Weather and climate significantly influence our lives and daily planning. Factors like temperature, humidity, and rainfall determine the conditions we experience. Weather reports, provided daily by meteorological departments, help us prepare for the predicted conditions.

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Weather

**Weather** refers to the **day-to-day condition of the atmosphere at a specific place** with respect to certain factors. These factors, known as the **elements of weather**, include:

• Temperature
• Humidity (amount of moisture in the air)
• Rainfall
• Wind-speed

Other factors like sunlight and cloud cover also contribute to weather conditions.

Weather conditions can **change frequently**, sometimes even within a short period on the same day (e.g., from sunny to cloudy and rainy). Because of this variability, weather is a complex phenomenon and not always easy to predict accurately.

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Activity 7.1

This activity involves collecting and recording daily weather reports from a newspaper over a week. By noting down the maximum and minimum temperatures, humidity levels (minimum and maximum), and rainfall for each day, it becomes evident that these weather elements vary considerably from day to day and week to week.

Table 7.1: Structure for recording weather data (Example):

Date	Max. temp. (°C)	Min. temp. (°C)	Min. humidity (%)	Max. humidity (%)	Rainfall* (mm)
...	...	...	...	...	...
...	...	...	...	...	...
...	...	...	...	...	...

*Rainfall is measured using a **rain gauge**, which collects rainwater in a measuring cylinder.

The **maximum temperature** of the day typically occurs in the **afternoon**, while the **minimum temperature** is usually recorded in the **early morning**. This explains why summer afternoons feel hottest and early mornings are cooler.

The **Sun** is the ultimate source of energy that drives all weather changes on Earth. The energy from the sun absorbed and reflected by the Earth's surface, oceans, and atmosphere plays a significant role in determining local weather conditions.

Climate

While weather describes the day-to-day atmospheric condition, **climate** refers to the **average weather pattern of a place taken over a long period of time**, typically 25 years or more.

Meteorological departments keep records of daily weather data for many decades. By analysing these records, scientists can determine the climate of a region.

• If a place has high temperatures for most of the year, its climate is described as **hot**.
• If a place also receives heavy rainfall on most days, its climate is described as **hot and wet**.

Different regions of India have distinct climates:

• **Srinagar (Jammu & Kashmir):** Has a moderately hot and wet climate for part of the year, with lower temperatures compared to southern India, especially in winter.
• **Thiruvananthapuram (Kerala):** Shows a climate that is very hot and wet throughout most of the year.
• **Rajasthan (Western India):** Has a climate that is generally hot for most of the year with low temperatures only for a few winter months. It receives very little rainfall, characteristic of a **hot and dry** desert climate.
• **North-east India:** Receives rain for a major part of the year, indicating a **wet** climate.

Comparing average daily minimum and maximum temperatures and mean monthly rainfall data for different locations (like in Tables 7.2 and 7.3 of the text) clearly illustrates these climatic differences.

Climate And Adaptation

The climate of a region has a profound influence on the types of life forms that can survive there. Animals are naturally selected over long periods (evolution) to possess specific **features and habits (adaptations)** that enable them to live and thrive in the particular climatic conditions of their habitat. These adaptations help them protect themselves against extreme temperatures, find food, and survive predators in that environment.

Let's examine the adaptations of animals in two regions with extreme climates: the polar regions and the tropical rainforests.

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Activity 7.2

This activity involves locating and marking the polar regions (near the North and South poles) and tropical regions (around the equator) on a world map. This helps visualize the geographical distribution of these distinct climate zones.

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(i) The Polar Regions:

These regions are located near the Earth's poles and experience an **extreme climate**. They are covered in snow for most of the year and are very cold. A unique feature is the occurrence of six months of continuous daylight followed by six months of continuous darkness at the poles. Winter temperatures can drop very low (e.g., to -37°C).

Animals living here have remarkable adaptations to survive the severe cold:

• Polar Bears:
• Possess **white fur** for camouflage against the snow, protecting them from predators and aiding in catching prey.
• Have **two thick layers of fur** and a layer of **fat under the skin**, providing excellent insulation against the cold. They might even overheat if they move too much in warm weather.
• Are excellent **swimmers** with wide, large paws that help both in swimming and walking on snow.
• Can close their nostrils and stay underwater for long periods while swimming.
• Have a **strong sense of smell** to locate prey.

These adaptations are summarised in a flow chart in the text (Fig. 7.3).

• Penguins:
• Are also **white** to blend with the snowy background.
• Have **thick skin** and a lot of **fat** for insulation.
• Huddle together in groups to keep warm by sharing body heat.
• Are good **swimmers** with a streamlined body and webbed feet.
• Other animals: Fishes, musk oxen, reindeers, foxes, seals, whales, and birds also live here. Fishes can tolerate cold water. Many **birds** cannot tolerate the extreme cold of winter and **migrate** to warmer regions during winter, returning when the cold season is over. India is a destination for many migratory birds, like the Siberian crane, which visits places like Bharatpur (Rajasthan) and Sultanpur (Haryana).

Migratory birds travel vast distances (up to 15000 km) to escape harsh climates. They fly at high altitudes where wind flow is favourable and allows heat generated by muscles to dissipate. How they navigate is still being researched, possibly using landmarks, the sun, stars, or the Earth's magnetic field. Migration is also observed in mammals, fish, and insects seasonally.

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(ii) The Tropical Rainforests:

These regions are located around the equator and generally have a **hot climate** (temperatures above 15°C even in coldest months, sometimes exceeding 40°C in summer) and receive **plenty of rainfall**. Days and nights are almost equal in length. This combination of continuous warmth and rain supports an enormous **variety and number of plants and animals**. Prominent rainforests are found in parts of India (Western Ghats, Assam), Southeast Asia, Central America, and Central Africa.

The high diversity of animals (monkeys, apes, gorillas, tigers, elephants, leopards, lizards, snakes, birds, insects) leads to intense **competition** for food and shelter. Animals have developed specific adaptations to cope with this competition and the hot, humid climate:

• **Adaptations for living on trees:** Many animals are adapted to live on trees to access food and shelter away from the ground. The **red-eyed frog** has sticky pads on its feet for climbing. **Monkeys** have long, strong tails for grasping branches and hands/feet adapted for holding onto branches.

• **Adaptations for accessing food:** Animals adapt to obtain food not easily available to others. The **Toucan** bird has a long, large beak that allows it to reach fruits on weak branches that cannot support its weight.

• **Adaptations for protection:** Many animals have developed features to avoid becoming prey. These include **sensitive hearing, sharp eyesight, thick skin, bright colours, sharp patterns**, and the ability to **camouflage** by blending with the surroundings (like big cats). A loud voice can also be an adaptation for communication or warning.
• **Specific Animal Examples:**
• **Lion-tailed macaque (Beard ape):** Lives in Western Ghats rainforests. Adapted for tree dwelling, with a distinctive silver-white mane. Feeds on fruits, seeds, leaves, stems, flowers, buds, and insects found under bark, rarely needing to descend to the ground.
• **Elephant:** Adapted in many ways. Its **trunk** serves as a nose (strong sense of smell) and is used for picking up food. Modified teeth form large **tusks** used to tear bark (a preferred food). Large **ears** help it hear soft sounds and also help dissipate heat, keeping it cool in the hot, humid climate.

These diverse adaptations demonstrate how animals evolve specific features to survive and thrive in the challenging conditions posed by different climates, whether extreme cold or hot and humid environments with intense competition.

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