Riya performs two set of experiments to study the length of the foam formed which are as follows

Riya performs two set of experiments to study the length of the foam formed which are as follows:

Set I: she takes 10 ml of distilled water in test tube “A” and adds 5-6 drops of liquid soap in it and shakes the test tube vigorously.
Set II: she takes 10 ml of distilled water in a test tube “A” and adds 5-6 drops of liquid soap with half spoonful of CaSO4 in it and shakes the test tube.

Write your observation and reason.

Set I will have more length of foam because it consist of soft water.

Set II will form less foam because it consist of hard water due to the presence of CaSO4.

15th April 2019

ncert solution




Another thought that occurred to Paheli and Boojho was about the kinds of living organisms that were present in different locations that they had visited. The goats and yak. Puri had some other creatures – crabs on the beach and such a variety of fish being caught by the fishermen at the sea! And then, there did seem to be some creatures like ants that were present in all these different locations. The kinds of plants found in each of these regions were so different from the plants of the other regions. What about the surroundings in these different regions? Were they the same?


What do you find from the plants and animals?  Did you find a large variety in them? Look at what you have entered in the column for the desert and the column for the sea. Did you list every different kind of organisms?

What are the surrounding like, in these two regions?

     In this sea, plants and animals are surrounded by saline (salty) water. Most of them use the air dissolved in water.

 These is very little water available in the desert. It is very hot in the day time and very cold at night in the desert. The animals and plants of the desert live on the desert soil and breathe air from the surroundings.

The sea and the desert are very different surroundings and we find very different kind of plants and animals in these two regions, isn’t it? Let us look at two very different kind of organisms from the desert and the sea – a camel and 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.

Let us look at different kinds of fish. There are so many kinds of fish, but, do you see that they all have something common about their shape? All the ones shown here have the streamlined shape that was discussed in chapter 8. This 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, We discussed in Chapter 8, that 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.

We have taken only two examples from a very wide variety of animals and plants that live on the Earth. In all this variety of organisms, we will find that that they have certain features that help them live in the surroundings in which they are normally found. The presence of specific features or certain habits, which enable a plants or an animals to live in its surroundings, is called adaptation. Different animals are adapted to their surrounding in different ways.

                                                        The surroundings where organisms live 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.

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. One 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 large variations in forests, grassland, deserts, coastal and mountain regions located in different parts of the world. This is true for all aquatic habitats as well.

                  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

                                         We know that some plants grow from seed. Let us look at some abiotic factors and their effect on seeds as they grow into young plants.



05th April 2019

Mansi Shaw