The World of the Living (VI–VIII) • Topic 5 of 5

Ecosystem, Health & Nutrition

This topic ties the living world together and brings in human health, both heavily tested. In an ecosystem, energy flows along a food chain: producers (green plants, which make their own food) -> primary consumers (herbivores) -> secondary consumers (carnivores/omnivores) -> and decomposers (bacteria and fungi) that break down dead matter and return nutrients to the soil. A simple chain to remember: grass -> grasshopper -> frog -> snake -> eagle. The arrow always points in the direction the energy/food flows (from the eaten to the eater). Many interconnected food chains make a food web. On nutrition and health, know the components of a balanced diet — carbohydrates and fats give energy, proteins build the body (the 'body-building' nutrient), vitamins and minerals protect it, plus roughage (dietary fibre) and water. Deficiency diseases are exam favourites: lack of vitamin C causes scurvy, vitamin D/calcium deficiency causes rickets, vitamin A deficiency causes night blindness, lack of iron causes anaemia, and lack of iodine causes goitre. Communicable diseases spread from person to person (through air, water, food or vectors like mosquitoes). The pedagogy angle: health and ecosystems are best taught through real surveys, charts of local food habits and a nature walk, building attitudes and habits — not by rote-learning lists. The misconception to correct: children read a food-chain arrow backwards (thinking the arrow points to what an animal eats). How it is tested: complete a food chain, identify producer/consumer/decomposer, or match a deficiency disease to its nutrient.

✅ Solved examples

1. In the food chain Grass -> Grasshopper -> Frog -> Snake, what is the role of the grass?
The grass is the producer. Green plants make their own food by photosynthesis and form the first link (the base) of every food chain.
2. A child suffers from bleeding gums and is found to lack vitamin C. Which deficiency disease is this?
Scurvy, caused by a deficiency of vitamin C (found in citrus fruits like oranges and lemons).
3. Organisms such as bacteria and fungi that break down dead plants and animals and return nutrients to the soil are called:
Decomposers. They recycle nutrients back into the ecosystem and are essential to the cycle of matter.
4. Which nutrient is mainly responsible for the growth and repair of the body (the 'body-building' food)?
Proteins. Carbohydrates and fats supply energy, while proteins build and repair body tissues. (Pulses, eggs, milk and fish are protein-rich.)

✏️ Practice — try these, take hints as needed

1. In a food chain, in which direction does the arrow point — towards the organism that is eaten, or towards the one that eats?
It follows the flow of energy/food.
From the eaten to the eater.
Towards the organism that eats (the direction energy flows)
2. Deficiency of which mineral in the diet causes anaemia?
Needed to make haemoglobin.
Found in green leafy vegetables and jaggery.
Iron
3. Many interconnected food chains in a habitat together form a:
Not a single chain.
Looks like a net.
Food web
4. Name the deficiency disease caused by a lack of iodine in the diet.
Swelling of the neck/thyroid.
Prevented by iodised salt.
Goitre

📝 Topic test — 8 questions

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