Probe and Ponder (Page 288)
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How might the loss of forest cover and changes in rainfall patterns lead to elephants to enter human farms and villages?
Loss of forest cover and dry waterholes mean elephants lack food and water in their natural habitat, forcing them to wander into nearby human settlements and farms in search of resources like sugarcane and bananas.
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Imagine you are a tree in a dense forest. What kind of relationships would you have with water, sunlight, other animals, and other components of the forest?
As a tree, I would rely on sunlight, water, and soil nutrients to make food and grow. I would provide shelter and food for animals and birds, help retain soil moisture, and release oxygen for other organisms to breathe.
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Do you think the Earth can thrive without humans? Can humans survive without the earth?
Earth can thrive without humans because nature maintains its own balance through complex, interconnected ecosystems. However, humans cannot survive without Earth, as we depend entirely on ecosystems for fresh air, water, food, and other resources.
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If two kinds of birds compete for the same fruit, how might their way of living change over time?
Competition helps control population size. Over time, the birds might adapt by feeding at different times of the day, finding alternative food sources, or moving to different areas to reduce competition and coexist.
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Can human actions cause natural disasters?
Yes, human actions like deforestation, over-extraction of groundwater, and pollution disrupt the natural ecosystem balance, which can worsen or trigger events like floods, droughts, and soil erosion.
Activity 3.1: Let us explore (Page 290 - 292)
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List the living beings and non-living things that you observe in these habitats. Record your observations in Table 3.1
Pond Forest Living beings Non-living things Living beings Non-living things Fish, frogs, snakes, lotus, algae Water, sunlight, soil, air Trees, grass, birds, rodents, insects Soil, rocks, sunlight, air, temperature
Activity 3.2: Let us record (Page 294)
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Can a habitat have only one type of living organism? What might happen then?
No, a habitat cannot sustainably have only one type of living organism. If all organisms were the same, they would have the exact same requirements for food, water, and space, leading to extreme competition, resource scarcity, and eventually an imbalance threatening their survival.
Activity 3.3: Let us record (Page 298)
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Think of a reason for these observations. Compare the number of dragonflies, bees, and butterflies in both the ponds. Do you find any relationship between the number of dragonflies and bees/butterflies? What does this study show? How does the population of fish in a pond affect the seed production in nearby plants?
Fish eat dragonfly larvae, so Pond A has fewer dragonflies. Since dragonflies eat bees and butterflies, fewer dragonflies allow more bees and butterflies to survive around Pond A. More bees and butterflies lead to better pollination of nearby flowers, increasing seed production. This study shows how biotic and abiotic components are highly interconnected.
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Similarly, can overfishing by humans change this balance? How do you think it may affect the living and non-living parts of the habitat?
Yes, overfishing removes a key predator. Without fish, dragonfly larvae would increase, leading to a drop in pollinators (bees/butterflies). This would reduce plant pollination and seed production, ultimately disrupting the entire community's food web and the habitat's overall balance.
Activity 3.4: Let us relate and identify (Page 300 - 302)
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Record your observations in Table 3.3 at the appropriate places.
Criterion 1: Interactions between biotic and abiotic components Criterion 2: Interaction between two abiotic components Criterion 3: Interaction among the biotic components Earthworms live in moist soil. The day temperature is high due to the bright sunlight. A frog eats insects. Many microbes are present in the pond. Water is evaporating fast due to the sunlight. A water snake eats fish. Plants absorb sunlight and carbon dioxide to make food. Air current is blowing slowly on the water surface creating gentle waves. Frogs and fish may compete for small insects larvae. A fish lays eggs in water. The soil near the pond is moist. A fish lays eggs in water near vegetation to protect them from other fish or frogs.
Activity 3.5: Let us classify (Page 304 - 306)
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Record your observations in Table 3.4 by identifying whether each organism feeds only on plants and plant products, only on animals, or on both.
