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

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Weather, Climate & Adaptations of Animals to Climate

WEATHER
Hot, humid, cold, windy, dry, cloudy, these are all weather words and tell us what the weather is like. Weather changes have a great impact on our lives. So before planning for activities like organizing a school sports or going out for vacation to a hill station, it is important to know weather conditions in advance. Newspapers therefore publish weather reports and weather forecast daily for the benefit of all. Weather report is also an integral part of news bulletins in television and radio. A sample of week’s weather report from the newspaper is:

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

Weather forecasting is one of those activities that is governed by United Nations in a common effort from which people benefit worldwide. It is based on the readings made by the Meteorological Department which studies various aspects of weather scientifically. Today, there is access to pictures from satellites with special remote sensing instruments that are continuously surveying the earth. Computer programmes analyse the data quickly and make enormous number of calculations.

Weather Tips
i) Don’t look at the sun directly.
ii) Prefer to stay indoors during a bad weather.
iii) If you are outside during a thunder storm, stay away from all objects like electric polls and tall trees.
iv) Stay on the lowest floor of the building during a cyclone.
We can define weather as the day to day conditions of the atmosphere at a particular place at a given time. The factors or elements determining the state of atmosphere include temperature air pressure humidity rainfall and conditions of sunshine. Weather conditions are temporary and can change over short period of time.

Elements of Weather

a) Temperature: Temperature is how hot or cold the atmosphere is, how many degrees celsius (centigrade) it is above or below freezing (0°C). Temperature is a very important factor in determining the weatherbecause it influences or controls other elements of the weather such as precipitation, humidity, clouds and atmospheric pressure.

b) Humidity: Humidity is the amount of water vapour in the atmosphere.

c) Atmospheric pressure (or air pressure): It is the weight of 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 given to moisture that falls from the air to the ground. Precipitation includes snow, hail, sleet, drizzle, fog, mist and rain.

e) Wind: Wind is the movement of air masses from high pressure areas to low pressure areas.

CLIMATE
Climate means the general sort of weather conditions that are to be found in an area or in a particular region. It is the average weather conditions or the pattern of weather conditions of that place. Climate and weather are inter related conditions prevailing in the atmosphere, i.e. rain, clouds, sunshine and wind. Their day-today changes make up the weather. Weather of a place may change from day to day or even from hour to hour. Climate tells us what it is usually like in a place round the year.
The climatic conditions of any place in the world vary and are dependent upon:

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

India has a large variation in climate from region to region due to its vast size. India as a whole experiences climate typical of four major climatic groups.
1. Tropical Rainy Climatic Group: The regions belonging to this group experience persistent high temperatures which normally do not go below 18°C. This climate group has two climatic types:

a) Tropical monsoon rain forest
Area: The west coastal low lands, the Western Ghats and Southern parts of Assam.
Characteristics: High temperature throughout the year even in the hills. Seasonal heavy rainfall from May to November.

b) Tropical wet and dry climate
Area: Most of the plateau of peninsular India except Tamil Nadu.
Characteristics: Early summer and long dry winter with temperature above 18°C. Very hot summers with temperature upto 45°C during May. Rainy season from June to September.

2. Dry Climate Group: This group consists of regions where the rate of evaporation of water is higher than the rate of moisture received through precipitation. It is sub-divided into three climatic type

1.a) Tropical semi-arid steppe climate

Area: Karnataka, interior Tamil Nadu, Western Andhra Pradesh and Central Maharashtra.

Characteristics: Zone with unreliable rainfall. December is the coldest month but even in this month the temperature remains between 20°C and 24°C. Climate is hot and dry from March to May, with temperature around 32°C.

1. b) Tropical and sub-tropical desert

Area: Most of Western Rajasthan

Characteristics: Scanty and erratic rainfall from July to September. Summer months of May and June are very hot, with temperature between 35°C to 50°C. Temperature drops below freezing in some areas during winter months due to cold waves.

1.c) Tropical and sub-tropical steppe

Area: Region towards the east of the tropical desert running from Punjab and Haryana to Kathiwar.

Characteristics: Unreliable rainfall which occurs during the summer monsoon reason between July and August maximum temperature during summer can rise to 40°C and fall to near zero in winters.

3.3. Humid sub-tropical climate group:

Area: The foothills of the Himalayas, Punjab, Haryana plains adjacent to the Himalayas, Rajasthan

(East of the Aravali ranges), Uttar Pradesh, Bihar and Northern part of West Bengal and Assam.

