named mollusca highlight the ecological adaptation of this mollusca.  Characteristic Features of the Phylum Mollusca They are bilaterally symmetrical Generally, there is a distinct head and a muscular foot; the dorsal body wall forms the mantle folds which enclose the mantle only. Uses gills and lungs for respiration, A hard, calcareous shell secreted by mantle, protecting the body is common. They have soft unsegmented bodies consisting of head, viscera mass and foot.  Classification of the Phylum Mollusca There are three important classes of this phylum. These include: Class Bivalvia. Example includes Oysters, Clams, and Mussels etc. Class Cephalopoda. Examples include Octopus, Nautilus, Cuttefish, squids, etc. Class Gastropoda e.g. snail Class Bivalvia Class Cephalopoda. Examples include Octopus, Nautilus  Snails Diagram of a Mollusca (Snail) Showing its external features. Snail Snails belong to the class gastropods which is the largest class of Mollusca They differ from other groups in four major ways based on their external features. These features are: There is development of a distinct head Body shows dorsoventral elongation. A spiral asymmetrical shell that serves as a protective retreat for the animal Visceral mass undergoes a 90 to 180 degree twist with respect to head and foot, a phenomenon known as torsion.  Adaptation of Gastropoda to Their Environment Their foot is a flat creeping sole. Ciliated and the glad cells located in the foot secrete mucus over which the animal moves (Locomotion). In burrowing forms, the foot acts like a plough and anchor Limpets, slipper snails are adapted for clinging to rocks and shells. In a group of pelagic gastropods (sea-butter fish), the foot is modified into effective fun-like swimming organs The land snails among gastropod have their mantle highly vascularized and converted limbs a lung for purposes of gas exchange.  Gastropods exhibit a variety of feeding habits. There are herbivores, carnivores, scavengers, parasites. Gastropods may be monocious or hermaphrodites or dioecious Fertilization is mostly internal Fertilized eggs may sometimes be enclosed in egg capsules  Summary - This Phylum possesses a soft unsegmented body which is distinctly differentiated into head, visceral mass and a muscular food. - There are three important classes of this phylum, namely; Bivalvea, Cephalopoda and Gastropoda. - Snail is an example of the class Gastropoda and it distinctively undergoes a 90 to 180 degree twist, a phenomenon known as Torsion. - Their foot is a flat creeping sole adapted for locomotion. - Gastropoda exhibit a variety of feeding habits which includes herbivorous, carnivorous, Parasitic etc. - Fertilization is internal which one of their adaptations in their environment is.  Evaluation Outline the features or habits in the class Gastropoda that adapts them to their environment.  Phylum ARTHROPODA OBJECTIVES At the end of this unit, you should be able to: outline the general characteristic features of the phylum arthropoda outline arthropoda into their various classes show the external features of some arthropoda outline the adaptive features of some arthropoda to their environment.  Introduction The Phylum Arthropoda is the largest group of the animal Kingdom surpassing in the number of species of all the other phyla combined. It contains over 700,000 species. The animals belonging to this Phylum occur all over the globe at altitudes of over 6,500 metres on mountains to depths of over 6,000 metres in the sea. Different species are adapted for life in the air, on land, in soil and in fresh or salt waters. Some are parasites on plants and on or in the bodies of other animals. Some are gregarious (live in groups) and several kinds of colonial insects have evolved social organizations with division of members into different castes. Many members are of very great economics importance, such as large crabs, shrimps and lobsters, which are eaten by men.  Distinguishing Features of Phylum Arthropoda 1. The body is usually segmented and bilaterally symmetrical. 2. Segments are fused to form head, thorax and abdomen. 3. Majority of the segments bear a pair of jointed appendages each. 4. A hardened, non-living exoskeleton containing chitin in secreted by the epidermis; it is periodically moulted as long as the animal continues to grow in size. 5. There is usually a highly developed muscular system, with numerous separate muscles, composed of finely striated and quickly contracting fibers. 6. The digestive tract is complete; the mouth parts are provided with lateral jaws, the mouth parts may be adapted for chewing or for piercing and sucking liquid food. 7. The cilia and flagella are absent. 