🐱 Cats in the Ecosystem!
Alishba, cats are obligate carnivores — they MUST eat meat to survive. In a food chain, a cat is a secondary consumer (grass → mouse → cat). Domestic cats are actually one of the most impactful invasive predators on the planet — outdoor cats in the US catch an estimated 1–4 billion birds per year! That is ecology in action: one species affecting entire populations.
✏️ Worked Example — Read This First!
In a food chain: grass → grasshopper → frog → hawk. If grass contains 10,000 kcal of energy, how much energy is available to the hawk?
1
Apply the 10% rule.
Only about 10% of energy is transferred from one trophic level to the next. The rest is lost as heat through cellular respiration.
Only about 10% of energy is transferred from one trophic level to the next. The rest is lost as heat through cellular respiration.
2
Calculate each level.
Grass (producer): 10,000 kcal.
Grasshopper (primary consumer): 10,000 × 0.10 = 1,000 kcal.
Frog (secondary consumer): 1,000 × 0.10 = 100 kcal.
Hawk (tertiary consumer): 100 × 0.10 = 10 kcal.
Grass (producer): 10,000 kcal.
Grasshopper (primary consumer): 10,000 × 0.10 = 1,000 kcal.
Frog (secondary consumer): 1,000 × 0.10 = 100 kcal.
Hawk (tertiary consumer): 100 × 0.10 = 10 kcal.
3
State the answer.
The hawk receives only 10 kcal out of the original 10,000 kcal.
The hawk receives only 10 kcal out of the original 10,000 kcal.
The hawk gets 10 kcal. Only 0.1% of the original energy reaches the top predator.
💡 Why this matters: This is why top predators (hawks, lions, sharks) are always rare — there simply is not enough energy at the top of the food chain to support large populations.
EasyQuestions 1–3
Question 1 EasySee Answer →
Define: ecosystem, biome, habitat, niche, population, community, biosphere. Arrange these in order from smallest to largest scale.
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Question 2 EasySee Answer →
What is the difference between a food chain and a food web? Why is a food web a more realistic model of an ecosystem? Describe a simple food web with at least 5 organisms.
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Question 3 EasySee Answer →
What is the difference between producers, primary consumers, secondary consumers, and decomposers? Give one example of each.
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MediumQuestions 4–7
Question 4 MediumSee Answer →
Describe the carbon cycle. Name FOUR processes that release carbon dioxide into the atmosphere and TWO processes that remove it.
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Question 5 MediumSee Answer →
What is the difference between a predator-prey relationship, mutualism, commensalism, and parasitism? Give one example of each type of ecological relationship.
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Question 6 MediumSee Answer →
What is population dynamics? Explain carrying capacity (K). Describe the shape of a logistic growth curve vs. an exponential growth curve. What causes the levelling off in logistic growth?
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Question 7 MediumSee Answer →
What is biodiversity? Why is biodiversity important for the stability of ecosystems? Name THREE human activities that reduce biodiversity.
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HardQuestions 8–10
Question 8 HardSee Answer →
Explain primary and secondary succession. How does a bare rock eventually become a forest? Name the stages and the concept of a climax community. Give a real-world example of each type of succession.
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Question 9 HardSee Answer →
Explain the greenhouse effect and global warming. a) What gases cause the greenhouse effect? b) What is the NATURAL greenhouse effect and why is it necessary for life? c) How have human activities enhanced the greenhouse effect? d) Name THREE consequences of enhanced global warming.
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Question 10 HardSee Answer →
A population of rabbits in a field is being monitored. In Year 1: population = 200. In Year 2: population = 240. a) What is the rate of growth? b) If this continues exponentially, what will the population be in Year 5? c) In reality, the population levels off at 350. What is the carrying capacity? d) What factors might limit population growth to reach carrying capacity?
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🌟 Great work, Alishba!
You are now seeing the big picture of life — how every organism is connected to every other through food webs, nutrient cycles, and the environment. Even your cat at home is part of a complex ecosystem! Tomorrow: the final topic — Body Systems!