NCERT Solutions for Class 8 Science Chapter 13 - Our Home: Earth, a Unique Life Sustaining Planet

NCERT Solutions For Class 8 Science Chapter 13 - PDF Download

NCERT Solutions for Class 8 Science Chapter 13 – Our Home: Earth, a Unique Life–sustaining planet provides detailed answers that aid the students in understanding the unique characteristics of the Earth that support Life. These NCERT solutions for class 8 Science include concepts such as Earth Atmosphere, Water Cycle, Biodiversity and Conservation to make learning interesting and exam-focused.

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NCERT Solutions for Class 8 Science Chapter 13: Solved Exercise Questions

NCERT solutions of Class 8 Science Chapter 13 Our Home -Earth, A Unique Life-sustaining Planet are clear and step-by-step solutions to all practice questions, which allow students to get the main ideas in an easy way. These solutions break down the difficult topics using examples, thus making them more understandable and ideal efor xam preparation.

Q1: What is one major reason Mars cannot currently support life like Earth?

(i) It has too many volcanoes.

(ii) It is too close to the Sun.

(iii) It lacks a thick atmosphere and liquid water.

(iv) Its magnetic field is too strong.

Answer:

(iii) It lacks a thick atmosphere and liquid water.

Reason:

The atmosphere of Mars is too thin (about 100 times thinner than that of the Earth) to trap sufficient heat or block the harmful rays. Also, the planet Mars lacks stable liquid water at the surface, which is deemed to be fundamental to life as we know it. Such a combination is one of the reasons why Mars is not life-supporting, unlike Earth.

Q2: Which of these is an example of geodiversity?

(i) A variety of birds chirping in a forest.

(ii) Different landforms like mountains, valleys, and deserts.

(iii) Changing weather during monsoons.

(iv) Number of different types of fish in a pond.

Answer:

(ii) Different landforms like mountains, valleys, and deserts.

Reason:

The concept of geodiversity denotes the range of physical characteristics (landforms, rocks, soils, etc.) on the Earth. This comprises mountains, valleys, deserts and rivers among others. The diversity of bird sounds within a forest refers not to geodiversity, but to biodiversity (life).

Q3: If the Earth were smaller with the same density, what might happen to its atmosphere?

(i) It would become thicker and hotter.

(ii) It would escape into space due to weaker gravity.

(iii) It would become frozen.

(iv) It would cause stronger winds.

Answer:

(ii) It would escape into space due to weaker gravity.

Reason:

A smaller Earth would have less gravitational pull. This lower gravity may not be capable of retaining our atmosphere and therefore most of the gases would escape into the outer space, making life impossible to be sustained as it currently is.

Q4: In sexual reproduction, why are offspring different from their parents?

(i) They grow in different climates.

(ii) They eat different food.

(iii) They acquire new instructions after birth.

(iv) They get mixed instructions (genes) from both parents.

Answer:

(iv) They get mixed instructions (genes) from both parents.

Babies do not look exactly like their mother or father. Even brothers and sisters in the same family can look different from each other. This is because every baby gets a mix of genetic information from both parents through gametes. Each gamete carries a different set of instructions for things like eye colour, hair type, and more. These instructions mix in different ways when the sperm and eggs join to form a baby. These instructions mix in different ways each time, so each child is unique.

Q5: You notice tiny green plants growing in cracks on your school wall after the monsoon. Where do you think the seeds came from? What conditions helped these plants grow there?

Answer:

The seeds could be borne by wind, rain, and birds. As an example, birds may consume fruits and discharge their excreta elsewhere; the wind may carry seeds to gullies or holes.

Environmental factors that aided in the growth of the plants:

Water: Rain in monsoons left the cracks wet.

Sunlight: The wall has adequate sunlight, which can allow photosynthesis.

Soil or organic material: Small pieces of soil or decayed matter became stuck in crevices, where the seeds were then allowed to germinate.

Warmth: Warm temperatures favour seed germination and growth.

Q6: A city has recently cut down a large patch of forest to build new roads and buildings. Discuss the possible effects this could have on the local climate and biodiversity. How might this affect water availability or quality in the area?

Answer:

Local Climate:

• Deforestation decreases the amount of shade and moisture, leading to the elevation of local temperatures (urban heat).