8. The circulatory system is of ‘open’ type; the heart is dorsal, distributing blood by artery to organs and tissues, from where it returns through the body spaces (haemocoels) to the heart. 9 The coelom is greatly reduced. 10. The nervous system is of the annelidan type, consisting of paired dorsal ganglia over the mouth, a ring or collar round the gullet and a ventral chain of ganglia. 11. The sexes are usually separate and the male and female are easily distinguishable. 12. Fertilization is internal and most arthropods undergo a more or less extensive metamorphosis Classification of Arthropods The Phylum arthropods are divided into the following classes. a. Crustacean e.g. Crabs, Prawns, Lobsters etc. b. Insecta e.g. grasshopper, cockroach, housefly etc. c. Arachnida e.g. Spiders, Scorpions, mites, ticks etc. d. Myriapoda e.g. Centipedes, Millipede Class Crustacean Class Myriapoda  Insecta About 70% of all known species of animals are insects. Although they are mainly land animals, they are widespread and adapted to all types of environment. They are also the only invertebrates that can fly. Most insects feed on plant materials, while some feed on animal tissues and wastes. Insects include ants, beetles, aphids and grasshoppers;  An insect has a well-defined head, a thorax and an abdomen. An insect carries out gaseous exchange by means of a network of open airtubes or tracheae inside its body. These tubes have openings called spiracles to the exterior.  Habitat and Habit of a Cockroach It is abundant in storehouses, restaurants, kitchens, bakeries, boilers and other situations where there is warmth, dampness and organic food. Cockroaches live in cracks and crevices in the walls. The Cockroaches are nocturnal insects. During day time they remain inactive in their hiding places. But they become active during the night,  run here and there in search of food. They are omnivorous and devour any vegetable or animal substance. They may eat even non-living materials such as leather, paper, cloth etc. Besides, the cockroaches are cursorial. i.e they are fast runners and rarely fly.  External Features of Arachnid- Spider An Arachnid has a body that is divided into two parts, a cephalothorax and an abdomen. The cephalothorax bears simple eyes, two pairs of appendages for feeding and four pairs of walking legs. An arachnid usually breathes by means of tracheae or book-lungs. The spider is the most familiar arachnid glands to spin webs for trapping its prey. One pair of its feeding appendages has fangs connected to a poison gland. Another arachnid, the scorpion, has a sharp poison sting on its last abdominal segment.  Adaptive Features of the Arthropods - Arthropods are one of the most successful animals. The success of the arthropods is due to some number of reasons. There reasons include: - Posses exoskeleton which protects them from predators, and in terrestrial species, prevents water loss from the body surface. - jointed limbs, capable of swift, complex movements; - Specialization of segments and appendages for specific tasks such as sensory (antenna or feelers) and feeding (proboscis, mandibles, etc.) - Specialized digestive system; - Specialized respiratory system for different habitats, such as aquatic ones; and well- developed sensory organs, e.g. eyes (simple and compound) and antennae. - Arthropods shed their exoskeletons at intervals to allow their bodies to increase in size. This is known as moulting or ecdysis.  Summary The Arthropods constitute largest group in the animal kingdom. The arthropods can be classified into Crustaean, Insects, Myriapods and Arachnids. Cockroaches and Spiders are both arthropods belonging to the class insects and arachnids respectively. The body of insect is divided into 3 parts the Heads, Thorax and abdomen. Arthropod has jointed limbs. Arthropods posses exoskeleton which prevents them against water loss for the terrestrial arthropods and predators.  Evaluation 1. Draw a well labeled diagram of a Cockroach showing its external features. 2. What makes the Arthropods a successful group of animal?  PHYLUM ECHINODERMATA OBJECTIVES By the end of this unit, you should be able to: state the characteristic features of the phylum echinodermata outline the external feature of a named echinoderm highlight the ecological adaptation of an echinoderm list the different classes of the phylum echinoderm  Introduction In this unit, we shall be looking at the Phylum Echinodermata. This group includes star fishes, sea urchins, sea-lilies and others, all of which live in the sea. Some of the Echinoderms crawl slowly in the shallow waters along the shore or lie partially concealed in the holes of the rooks while other like sea-lilies are found attached deep down at the bottom. The Phylum includes some 6000 species.  