How Nature Works in Harmony — NCERT Solutions

Concept: An ecosystem requires the continuous flow of energy and cycling of nutrients among producers, consumers, and decomposers.

Reasons why an ecosystem cannot survive with only producers:

1. Accumulation of dead matter: Producers (plants) eventually die. Without decomposers (bacteria and fungi), dead plant matter would accumulate and not be broken down. Nutrients locked in dead matter would never be returned to the soil.

2. Nutrient depletion: Plants absorb nutrients (like nitrogen, phosphorus, potassium) from the soil. Without decomposers to recycle nutrients from dead matter back into the soil, the soil would become nutrient-poor over time, and plants themselves would stop growing.

3. Disruption of nutrient cycles: Important cycles like the carbon cycle and nitrogen cycle depend on decomposers to break down organic matter and release nutrients. Without them, these cycles would be incomplete.

4. No energy flow beyond the first trophic level: Energy flows from producers → consumers → decomposers. Without consumers, energy captured by producers through photosynthesis would not flow through the ecosystem. The ecosystem would be energetically incomplete.

5. Overgrowth and competition: Without consumers to feed on plants, plant populations would grow unchecked, leading to intense competition for sunlight, water, and soil nutrients, eventually causing the collapse of even the producer population.

6. Pollination disruption: Many producers depend on animal consumers (bees, butterflies, birds) for pollination and seed dispersal. Without consumers, reproduction in many plants would fail.

Conclusion: An ecosystem is a complex, interdependent system. Producers, consumers, and decomposers each play a unique and essential role. The absence of any one group breaks the flow of energy and cycling of nutrients, making the ecosystem unsustainable. All three components are necessary for an ecosystem to function and maintain balance.

Given: Two ecosystems to be observed and compared — a Park and a Roadside.

(Note: This is an observation-based activity. A sample answer is provided below. Students should record their own actual observations.)

Observations:

Ecosystem 1: Park

Ecosystem 2: Roadside

How the two ecosystems are different:

Conclusion: A park is a more balanced and diverse ecosystem compared to a roadside. The park supports greater biodiversity and has healthier abiotic conditions. The roadside ecosystem is degraded due to pollution, habitat loss, and human interference. This comparison shows how human activities affect the quality of ecosystems.

Statement: Human-made ecosystems like agricultural fields are necessary, but they must be made sustainable.

I agree with this statement. Here is a detailed explanation:

Why human-made ecosystems are necessary:

1. Food security: With a growing population, agricultural fields are essential to produce enough food (grains, vegetables, fruits) to feed billions of people.
2. Livelihood: Farming is the primary livelihood for a large section of India's population.
3. Economic importance: Agriculture contributes significantly to India's economy through domestic consumption and exports.
4. Meeting human needs: Human-made ecosystems like fish ponds, orchards, and parks also provide food, recreation, and environmental benefits.

Why they must be made sustainable:

1. Overuse of synthetic chemicals: Excessive use of synthetic fertilisers and pesticides degrades soil health, pollutes water bodies, and harms beneficial organisms like earthworms, bees, and frogs.
2. Monoculture farming: Growing only one type of crop repeatedly on the same land depletes specific soil nutrients, reduces biodiversity, and makes crops more vulnerable to pests and diseases.
3. Groundwater depletion: Excessive irrigation extracts groundwater faster than it can be replenished, leading to water scarcity.
4. Loss of biodiversity: Clearing natural habitats for farmland destroys the homes of many species, reducing biodiversity.
5. Long-term productivity: Unsustainable practices reduce soil fertility over time, threatening future food production.

How to make agriculture sustainable:

• Use organic fertilisers (compost, vermicompost) instead of synthetic ones.
• Practice crop rotation and mixed cropping to maintain soil health.
• Use biological pest control (natural predators) instead of chemical pesticides.
• Adopt rainwater harvesting and drip irrigation to conserve water.
• Maintain hedgerows and natural vegetation around farms to support pollinators and beneficial insects.
• Follow traditional/indigenous farming practices that are eco-friendly.

Conclusion: Human-made ecosystems like agricultural fields are indeed necessary for human survival. However, if managed unsustainably, they cause long-term damage to the environment and human health. By adopting eco-friendly and sustainable farming practices, we can meet our food needs while also protecting the natural environment for future generations. This balance between human needs and ecological health is the essence of sustainable development.

Given: The Indian hare population drops significantly due to a disease.

Concept: In a food web, organisms are interconnected through feeding relationships. A change in the population of one organism causes a cascading effect on others.

Typical food chain/web involving the Indian hare:
$$\text{Grass/Plants} \rightarrow \text{Indian Hare} \rightarrow \text{Fox / Leopard / Eagle / Snake}$$

Effects on other organisms:

1. Effect on Producers (Grass and Plants):

• Hares eat grass and plants. With fewer hares, less grass will be consumed.
• As a result, the population of grass and plants will increase initially.

2. Effect on Predators (Fox, Leopard, Eagle, Snake — organisms that eat hares):

• Hares are an important food source for predators like foxes, leopards, eagles, and snakes.
• With fewer hares available, these predators will face food scarcity.
• Their populations will decrease due to starvation or they may shift to hunting other prey.

3. Effect on other prey organisms (e.g., mice, squirrels, other small animals):

• Since predators (foxes, eagles, snakes) now have less food (hares), they may increase their predation on other prey like mice and squirrels.
• This could cause a decline in the populations of these alternative prey organisms.

4. Effect on the overall ecosystem balance:

• The reduction in hares disrupts the balance of the food web.
• Overgrowth of vegetation (due to fewer hares eating plants) may lead to competition among plants.
• Decline in predator populations may eventually allow other prey populations to grow unchecked.

Summary:

Conclusion: The decline of the Indian hare population due to disease would have far-reaching effects throughout the ecosystem. This demonstrates that every organism, no matter how small, plays a vital role in maintaining the balance of an ecosystem. The interconnected nature of food webs means that a change in one population affects many others — a concept known as a trophic cascade.