Maharashtra Board Class 7 Science Chapter 1 The Living World Adaptations and Classification PDF Download

The Living World: Adaptations And Classification

Let's Recall

In what different ways is the diversity in living things seen?

A great variety of plants is found on the earth. Some plants have colourful flowers. Some plants grow in water whereas some are to be found in deserts which have a scarcity of water. Some plants are found only in snowy regions. Some plants cannot be seen without a microscope whereas some are huge in size. Like plants, animals too show diversity. Some are unicellular, others, multicellular. Some are vertebrates whereas others are invertebrates. This world is full of a variety of animals – aquatic, terrestrial, amphibian, reptilian, aerial, etc. These observations give rise to the question – How did this great diversity come into being?

Can You Tell?

Are the plants and animals from Kashmir and Rajasthan of the same type? Can you elaborate on any differences between the two?

Coniferous trees like pine and deodar flourish in snowy regions like Kashmir. However, in the deserts of Rajasthan, plants like cactus and acacia are to be found. The camel, a desert animal, is not found in Kashmir. What is the reason for these differences?

Adaptation

Gradual changes occur in the body parts and also in the behaviour of organisms which help them to adjust to their surroundings. Such changes are called adaptations. They take place over a long period of time.

Teacher's Note

Adaptation means changing to fit the environment. For example, coconut trees grow near water because they need water to live.

Exam Trick

Remember: Adaptation takes long time. It is not sudden. Just like a baby slowly learns to walk, animals and plants slowly change over many years.

Points to Remember

Adaptation helps living things fit their home.
Adaptation happens slowly over long time.
Different places need different adaptations.
Animals and plants change their body to survive.

Adaptation In Plants

Observe and complete the chart. (Include other plants from your own region too.)

Adaptation In Aquatic Plants

Visit various water bodies such as a river, brook, pond, lake, in your surroundings. What differences do you observe between terrestrial and aquatic plants?

Some of the aquatic plants are firmly rooted in the soil at the bottom of the water bodies. Their stems are submerged, while leaves and flowers float on the surface. However, some plants are entirely afloat. Their roots are not anchored in the soil.

The surfaces of leaves and stems of many aquatic plants are covered with a waxy layer. Leaves of some aquatic plants are thin and slender like a ribbon. This shape helps them to withstand fast currents of water. Air spaces in stems and petioles of aquatic plants are useful for floating in water.

Teacher's Note

Water plants have special leaves and stems to float. For example, lotus leaves have a waxy coating so water slides off them.

Exam Trick

Remember: Aquatic plants float because they have air spaces inside. Think of it like tiny balloons inside the plant that help it float in water.

Points to Remember

Aquatic plants have thin, ribbon-like leaves.
They have air spaces inside stems to float.
Their leaves have waxy coating.
Some roots do not touch the soil.
Water plants are soft and bendy.

Use Your Brain Power

Why does water trickle off lotus leaves?

Why don't the leaves of these plants rot in water?

Why are their roots short and fibrous?

Adaptation In Desert Plants

Take two potted plants – one, a cactus and the other, a leafy plant. Tie plastic bags loosely around the leaves of these plants and keep them in sunlight from early in the morning. In the afternoon, bring those pots into the classroom and observe them.

Has the same quantity of water collected in both bags?

Desert plants are either leafless or their leaves are like small needles or have been modified into thorns. As a result, they lose very little water by evaporation. The stem stores water and food and is therefore fleshy. The stems are green as they perform photosynthesis in the absence of leaves. Their roots penetrate deep into the soil in search of water. There is a thick layer of a waxy substance on the stems of these plants, too.

Teacher's Note

Desert plants like cactus store water in their stems. They have small leaves so they do not lose water in hot sun, just like how we drink more water in summer.

Exam Trick

Remember: Cactus = less leaves. Less leaves = less water lost. The thicker the plant, the more water it stores underground and in stem.

Points to Remember

Desert plants have thick, fleshy stems to store water.
Their leaves are small or like needles.
They have a waxy coating on stems.
Their roots go very deep into soil.
They lose very little water.

Adaptation In Plants Of Snowy Regions

Can You Tell?

In what way are sloping branches useful to plants in a snowy region?

Plants of snowy regions mainly include conifers like deodar and pine. These trees are conical in shape due to their sloping branches. In the heavy snowfall and extreme cold in these regions, their conical shape prevents the snow from accumulating on the tree and the thick bark helps the tree to withstand the cold.

Teacher's Note

Snow trees like pine have sloping branches. This helps snow to slide off. Otherwise snow would break the branches, just like a roof slopes so water runs down.

Exam Trick

Remember: Conical = cone shape. Cone shape = snow slides off. No snow on top = branches don't break. Smart design by nature!

Points to Remember

Pine and deodar trees are cone-shaped.
The slope helps snow to slide off.
Snow does not break their branches.
Thick bark keeps them warm in cold.
They have few branches at bottom.

Adaptation In Plants Of Forest Regions

A variety of plants – trees, shrubs and herbs – are found in forests. These plants compete amongst themselves for sunlight. Hence, trees grow tall to get sunlight and climbers and vines grow to a great height with the support of trees. Spring-like tendrils on the stems of some climbers is an example of adaptation.

Teacher's Note

Forest plants fight for sunlight. So trees grow tall and vines use tendrils to climb up. This is like children standing on toes to see over a crowd in the market.

Exam Trick

Remember: Forest = dark and crowded. Plants grow tall to catch sunlight. Vines use tendrils like ropes to climb. Think of it like a race to the top for light.

Points to Remember

Forest has many plants competing for light.
Trees grow tall to get more sunlight.
Climbers use tendrils to climb trees.
Vines wrap around tree trunks.
More plants = more fighting for sunlight.

Adaptation In Grassland Plants

Diverse types of bushes and grasses are found in the grasslands. Fibrous roots of grasses prevent soil erosion. Grasses in the equatorial region are very tall. Animals like tiger, elephants and deer can remain hidden in these grasses. However, grasses in cold regions are very short. Animals like the rabbit are found in such grasses. Vast meadows are found in hilly areas as well as plains.

Observe And Discuss

Observe and note down the adaptations in the parts of plants like potato, groundnut, yam, water hyacinth, aloe, acacia, carrot, onion, beet, bitter-gourd, grape vine, etc. and other plants in your surroundings.

Teacher's Note

Grassland plants have fibrous roots to prevent soil erosion. This is like how roots hold soil together so wind cannot blow it away, like hair holds the skin on your head.

Exam Trick

Remember: Grassland grass can be tall or short. In hot places, grass is tall. In cold places, grass is short. Animals hide in tall grass. Rabbits hide in short grass.

Points to Remember

Grassland plants have fibrous roots.
Roots prevent soil from washing away.
Tall grass helps animals hide from enemies.
Short grass helps small animals hide.
Vast meadows are in plains and hills.

This is a preview of the first 3 pages. To get the complete book, click below.