Class 7 Science Weather Climate Adaptations of Animals to Climate Chapter Notes

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This Class 7 Science chapter notes page on Weather, Climate and Adaptations of Animals to Climate covers weather and its elements, the climate of India and its climatic groups, seasons, the adaptations of polar animals, desert animals and tropical rainforest animals, hibernation, predator protection mechanisms, and the exercise questions with answers.

Topics Covered

1. Weather
2. Elements of Weather
3. Climate
4. Climatic Groups of India
5. Season
6. Climatic Adaptations of Animals
7. The Polar Regions
8. Adaptations for Desert Life
9. Hibernation
10. Adaptations in Animals of Tropical Rainforests
11. Predator Protection Mechanisms
12. Exercises

Weather

Hot, humid, cold, windy, dry and cloudy are all weather words, and they tell us what the weather is like. Weather changes have a great impact on our lives. Before planning activities such as a school sports day or a trip to a hill station, it is important to know the weather conditions in advance. For this reason, newspapers publish a daily weather report and forecast, and the weather report is also an integral part of television and radio news bulletins.

The daily weather report gives information on temperature, humidity and rainfall. It includes the conditions that prevailed on the previous day and a forecast for the current day. On television, satellite pictures of the earth show where a storm is blowing, which places are expected to have rain or snow, and which places will have calm weather.

[Figure: Fig. 1 Daily Weather Report - a sample weekly weather forecast from a newspaper, showing for each day of the week (Mon to Sun) a weather symbol with the temperature, precipitation and humidity for that day]

Weather forecasting is governed by the United Nations in a common effort, from which people benefit worldwide. It is based on readings made by the Meteorological Department, which studies the various aspects of weather scientifically. Today, satellites with special remote sensing instruments continuously survey the earth, and computer programmes analyse the data quickly and carry out an enormous number of calculations.

Weather Tips

1. Do not look at the sun directly.
2. Prefer to stay indoors during bad weather.
3. If you are outside during a thunderstorm, stay away from objects such as electric poles and tall trees.
4. Stay on the lowest floor of a building during a cyclone.

Weather: Definition and Elements

Weather is the day to day condition of the atmosphere at a particular place at a given time. The factors that determine the state of the atmosphere include temperature, air pressure, humidity, rainfall and sunshine. Weather conditions are temporary and can change over a short period of time.

Elements of Weather

(a) Temperature: It is how hot or cold the atmosphere is, measured in degrees Celsius (centigrade) above or below freezing (0°C). Temperature is very important because it influences the other elements of weather, such as precipitation, humidity, clouds and atmospheric pressure.
(b) Humidity: It is the amount of water vapour in the atmosphere.
(c) Atmospheric pressure (air pressure): It is the weight of the air resting on the earth's surface. Pressure is shown on a weather map, often called a synoptic map, with lines called isobars.
(d) Precipitation: It is the term for moisture that falls from the air to the ground. Precipitation includes snow, hail, sleet, drizzle, fog, mist and rain.
(e) Wind: It is the movement of air masses from high pressure areas to low pressure areas.

Climate

Climate means the general sort of weather conditions found in an area or a particular region. It is the average weather condition, or the pattern of weather conditions, of that place. Weather and climate are interrelated, because the rain, clouds, sunshine and wind that make up the weather also make up the climate. The day to day changes make up the weather, while climate tells us what a place is usually like throughout the year. The weather of a place may change from day to day, or even from hour to hour.

Factors Affecting Climate

1. Distance from the sea or high mountain ranges: Places near the sea have a moderate climate, neither too hot nor too cold. Mountain ranges affect rainfall and winds, and hence the climate of an area. For example, the climate of Darjeeling is cold, that of Mumbai is warm and humid, and that of Jaisalmer is hot and dry.
2. Height above sea level: The higher we go above sea level, the cooler the climate becomes.
3. Winds blowing from or towards the sea: Hot or cold, and humid or dry, winds affect the climate.
4. Humidity: The amount of moisture in the air affects the climate. High humidity makes the climate hot and humid.
5. Distance from the equator: It is a very important factor that affects the climate of a region.

Climatic Groups of India

India has a large variation in climate from region to region because of its vast size. India as a whole experiences the climate typical of four major climatic groups.