Name of the organism Performs photosynthesis Feeds on plants and plant products Feeds on animals Feeds on both plants and/or animals Deer No Grass and leaves of plants No Only on plants Horse No Grass and grain No Only on plants Vulture No No Dead animals Only on animals Bengal Fox No Fruits, berries Insects, mice Feeds on both Bird (Shikra) No No Small birds, mice Only on animals Squirrel No Nuts, seeds, fruits No Only on plants Mouse No Seeds, grains Small insects Feeds on both Mushroom No No No Feeds on dead organic matter Tree Yes No No Makes its own food -
How do plants get their food?
Plants make their own food through the process of photosynthesis using sunlight, carbon dioxide, and water. Thus, they are called producers or autotrophs.
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List the heterotrophs from Table 3.4.
Deer, Horse, Vulture, Bengal Fox, Bird (Shikra), Squirrel, Mouse, and Mushroom.
Activity 3.6: Let us link (relate) (Page 308)
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Which is another food chain that can be drawn for the organisms given in this activity?
Grass → Hare → Fox.
Activity 3.7: Let us draw (Page 308)
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Count the number of each type of organism in Fig. 3.10(a). Make a table and set a number in the table against each of the organisms. Place the mouse, millet, and eagle appropriately in Fig. 3.10(b).
The millet plants are the highest in number, mice are fewer, and the eagle is the lowest in number. In the pyramid, the millets (producers) are placed at the wide base, the mice (herbivores/primary consumers) in the middle tier, and the eagle (carnivore/top consumer) at the narrow top.
Activity 3.8: Let us trace and link (Page 310)
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How many other organisms might be connected to one organism through a feeding relationship in an ecosystem?
One organism can be connected to multiple other organisms. For example, a single plant species might be eaten by grasshoppers, mice, and rabbits, while a mouse could be eaten by a fox, hawk, or owl.
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Are these food chains interlinked?
Yes, in an ecosystem, food chains are heavily interlinked with each other to form a complex network known as a food web.
In-text Questions (Page 310 - 318)
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Does nature really waste anything?
No, in nature nothing is wasted. Organisms like fungi and bacteria (decomposers) break down dead plants, animal matter, and waste into simpler substances, returning important nutrients back to the soil to be reused by plants.
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What happens when we intervene in nature? (Based on Activity 3.9)
Intervening disrupts the natural balance. For example, over-harvesting frogs led to a rise in agricultural pests. This forced farmers to use synthetic pesticides, which harmed soil, water quality, and human health.
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Based on the example given in Fig. 3.16, what do you observe?
Organisms engage in different types of interactions: Mutualism where both benefit (bees and flowers), Commensalism where one benefits without affecting the other (orchids on trees), and Parasitism where one benefits while harming the other (ticks on dogs).
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Can you name any human made ecosystem in your area?
Examples of human-made ecosystems include agricultural farms, fish ponds, botanical gardens, and urban parks.
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How do these practices harm both the environment and human health? (Green Revolution farming practices)
Overuse of synthetic chemicals, excessive groundwater extraction, and monoculture farming lead to soil degradation, pollution of water bodies, loss of beneficial microorganisms, and potential health hazards from pesticide residues in food.
Activity 3.10: Let us survey (Page 320 - 322)
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What inference do you draw from your interactions with farmers?
Synthetic fertilizers and pesticides initially boost production, but long-term overuse reduces soil fertility by destroying humus and friendly microbes. It also harms natural predators, leading to increased pest populations and making farming unsustainable over time.
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Based on your learning, what practices do you think can help farmers protect the soil, the environment, and our food security for the future?
Farmers can adopt sustainable methods like organic farming, using natural compost and manure (like Kunapa Jala), practicing crop rotation, avoiding monoculture, and reducing dependence on synthetic fertilizers and pesticides.
Keep the curiosity alive (Page 326 - 328)
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1. Selvam from Cuddalore district, Tamil Nadu, shared that his village was less affected by the 2004 Tsunami compared to nearby villages due to the presence of mangrove forests. This surprised Sarita, Shabnam, and Shijo. They wondered if mangroves were protecting the village. Can you help them understand this?
