12. How Nature Works in Harmony

Answer: (iii) An ecosystem is part of a community.

It is the other way round. A community is a part of an ecosystem. A population is a part of a community.

Changes:

• Dead plants, dead animals and animal wastes would pile up everywhere.
• Nutrients locked in them would not return to the soil.
• The soil would become less fertile, and plants would not grow well.
• With fewer plants, herbivores and then carnivores would also decrease.

Why decomposers are essential: decomposers such as bacteria and fungi break down dead matter into simple substances. They return nutrients to the soil and clean the environment. So they keep the cycle of nutrients going in an ecosystem.

• Mangrove trees grow thickly along the coast. Their dense, tangled roots and trunks act like a natural wall.
• They slow down strong waves and reduce their force before the water reaches the village.
• Their roots hold the soil firmly and prevent the coast from being washed away.

So mangroves act as a natural barrier against tsunamis, cyclones and storm waves. That is why we must protect them.

• Grasshoppers will increase. Frogs eat grasshoppers. Without frogs, nobody eats them, so their number grows.
• Snakes will decrease. Snakes eat frogs. Without frogs, snakes lose their food, so their number falls.

Possible reasons:

• Flowering plants that give nectar were removed or reduced.
• Pesticides were sprayed in the garden.
• Host plants on which butterflies lay eggs were cut down.
• Changes in weather, such as more heat or less rain.

Steps to bring back butterflies:

• Plant nectar-giving flowers like marigold, ixora and lantana.
• Grow host plants such as curry leaf, lemon and milkweed.
• Stop using chemical pesticides.
• Keep a shallow dish of water or a wet patch of soil.

• Without decomposers, dead plants would pile up. Nutrients would not return to the soil. Soon the producers would not get nutrients to grow.
• Without consumers, there would be no control on the growth of plants, and no flow of energy to other levels.

An ecosystem works only when producers, consumers and decomposers all interact with each other and with the non-living components.

Park:

• Living: trees, grass, shrubs, flowers, birds, squirrels, butterflies, ants, earthworms, people.
• Non-living: soil, water, sunlight, air, stones, benches.

Roadside:

• Living: a few trees, weeds, crows, pigeons, stray dogs, people.
• Non-living: road, dust, smoke, vehicles, buildings, garbage.

Difference: the park has many more kinds of plants and animals, and has cleaner air and soil. The roadside has fewer living things because of traffic, pollution and less green cover.

Agricultural fields are necessary because they give us food, fibre and income for farmers.

But overuse of chemical fertilisers and pesticides harms the soil, water and useful insects. Excess water use and clearing forests also damage nature.

To make them sustainable, we can:

• use organic manure and compost,
• practise crop rotation and mixed cropping,
• use drip irrigation to save water,
• protect pollinators like bees and birds.

This way, fields keep producing food without harming the environment for future generations.

• Fox: the hare is its food. The fox population will decrease, or foxes may hunt other animals more.
• Grass and plants: fewer hares eat them. So they may increase.
• Deer: more grass is available for deer. So deer may increase.
• Eagle: with more deer available, it may not be affected much.