1. Tropical Rainy Climatic Group

The regions in this group experience persistent high temperatures, which normally do not fall below 18°C. This group has two climatic types.
(a) Tropical monsoon rain forest: It is found in the west coastal lowlands, the Western Ghats and the southern parts of Assam. Temperatures are high throughout the year, even in the hills, and heavy seasonal rainfall occurs from May to November.
(b) Tropical wet and dry climate: It is found over most of the plateau of peninsular India, except Tamil Nadu. There is an early summer and a long dry winter, with temperatures above 18°C. Summers are very hot, with temperatures up to 45°C in May. The rainy season runs from June to September.

2. Dry Climatic Group

This group consists of regions where the rate of evaporation of water is higher than the rate of moisture received through precipitation. It has three climatic types.
(a) Tropical semi-arid steppe climate: It is found in Karnataka, interior Tamil Nadu, western Andhra Pradesh and central Maharashtra. Rainfall is unreliable. December is the coldest month, with temperatures between 20°C and 24°C. The climate is hot and dry from March to May, with temperatures around 32°C.
(b) Tropical and sub-tropical desert: It is found over most of western Rajasthan. Rainfall is scanty and erratic from July to September. May and June are very hot, with temperatures between 35°C and 50°C. In some areas, temperatures drop below freezing in winter due to cold waves.
(c) Tropical and sub-tropical steppe: It is found to the east of the tropical desert, running from Punjab and Haryana to Kathiawar. Rainfall is unreliable and occurs during the summer monsoon between July and August. Maximum temperatures in summer can rise to 40°C, and fall to near zero in winter.

3. Humid Sub-Tropical Climatic Group

This group is found in the foothills of the Himalayas, the Punjab and Haryana plains adjacent to the Himalayas, Rajasthan (east of the Aravalli ranges), Uttar Pradesh, Bihar, the northern part of West Bengal and Assam. Winters are mainly dry, but frost occurs for a few weeks. Summers are hot, with temperatures soaring up to 46°C. May and June are the hottest months, and most of the rainfall is received during summer.

4. Mountain Climate

In the Himalayan mountains, the temperature falls by 0.6°C for every 100 metres rise in altitude. This gives rise to a variety of climates, from near-tropical in the foothills to tundra type above the snow line.

India is mainly a tropical country, but because of its great altitudinal variation, almost all climatic conditions, from hot deserts to cold deserts, are found here. India has four seasons:
(i) Winter (December to February)
(ii) Summer (March to June)
(iii) South-West monsoon season (July to September)
(iv) Post-monsoon season (October and November)

Season

The twelve months of a year can be divided into different climatic patterns, which we call seasons, such as spring, summer, autumn and winter. The seasons in the Northern and Southern hemispheres are reversed. When it is summer in the Northern hemisphere, it is winter in the Southern hemisphere. This is because of the earth's permanent tilt of its axis and its revolution around the sun.

Climatic Adaptations of Animals

Climate is the most important element of the natural environment. The types of organisms, and where they are found, depend on it. All living organisms have adapted in different ways to the climates in which they live. The effects of climate on the adaptations of animals living in polar regions and in the tropical rainforest are described below.

The polar regions include the Arctic and the Antarctic. Countries in this region include Greenland, Alaska, Finland and Siberia, and the entire Antarctic continent. Tropical rainforests are found in the tropics. India, Malaysia, Indonesia, Brazil and Kenya are examples of countries where these forests are found.

The Polar Regions

The polar regions are the coldest, driest, iciest and windiest regions of the world. The coldest temperature recorded in the inland regions of Antarctica was as low as -89°C in winter, and in summer it rises to about -30°C. There is no permanent settlement in Antarctica. The Arctic region is sparsely populated, and people live on the highlands along the sea coast. Normal winter temperatures are as low as -40°C, while the warmest month, June, has a temperature of about 10°C. Because of the tilt of the earth's axis as it orbits the sun, the polar regions get no sunshine for some months of the year.

There is very little vegetation in the polar regions, and the population of animals is also very small. The animals have adapted well to these very low temperatures, which make it hard to compete for food, protect themselves from predators and breed. Some birds migrate to warmer climates to avoid the harsh winter. Birds fly thousands of kilometres to warmer climates to breed. The Siberian crane is one such example, migrating to Haryana, Rajasthan and Bihar in India during the winter months.

