Students can keep Class 8 Science Extra Questions and Class 8th Curiosity Chapter 13 Our Home: Earth, A Unique Life Sustaining Planet Important Extra Question Answer handy for quick reference during exams.
Class 8 Science Chapter 13 Our Home: Earth, A Unique Life Sustaining Planet Extra Questions
Class 8 Science Chapter 13 Extra Questions on Our Home: Earth, A Unique Life Sustaining Planet
Our Home: Earth, A Unique Life Sustaining Planet Class 8 Very Short Question Answer
Question 1.
What is the habitable zone?
Answer:
The habitable zone is the range of distances from the Sun where temperatures allow liquid water to exist, supporting life.
Question 2.
Why is Earth called the Blue Planet?
Answer:
Earth appears blue from space because about 70% of its surface is covered with water.
Question 3.
What is the role of the ozone layer?
Answer:
The ozone layer absorbs harmful ultraviolet (UV) rays from the Sun, protecting living organisms.
Question 4.
What generates Earth’s magnetic field?
Answer:
The movement of molten iron in Earth’s core generates its magnetic field.
Question 5.
What is vegetative propagation in plants?
Answer:
Vegetative propagation is asexual reproduction where plant parts like stems, roots, or leaves grow into new plants.
Question 6.
What are gametes in sexual reproduction?
Answer:
Gametes are specialised cells (e.g., sperm, eggs, pollen, ovules) carrying half the genetic material of a parent.
Question 7.
Name one component of the triple planetary crisis.
Answer:
Climate change is a component of the triple planetary crisis.
Question 8.
What is geodiversity?
Answer:
Geodiversity is the variety of landforms, rocks, soils, and geological processes creating diverse habitats.
Question 9.
What is pollination in plants?
Answer:
Pollination is the transfer of pollen to the ovule, enabling fertilization and seed production.
Question 10.
How does the greenhouse effect benefit Earth?
Answer:
The greenhouse effect traps heat to maintain Earth’s temperature, allowing liquid water and life to exist.
Our Home: Earth, A Unique Life Sustaining Planet Class 8 Short Question Answer
Question 1.
Why is Venus the hottest planet despite being farther from the Sun than Mercury?
Answer:
Venus is the hottest planet (average 450°C) due to its thick carbon dioxide atmosphere, which causes a strong greenhouse effect, trapping heat. Mercury, despite being closer to the Sun, lacks an atmosphere to retain heat, resulting in a lower average temperature (170°C).
Question 2.
How does Earth’s geography contribute to its habitability?
Answer:
Earth’s gravity is strong enough to hold its atmosphere, preventing gases from escaping into space, unlike Mars. It is not too strong to crush organisms, unlike a larger planet, ensuring a balanced environment for life with oxygen and protection.
Question 3.
What role does the hydrosphere play in sustaining life?
Answer:
The hydrosphere, covering 70% of Earth’s surface, provides water for drinking, crop growth, and aquatic ecosystems. It drives the water cycle, producing rainfall that supports plants and animals, and acts as a solvent for nutrient transport.
Question 4.
Differentiate between asexual and sexual reproduction in terms of offspring variation.
Answer:
- Asexual reproduction produces offspring identical to the single parent, with no variation (e.g., vegetative propagation).
- Sexual reproduction involves two parents, combining gametes to create offspring with mixed genetic traits, leading to variation.
Question 5.
How does the magnetic field protect life on Earth?
Answer:
Earth’s magnetic field deflects harmful cosmic rays and solar wind, preventing atmospheric erosion and ozone depletion. This protects living organisms from damaging UV radiation and maintains conditions for life.
Question 6.
What is biodiversity loss, and why is it a concern?
Answer:
Biodiversity loss is the extinction or reduction of species due to habitat destruction, disrupting ecosystems. It is a concern because each species plays a role (e.g., plants provide food), and their loss weakens nature’s ability to support life.
Question 7.
Explain the significance of India’s Mangalyaan mission.
Answer:
Launched in 2013 by ISRO, Mangalyaan studied Mars’ atmosphere, surface, and past water presence, exploring its potential to support life. It showcased India’s low-cost space technology and contributed to global Mars research.
Our Home: Earth, A Unique Life Sustaining Planet Class 8 Long Question Answer
Question 1.
Explain how Earth’s position, atmosphere, and magnetic field make it uniquely suitable for life.
Answer:
Earth’s unique suitability for life stems from:
- Position: Located in the habitable zone, Earth’s distance from the Sun allows liquid water to exist, essential for all known life forms. Its nearly circular orbit ensures stable temperatures, avoiding extreme heat or cold.
- Atmosphere: The atmosphere provides oxygen for respiration, supports photosynthesis, and includes an ozone layer that blocks harmful UV rays. The greenhouse effect traps heat, maintaining temperatures suitable for liquid water.
