Class 7 Science Notes Chapter 7 (Weather; Climate and Adaptations of Animals to Climate) – Science Book

Okay, let's focus on the key concepts from NCERT Class 7 Science Chapter 7: 'Weather, Climate and Adaptations of Animals to Climate' for government exam preparation.

Chapter 7: Weather, Climate and Adaptations of Animals to Climate

1. Weather

• Definition: The day-to-day condition of the atmosphere at a particular place with respect to temperature, humidity, rainfall, wind speed, etc.
• Key Characteristics:
  • Short-term phenomenon (changes daily, even hourly).
  • Complex and variable.
• Elements of Weather:
  • Temperature: Degree of hotness or coldness of the air. Measured using a thermometer (specifically, maximum-minimum thermometers record the highest and lowest temperatures of the day).
  • Humidity: Amount of water vapour present in the air. Indicates the likelihood of precipitation, dew, or fog. High humidity makes us feel sweaty.
  • Rainfall: Precipitation in the form of water drops. Measured using a Rain Gauge.
  • Wind Speed: The speed at which air moves.
• Weather Reports:
  • Prepared by the Meteorological Department of the Government.
  • Provide information about the weather of the past 24 hours and predict future weather.
  • Include data on temperature, humidity, rainfall, sunrise/sunset times, moonrise/moonset times.
• Source of Weather Changes: Almost all weather changes are caused by the Sun. The Sun is the primary source of energy that causes changes in the weather. Energy absorbed and reflected by the Earth's surface, oceans, and atmosphere plays a crucial role.

2. Climate

• Definition: The average weather pattern taken over a long time, typically 25 years or more, for a particular place.
• Key Characteristics:
  • Long-term phenomenon.
  • Relatively stable for a given region.
• Distinction from Weather: Weather is short-term and changes frequently; Climate is the long-term average of weather.
• Factors Determining Climate (General Understanding):
  • Latitude (Distance from Equator): Places near the equator receive more direct sunlight and are generally hotter. Places near the poles receive slanted sunlight and are colder.
  • Altitude (Height above sea level): Places at higher altitudes are generally cooler.
  • Distance from the Sea: Coastal areas tend to have more moderate climates (cooler summers, warmer winters) than inland areas.
  • Ocean Currents: Warm or cold currents can significantly affect the climate of coastal regions.
  • Winds: Prevailing wind patterns distribute heat and moisture.
• Examples of Climates Mentioned:
  • Kerala vs. Jammu & Kashmir: Kerala (near the coast and equator) is very hot and wet compared to Jammu & Kashmir (hilly, farther from the equator) which is moderately hot and wet for part of the year.
  • Rajasthan (Desert): Hot and dry (high temperature, low rainfall).

3. Climate and Adaptations

• Definition of Adaptation: Features (physical characteristics) and habits (behaviours) that help an animal or plant to survive successfully in its specific habitat (environment/climate).
• Necessity: Animals living in specific climatic conditions must possess adaptations to cope with the extremes of temperature, water availability, food sources, and protection from predators in that climate.

4. Adaptations in Polar Regions

• Climate Characteristics:
  • Extreme cold throughout the year.
  • Covered with snow for most of the year.
  • Six months of daylight and six months of darkness at the poles.
  • Examples: Arctic (North Pole region), Antarctic (South Pole region).
• Key Animals & Adaptations:
  • Polar Bear:
    • White Fur: Camouflage against snow (helps catch prey and avoid predators); Provides insulation.
    • Two Thick Layers of Fur: Trap air, providing excellent insulation against cold.
    • Layer of Fat (Blubber) under the skin: Insulates the body from cold and acts as an energy reserve.
    • Wide and Large Paws: Help in walking on snow and swimming.
    • Strong Sense of Smell: Helps locate prey (like seals) from afar.
    • Long, Curved, Sharp Claws: Help walk on ice and catch prey.
    • Ability to close nostrils: Can remain underwater for long durations while swimming.
    • Slow movement & rest periods: Avoid overheating.
  • Penguin:
    • White front, Black back (Countershading): Camouflage in water (white belly blends with bright surface from below, black back blends with dark depths from above).
    • Thick Skin and thick layer of Blubber: Protection against cold.
    • Huddling Together: Penguins crowd together in groups to keep warm.
    • Streamlined Body: Efficient swimming.
    • Webbed Feet: Aid in swimming.
    • Found primarily in the Antarctic region (Southern Hemisphere).
• Other Polar Animals: Many types of fishes, musk oxen, reindeer, foxes, seals, whales, and birds (many birds migrate to warmer regions during winter).
  • Migration: A behavioural adaptation where animals (especially birds) undertake long journeys to escape harsh, cold conditions and find food or breeding grounds, returning when conditions improve. Siberian Cranes migrating to India (e.g., Bharatpur, Rajasthan) is a classic example.