Large warm-blooded animals such as polar bears, reindeer, musk oxen and wolves can survive the harsh winter. They lose less heat because they have a small surface area compared with their large size. They are also well insulated by a thick layer of fat and dense fur. Whales, seals and walruses living in the sea also have protective layers of fat.

[Figure: Fig. 2 Wolves, musk ox and reindeer, shown in snowy surroundings]

Adaptations of the Polar Bear

1. The dense fur, made of keratin, keeps the polar bear warm and dry. The white fur merges with the snowy background and protects it from predators.
2. Polar bears have a thick layer of fat under their skin, called blubber, which can be up to 11 cm thick. It gives complete insulation from the cold.
3. The ears are short to prevent heat loss.
4. The feet have soft bumps which provide traction on ice, and short, tough claws grip the ice.
5. Polar bears are strong swimmers and are known to swim at a speed of 100 km/hour. Their nostrils can remain closed underwater for over two minutes. They can catch fish, with their front paws propelling them through the water while their hind feet act like rudders.
6. The keratin fur of the polar bear is transparent with a hollow core. It absorbs the ultraviolet light of the sun, which provides extra warmth.
7. Polar bears have a unique thermoregulation system. They are so well protected against cold that they can often overheat. They cool down by moving slowly, resting, and dropping into cold water. Heat is also released from areas with thin fur, such as the nose, ears, foot pads and inner thigh.

[Figure: Fig. 3 Polar bear standing on snow]

Adaptations of Penguins

Penguins are the birds most closely identified with the Antarctic regions. Their unique features are:
1. They are birds, but are designed for life in the sea. They cannot fly but are very good swimmers.
2. A coat of fat up to 3 cm thick helps them survive in freezing conditions.
3. Their feathers are stiff and lightly packed, which act like a waterproof coat.
4. The dark plumage absorbs heat.
5. On land, most penguins walk upright on their hind feet. They can rest on their heel and tail, which reduces contact with the cold ice.
6. Penguins have a unique social behaviour. They live in huge clusters and huddle close together to keep warm.
7. Unlike flying birds, they have heavy, solid bones, which allow them to stay underwater effortlessly.
8. Their wing-shaped flippers make them fly underwater at a speed of about 14 to 15 km/hour.
9. Their streamlined body and webbed feet make them good swimmers.

Penguins are the only birds that migrate hundreds of kilometres by swimming. They can drink salty water without ill effects. They have much better vision underwater, but on land they are almost short-sighted.

[Figure: Fig. 3 Penguins standing together on ice]

Adaptations for Desert Life

Desert climate is dry and hot in the daytime but cold at night. There is an excessive shortage of water, so desert vegetation is scarce. Desert plants are succulent and spiny, and are called cacti. Their leaves are modified into spines to avoid the loss of water by evaporation. Their stems become green to carry out photosynthesis in the absence of leaves, and they become fleshy for storing water.

Adaptations in Desert Animals

Animals living in deserts include insects, reptiles, birds, small mammals and camels. They show adaptations for protection from the scorching heat and for the conservation of water.

Protection from heat: Many animals escape the hot and dry conditions by avoiding movement during the day. They go deep into burrows, and are called burrowing animals. Many desert animals live in burrows and come out to feed at night, when it is cooler. Such animals are called nocturnal animals, for example, desert rats.

[Figure: Fig. 5 Desert animals in burrows, with cacti and a desert tree in the background]

Conservation of water

Desert animals conserve water in the following ways:
(i) Their skin has no sweat glands, which avoids the loss of water by evaporation.
(ii) They excrete concentrated urine, again to avoid the loss of water.

The Camel: The Ship of the Desert

The camel is so well adapted to the desert that it is called the ship of the desert. The height of a camel can vary from 1.8 m to just over 2 m at the shoulders. It can weigh from 250 kg to 680 kg. In spring, camels lose their fur and grow a new coat. They look sleek after losing their fur, and look normal after a new layer of fur comes in autumn. The Bactrian camel has long hair, while the Arabian camel has short hair.