Characteristic Features of Phylum Echinodermata i. All Echinoderms are marine animals, and the adults are mostly with Pentamerous radial symmetry (ie can be divided into 5 equal parts). Body is not metamerically segmented; ii. Could be rounded, cylindrical or star shaped without head. iii. They have no brain, only few specialized sense organs. iv. They have a complete digestive system. v. Locomotive is mainly by tube feet, in some by means of spines or by movement of arms. vi. They have no olfactory organs. vii. Sexes are separate, fertilization is external. viii. They have indeterminate type of development. ix. Respiration is by dermal branchiae, tube feet or respiratory trees. x. They have an internal skeleton (endoskeleton) made up of plates of calcium carbonate, imbedded in the body wall. Classification of Echinoderms The Phylum Echinodermata includes five classes. They are: a. Class Asteroidea e.g. Star Fishes b. Class Opliuroidea e.g. Brittle Stars c. Class Echinoidea e.g. Sea Urchiris d. Class Holothuroidea e.g. Sea- Cucumbers e. Class Crinoides e.g. Sea Lilies  Starfish External Features - They are star shaped. - Arms are not sharply demarcated from central disc; - Tube feet are on oral side and with suckers - Arms and Madreporite (a hole through which water enters the body) are on the aboral side (the upper surface of the animal) - Pedicellaria are present (this are specialized jaw-like or pincer like appendages).  Ecological Adaptation - Possession of specialized jaw-like or pincer like appendages on their body surface for the protection of the animals from small animals and larvae that try to settle on the sea stars. - Possession of a well developed water vascular system which functions as a locomotor and for food gathering. - The water vascular system also serves in respiration and excretion. - Most are scavengers or carnivores feedings on snails, other echinoderms, fish, sponges, sea anemones etc. some feeds on plankton. - Possession of Tube feet which also, principally serves as respiratory organs.  SUMMARY In this Unit, you have learnt that: All Echinoderms are marine animals Echinoderms are mostly Pentamerous, radially symmetrical in nature (i. e. they can be divided into 5 – equal parts). There are basically 5 classes of echinoderms. Echinoderms posses an endoskeleton made up of plates of Calcium Carbonate. Echinoderms have a peculiar apparatus known as a vascular system. Echinoderms posses tube feet which apart from its function in respiration, also help in locomotion and firm attachment.  Evaluation The water vascular system is a peculiar and very important apparatus of the phylum Echinodermate. State its functions.  VERTEBRATES/VERTEBRATA (FISHES) OBJECTIVES At the end of this unit, you should be able to: outline the general characteristics or features of vertebrates classify the phylum vertebrata give the general characteristics of the fishes draw a well labeled diagram of a bony fish outline the adaptive features of fishes.  Introduction we shall be looking at the vertebrates. However, in this unit we shall be looking at the general features of vertebrate and the class of vertebrates known as Pisces (Fishes).  Vertebrata The Vertebrata is a subphylum of the Phylum Chordata. The Chordates have a notochord, a flexible rod of tightly packed cells, a tubular nerve cord (dorsal) and gill slits at some stage in their life histories. Note: a backbone or vertebral column replaces the notochord in vertebrates.  Characteristics A bilaterally symmetrical body, divided into a head, a trunk and a tail. In Most vertebrates, a neck joins the head to the trunk. An internal skeleton or endoskeleton of bone and cartilage, with a backbone or vertebral column made up of a series of small bones called vertebrae. A well-developed central nervous system with a brain (within a brain case) and a spinal chord (dorsal position). Well-developed sense organs. A ‘closed’ blood system made up of a muscular heart (ventral position).  Two pairs of limbs (tetrapods.) Kidneys for eliminating body wastes. Skin may be naked or have a covering of scales, feathers or hairs.  Vertebrates are divided into five classes: - Pisces - Amphibia - Reptilia - Aves, and - Mammalia.  