• Reduced transpiration may imply reduced rainfall, and so the region may become drier.

• The decrease in the number of trees can also lead to an increase in air pollution through the inability of the leaves to absorb and trap CO2 and other pollution elements.

Biodiversity:

• Animals, birds, and insects cannot have their homes anymore; certain of them can disappear in the area.

• Specific plants found only within the forest can cease to exist.

• Food chains are disrupted (predators/prey lose food).

Water Availability/Quality:

• Fewer roots absorb the water, causing increased water run-offs, floods, and soil erosion.

• Rainwater does not get filtered by trees and soil, and therefore has a higher capability of bringing pollutants into rivers and lakes.

• The removal of shade can lead to the warming of small ponds/streams, and they will become unfriendly to aquatic life.

Q7: A friend says, “The Earth has always had climate changes in the past, so today’s global warming is nothing new.” How would you respond using what you’ve learnt in this and other chapters of your science book?

Answer:

Yes, the climate has changed in the past, but the rate of global warming now is far quicker, and mainly the fault of people changing the Earth by burning fossil fuels and cutting trees (deforestation). Previously, the climate transformations occurred during thousands or even millions of years. Today, though, temperatures have been rising very fast over the past century. Human activities introduce additional greenhouse gases, locking in more heat. Unlike natural changes, today, we can decrease the warming through reduced consumption of fossil fuels and increased protection of the forests. So, by not doing something, it could be far worse (damage to crops, rising seas, loss of biodiversity).

Q8: Imagine Earth’s magnetic field suddenly disappeared. What kinds of problems could arise for life on Earth? Explain.

Answer:

If Earth’s magnetic field disappeared:

• The abusive particles (solar wind and cosmic rays) of the outside space would approach the Earth in a more direct manner.

• There is a chance that the atmosphere would begin being removed, as is the case on Mars.

• More damaging UV and other radiation would get to the surface, which would pose more danger of DNA damage to the plants and animals, as well as cancers to humans.

• Solar storms would be able to damage the Grid and satellites more easily.

• Animals that depend on the magnetic field to migrate (e.g. some birds and turtles) would lose their way.

Generally, it would make the earth less safe, and it would be a danger to all other living creatures.

Q9: You are tasked with designing a new settlement for humans on Mars. Name three things you would need to recreate from Earth to support human life there. Which of these do you think is the hardest to replicate, and why?

Answer:

There are three things to recreate:

• An ambience in which there is sufficient oxygen and pressure.

• Water in liquid form, to drink and to use in farming.

• Blocking of radiation (such as a magnetic field or thick shielding).

Most difficult to replicate:

The atmosphere is the most difficult. The establishment of a stable, pressurised and breathable place that does not expose one to the harmful space radiation demands advanced technology and a lot of resources. It would also be very hard to sustain this artificial atmosphere over a long period of time on Mars.

Q10: In a village, the temperature has been increasing and rainfall has become unpredictable over the past few years. What could be causing this change? Suggest two ways the village could adapt to these new conditions.

Answer:

The change to this is mostly influenced by changes in climate change, which are a result of increasing greenhouse gases, deforestation or pollution.

Adaptation strategies:

• Water conservation: Create a rainwater harvesting infrastructure, store more water on rainy days, so it may be used in a later period.

• Plant crops which are drought-tolerant: Plant crops requiring less water or crops that can withstand longer dry spells.

• Additional thoughts: plant more trees to provide shade and rain, put mulch on the ground to protect the earth, or use efficient irrigation.

Q11. If there were no atmosphere on the Earth, would it affect life, temperature, and water on the planet? Explain.

Answer:

Yes--it would be impossible to live!

• Life: No Air to breathe; no shield against harmful sun and cosmic risky radiation; no weather.

• Temperature: It would be very hot during the day and extremely cold at night, like the Moon, due to the lack of an insulating blanket to keep the heat or to shield it from the Sun.

• Water: The Bulk of the liquid water would tend to boil very quickly and fly off into space, as there is no atmospheric pressure holding it down.

Q12. Discuss five examples of vegetative propagation.

Answer:

• Potatoes: New plants develop from the "eyes" (buds) on potatoes.

• Ginger: New plants can be produced by cutting the underground stem (rhizome) of ginger and planting it.