Adaptations of a Camel

1. Deserts are hot and dry, and when the winds blow, sand blows all around. A camel has long eyelashes and three layers of eyelids to prevent sand from getting into its eyes.
2. A camel can go for weeks without food or water, because it stores fat and water in its humps. Its long intestine helps maximise water absorption.
3. Unlike most mammals, a healthy camel's body temperature fluctuates according to the temperature of its surroundings.
4. The camel's feet are broad and hoofed, so that it can walk on sand without its feet sinking into it.
5. Its nostrils can open or close, so that sand does not enter the nose.
6. The colour of its body helps it to camouflage.
7. Camels have thick lips, so that the spiny plants do not harm them when they eat desert plants.
8. It has thick, leathery patches on its knees, which protect it from the heat of the sand.
9. Thick fur and underwool help camels stay warm during desert nights and keep them insulated in the day.
10. Long and strong legs keep the camel away from the hot sand and help it carry heavy loads.

[Figure: Fig. 6 A camel showing adaptations to desert conditions, with labels for long eyelashes, thin nostrils, long intestine, and wide feet for walking on sand]

Hibernation

Hibernation is the process by which animals escape cold, freezing temperatures. Many animals of cold climates go into a long winter sleep. They remain inactive and do not take any food. Frogs and lizards are examples of animals that show hibernation.

Adaptations in Animals of Tropical Rainforests

Geographic location: Tropical rainforests are located around the equator. They are found in the Western Ghats and Assam in India, southern Asia, Central America and Central Africa.

Climatic conditions: Tropical rainforests are hot and humid. In summer the temperature is usually above 40°C, and in winter it is never below 15°C. The length of the day and night remains almost equal throughout the year. Rainfall is plentiful and occurs almost the whole year.

Animals living in rainforests

Tropical rainforests have a large variety of plants and animals, because the climate is conducive and the weather is mild throughout the year. The major types of animals living in these forests are monkeys, snakes, lizards, birds, amphibians and insects.

Since the climatic conditions in tropical rainforests are most suitable to support life, animal life is abundant and shows great variety. Animals face tough competition for food and space, so they have adapted to various modes of existence.

Arboreal Habit

Many animals living in tropical rainforests are adapted to live on trees. They are called arboreal animals. For example:
- Monkeys have a long, coiled prehensile tail for grasping tree branches. Their hands and feet are also modified to hold on to branches, that is, they have grasping feet with an opposable thumb.
- Red-eyed frogs and other tree frogs have sticky pads on the tips of their digits, which help them cling to and climb trees.
- Birds roost on trees, and snakes and lizards can move on tree twigs.

[Figure: Fig. 7 Tree frog clinging to a leaf]

Note: A tail that can be used to grasp tree branches, just like hands, is known as a prehensile tail.

Feeding Habits

Because tropical rainforests are thickly populated, there is competition for food. Animals living there have developed several methods of obtaining food. For example:
- The toucan has a long, large beak, which helps it reach fruits on branches on which it cannot sit.
- Most forest dwellers are herbivorous, because there is plenty of vegetation.

[Figure: Fig. 8 Toucan with a large, colourful beak]

Camouflaging

Forest animals have thick skin, and their skin colour camouflages them and blends them with the surroundings. This enables the predator to locate its prey, and it also protects the prey from the predator because it cannot be spotted easily.

Sense Organs

Animals living in tropical forests depend on their senses and agility. They have sharp eyesight and are sensitive to hearing.

Animals of Indian Tropical Forests

The loin-tailed macaque, the bearded ape and the Indian elephant are animals found in Indian tropical forests. The loin-tailed macaque has a silver-white mane that surrounds the head, cheeks and chin, as in a lion. It is a good climber. It feeds mainly on fruits, but also enjoys seeds, young leaves, flowers and buds. It also eats insects found under tree bark.

[Figure: Fig. 9 Loin-tailed macaque with a silver-white mane]

Elephants are adapted to live in tropical rainforests. They have large, fan-like ears, long pointed tusks, a long prehensile trunk and pillar-like legs.
1. Large, fan-like ears help regulate body temperature. The skin over them is thin and highly vascular, so it loses heat quickly.
2. The tusks are used to dig up roots of food plants, to debark trees, or to dig into trees to get the pulp inside.
3. The trunk acts as a human hand for picking and holding things. The elephant's trunk can pick up a single blade of grass or tear off a tree branch, and it can put food in the mouth.
4. The pillar-like legs balance the bulky body, and cushion-like pads of tough, gelatinous material act as shock absorbers while the animal moves on the ground.

