Science Education Form 2

3.1 Variety Of Living Organisms And Their Classifications


A) Diversity of Living Organisms
1. Human beings, animals and plants are living organisms.
2. Human beings are different from one another. No two human beings are exactly alike.
3. Scientists estimate that there are about 30 million species of animals and plants on the Earth.
4. These animals and plants vary in appearance, shape and size.
5. The blue whale measures about 33 metres long, whereas some organism (virus,bacteria) are so tiny that      they can only be seen under a microscope.
6. The large variety or diversity of living organisms is called biodiversity.
7. The diversity of living organisms is due to the organisms adapting themselves to live in different habitats.
8. A habitat is a natural environment in which plants and animals live (forest, sea-shore, pond).
9. Organisms live in habitats which can provide them food, protection and suitable temperature.

Examples of Organisms and Their Habitats.


1. Tigers, elephants, snakes, monkeys, tall trees (Jungle)
2. Camels, snakes, scorpions, cactus plants (Desert)
3. Polar bears, penguins, seals, pine trees (Tundra)
4. Snakes, whales, fish, sea-weeds (Sea)
5. Fish, Amoeba, tadpoles, Spirogyra, duck- weeds (Pond)

B) Classification of Animals


1)Fish, Amphibians, Reptiles, Birds, Mammals (Vertebrates)
2) Many legs, 8 legs, 6 legs, no legs (Invertebrates)

Characteristics Of Vertebrates


-Fish-

a) Live in water
b) Body covered with slimy scales
c) Possess fins for moving about and for balancing the body
d) Breathe through the gills which absorb oxygen from the water
e) Possess a lateral line canal on each side of the body fro detecting stimuli
f) The young are hatched from eggs
g) Practice external fertilization
h) Cold-blooded

-Amphibians-
a) Can live on land and in water
b) Body covered with a moist skin
c) Breathe through gills at the tadpole stage. Breathe through lungs and moist skin skin during the adult stage
d) The young are hatched from eggs
e) Practice external fertilization
f) Cold-blooded

-Reptiles-
a) Most reptiles live on land, but some live in water
b) Body covered with scales which are non-slimy
c) Some move about on four legs, but some have no legs
d) Breathe through lungs
e) The young are hatched from eggs which are protected by hard shells
f) Practice internal fertilization
g) Cold-blooded

-Birds-
a) Live on land
b) Body covered in feathers
c) Posses a pair of wings and most of them can fly
d) Breathe through lungs
e) The young are hatched from eggs which are protected by hard shells
f) Practice internal fertilization
g) Warm-blooded

-Mammals-
a) Most mammals live on land
b) Body covered with fur or hair
c) Possess ear lobes and also sweat glands which release sweat
d) Possess a diaphragm which seperates the chest from the abdomen
e) Breathe through lungs
f) The female gives birth to her young and suckles them
g) Practice internal fertilization
h) Warm-blooded

Characteristics Of Invertebrates


1. An invertebrate is an animal which does not have a backbone
2. Invertebrates form a very large group of animals. Some are microscopic in size
3. Some live in water, and some on land
4. Some have many legs and some don't have any

Example Of Invertebrates:-

a) Cockroach , Beetle (6 legs)

b) Spider, Scorpion (8 legs)

c) Centipede, Millipede (Many legs)

d) Earthworm, Slug (No legs)


C) Classification of Plants


1. Flowering Plants (Dicotyledons & Monocotyledons)
2. Non-flowering Plants
3. Flowering plants produce seeds which are enclosed (beans, apples)
4. Some non-flowering plants produce seeds which are not enclosed (cones of pine trees)

Flowering Plants:-
1. Examples of dicotyledons are balsam, bean and mango.
2. Characteristics of dicotyledons are leaves with network veins, tap roots, two cotyledons in each seed, and usually woody stems.
3. Examples of monocotyledons are maize, sugar-cane and paddy plants.
4.. Characteristics of monocotyledons are leaves with parallel veins, fibrous roots, one cotyledon in each seed and usually non-woody stems.


Non-flowering Plants:-
1. Do not produce flowers.
2. Conifer, Moss, Ferns and Algae are the four main groups of non-flowering plants.