SPI Biology · Ecology and Environment

Waste and Wildlife Conservation

Waste that microbes cannot break down piles up and harms the environment, and many wild species are shrinking in number and are sorted into categories by how threatened they are.

All Ecology and Environment notes

Why this matters

Four questions in the bank, two EASY and two MODERATE: why disposable plastic plates are a problem, which human habit harms the environment, the threatened category of the red panda and musk deer (from the 2022 paper), and the month Siberian cranes arrive in India. The 2022 question copies the Maharashtra Class 10 book's definitions word for word, so learn those.

Concept 1 of 2: Biodegradable and non-biodegradable waste

Peels and paper rot away because bacteria and fungi eat them. Plastic, glass and metal cans do not: no microbe can break them down, so they stay for hundreds of years.

Definition

Biodegradable: broken down by microbes. Vegetable peels, paper, cotton, wood, dung.
Non-biodegradable: not broken down by microbes. Plastic, polythene, glass, metal cans, DDT.
Non-biodegradable waste piles up, chokes drains and soil, and harms animals that swallow it.
Good habits: segregate waste into the two kinds, reuse utensils instead of disposable ones, carry cloth bags, use less of the CFCs that thin the ozone layer.
Bad habits: excessive use of disposable plates, cups and plastic bags; burning plastic.

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

Practice this conceptself-check · 4 quick reps

The same idea in a practice question:

Practice questionEasy

Example 1 · Ecology and Environment · Waste and Wildlife Conservation

Disposable plastic plates should not be used because:

Taking a good habit for the harmful one

Segregating waste, reusing utensils and cutting down CFCs protect the environment. A question asking what harms it wants the bad habit, such as using piles of disposable plates.

Drill 1 more on biodegradable and non-biodegradable waste

Concept 2 of 2: Threatened species and migratory birds

Species whose numbers are falling are put in categories, from 'gone for ever' to 'not enough known'. The questions read out a definition and ask for its name, so learn each definition in the book's words.

Definition

Extinct: no longer found anywhere on Earth. The dodo.
Endangered: on the verge of extinction; will die out unless saved.
Vulnerable: numbers falling; likely to become endangered if the decline goes on.
Rare: numbers have declined considerably; being endemic (found in one region only) they may become extinct very fast. The red panda and musk deer.
Indeterminate: thought to be threatened, but there is not enough information to place them.
Migratory birds fly to India for the winter. The Siberian crane used to arrive at Keoladeo (Bharatpur, Rajasthan) in December and leave around March.

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.

Practice this conceptself-check · 4 quick reps

The same idea in a real exam question:

SPI · 2022 · SPI Entrance Examination 2022 · Q104Moderate

Example 2 · Ecology and Environment · Waste and Wildlife Conservation

____species are the species whose number of organisms is considerably declined. Organisms of these species, like red panda or musk deer, being endemic may become extinct very fast.

Endangered for every shrinking species

Endangered means on the very edge of extinction. A species whose numbers have dropped sharply and which lives in one region only is called rare in the Class 10 book.

Thinking winter migrants arrive in the middle of winter

Siberian cranes arrive at the start of winter, in December, and stay till about March. January and February fall in the middle of their stay.

Drill 1 more on threatened species and migratory birds

Summary — formulas & gotchas at a glance

A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.

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

Test yourself on a real paper

Sit a past SPI paper, timed and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.

Sit an SPI past paper Drill all 4 questions