Elephants can lift 200 kg or more with their trunk. Therefore, they are used to transport logs of wood in forests where other means of transport cannot be used.

[Figure: Fig. 10 An Indian Elephant carrying logs of wood in a forest]

Insects form the largest community in a tropical rainforest. Termites, mosquitoes, spiders, ants and butterflies are found here, and many of them have brilliant colours.

Predator Protection Mechanisms

There is intense competition for food and survival in the tropical rainforest. Since a huge variety of species live here, protection from predators is a priority, and it depends largely on adaptations.
(i) Hiding: Animals hide in burrows, under rocks, under leaves or under tree bark.
(ii) Camouflage: Animals blend into their surroundings. Walking stick insects and some butterflies are almost invisible when they are still.
(iii) Scaring the predators: Some animals make predators believe that they are bigger or fiercer than they really are. For example, many butterflies have large "eye designs" on their wings, which make them look like the heads of large animals.
(iv) Warning colour and scent: Poisonous animals openly advertise their defence with colour and scent. When a predator eats one member of the group, it becomes sick. The predator remembers this and avoids that animal in future.

Exercises

Answer the following very briefly.

1. Why is the Arctic region sparsely populated?

Answer: The Arctic region is very cold, harsh and windy, and has very little vegetation and food, so very few people can live there.

Teacher's Note:
a) The source question says "shapelessly populated", which is corrected here to "sparsely populated".
b) People in the Arctic live on the highlands along the sea coast.

2. What is migration?

Answer: Migration is the movement of animals, usually birds, from one place to another, often over long distances, to find food or a warmer climate for breeding.

Teacher's Note:
a) Migration is seasonal and the animals usually return to their original place later.
b) The Siberian crane is an example of a migrating bird.

3. Who are meteorologists?

Answer: Meteorologists are scientists who study the weather and climate, and who prepare weather forecasts.

Teacher's Note:
a) The Meteorological Department in India is the body that studies weather scientifically.
b) Weather forecasts are based on readings and satellite data that meteorologists analyse.

4. What do you mean by prehensile?

Answer: Prehensile means able to grasp or hold things, like a hand. A prehensile tail can grip tree branches.

Teacher's Note:
a) Monkeys have prehensile tails, which help them move through trees.
b) The word comes from the Latin word for grasping.

5. Name two animals that migrate.

Answer: The Siberian crane and the Arctic tern are two animals that migrate.

Teacher's Note:
a) Any two migrating birds, such as the bar-headed goose, are also correct.
b) Penguins migrate by swimming, which is an unusual form of migration.

6. When are maximum and minimum temperatures recorded?

Answer: The maximum temperature is recorded during the afternoon, when it is hottest, and the minimum temperature is recorded in the early morning, before sunrise.

Teacher's Note:
a) Both temperatures are recorded with a maximum-minimum thermometer.
b) The difference between them is the daily temperature range.

Answer the following in brief.

1. How does the weather of a place affect the lives of people?

Answer: Weather affects what we wear, what food we eat, how we travel, and how we plan activities. It affects farming, transport and health. Heavy rain can cause floods and disrupt daily life, while extreme heat or cold can cause illness.

Teacher's Note:
a) Weather forecasts help people plan their day and protect themselves.
b) Farmers decide when to sow and harvest on the basis of the weather.

2. List any three ways by which weather forecasting can be helpful.

Answer: (i) Farmers can plan sowing and harvesting. (ii) People are warned of cyclones, storms and floods, so they can take shelter or move to safety. (iii) People can plan travel, sports events and holidays.

Teacher's Note:
a) Forecasts also help airlines and shipping to plan safe journeys.
b) Early warnings save lives and reduce damage to property.

3. Why do tropical rainforests have a large population of animals?

Answer: Tropical rainforests have hot and humid weather, plenty of rainfall throughout the year, and a large variety of plants. This gives animals plenty of food, shelter and mild conditions for life throughout the year.

Teacher's Note:
a) The plant life provides food for herbivores, which in turn support predators.
b) Because the climate is mild all year, animals can breed and survive throughout the year.

