6th Science Lesson 5 Notes in English
5] Living World Of Animals
Biodiversity
- In the living world, a lot of diversity is seen both in animals and plants. Every plant and animal is unique.
- The term biodiversity refers to the totality of species, populations, communities and ecosystems, both wild and domestic.
- It may also be defined as the variety and variability among living organisms and the habitats in which they live.
- Biodiversity includes a variety of ecosystems such as those that occur in deserts, forests, mountains, lakes, rivers and agricultural fields.
- In each ecosystem, living creatures, including humans, form a community interacting with one another and with other animals, plants, air, water and soil around them. The living things form biotic community and non-living things form abiotic community.
Habitat
- Fishes and crabs grow only in water while many animals like elephants, tigers and camels live on land.
- The geographical features and environmental conditions on earth differ from one place to another.
- Though camel can live anywhere it is able to live in deserts more comfortably. Polar Bear and Penguins dwell in cold regions.
- Living in such harsh conditions requires special features in these animals which help these organisms to live breed and excel well in that particular place.
- Living or dwelling place of an organism is known as habitat.
Unicellular and Multicellular Organisms
- Living things are made of small units called cells. All the functions and processes in the body of living things are brought about with the help of these microscopic cells.
- Some organisms are made up of a single cell and these are called unicellular organisms, whereas, the organisms that are made of many cells are called multicellular organisms.
- Amoeba, Paramecium and Euglena are unicellular while, fish, frog, lizard, bird and man are multicellular.
Unicellular organism
- Unicellular organisms are small, usually microscopic, cannot be seen with naked eye. They are aquatic, simplest and most primitive of all animals.
- They perform all their physiological activities by the special structures present inside the body called organelles.
- We know Amoeba is a unicellular organism It does all the activities like digestion, locomotion, respiration and reproduction.
- It swallows food from the water and the food is digested in the food vacuole. Contractile vacuoles help in excretion.
- Respiration is by simple diffusion through the body surface. They have finger-like structures called Pseudopodia, (false foot) which help in movement or locomotion.
Amoeba
- Paramecium is also a unicellular organism which lives in water and move with the help of cilia.
Paramecium
- Euglena is a unicellular animal which moves with a flagellum.
Euglena
Multicellular organisms:
- Majority of organisms we see around us, including animals are multicellular.
- In such organisms, different functions are carried out by different groups of cells or organs in their body. E.g. Jelly fish, Earth worm, snails, fish, frog, snakes, pigeon, tiger, monkey and man.
Adaptation in Animals
Animals vary in size, shape and behavior
- A Living thing can survive in a particular habitat if its body is adapted to the conditions of that habitat.
- Plants and animals develop special characteristics or features in their body in order to survive in their habitat (the surroundings).
- The presence of specific body features for certain habits which enable a plant or an animal to live in a particular habitat is called adaptation.
- The fish lives in either freshwater or marine water. Let us analyze the adaptations seen in a fish for its aquatic life.
Fish
- The head, trunk and tail of a fish merge to form a streamlined shape. The streamlined body shape helps the fish to move through the water easily.
- The fish has special organs called “Gills” which is a respiratory organ helps to absorb oxygen dissolved in water for breathing. It is adapted to breathe in water.
- Most of the fishes have slippery scales all over the body which protect the body.
- The fish has fins for swimming.
- The fish has strong tail which acts as rudder to change direction and keep its body balance in water.
Lizard
- Lizards are scaly-skinned reptiles that are usually distinguished from snakes by the possession of legs, movable eyelids, and external ear openings.
- They mostly inhabit warm regions. Most lizards are quadripedal (walk with four legs) and have a powerful limb.
- Some lizards have the capacity to rotate the head around the head joint.
- They breathe through lungs. Some lizards are able to run bipedally with two legs. In this the tail is held out backward and upward and acts as a counterweight.
- Most lizards eat a variety of insects like mosquitoes and Cockroaches with sharp, tricuspid, teeth adapted for grabbing and holding 6 Some lizards (Dinosaurs) have web in the toes, and few lizards are able to glide or parachute the air and make soft landings.
Birds
- They have streamlined body covered with feathers.
- This body shape provides minimum resistance to air.
- They have beak instead of mouth.
- They breathe through lungs. They have a pair of wings that are modified forelimbs.
- They have hollow and light bones.
- Usually we see birds fly, however they can also hop, move, run, etc., on the ground and they perch well on the branches of tree with the help of a pair of clawed feet.
- The tail of the bird helps it to control the direction of the movements.
- They have strong chest muscles which help them withstand the pressure of the air while flapping their wings during flight.
- At a time, birds can see one object with one eye and another object with the other eye. (Binocular vision)
Adaptation in Camel:
- Camel lives in hot desert where water is scarce. The body structure of a camel helps it to survive in desert because of its following special features which are listed below:
- The camel has long legs which help it to keep its body away from the hot sand in the desert.
- A camel can drink large amount of water (when it is available) and store it in the body.
- A camel’s body is adapted to save water in the dry desert as follows: A Camel passes small amount of urine; its dung is dry and it does not sweat. Since a camel loses very little water from its body, it can live for many days without drinking water.
- A camel’s hump has fat stored in it. In case of emergency a camel can break down stored fat for nourishment.
- A camel has large and flat padded feet which help it to walk easily on soft sand. Thus it is called “The ship of the desert”.
- Camel has long eye lashes and hairs to protect its eyes and ears from the blowing dust.
- It can keep its nostrils closed to avoid dust.
Adaptive Features of Animals from different Habitats
More to know:
In Jurong Birds Park, Singapore, Penguins are kept in a big glass case with ice bergs and temperature is maintained at 0° C and below.
The Differences between Unicellular and Multicellular Organisms.
- When an animal moves its location as the season changes it is said to be Migration. In Tamil Nadu Bird Sanctuaries are located at Vedanthangal, Kodiyakkarai and Koondhankulam.
- There are many birds from foreign countries like Siberia and Russia migrate to our Vedanthaangal. Likewise during summer and drought conditions birds from our country migrate to foreign countries. These birds are called Migratory Birds.
- Spending winters in a dormant condition is called Hibernation. Eg. Turtle
- On the other hand, spending the hot and dry period in an inactive state is known as Aestivation. Eg. Snail
- Kangaroo rat does not drink water at all. Whatever food it eats and oxygen it gets from air combine together to form water inside the body.
- The mountain goat namely Nilgri Tahr can find small spaces on rock to climb with ease and keep its balance as it feeds.