• Stem cuttings money plant: The small piece of the stem with several nodes is put in water or soil to make a new plant.

• Bryophyllum: Small complete plants grow out of the edges of a leaf and fall off to give rise to new plants.

• Onion: New bulbs develop in the vicinity of the main bulb, which is separable and growable.

Explanation:

All of these enable plants to grow by non-seed generation and are accurate replicas (clones) of the parent plant.

NCERT Solutions for Class 8 Science Chapter 13: Discover, design, and debate

Q1: Design an ‘Earth Survival Kit’. Imagine you’re building a tiny model of Earth for another planet. What must it have to support life, and why?

Answer:

If I’m making a model of Earth for another planet to support life, my “Earth Survival Kit” would contain:

• Air (Atmosphere): Includes the oxygen to breathe, the carbon dioxide to feed the plants and the nitrogen to keep things in check.

• Water: Water to drink and grow plants in, and to maintain the temperature.

• Soil: Rich in nutrients that will make plants grow.

• Light (sunlight or artificial): To give power and to assist plants in the manufacture of food by means of photosynthesis.

• Temperature regulation: Uncomfortable temperatures are not allowed in order to accommodate living things.

• Protective layer: Just like the ozone layer to block the harmful UV light, and a magnetic field to steer away the harmful space radiation.

Why?

All these will be essential since living organisms require air, water, and a good temperature, just like on Earth. Plants, animals, and humans cannot live without it.

Q2: India is planning for a challenging lunar mission, Chandrayaan-4, which will bring back samples of soil from the Moon. If the Moon had water, could plants grow in that soil? Think of some experiment that could help you explore whether plant growth is possible on the Moon.

Answer:

There may be possible plant growth in the soil of the Moon as long as it has water, which again remains unknown because the Moon soil is unlike the soil of the Earth; it may be nutrient-deficient and might even prove toxic to plants.

Experiment Idea:

• A couple of Moon soils (brought back by Chandrayaan-4) should be taken and kept in a pot.

• Put in a little water and put in a few seeds, such as mustard seeds or beans (they grow quickly).

• Place the pot in the sun and check on a daily basis.

• You should also plant the same seeds in the Earth's soil.

• Compare the growth, germination and health of plants in the different soils.

We can observe whether the plants will germinate and produce healthy roots, stems and leaves in Moon soil in the presence of water. Otherwise, possibly something needs to be added in terms of fertilisers or other nutrients.

Q3: Flowers are often brightly coloured and have a pleasant smell. How do you think these features help the plant reproduce?

Answer:

Bees, butterflies, birds, and other pollinating agents are attracted by the use of bright colours and pleasant aromas. When these creatures arrive to flowers in search of nectar, they take pollen and deposit it in other flowers, thus pollinating them. This assists the plant in bearing seeds and fruits to reproduce itself. Bright colours and fragrances act like a call to the pollinators!

Q4: Why do animals like fish and frogs lay hundreds or even thousands of eggs at a time, while other animals lay only a few? What might be the advantages and disadvantages of laying so many eggs?

Answer:

Fish and frogs lay lots of eggs at once because most won’t survive—many get eaten by other animals or don’t get the right conditions. By laying hundreds or thousands of eggs, they increase the chance that at least a few young will grow to adults.

Advantages:

More chances of survival, even if most eggs are lost.

Disadvantages:

The parents can’t protect all the eggs or babies, so most die. For animals that lay fewer eggs (like birds), they can take better care of their young, but if one is lost, it matters more.

Q5: Birds like sparrows build nests and care for their eggs and chicks, while reptiles like snakes usually lay their eggs and leave them without protection. How might this difference in parental care affect the chances of survival for the young ones in each case?

Answer:

Birds like sparrows protect, feed, and keep their eggs and chicks warm in nests, so more of their babies survive. Snakes and most reptiles just lay eggs and leave them, so the eggs are unprotected, and many get eaten or destroyed—only a few hatch and grow up.

So, parental care increases the chances that the young will survive. Without care, more eggs or babies are lost, but reptiles often lay more eggs to make up for it.