Mangrove forests act as natural physical barriers along the coast. Their dense, strong root systems help slow down strong winds and absorb the immense energy of waves during storms and tsunamis, effectively protecting nearby inland villages from severe flooding and damage.
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2. Why is it not possible to have an ecosystem with only producers and no consumers or decomposers?
Without consumers, producers would overpopulate, exhaust abiotic resources (like space and nutrients), and eventually die off. Without decomposers, dead plant matter would accumulate, and essential soil nutrients would not be recycled, causing the ecosystem to permanently collapse.
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3. A farmer notices that his cow often has small birds (Cattle Egrets) sitting on its back. He observes that the birds are eating ticks and other parasites from the cow's skin. The cow does not chase the birds away and seems relieved. Which of the following explain the interaction between cow and birds?
Answer: C. Mutualism: Because the bird gets food (ticks) and the cow gets pest control (relief).
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4. A Farmer has used chemical fertilizers for many years. Now the soil holds less water, and gets washed away during rains. Explain how too much chemical fertilizer can reduce humus in the soil and lead to soil erosion.
Overusing chemical fertilizers kills friendly soil microorganisms and earthworms that are responsible for breaking down organic matter into humus. Humus acts like a glue that binds soil particles and holds moisture. Without it, the soil becomes loose and is easily washed away by rain, leading to erosion.
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5. Refer to the given diagram (Fig. 3.19) and select the wrong statement.
The wrong statement is: iii) An ecosystem is part of a community. (The correct relationship is that a community is a part of the larger ecosystem, which includes both biotic communities and abiotic factors).
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6. Observe two different places near your home or school (e.g., a park and a roadside). List the living and non-living components you see. How are the two ecosystems different?
Park: Living (trees, grass, butterflies, birds); Non-living (soil, sunlight, benches, sprinkler water).
Roadside: Living (weeds, ants, stray dogs); Non-living (asphalt, dust, exhaust fumes, concrete).
The park is a managed human-made ecosystem designed to support biodiversity and recreation, whereas the roadside is a highly disturbed environment with limited resources and high pollution, supporting fewer species. -
7. Look at this food chain: Grass → Grasshopper → Frog → Snake. If frogs disappear from this ecosystem, what will happen to the population of grasshoppers and snakes? Why?
If frogs disappear, the grasshopper population will rapidly increase because their primary predator is gone. The snake population will decrease or migrate away because their primary food source (frogs) is missing, breaking the energy flow in the food chain.
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8. 'Human-made ecosystems like agricultural fields are necessary, but they must be made sustainable.' Comment on the statement.
Agricultural fields are essential to produce enough food for the growing human population. However, they must be sustainable to prevent long-term environmental damage like soil degradation, water pollution, and loss of biodiversity, ensuring that the land remains fertile for future generations.
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9. A population is part of a community. If all decomposers suddenly disappear from a forest ecosystem, what changes do you think would occur? Explain why decomposers are essential.
If decomposers disappear, dead plants, animal bodies, and waste would pile up. The complex organic matter would not break down, meaning essential nutrients would not return to the soil. Eventually, plants would die from nutrient starvation, causing the entire forest food web to collapse.
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10. If the Indian hare population (Fig. 3.20) drops because of a disease, how would it affect the number of other organisms?
A drop in the hare population would decrease the food supply for their predators (like foxes and eagles), likely causing predator populations to decline. Conversely, the grass and plants that the hares eat would grow more abundantly due to reduced grazing pressure.
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11. In a school garden, students noticed fewer butterflies the previous season. What could be the possible reasons? What steps can students take to have more butterflies on campus?
Reasons: Increased use of chemical pesticides, pollution, or a lack of specific flowering plants and host plants needed for butterfly larvae.
Steps to take: Stop using synthetic pesticides, plant a diverse range of native nectar-rich flowers, and create an organic, sustainable herbal garden to naturally attract and support butterflies.
