Class 6 Science Chapter 6 Important Questions

Those things which need food, water and air for their survival are called organisms or living things. All the animals (including human beings) and plants need food, water and air to survive or live. As example, a boy, a girl, cat, dog, monkey, goat, tiger, birds, frog, fish, snake, lizard etc. all are living things because they all are animals. And all the different types of plants are also, called living organisms.

All the living things have some common characteristics which make them different from non-living things. There are given some characteristics of living things as:
i)Living things need food, air and water.
ii)Living things respire.
iii)Living things can grow.
iv)Living things can respond to stimuli.
v)Living things can move by themselves.
vi) Living things excrete.
vii) Living things can reproduce
viii)Living things have a definite life span.

The presence of specific features or certain habits, which enable a plant or an animal to live in its surroundings, is called adaptation. The sea and the desert are very different surroundings and we find very different kind of plants and animals in these two regions. Two very different kinds of organisms from the desert and the sea – a camel and a fish. The body structure of a camel helps it to survive in desert conditions. Camels have long legs which help to keep their bodies away from the heat of the sand.They excrete small amount of urine, their dung is dry and they do not sweat. Since camels lose very little water from their bodies, they can live for many days without water. There are so many kinds of fish, but, the shape helps them move inside water. Fish have slippery scales on their bodies. These scales protect the fish and also help in easy movement through water. Fish have flat fins and tails that help them to change directions and keep their body balance in water. Gills present in the fish help them to use oxygen dissolved in water. We see that the features of a fish help it to live inside water and the features of a camel help it to survive in a desert. Different animals are adapted to their surroundings in different ways, called adaptation.

The surroundings where organisms live is called a habitat. The organisms depend for their food, water, air, shelter and other needs on their habitat. Habitat means a dwelling place (a home). Several kinds of plants and animals may share the same habitat.
Some of the examples, of habitat are deserts, mountain region, forests, grassland, tree, pond, lake, river, ocean etc.

The term “biotic” means “living” and the term “abiotic” means “nonliving”. The living things such as plants and animals, in a habitat, are its biotic components. Various non-living things such as rocks, soil, air and water in the habitat constitute its abiotic components. Sunlight and heat also form abiotic components of the habitat.

The plants and animals that live on land are said to live in terrestrial habitats. Some examples of terrestrial habitats are forests, grasslands, deserts, coastal and mountain regions. On the other hand, the habitats of plants and animals that live in water are called aquatic habitats. Ponds, swamps, lakes, rivers and oceans are some examples of aquatic habitats.

There are desert animals like rats and snakes. To stay away from the intense heat during the day, they stay in burrows deep in the sand. These animals come out only during the night, when it is cooler. Desert plants lose very little water through transpiration. The leaves in desert plants are either absent, very small, or they are present in the shape of spines. This helps in reducing loss of water from the leaves through transpiration. The leaf-like structure you see in a cactus is, in fact, its stem. Photosynthesis in these plants. Desert animals in burrows is usually carried out by the stems. The stem is also covered with a thick waxy layer, which helps to retain water. Most desert plants have roots that go very deep into the soil for absorbing water.

Animals living in the mountain regions are also adapted to the conditions there. They have thick skin or fur to protect them from cold. For example, yaks have long hair to keep them warm. Snow leopard has thick fur on its body including feet and toes. This protects its feet from the cold when it walks on the snow. The mountain goat has strong hooves for running up the rocky slopes of the mountains.

A deer is another animal that lives in forests and grasslands. It has strong teeth for chewing hard plant stems of the forest. A deer needs to know about the presence of predators (animals like lion that make it their prey) in order to run away from them and not become their prey. It has long ears to hear movements of predators. The eyes on the side of its head allow it to look in all directions for danger. The speed of the deer helps them to run away from the predators. There are many other features of a lion, a deer or other animals and plants that help them to survive in their habitat.

Organisms that spend a considerable amount of time flying in air, called “aerial organisms”. Organisms that is spend most part of their lives on trees, called “arboreal organisms”.

Organisms that can live on land as well as in water, called “amphibians”. A condition in which the animals undergo a long sleep in polar regions, called “hibernation”.