5. Adaptations in Tropical Rainforests

• Climate Characteristics:
  • Generally hot and humid climate (located around the equator).
  • Even temperatures throughout the year (little variation between summer and winter).
  • Plentiful rainfall throughout the year.
  • Days and nights are almost equal in length throughout the year.
• Key Features: Rich biodiversity (supports a wide variety of plants and animals). Intense competition for food and shelter.
• Location Examples: Western Ghats and Assam in India, Southeast Asia, Central America, Central Africa.
• Key Animals & Adaptations:
  • Red-Eyed Frog:
    • Sticky Pads on Feet: Help climb trees easily (arboreal adaptation).
    • Green Colour: Camouflage among leaves.
  • Monkeys:
    • Long Tails: Used for grasping branches (prehensile tails in some).
    • Hands and Feet: Adapted for holding onto branches securely.
  • Toucan:
    • Large, Long, Colourful Beak: Helps reach fruits on branches that are too weak to support its weight; also possibly involved in display.
  • Big Cats (Lions, Tigers, Leopards):
    • Thick Skin & Camouflaged Colour: Blend with surroundings (e.g., yellow-brown skin of lion, stripes of tiger).
    • Sensitive Hearing & Sharp Eyesight: Help locate prey.
  • Lion-Tailed Macaque (Beard Ape):
    • Habitat: Rainforests of Western Ghats (India).
    • Distinctive Feature: Silver-white mane surrounding its head.
    • Arboreal: Excellent climber, spends most of its life on trees.
    • Diet: Feeds mainly on fruits, seeds, young leaves, stems, flowers, and buds; also searches for insects under the bark. Rarely comes down to the ground.
  • Elephant:
    • Trunk: Used as a nose (strong sense of smell); used for picking up food; used for drinking water.
    • Tusks (Modified Teeth): Can tear bark of trees (food); used for defense.
    • Large Ears: Help hear even very soft sounds; also help the elephant keep cool in the hot, humid climate (large surface area radiates heat).
    • Large, Padded Feet: Support large body weight, move quietly.

Key Terms Summary:

• Weather: Day-to-day atmospheric conditions.
• Climate: Long-term average weather pattern.
• Elements of Weather: Temperature, humidity, rainfall, wind speed.
• Humidity: Measure of moisture (water vapour) in the air.
• Maximum/Minimum Temperature: Highest/Lowest temperature recorded, usually in a day.
• Rain Gauge: Instrument to measure rainfall.
• Adaptation: Feature or habit helping an organism survive in its habitat.
• Polar Region: Cold regions near Earth's poles.
• Tropical Rainforest: Hot, humid regions near the equator with high rainfall.
• Migration: Seasonal mass movement of animals from one place to another.
• Camouflage: Blending with surroundings for protection or hunting.
• Blubber: Thick layer of fat under the skin for insulation.

Points to Remember for Exams:

• Clearly distinguish between Weather and Climate (time scale is key).
• Know the elements of weather and the instruments used for measurement (temperature - thermometer, rainfall - rain gauge).
• Understand the concept of Adaptation and its importance for survival.
• Be able to list and explain specific adaptations of key animals from Polar regions (Polar Bear, Penguin) and Tropical Rainforests (Toucan, Red-eyed Frog, Lion-tailed Macaque, Elephant), linking the adaptation to the specific climatic challenge it addresses.
• Know the general climatic characteristics of Polar Regions and Tropical Rainforests.
• Understand Migration as an adaptation to escape harsh conditions.

This detailed breakdown covers the essential points from the chapter relevant for competitive government exams. Focus on definitions, examples, and the specific adaptations linked to climatic conditions.