Test: Our Home: Earth, a Unique Life Sustaining Planet - Class 8 MCQ

Carbon dioxide is essential for photosynthesis, the process by which plants convert sunlight into energy. During this process, plants absorb carbon dioxide from the atmosphere and release oxygen, maintaining the balance of gases in the environment.

The Earth's atmosphere is crucial for life because it contains oxygen for respiration and forms the ozone layer, which protects living organisms from harmful ultraviolet (UV) radiation from the Sun. This protective layer is essential for the survival of many life forms, it also provides oxygen, traps heat, and enables weather.

Microorganisms play a crucial role as decomposers in ecosystems. They break down dead organic matter, returning valuable nutrients to the soil, which supports new plant growth and maintains the nutrient cycle essential for ecosystem health.

Air pollution is predominantly caused by industrial emissions and vehicle exhaust, which release harmful substances into the atmosphere. These pollutants can lead to serious health issues and environmental problems, including smog and acid rain.

The Earth's magnetic field acts as a shield against solar winds and cosmic rays, which can harm the atmosphere and living beings. By deflecting these high-energy particles, the magnetic field helps maintain the conditions necessary for life on Earth.

Biodiversity is crucial because it enhances the stability and resilience of ecosystems. A diverse range of species contributes to a balanced environment, helping ecosystems adapt to changes and recover from disturbances, such as disease or climate fluctuations.

Gametes are specialized reproductive cells (sperm and eggs) that fuse during fertilization to form a zygote. This zygote contains genetic material from both parents, leading to the development of a new organism.

Sustainable practices include using renewable energy (like solar or wind), conserving water, reducing waste, and protecting biodiversity. These actions maintain ecological balance, reduce environmental damage, and ensure that natural resources remain available for future generations.

The Earth's crust is likened to the thin skin of an apple, emphasizing its relatively thin layer compared to the overall size of the Earth. This analogy highlights how life exists on a very thin surface layer, making it crucial for all living organisms.

The "habitable zone," or Goldilocks zone, refers to the region around a star where conditions are just right for liquid water to exist, which is essential for life. Earth is located in this zone, allowing it to maintain temperatures that support life.

Venus is the hottest planet due to its thick atmosphere composed mainly of carbon dioxide, which creates a strong greenhouse effect. This traps heat efficiently, making surface temperatures higher than those on Mercury, despite being further from the Sun.

Satellites provide detailed images that help scientists monitor vegetation health, track water levels, observe changes in land use, and detect environmental problems such as deforestation, pollution, or urban growth. These images, often enhanced with false colours, allow for accurate and large-scale environmental analysis.

Water is vital for all life forms as it facilitates hydration, nutrient transport, and serves as a habitat for countless species. It plays a crucial role in physiological processes, such as digestion and temperature regulation.

Cutting down forests disrupts ecosystems and food chains, leading to biodiversity loss. Each species plays a unique role in maintaining ecological balance; removing one can have cascading effects on other species and the environment.

Earth is deemed unique because it supports life in diverse forms, including plants, animals, and humans. Its ability to sustain life stems from its specific environmental conditions, including the presence of water, an atmosphere, and the right temperature range.

The greenhouse effect is the process by which certain gases in the Earth's atmosphere trap heat, preventing it from escaping into space. This natural phenomenon is essential for maintaining the planet's temperature and allowing life to thrive.

Plants contribute to the balance of gases in the atmosphere by absorbing carbon dioxide during photosynthesis and releasing oxygen as a byproduct. This process is vital for maintaining the levels of these gases necessary for the survival of most living organisms.

One significant consequence of climate change is rising sea levels, largely due to melting ice caps and glaciers. This rise poses a threat to coastal communities and ecosystems, leading to increased flooding and habitat loss.

The Earth's size is critical because it has enough gravitational force to retain a sufficient atmosphere. If Earth were smaller, it would lose its atmosphere to space, making it inhospitable for life as we know it.

The ozone layer is significant because it absorbs and blocks the majority of the Sun's harmful ultraviolet (UV) radiation. This protection is essential for the health of living organisms, as excessive UV exposure can lead to skin cancer and other health issues.