- Magnetic Field: Generated by molten iron in the core, it shields Earth from cosmic rays and solar wind, preventing atmospheric loss and protecting life from radiation damage. These factors create a balanced environment, unlike Venus (too hot) or Mars (too cold, thin atmosphere), enabling diverse life forms to thrive.
Question 2.
Describe the processes of sexual reproduction in plants and animals and highlight their key differences.
Answer:
- Plants: Sexual reproduction involves flowers with male (anther, producing pollen) and female (ovule) parts. Pollination, often by wind or insects, transfers pollen to the stigma. Fertilization forms a zygote, developing into a seed, with the flower’s fleshy part becoming a fruit for dispersal.
- Animals: Sexual reproduction involves male (sperm) and female (egg) gametes. In aquatic animals like fish, fertilization is external in water. In birds, internal fertilization produces eggs that develop externally during hatching. In mammals, internal fertilization and embryo development occur inside the female, who provides nutrition.
- Differences: Plants use pollination for gamete transfer, while animals rely on direct sperm-egg interaction. Plant zygotes form seeds, while animal zygotes develop into embryos. Animals may provide parental care (e.g., bird egg incubation), unlike plants, which rely on seed dispersal.
Question 3.
Discuss the triple planetary crisis and suggest three measures to mitigate its impact.
Answer:
The triple planetary crisis includes:
- Climate Change: Burning fossil fuels releases greenhouse gases, intensifying the greenhouse effect, causing global warming, sea level rise, and extreme weather.
- Biodiversity Loss: Habitat destruction reduces species, disrupting ecosystems (e.g., loss of grasses affects herbivores and predators).
- Pollution: Air, water, and soil pollution from factories, vehicles, and waste harms health, crops, and aquatic life.
- Mitigation Measures:
- Use Renewable Energy: Adopt solar and wind energy to reduce greenhouse gas emissions.
- Conserve Habitats: Protect and restore ecosystems like forests to maintain biodiversity.
- Improve Waste Management: Promote recycling and sustainable practices to reduce pollution in the air, water, and soil. These measures help restore Earth’s balance, ensuring long-term habitability.
Question 4.
How do Earth’s systems (atmosphere, hydrosphere, geosphere, biosphere) interact to sustain life?
Answer:
Earth’s systems interact to support life:
- Atmosphere: Provides oxygen for respiration, carbon dioxide for photosynthesis, and traps heat via the greenhouse effect, maintaining suitable temperatures.
- Hydrosphere: Water (70% of Earth’s surface) supports aquatic life, provides freshwater, and drives rainfall through the water cycle, influencing habitats.
- Geosphere: Soil and rocks supply nutrients (e.g., nitrogen, potassium) for plants, while geodiversity creates varied habitats.
- Biosphere: Plants produce food and oxygen, animals consume plants or other animals, and decomposers recycle nutrients, maintaining ecosystem balance.
- Interactions: Plants use water, sunlight, and carbon dioxide to produce oxygen, supporting animals. Water transports nutrients in plants and regulates animal temperature. Soil supports plant growth, sustaining food chains. Disruptions like deforestation affect all systems, reducing rainfall and biodiversity.
Question 5.
Explain how reproduction ensures the continuity of life and allows adaptation to changing environments.
Answer:
Reproduction ensures life’s continuity and adaptation:
- Continuity: Reproduction produces new individuals, preventing species extinction. Asexual reproduction creates identical offspring, ensuring continuity in stable environments (e.g., bacteria dividing). Sexual reproduction produces offspring with mixed traits, maintaining species diversity.
- Adaptation: Sexual reproduction introduces genetic variation through the combination of gametes from two parents, allowing offspring to develop new traits (e.g., camels’ humps for desert survival). Over generations, these variations enable species to adapt to environmental changes, like bacteria becoming antibiotic-resistant.
- Mechanisms: In asexual reproduction, a single parent produces exact copies (e.g., vegetative propagation in plants). In sexual reproduction, gametes combine to form a zygote with unique traits, promoting variation (e.g., pollination in plants, fertilization in animals). This dual ability ensures species survival and evolution in changing conditions.
Our Home: Earth, A Unique Life Sustaining Planet Class 8 Case Based Questions
Question 1.
A village near a forest has experienced hotter summers and reduced rainfall over the past five years. The forest has been partially cleared for farming, and a nearby factory releases smoke and waste into a river. The village’s crops are failing, and fish populations in the river are declining.
(a) What human activities are likely causing the hotter summers and reduced rainfall?
(b) How does forest clearing contribute to these changes?
(c) Suggest two measures to improve the village’s crop and fish populations.
