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diversity in living animals


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INTRODUCTION Every organism whether plant or animal is unique in itself. There is a wide diversity in the flora (plants) and fauna (animals) in the world. The diversity we see today is the result of 3.5 billion years of organic evolution. During the course of this evolution several species vanished from the surface of the Earth and became extinct. It is estimated that more than fifty times the existing species have become extinct. With such a vast number of organisms - both living and extinct, it becomes impossible to study every one of them at individual level. This task of studying the diversity of living organisms can be made easier and more effective if the various organisms are arranged in an orderly manner.



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Eichler in 1883 suggested a system to classify the plant kingdom which is well accepted. He said that the plant kingdom is subdivided into two subkingdoms: Cryptogamae and Phanerogamae . sub kingdom cryptogamae are lower plants that do not bear flowers or seeds. They form three divisions.


THALLOPHYTA The plant body is not differentiated into stem, root and leaves but is in the form of an undivided thallus. Vascular tissues are absent. The reproductive organs are single-celled and there is no embryo formation after fertilization. This division includes three sub-divisions: algae, fungi and lichens.


BRIOPHYTA Moss and Liverwort belong to this variety of plants. There are the simplest form of land plants. The plant body is flat and lack true leaves and roots. The upper surface of the plant body produces a stalk which bears a capsule. The capsule contains spores.


PTERIDOPHYTA The plant body is differentiated into stem, leaves and roots. Vascular system is present. Leaves usually have leaflets. Spores are borne on the undersurface of the leaf. They grow in damp cool shady places.




ALGAE Occur in ponds, lakes and fresh water bodies. Sea weeds are found in marine waters. May be single celled, colonial or filamentous. Are autotropic i.e., they can prepare their own food with the help of the green pigment i.e., chlorophyll present in the plant. Sometimes red, blue, yellow and brown pigments are found. Blue-green bacteria (cyanobacteria) are included in this group of plants.




FUNGI These do not contain chlorophyll and hence are heterotropic and have diverse modes of nutrition. They may be saprophytic i.e., depending on dead or decaying organic matter for their food, or may be parasitic i.e., depending on living organisms for their food




LICHENS This is a group which has two varieties of plants, an algae and a fungus living in perfect harmony. They co-exist for mutual benefit. This relationship is known as symbiosis. The fungus absorbs water and mineral salts and supplies it to the alga. The alga prepares food and supplies it to the fungus.




KINGDOM PHANEROGAMAE This division is made up of plants that bear flowers and seeds and make up the majority of the larger plants. The body is differentiated into true stem, leaves and roots. Propagation of the plant takes place with the help of seeds. Seeds are formed as a result of sexual reproduction. The male and female gametes (sex cells) fuse together inside the ovary (female part of the flower) and develop into the seed. In some plants seed is not produced inside an ovary. Phanerogamae is made into two further divisions. Gymnosperms (naked seeded plants) Angiosperms (Seed borne within a fruit)


DIVISION GYMNOSPERMAE Gymnosperms are intermediate between cryptogams and angiosperms. The male flower is a cone which produces pollen. The female flower is much larger and consists of a rosette of carpels which bear ovules along the two margins.


DIVISION ANGIOSPERME This group constitutes the largest group of plants. Seeds are produced inside an ovary which later becomes the fruit. These are highly evolved group of plants. The plant body is distinctly differentiated into roots, stem and leaves. Based on the number of cotyledons (seed-leaves) that form the seed this group is divided into: Monocotyledons (One seed leaf) Example: Rice, Wheat Dicotyledons (two seed leaves) Example: Beans, Mango

Animal Kingdom:- The following classification “telescope” clearly indicates the mechanism behind the classification of the Animal Kingdom:

Animal Kingdom:- The following classification “telescope” clearly indicates the mechanism behind the classification of the Animal Kingdom

The chart given below briefly outlines the classification of the Animal Kingdom. :

The chart given below briefly outlines the classification of the Animal Kingdom .