All the living things respond to changes around them. The changes in surroundings to which living things respond are called stimuli. When we suddenly move from a dark place into bright sunlight. Our eyes shut, automatically for a moment till they adjust to the changed bright surroundings. If we see our favourite food our mouth starts watering. In this case, the sight of favourite food is the stimulus and watering of mouth is our response to it. Favorite food, bright light and quickly remove our body when it cuts these situations are some examples of changes in your surroundings. All of us respond immediately to such changes. When you move towards a bird, birds flies. Wild animals run away when bright light is flashed towards them. Similarly, cockroaches begin to move to their hiding places if the light in the kitchen is switched on at night. Flowers of some plants bloom only at night. In some plants, flowers close after sunset. In some plants like mimosa, commonly known as ‘touch-me-not’, leaves close or fold when someone touches them. These are some examples of responses of plants towards changes in their surroundings.

Photosynthesis for food making in plants take place only during day time when sunlight is available but respiration in plants take place during day time as well as at night time.

The process by which living organisms produce new members of their species is called reproduction. All the living things reproduce themselves. The modes or methods of reproduction in different animals are different. Some animals reproduce by giving birth to their young ones whereas some animals reproduce their young ones through eggs. For example, human beings reproduce by giving birth to babies. The animal such as dogs, cat, cow, horse, lion and tiger etc. also reduced by giving birth to their young ones. The animal like birds and fish reproduce through eggs. Birds lay eggs which on hatching produce young ones. The birds such as hens, pigeons, sparrow, parrot, duck etc. lay eggs. When these eggs are hatched, young ones or baby birds come out of these eggs. Plants also reproduce like animals; plants also differ in their mode of reproduction. Many plants reproduce through seeds. Plants produce seeds, which can germinate and grow into new plants. Some plants also reproduce through parts other than seeds. For example, a part of a potato with a bud, grows into a new plant.

Discuss the adaptive features of yak as a mountain habitat.

Respiration is the chemical process in which food taken by an organism combines with oxygen to release energy. This energy is used by the organism to carry out its various life processes.
The process of respiration takes place inside the body of plant or animal. As example, our body takes in oxygen from air for respiration. At the same time, it gives out carbon dioxide produced by respiration. The process of taking air into the lungs through nose and then expel it through nose is called breathing. The purpose of breathing in air is to provide oxygen to our body for carrying out respiration. Thus, breathing is a part of the process of respiration.

Adaptation does not take place in a short time. The abiotic factors of a region change over thousands of years. The animals and plants which cannot change themselves and do not adapt to these changes die out and those who adapt are able to survive.

Snakes in the desert burrow deep into the sand during the day time when it is very hot because the deeper layers of sand are cooler. This allows them to stay away from heat of the desert that persist through the day time as well as prevent loss of water from their body.

Acclimatization: It is the process in which an individual organism adjusts to a gradual change in its environment (such as a change in temperature, humidity, photo-period) allowing it to maintain performance across a range of environmental conditions. Acclimation occurs in a short period of time (days to weeks), and within the organism’s lifetime. Adaptation: In biology, an adaptation, also called an adaptive trait, is a trait with a current functional role in the life history of an organism that is maintained or developed by means of natural selection. Adaptation refers to both the current state of being adapted and to be in the dynamic evolutionary process that leads to the adaptation.

Desert plants have very small leaves or spines as adaptation to dry conditions of the desert because of these modifications of leaves, the surface of lamina is reduced which reduces water loss from the leaves through transpiration.
Since very little water is lost through transpiration, that benefits the desert plants to survive on stored food for long time.

A moving car although moves is a not considered as a living organism because of the following reasons:
(i) Living organisms have the ability to move on their own, whereas a car moves by burning of fuels like diesel and petrol.
(ii) A car does not show any other living characteristics like respiration, digestion, reproduction or growth that are shown by all living organisms and these processes are essential for living beings.

‘Cactus’ is mostly found in the deserts. It has the following special features to adapt itself to survive in the desert. As:
(i)Leaves are modified into the spines to reduce the rate of loss of water.
(ii) Seam becomes green and fleshy to take over the function of photosynthesis.
(iii)Stem is also covered with thick layer of wax to retain water.
(iv)Its roots go deeper into the soil for better absorption of water.

Cactus lose very little water through transpiration. The leaves in cactus plants are present in the shape of spines. This helps in reducing loss of water from the leaves through transpiration. Its stem is converted into a leaf like structure. Photosynthesis in these plants is usually carried out by the stems. The stem is also covered with thick waxy layer, which helps to retain water. Cactus plants have roots that go very deep into the soil for absorbing water.

In the grassland, there are less number of trees and places to hide. The animals are vulnerable to predators (e.g. lions, tigers, wolves, etc.). They can only survive and escape if they can run faster. Therefore, speed is important for survival in the grasslands for animals (e.g. deer) that live there.