SPI Biology · Free notes

Ecology and Environment: SPI Biology

Ecology and Environment has 7 questions in the SPI bank, and one is from the 2022 paper: the threatened category of the red panda. Only three are EASY. Three are MODERATE and one is HARD, so this is one of the harder Biology chapters even though it is short. The marks are lost on exact definitions: what a food chain contains, which pyramid can stand on a narrow base, and which category a shrinking species belongs to. Learn each definition in the book's own words.

The handout has every subtopic, worked example, formula and trap with answers shown. The formula sheet is the chapter’s formulas and traps alone, on one page.

SPI home All formulas on one page

Subtopic notes

Formula & revision sheet

1 formulas · 4 reference tables · 7 gotchas across all subtopics — the exam-eve cheat-sheet

Ecosystems and Food Chains

Formulas (1)

The ten percent law of energy flow · Energy at the next level $E_{\text{next}} = \frac{10}{100} \times E_{\text{this}}$

Reference tables (2)

The parts of an ecosystem4 rows

Component	Living or not	Examples
Producers	Living	Grass, trees, algae
Consumers	Living	Deer, frog, lion
Decomposers	Living	Bacteria, fungi
Abiotic factors	Non-living	Air, water, soil, sunlight An ecosystem includes the non-living part too, not living things alone.

Food chains, trophic levels and pyramids4 rows

Trophic level	Name	Example (grassland)	Example (pond)
First	Producer	Grass	Phytoplankton
Second	Herbivore (primary consumer)	Grasshopper	Small crustaceans
Third	Carnivore (secondary consumer)	Frog	Small fish
Fourth	Top carnivore	Snake	Large fish Decomposers are not a level in the chain.

The pyramid of energy is always upright; a pond's pyramid of biomass can have a narrow base.

Watch out for (4)

An ecosystem as living things only
→ The parts of an ecosystem
Putting decomposers in the chain
→ Food chains, trophic levels and pyramids
Every pyramid is upright
→ Food chains, trophic levels and pyramids
Mixing up the 1% and the 10%
→ The ten percent law of energy flow

Waste and Wildlife Conservation

Reference tables (2)

Biodegradable and non-biodegradable waste4 rows

Waste	Kind	Why
Fruit and vegetable peels	Biodegradable	Microbes break them down
Paper	Biodegradable	Microbes break it down
Plastic plates and bags	Non-biodegradable	No microbe can break them down Plastic is avoided because it is non-biodegradable, not because it is light or toxic.
Glass bottles	Non-biodegradable	No microbe can break them down

Threatened species and migratory birds4 rows

Category	What it means	Example
Extinct	Found nowhere any more	Dodo
Endangered	On the verge of extinction	Bengal tiger
Vulnerable	Falling, likely to become endangered	One-horned rhinoceros
Rare	Numbers much declined, endemic, may vanish fast	Red panda, musk deer Endemic plus a sharp decline: that is the book's definition of rare.

Indeterminate has no fixed example: it is for species too little known to place.

Watch out for (3)

Taking a good habit for the harmful one
→ Biodegradable and non-biodegradable waste
Endangered for every shrinking species
→ Threatened species and migratory birds
Thinking winter migrants arrive in the middle of winter
→ Threatened species and migratory birds

Question weightage by concept

5 concepts · 7 questions — where the marks actually sit, so you know what to drill first

Ecosystems and Food Chains3 questions · 43%

Concept	Qs	Share
Food chains, trophic levels and pyramids	2	29%
The parts of an ecosystem	1	14%
The ten percent law of energy flowfoundation	—	—

Waste and Wildlife Conservation4 questions · 57%

Concept	Qs	Share
Biodegradable and non-biodegradable waste	2	29%
Threatened species and migratory birds	2	29%

Test yourself on a real paper

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