PORIFERA The simplest multicellular animals. The cells are loosely held together and do not form tissues Aquatic in habitat (mostly marine) Ostia (pores) are present all over the body, with a single large opening on top called osculum Food and oxygen enter the organism along with water into a canal system Support system made up of tiny needle-like formations. They may be made of silica, calcium or spongin fibres Reproduction may be sexual, asexual or budding Example: Sycon, Spongilla, Euptectella


COLLENTERATA Two layered body which is radially symmetrical Aquatic in habitat which includes both fresh water and marine The outer layer has tentacles armed with stinging cells cnidoblasts which can release venom into the victim. The inner layer encloses a body cavity called gastro vascular cavity Animals in this group exist in two types of individuals called zooids - polyps and medusae. Polyps are fixed and lead solitary or colonial life, while medusae are free swimming Alternation of generation takes place in colonial forms. Polyps and medusae alternate with each other during the life cycle Reproduction is usually asexual i.e., by budding in the polyp form and sexual in medusa form Exoskeleton made of lime is found in corals Example: Hydra, Obelia, Aurelia, Metridium


PLATYHELMINTHES Simplest triploblastic organisms showing bilateral symmetry Mostly parasites in other animals Body in dorsoventrally flat and leaf-like or ribbon-like with bilateral symmetry The body cavity has only one opening which serves as both the mouth and the anus Hermaphrodites i.e, male and female sex organs present in one individual Example: Planaria, Liver Fluke, Tape Worm


ANNELIDA Occur in moist soil, fresh water and sea Body is soft and segmented, triploblastic with bilateral symmetry First animal with the coelom (body cavity) Body is covered by a non-chintinous cuticle which may have chitinous setae, or parapodia Reproduction is generally sexual, but some may reproduce asexually by rejuvination i.e, by regrowing broken segments Example: Nereis (sand worm), Aphrodite (sea mouse), Pheretima (earthworm), Hirudinaria (leech)


ARTHROPODA This is the largest phylum with almost 80% of the animal kingdom Body is bilaterally symmetrical and segmented. It is divided into head, thorax and abdomen Possess jointed legs which may be modified for walking, swimming feeding and feeling Exoskeleton is chitinous which is shed periodically by moulting Body cavity is reduced and filled with blood (haemocoel) Respiration is by lungs, book lung and trachea Example: Apis (honey bee), Araneae (Spider), Palaemon (prawn), Scolopendra (Centipede)


MOLLUSCA Aquatic in habitat but some land forms are also seen Body is soft and divided into three regions (head, dorsal visceral mass and ventral foot) Body enclosed in a hard calcareous she Breathe through gills, land molluscs have lungs Sexes are separate Example: Chiton, Pila (snail), unio (fresh water mussel), octopus


ECHINODERMATA Marine in habitat Body is radially symmetrical, star shaped, spherical or elongate, Exoskeleton is spiny Head is absent and five radially arranged arms present Locomotion is with the help of tube feet Sexes are separate Example: Asterias (star fish), Echinus (sea urchin), Holothuria (sea cucumber), Antedon (feather star)


REPTILE Body covered with scales Mostly terrestrial Heart is 3 chambered, is cold blooded Breathe through lungs Body covered with scales Have two pairs of pentadactyl (five digit) limbs which are absent in snakes Example: Hemidactylus (wall lizard), chameleon, Draco (flying lizard)


AMPHIBIA Live in both water and on land Respiration is by gills, lungs or skin 3 chambered heart Is cold blooded Have two pairs of pentadactyl (5 digit) limbs which may be absent in some cases


AVES Arboreal in habitat i.e, they live on trees Warm blooded. 4 chambered heart Body covered with feathers Lungs have membranous extensions called air sacs to make the body light Mouth is surrounded by a beak. Teeth are absent Fore-limbs are modified into wings


MAMMALIA Most intelligent of all organisms Warm blooded with 4 chambered heart Give birth to young ones The mother suckles her young ones on milk secreted by special glands called mammary glands Body covered with hair Have two pairs of pentadactyl limbs Breathe through lungs I AM I A MAMMAL?

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