4. Weather is an important part of our lives. Justify the statement.

Answer: Weather affects almost everything we do. It decides what clothes we wear, and whether we can go to school, travel or play outdoors. It affects farming, which provides our food, and it affects our health. Weather forecasts help us prepare for storms, floods and heat waves, so weather is an important part of our lives.

Teacher's Note:
a) The source spelling "Whether" is corrected to "Weather", which is the word that makes sense in this question.
b) A good answer should give at least two examples from daily life.

5. Why do Mumbai and Delhi experience different climates?

Answer: Mumbai is near the sea, so its climate is moderated by the sea breeze and it is warm and humid. Delhi is far from the sea, so it has very hot summers and cold winters, and its climate is drier.

Teacher's Note:
a) Distance from the sea is one of the main factors affecting climate.
b) Delhi is also at a higher altitude than Mumbai, which adds to its cooler winters.

Answer the following in detail.

1. Write in detail about the factors affecting climate.

Answer: The climate of a place depends on several factors. (i) Distance from the sea or high mountain ranges: places near the sea have a moderate climate, while mountains affect rainfall and winds. (ii) Height above sea level: the higher the place, the cooler the climate. (iii) Winds blowing from or towards the sea: hot or cold, and humid or dry, winds change the climate. (iv) Humidity: high humidity makes the climate hot and humid. (v) Distance from the equator: places near the equator are generally hotter than places far from it.

Teacher's Note:
a) Darjeeling is cold because of its height, Mumbai is warm and humid because of the sea, and Jaisalmer is hot and dry because it is far from the sea.
b) Each factor should be explained with an example to score full marks.

2. List the adaptations of the polar bear.

Answer: (i) Dense, keratin fur, which is white for camouflage and keeps the bear warm and dry. (ii) A thick layer of blubber, up to 11 cm, for insulation. (iii) Short ears to prevent heat loss. (iv) Soft bumps on the feet and short, tough claws for grip on ice. (v) Strong swimming, with nostrils that close underwater. (vi) Transparent, hollow fur that absorbs ultraviolet light. (vii) A thermoregulation system that releases heat from areas with thin fur.

Teacher's Note:
a) The source says polar bears swim at 100 km/hour, which is not correct; they are strong swimmers but swim far more slowly, so this figure is not included.
b) Mention any four adaptations in a short answer, and all of them in a detailed answer.

3. List the adaptations of penguins.

Answer: (i) They have wing-shaped flippers and streamlined bodies with webbed feet, which make them good swimmers. (ii) A layer of fat up to 3 cm thick keeps them warm. (iii) Stiff, lightly packed feathers act as a waterproof coat. (iv) Dark plumage absorbs heat. (v) They huddle in large clusters to keep warm. (vi) They have heavy, solid bones that help them stay underwater. (vii) They walk upright and rest on their heels and tails to reduce contact with the ice. (viii) They can drink salt water and have good vision underwater.

Teacher's Note:
a) Penguins are birds that cannot fly, but they fly underwater with their flippers.
b) The speed of 14 to 15 km/hour given in the source is an approximate value for penguin swimming.

4. Write the differences between weather and climate.

Answer:

Teacher's Note:
a) Weather tells us what it is like today, and climate tells us what it is usually like.
b) The source gives no answer key, so the table above is the model answer.

5. Write notes on tropical rainforests.

Answer: Tropical rainforests are located around the equator, including the Western Ghats and Assam in India. They are hot and humid, with temperatures above 40°C in summer and never below 15°C in winter. Rainfall is plentiful throughout the year, and day and night are almost equal in length. They have a great variety of plants and animals, including monkeys, snakes, lizards, birds, amphibians and insects. Animals show adaptations such as arboreal habits, prehensile tails, sticky pads on frogs, large beaks in toucans, camouflage, and predator protection such as hiding, camouflage, scaring predators, and warning colour. Elephants have large ears, tusks, a trunk and pillar-like legs.

Teacher's Note:
a) The rainforest has a very large number of species because of its stable and mild climate.
b) Notes should include both the climate and the animal adaptations, as in the chapter above.

1. ii) Polar bears have thick layer of fat under their skin called blubber. They are as thick as 11 cm. T his p r ovides comp let e ins u la t ion from cold.