Characteristics: Mainly dry winter, but frost occurs for a few weeks in winter. Hot summers with temperatures soaring upto 46°C, May and June are the hottest months. Most of the rainfall is received during summers.

4. Mountain Climate: In the Himalayan mountains, the temperatures falls by 0.6°C for every 100 meters 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 due to great altitudinal variations, almost all climatic conditions from hot deserts to cold desert are found here. There are four seasons:

1. i) Winter (December - February) ii) Summer (March - June)

iii) South - West monsoon season (July - Sept.) iv) Post - monsoon season (October - November)

SEASON

The twelve months of a year can be divided into different climatic pattern. This we call the season such as spring, summer, autumn and winter.

It is important to understand that the seasons in the Northern and Southern hemisphere are reversed. When it is summer in the Northern hemisphere, it is winter in the Southern hemisphere. This is again because of the earth’s permanent inclination of its axis and earth’s revolutions 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 depends on it. All living organisms have adapted in different ways to the climates in which they live.

The effect of climate on the adaptations of animals living in polar regions and in the tropical rainforest are given below:

Polar regions constitute the Arctic and the Antarctic regions. Some countries belonging to this region are Greenland, Alaska Finland, Siberia and the entire of Antarctica continent. The tropical rainforests as the name suggests are the regions in the tropics. India, Malaysia, Indonesia, Brazil and Kenya are example of some of the countries where these forests are found.

The Polar Regions

These are the world’s coldest, driest, iciest and windiest regions. The coldest temperature recorded in the inland regions of Antractica was as low as –89°C in winter, going up to –30° in summer. 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 temperature are as low as –40° while the warmest month of June has a temperature of about 10°. Due to the tilt of Earth’s axis while it is orbiting the sun, the polar regions do not get any sunshine for some months of the year.

ANIMAL LIFE

There is very little vegetation in the Polar region. The population of animal life is also very small. As these regions have very lone temperature, the animals have adapted themselves well. This makes them compete for food, protect themselves from predators and breed. Some adaptations as in birds is to migrate to warm climates thus avoiding, the harsh months of winters. Birds fly thousands of kilometers to warmer climates and breed. Siberian crane is one such example that migrates to different parts of India like Haryana, Rajasthan and Bihar during winter months.

Large warm-blooded animals like Polar bear, Reindeer, Musk ox and Wolves can survive harsh winter. They lose less heat since they have a small surface as compared to their large size. They are also well insulated by a thick layer of fat and dense fur. Whales, Seal and Walrus living in the sea also have protective layers of fat.

Adaptations of Polar Bear

1. i) The dense fur made of keratin keeps the polar bear warm and dry. The white fur merges with the snowy background and hence protects them from predator

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.

iii) Ears are short to prevent heat loss.

1. iv) The feet has soft bumps which provide traction on ice and short tough claws grip the ice. v) Polar bears are strong swimmers and are known to swim at a speed of 100 km/hour

1. vi) Their nostrils can remain closed underwater for over two minute They can catch fish. Their front paws propel them through water while hind feet act like rudders.

The keratin fur of polar bear is transparent with a hollow core. It absorbs the UV light of sun which provides it with extra warmth.

Polar bears have a unique thermoregulation system. They are so well protected against cold, that they can often get over heated. They cool down by moving slowly, resting and dropping in cold water. Heat is also released from areas where there is thin fur coat as nose, ear, foot pad and inner thigh.

Adaptations of Penguins

Penguins are birds most closely identified with the Antarctic regions, their unique features are:

1. They are birds, but designed for life in the sea. They cannot fly but are very good swimmer

2. A coat of fat which is upto 3 cm thick helps them to survive in freezing condition

3. Their feathers are stiff and very lightly packed which act like a water proof 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, thereby reducing contact with cold ice.

6. Penguins have a unique social behaviour. They live in huge clusters and also huddle close together to keep warm.

7. Unlike the flying birds, they have heavy solid bones which allow them to stay underwater effortlessly.

8. Their wing-shaped “flippers” make them “fly underwater” at speed of 14-15 km/hour.

9. Their streamlined body and webbed feet make them good swimmer

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

Adaptations for Desert Life

Climatic Conditions: Desert climate is dry and hot in the daytime but becomes cold at night. There is excessive shortage of water. Because of this, desert vegetation is scarce. The desert plants are succulent

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