Pisces (Fishes) These are the fishes which are all aquatic. The jawless fishes like the hagfish and lamprey are the most primitive. They have sucker-like mouths and no paired fins. The cartilaginous fishes like sharks, skates and rays have jaws and paired fins, but their skeletons are made of cartilage like the jawless fishes. The bony fishes like the Tilapia and carp are the largest and most successful group features  It is a cold-blooded (poikilothermic) animal, i.e its body temperature varies with that of its surroundings. Its body is covered with scales (absent in jawless fishes) and a layer of slime. A cartilaginous fish has sharp, tooth-like scales that do not overlap, while a bony fish has thin, flat rounded scales that overlap. It has fins. The paired fins are adaptations of the fore-and hind limbs. It carries out gaseous exchange by gills. A bony fish has gill covers while a cartilaginous fish does not.  It has a well-developed sense of smell, and a lateral line system which enables it to detect movements and changes in water pressure. It only has inner ears. A bony fish possesses a swim bladder, a gas-filled sac which allows it to regulate its density so that it can remain still at any depth in the water. It has a two-chambered heart. Fertilization is usually external. The eggs are tiny and may develop directly into a young fish or pass through a larval stage. 1. External Features of a bony fish Adaptive Features of Fishes Living organisms are found in many types of ecosystems. The environment in this ecosystem varies considerably. Generally, organisms show features that enable them to go live successfully and reproduce in a particular environment. These features may be structural, functional or behavioral. Such features are known as adaptations. Adaptations to a particular environment are evolved over a long period of time.  Nature of Medium Water is a denser medium than air. It is difficult to move rapidly through it. As a result active aquatic animals like fish have streamlined bodies. Water, however, helps to support the body mass of large aquatic animals. Osmoregulation and Water Loss Most marine organisms have body fluids that are nearly the same concentration as the sea water in which they live. So the rate at which water enters and leaves the body cells is the same. However, the body fluids of freshwater organisms are at a much higher concentration than the surrounding water. So much water enters the body cells than leaves them. Successful freshwater organisms have osmoregulatory structures that get rid of the excess water that enters the body cells.  Bony fishes are the most successful aquatic organisms. The Body fluid of the marine bony fish is less concentrated than its surrounding water, while the body fluid of the freshwater bony fish is more concentrated. Osmoregulatory Adaptation of freshwater and marine bony fishes.  The adaptations are mainly functional. Thus, to conserve water, terrestrial organisms had to adapt both structurally and functional. NOTE: In aquatic organisms where there is no need to conserve water, gaseous exchange occurs through the whole body surface or through special structures called gills.  Movement Aquatic organisms that move actively use appendages like fins which are modified for swimming.  Adaptations of the Fish The fish show the following structural adaptations to life in water. Have a streamlined body shape without a neck that enables them to move easily through water. The tail and tail fin of a fish are special adaptive structures for swimming. Gills are gaseous exchange organs that are adapted for an aquatic environment. They are found in the fish.  SUMMARY In this unit, you have learnt that: Vertebrates are bilaterally symmetrical, have well developed nervous systems and sense organs. Vertebrates are generally grouped into five classes. Pisces or fishes are cold-blooded organism with the possession of fins, scales, swim bladders, etc. Fishes has a stream-line body, fins and lateral lines which aided their adaptation to the aquatic environment.  Evaluation 1. Draw an annotated diagram of a bony fish. 2. What characteristic of the Pisces aids their ecological adaptation?  Phylum AMPHIBIA Objectives At the end of this unit you should be able to: give the characteristic features of amphibians outline the external features of a named amphibian list the adaptive features of an amphibian draw a well labeled diagram of a toad differentiate between toads and frogs  Introduction The Amphibians made the first transition from the aquatic to the terrestrial mode of life; they were the first to venture out of the water and live on land. Examples of amphibians include the frogs, toads, Newts and Salamanders. Most of them live in moist environments and return to water to breed.  