Answer:
(a) Human Activities: Burning fossil fuels in the factory releases greenhouse gases, intensifying the greenhouse effect and causing hotter summers. Deforestation for farming reduces water vapour, disrupting rainfall patterns.
(b) Forest Clearing: Forests contribute to the water cycle by releasing water vapour, forming clouds, and producing rainfall. Clearing trees reduces this process, leading to less rainfall and higher temperatures due to less shade and carbon dioxide absorption.
(c) Measures:
- Reforestation: Plant trees to restore the water cycle, increase rainfall, and provide shade, improving crop growth.
- Reduce Pollution: Regulate factory waste to prevent river pollution, protecting fish populations and ensuring clean water for irrigation.
Question 2.
In animals, gametes are called sperm (male) and eggs (female). Fertilisation may take place in water, for example, male and female fish or frogs eject sperm and eggs, respectively, into the water where they combine to form the zygote. In birds and mammals, including humans, sperm are deposited inside the female, and fertilisation takes place when the sperm swim towards the egg produced by the female.
(a) What is the difference between fertilisation in fish and birds?
(b) Why do fish produce many eggs compared to birds?
(c) How does internal fertilisation benefit mammals like humans?
Answer:
(a) Difference in Fertilisation: In fish, fertilisation is external, with sperm and eggs released into water to form a zygote. In birds, fertilisation is internal, with sperm deposited inside the female, and the zygote develops into an egg laid for hatching.
(b) Fish Produce Many Eggs: Fish produce many eggs because external fertilisation in water exposes eggs to predators, currents, and environmental risks, so a large number increases the chance of some surviving. Birds produce fewer eggs as they provide parental care, like incubation, improving survival rates.
(c) Benefit of Internal Fertilisation: Internal fertilisation in mammals allows the embryo to develop inside the female, receiving nutrition and protection from the mother’s body, increasing survival chances compared to external development in harsh environments.
Question 3.
A science team is planning to create a small habitat on Mars to grow plants for future settlers. They know Mars has a thin atmosphere, extreme cold, and no liquid water, but they can bring Earth soil and water.
(a) Why does Mars’ thin atmosphere make plant growth difficult?
(b) What conditions must the team provide to grow plants in the Martian habitat?
(c) Suggest one challenge the team might face in maintaining the habitat.
Answer:
(a) Thin Atmosphere: Mars’ atmosphere is 100 times thinner than Earth’s, lacking sufficient oxygen for plant respiration and carbon dioxide pressure for photosynthesis. It also fails to protect against UV radiation and extreme cold, hindering plant growth.
(b) Conditions Needed: The team must provide liquid water, nutrient-rich Earth soil, an oxygen-rich atmosphere, temperature control (around 15°C), artificial sunlight for photosynthesis, and radiation shielding to mimic Earth’s habitable conditions.
(c) Challenge: Maintaining a stable oxygen-rich atmosphere is challenging due to Mars’ low pressure and potential leaks in the habitat, requiring constant oxygen production and monitoring to support plant respiration.
Our Home: Earth, A Unique Life Sustaining Planet Extra Questions for Practice
Question 1.
What is the role of Earth’s magnetic field in sustaining life?
Question 2.
Why is Earth’s atmosphere essential for life?
Question 3.
What is meant by geodiversity?
Question 4.
Name one example of vegetative propagation in plants.
Question 5.
What is one cause of biodiversity loss?
Question 6.
How does the greenhouse effect differ on Earth compared to Venus?
Question 7.
Explain the role of the hydrosphere in supporting life on Earth.
Question 8.
Differentiate between external and internal fertilisation in animals.
Question 9.
Why is the triple planetary crisis a threat to life on Earth?
Question 10.
Describe how Earth’s position in the solar system, atmosphere, and geosphere contribute to its ability to support life.
Question 11.
Explain the processes of asexual and sexual reproduction, highlighting how they contribute to the continuity and variation of life.
Question 12.
Discuss the impact of climate change on Earth’s ecosystems and suggest two measures to mitigate it.
Question 13.
A town near a river has seen declining fish populations and poor crop yields. Local industries dump waste into the river, and deforestation has occurred for urban expansion.
(a) What type of pollution is affecting the river, and how does it impact fish?
(b) How might deforestation contribute to poor crop yields?
(c) Suggest one solution to address the river pollution.
Question 14.
“Earth is like a giant teamwork project between nature, weather, and life itself. It is a vast, living system where land, air, water, and living things support and affect one another. Even a small change in one part, like cutting down a forest, can impact rainfall, soil, air quality, and the animals that live there.”
(a) What are the four main systems mentioned in the excerpt?
(b) How can cutting down a forest affect rainfall?
(c) Why is the balance between these systems important for life?