Our Home: Earth, a Unique Life Sustaining Planet Class 8 Science Chapter 13: Topics

Our home: Earth, a unique life-sustaining planet, Class 8 Science, Chapter 13 presents students with a unique life-sustaining planet, which is Earth. The chapter talks of the special environmental systems on our planet and the natural resources that the planet maintains as well, showing how there is a very fine balance that helps to support life. It also promotes the idea of conservation and sustainability.

13.1 Why Is Earth a Unique Planet?

Earth is special since there is no other planet that is known to be habitable. It possesses the right amount of temperature, atmosphere, and resources, which enable survival. It also stands out due to the presence of water, oxygen and proper climate.

13.2 What Do the Planets of Our Solar System Look Like?

Each planet in the solar system is of a different size, colour, surface and atmosphere. For instance, Mercury is covered in rock and dust, Jupiter is a gas giant with tempests and Saturn has the lovely rings. Comparing them to the Earth points out why our planet is unique.

13.3 What Makes the Earth Suitable for Life to Exist?

The conditions of earth make it an ideal habitat to lives. These are its location in the solar system, moderate size, and natural protective qualities.

13.3.1 Position of the Earth

Earth is in the Goldilocks zone, not too near to the Sun, or too far, where moderately cool temperatures can be sustained on the planet, enabling the liquid water.

13.3.2 Size of the Earth

The size ensures adequate gravity to hold the atmosphere and allow a stable surface environment.

13.3.3 Magnetic field of the Earth

The magnetic field shields the planet from harmful solar radiation and cosmic rays, making it safer for life forms.

13.4 What Allows Life to Be Sustained on Earth?

Earth provides all the essential components to sustain life in a balanced manner.

13.4.1 Air, water, and sunlight

Air that contains a high amount of oxygen, numerous water sources and sunlight for photosynthesis are what survival depends on.

13.4.2 Soil, rocks, and minerals

Soil, rocks and minerals supply plants, animals, and people with food, resources.

13.4.3 Plants, animals, and microorganisms

All life forms have a role to play in creating an ecological balance and help each other by using food chains.

13.4.4 The importance of balance

A necessary balance between natural resources and the consumption of such resources is vital to maintain stability in ecosystems.

13.5 What Keeps Life from Disappearing?

Life continues on Earth because of the ability of organisms to reproduce and adapt.

13.5.1 Asexual reproduction

Asexual reproduction involves the production of offspring by a single organism without requiring the other organism to procreate to make a new organism, which means that the population grows fast.

13.5.2 Sexual reproduction

Sexual reproduction is the form that involves two parents, thus resulting in genetic variety, which aids in the adaptation of species to dynamic environments.

13.6 What Are the Threats to Life on Earth?

NCERT Solution for Class 8 Chapter Our Home: Earth, a Unique Life Sustaining Planet Overview

Chapter Thirteen, titled "Our Home: Earth, a Unique Life Sustaining Planet," attempts to explain why Earth is the only known planet sustaining life. Foremost is Earth's favoured distance from the Sun, the availability of water, atmosphere, gravity, and magnetic field. The chapter of NCERT Solution for class 8 science essentially lays out how natural systems-breathing air, flowing water, living soil, and living organisms-cooperate to foster life. It continues to the reproduction methods of plants and animals and how they perpetuate and diversify life. Last, the chapter warns of threats like climate change and pollution, thereby stressing the importance of maintaining Earth's balance for future generations.

Approach to Solve the Questions of Class 8 Science Chapter 13

The questions in Class 8 Science Chapter 13: Our Home: Earth, a Unique Life-Sustaining Planet, can be solved effectively by first reading the chapter before attempting the remaining steps that include understanding important concepts like the atmosphere on Earth, water availability, the presence of oxygen, and how these aspects sustain life. Concentrate on the natural systems such as the biosphere, hydrosphere, and the significance of the ozone layer. However, as you answer questions, attempt to take responses back to real-life examples where situations like climate change, pollution and conservation measures can be inspiring examples. Practising and revising objective as well as descriptive questions after exercises and example problems will also assist in the achievement of accuracy and confidence.

Chapter-wise NCERT Solutions of Class 8 Science

NCERT Solutions Class 8 Science is a comprehensive, correct and simple solution to all the textbook questions on each and every chapter based on the newest syllabus. These chapter-wise links make the students find solutions easily, do revision faster and develop a grip of the major concepts of science.