Characteristics Features of Amphibians An amphibian has these features i. It is cold-blooded. ii. It has paired fore-and hind limbs in the adult stage. iii. It has a naked, moist skin. iv. It has a sticky tongue which can be protruded and retracted quickly. v. It has inner and middle ears. vi. It carries out gaseous exchange by gills, lungs, skin or mouth lining, separately or in combination. Gills are present at some stage in its life cycle. vii. It has a three-chambered heart. viii. Fertilization is external. The eggs are small. ix. An aquatic larval stage is usually present  External Features of a Toad and Frog Toads are clumsily built creatures, usually 10cm long but at times growing to larger size. They have brown, wrinkled and warty skin with darker spots and markings on the upper surface and white undersurface. There are swellings like rough warts over the eyes. The legs are shorter than the frogs; the hind legs being a little longer than the body. They do not posses teeth. The tongue, which is attached in front of the mouth but is free behind, is only slightly cleft at the tip but still it is an insectcatching apparatus of great perfection. The male toad is smaller than the female.  Toads are terrestrial and nocturnal in habit. During day time they generally lie concealed under stones or in other damp and shady localities and come out only towards evening. FROG TOAD It is mainly aquatic It lives on land among It is diurnal in habit, that stones in damp places. is, it comes out mainly It is mainly nocturnal. during the day time. As it has a good sense it It does not possess good can keep within a certain sense of locality locality for a long time. It shows quick and It shows sluggish creeping nervous movement. movements, which seem to be carried on with greater sense of security. The skin is smooth and The skin is always rough, slippery. nearly dry, wrinkled and warty. Skin is provided with Skin is abundantly relatively few poison supplied with poison glands. glands  The amphibians are as class, typically furnished with five fingered limbs which are adapted for locomotion both on land as well as in water. They are cold –blooded or poikilothermic animals of jumping and swimming habits. Their skin is smooth, clammy and naked, that is without scales. There is remarkable difference between the young and the adults; the limbless but tailed young forms or tadpoles, as they are called, live in water and breathe by gills while almost in every case the adults breathe by lungs and can live both on land as well as in water and hence the name amphibian. The skin is usually soft and moist in order to carry on the important functions of skin or cutaneous respiration and this is the reason why the presence of moisture is essential for the well being of all amphibians.  The tailless amphibians, such as frogs and toads, numbering some thousand species, have a world wide distribution. They are most abundantly found in tropical countries. Bu it is remarkable that notwithstanding their natural inclination to live in and around water no amphibian has been discovered to live in salt and marine waters. Outline of Adaptive Features Skin secretes substances that scare away enemies (other animals) e.g. Snakes from attack. The tongue is an insect-catching apparatus which aids feeding. Have five (5) fingered limbs for locomotion. Has webbed feet for swimming Has powerful hind –legs for jumping/leaping. Soft, moist skin for skin or cutaneous respiration. The young ones, Tadpoles lives in water and breathe by gills. The tadpoles have a streamline body. The tadpole has a fin-like tail that aids swimming Adults breathe by lungs hence can live in land and water  Evaluation 1. Give a diagram of a toad showing its external features. 2. The amphibian, toad is known to be both aquatic and terrestrial. 3. What features enable it to live in water?  REPTILES OBJECTIVES At the end of this unit, you should be able to: give the characteristic feature of reptiles draw a well labeled diagram of a named reptile showing the external features outline the adaptive features of a Reptile.  Characteristic Features of Reptiles The name Reptile (L. repere – to crawl), by which these animals are collectively known, indicate one of the main characteristics of the typical members of this group, their crawling method of locomotion. They are the lowest vertebrates which are truly terrestrial and as a class they are neither well adapted for walking nor for running. Their body is covered with scales which are, however, very different from those of fishes:  they are developed only from the outer layers of the skin, having connection with blood vessels and nerves. The whole skin is characterized by being dry and devoid of glands. They are poikilothermic and most of them have imperfectly four chambered heart.  