NCERT Solutions Curiosity Chapter 13 –227End-of-chapter questions — Keep the curiosity alive

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

Why the others are wrong:

• (i) Volcanoes are not what makes a planet uninhabitable — Earth has plenty of them.
• (ii) Mars is farther from the Sun than Earth, not closer; it lies at the outer edge of the habitable zone.
• (iv) A strong magnetic field is a protection, not a problem — and Mars's problem is that it lacks the protection Earth's field provides.

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

Why the others are wrong: (i) and (iv) describe the variety of living things, which is biodiversity. (iii) describes changing weather, which belongs to the atmosphere, not to the solid Earth.

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

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

Why the others are wrong: Climate and food can affect how an individual grows, but they are not what is inherited. And (iii) is simply not how genes work — the instructions are received at the moment the gametes join, not acquired afterwards.

The seeds were almost certainly carried there — most likely by birds, and some by the wind.

How they arrived. When birds or animals eat fruits, the seeds are dropped far from the parent plant. The chapter's own example is a banyan seed, dropped by a bird that ate the fruit and excreted the seed, sprouting in a crack in a wall after the rains. Light seeds of grasses and ferns can also be blown into a crack by the wind, and spores may be washed down by rain.

Why they could grow there. A crack after the monsoon happens to supply everything a germinating seed needs:

• Water — rainwater collects in the crack and the shade keeps it from drying out quickly.
• Air — the crack is open, so oxygen reaches the seed.
• A little soil — dust, bits of leaf and droppings collect in the crack and supply nutrients.
• A stable anchorage — the narrow gap grips the seed so it is not washed away.
• Sunlight — available as soon as the first leaves open.

Removing a forest does not remove one thing — it breaks several links at once, and the effects reach the climate, the living community and the water.

Effect on the local climate.

• Trees release large amounts of water vapour into the air. With the trees gone there is less vapour, so fewer clouds form and local rainfall tends to fall.
• Shade is replaced by roads and buildings, which absorb and hold heat, so the area becomes hotter.
• The forest was absorbing carbon dioxide as it grew. That absorption stops, adding to the greenhouse gases in the air.

Effect on biodiversity. When natural habitats are destroyed, plants and animals may disappear, upsetting the ecosystem. Following Chapter 12: if the plants that herbivores eat vanish, deer and insects struggle to survive; without herbivores, predators lose their food too. Every type of living thing has a role, and losing even a few weakens nature's ability to support life.

Effect on water availability and quality.

• Availability: roots and leaf litter used to slow the rain so it could soak in and refill groundwater. On bare ground and concrete the same rain runs straight off, so wells and springs get less. Less rainfall makes this worse.
• Quality: with no roots holding it, soil is washed into streams — the water becomes muddy. Run-off from roads and construction carries oil, dust and waste with it, and there is no longer any vegetation to filter it.

Your friend is right about the first half and wrong about the conclusion. The Earth's climate has changed before — but what is happening now differs in its cause and in its speed.

1. The cause is different. The chapter is specific about where today's extra heat comes from. Burning fossil fuels like coal and oil releases greenhouse gases such as carbon dioxide and methane, which trap more of the heat the Earth gives off. Normally trees, plants and even tiny ocean planktons absorb carbon dioxide as they grow and Earth keeps a balance. But burning fossil fuels releases carbon that has been locked underground for millions of years, and the Earth cannot absorb it fast enough — so the heat builds up.

2. The speed is different. Past changes generally unfolded over very long periods. That matters because adaptation, as this chapter explains, works through reproduction over many generations. A change that arrives faster than species can adapt to it leads to their disappearance rather than their adjustment.

3. What is at stake now is a system we depend on. Even a small increase in temperature can melt ice caps, raise sea levels which could flood many coastal cities, cause extreme weather, and lead to many plants and animals disappearing. Together with biodiversity loss and pollution, this forms what the chapter calls the triple planetary crisis.

The shield that keeps high-energy particles away from the planet would be gone, and the damage would work its way inward, step by step.

1. Cosmic rays and the solar wind would reach the atmosphere directly. These tiny, high-energy particles come from far across the universe and from the Sun. At present the magnetic field pushes many of them away.
2. The atmosphere would be damaged and the ozone layer reduced. That is the specific harm the chapter names.
3. More harmful ultraviolet rays would reach the surface. With a thinner ozone shield, UV rays that damage living cells would get through — harming skin and eyes, damaging crops, and affecting the plankton at the base of ocean food chains.
4. Over long periods the atmosphere itself could be stripped away, and with it the greenhouse warming that keeps water liquid.

Everyday technology would suffer too — compasses would no longer point north, and the particle storms from the Sun would disturb satellites and communications.

The three I would recreate:

The hardest to replicate: protection from radiation.

What could be causing it. These are exactly the signs the chapter describes as climate change — long-term changes in temperature, rainfall and weather patterns. Two kinds of cause are likely to be acting together:

• Global: greenhouse gases released by burning fossil fuels trap more of the heat the Earth gives off, and the resulting global warming changes weather patterns everywhere — including the timing and amount of rainfall.
• Local: if trees around the village have been cut for fields, fuel or building, less water vapour enters the air and the bare ground heats up more. Both make the village hotter and its rain less dependable.

Two ways the village could adapt.

1. Harvest and store the rain when it comes. Repair the village pond, build check dams across the seasonal stream, and add rooftop rainwater harvesting with recharge pits. If the rain is unpredictable, the answer is to hold on to it when it does fall instead of letting it run off.
2. Change what is grown and how. Shift part of the land to crops that need less water and tolerate heat — millets such as bajra and jowar, and pulses — and water them with drip irrigation rather than flooding the field. Mulching the soil and planting shade trees along the field boundaries reduce evaporation and cool the ground.

Yes — and in each of the three ways the question names. The atmosphere is not just something we breathe; it is what keeps the other two possible.

Life. There would be no oxygen for respiration, and no carbon dioxide for plants to use in photosynthesis. There would also be no ozone layer, so harmful ultraviolet rays from the Sun would strike the surface directly and damage living cells. Life as we know it could not exist.

Temperature. Without an atmosphere there would be no greenhouse effect. The Earth would radiate its heat straight out to space and become too cold, and with nothing to spread the heat around, the sunlit side would be scorching while the dark side froze.

Water. This is the part that surprises people. With no atmosphere there is no air pressure holding water down, so liquid water at the surface would boil away into space; whatever remained would freeze in the cold. And there would be no water cycle at all — no evaporation into air, no clouds, no rain or snow, so rivers, lakes and groundwater would never be refilled.

Vegetative propagation is asexual reproduction in plants: a leaf, stem or root of the parent grows into a whole new plant. Five clear examples, each using a different part:

Other examples worth adding: onion and garlic from bulbs, sweet potato and dahlia from roots, banana from suckers, and grass and mint from runners.