The reptiles have become independent of water due to the development of embryonic membranes. The embryo always lies in a fluid-filled sac known as amnion. The allantois arises as an outgrowth from the hinder part of the gut and serves as a receptacle for the storage of embryonic urine. Part of the allantois becomes closely applied to the shell for respiration. Gills are absent and the lungs form the respiratory organs.  Lizard Lizard is a typical example of reptilian. They are typically dry-land animals, loving the sun and its heat. They are very common reptiles most of them are four-legged animals and are capable of very active movement. They are usually rather small and slender creatures. The common garden lizard has a very long tail. Different types of Lizards The ordinary wall lizards or Geckos are equipped with vacuum –cupped toes which enable them to chase insects along vertical walls and ceilings of rooms. A very interesting protective feature, possessed by some of these lizards, is the power to break off their tail automatically. They have a peculiar kind of joint between two of their caudal vertebrae, which enables them in an emergency to break off the tail. The part of the tail thus sacrificed continues for some time to move about, thus tending to divert the attention of the pursuing enemy and thereby giving a chance to the lizard to escape. It can grow a new tail in due course of time. This power of automatically breaking off certain parts of the body is called autonomy. Other adaptive features as follows: i. They are cold blooded animals. ii. Has a well developed tongue which can be protruted and retracted iii. Quickly. iv. Its jaws have teeth of the same kind embedded in sockets. v. It usually has paired fore and hind limbs each with five toes ending in claws.  vi. It has inner and middle ears. vii. It has a skin that is covered with scales. viii. It carries out gaseous exchange through its lungs. ix. Fertilization is internal. The females lay large fertilized eggs in land. Even aquatic reptiles return to the land to lay eggs.  Evaluation 1. Make an annotated diagram of a named reptile. 2. How do Reptiles differ from Amphibians?  AVES (BIRDS) OBJECTIVES At the end of this unit, you should be able to: give the characteristic features of birds outline the external features of birds draw a well labeled diagram of a bird outline the adaptive features of birds to their environment.  Introduction The aves or bird are warm-blooded vertebrates specially adapted for flight. Their body is covered with soft feathers which are epidermal outgrowths like the scales of reptiles and their hairs of mammals. Scales are also present on the lower part of the legs and on the feet. They have a four- chambered heart. The fore limbs are modified to form wing axes (in flying birds) or reduced in non- flying birds. The hind limbs have clawed digits which are variously modified for walking, perching, hopping, running or swimming. The head is usually small and rounded, the neck is well marked and the whole body is oval and streamlined. Tail is short and the caudal vertebrae are fused to form a pygostyle. The jaw bones are modified in relation to the back and are devoid of teeth.  External Features of Birds The body of the birds is steamlined or spindle-shaped well adapted for aerial life. The neck is usually long and flexible. The head is rounded and the facial portion is produced into beak. Close to the base of the beak are two slit-like nostrils. The eyes of the bird are of considerable size for the sense of smell seems to be feebly developed but the power vision is correspondingly advanced, especially in some birds of prey.  Each eye is provided with three eyelids: the upper and lower eyelids are like fold of skin while the third eyelid, the nictitating membrane, is a delicate transparent membrane which can be drawn across the eye. Usually the lower lid is movable. On each side of the head there is a small aperture with a short passage leading to the ear-drum. It lies behind and below the eyes and is usually hidden by the features. Unlike mammals, the external ears are absent.  Adaptive Features of Birds to Their Environment The fore limbs form the wings which are organs of flight while the hind limbs are adapted for bearing the entire weight of the body when walking. For this purpose the hind limbs are usually attached some what for forward and the skeleton is also modified to this end. The legs are covered with scales. The cloaca lies on the ventral surface at the root of the tail and on the dorsal surface of the same region is an oil gland. Its oily secretion is used for preening feathers.  The feet, break and the tongue present very large number of variations of form which are closely associated with the habits of the birds. The typical number of the toes is four, of which, three are directed forwards and one backwards. In perching birds the toes are adapted for grasping and automatically clutching the support. Three toes are directed forwards and one backwards. The same arrangement of the toes is also found in birds of prey which use their feet for seizing. The claws form great talons as in the eagles, hawks, kites, falcons, etc. The legs of the wading birds are usually very long and partly or completely unfeathered up to the tibial region. They have very long toes. Swimming birds like ducks have webbed feet which serve as paddles. Outline of Adaptive Features of Flight 1. The wings act as propeller. 2. The streamlined body is well adapted for movement through the air. 3. There is considerable shifting of the weight of the body from the periphery to the centre due to the loss of teeth; moreover as the wings are placed high up on the trunk the body is prevented from turning over. 4. The skull is very light and most of the bones are welded together.  5. Feathers which clothe a bird, hold a blanket of enveloping air next to the body; since this air is warmed by the body and is consequently lighter than the surrounding air, it adds somewhat to the buoyancy of the bird. 6. The rectum where the faeces is carried is very much reduced in length. Since flying birds would be greatly handicapped by the presence of too much of faecal matter there.  Evaluation 1. Diagrammatically show the external features of birds. 2. Outline the adaptive features of birds to their environment.  MAMMALIA OBJECTIVES At the end of this unit, you should be able to: give the main distinguishing characteristics of mammals outline the external features of a named mammal list the adaptive features of a named mammal draw a well labeled diagram of a rabbit showing the external features.  Introduction The class mammalia is made up of the most advanced animals which include Man, Rabbit, goat, cow etc.  Mammals, of which there are three to four thousand species, have attained the most complete structural, developmental and physiological adaptations to the terrestrial mode of life. They are characterized by their great activity, high metabolism, intelligence and by the display of their parental care – a feature in which they are only rivaled by birds. Various mammals live in all sorts of habitat from Polar Regions to tropics and from the sea to the densest forests and driest deserts. Many are of the retiring habits or nocturnal so that they are seldom seen. They are a dominant group and play leading role in the present day world. Mammals generally are of great aesthetic interest, some wild species are hunted as game and others for their fur. Some rodents and flesh eaters damage man’s crop and livestock and certain species are reservoirs of disease- germs. The domestic mammals provide man with food clothing and means of transport.  As a matter of fact the mammals represent the top of the evolution of the living animals and this claim rests almost exclusively on the superiority of their nervous system.  Characteristic Features of a Mammal The main Characteristics of a mammal are as follows: It is warm-blooded. Its skin has sweat and sebaceous glands and a covering of hairs. It has different types of teeth, with each type carrying out a specific function. It has external ears called pinnae. Its body cavity is separated into two by a muscular sheet called a diaphragm. The upper thoracic cavity contains the lungs and the heart while the lower abdominal cavity contains the alimentary canal, the Kidneys and the reproductive organs.  It has a well-developed heart. It has a well-developed brain. Fertilization is internal. In most mammals, the tiny fertilized egg develops inside the body of the female parent for a period. During this time, the young is attached to the mother by a placenta, an organ through which it obtains nourishment from the mother. The young is born alive (Vivipary) and feeds on the milk secreted by the mother’s mammary glands. It is looked after by the parents until it learns to be independent. External Feature of a Rabbit Rabbit, a typical example of the class mammalian, is taken as a convenient type of mammals for a detailed study. The head of the rabbit is large and spherical behind but is pomtal anteriorly to form the snout. At sides of the snout are long stiff sensory hairs called whiskers or vibrissae. Has a pair of large and protuberant immobile eyes. Have two long erect external ears or pinnae situated at the spherical top of the head. The head is followed by a very short neck which passes abruptly behind to the trunk.  The truck consists of a narrow chest or thorax. Has short and rigid fore limbs divided into upper arm, fore arm wrist and hand