GCSE · Biology · AQA · Spec 8461

Extinction

Picture the very last individual of a species — not the last few, the last one anywhere. When it dies, the species is extinct. So what gets a species there?

Build it yourself

What can drive a species to extinction?

Every factor here can help push a species towards extinction. Add an arrow for each 'this can lead to that'. Most lead straight to the outcome — but watch for one factor that can also work through another one on the way.

The species becomes extinct (outcome)
Human activity
Environmental change (such as climate change, drought or an ice age)
Its habitat is destroyed, or changes
The organisms it feeds on become extinct
New predators, new diseases, or competition for food or mates
A single catastrophic natural event (such as volcanic activity or an asteroid strike)

Add a link

This factor……made this happen or worse

No links yet.

Exam line: For each factor, say what it does on the way: 'the environment changes, so the species is no longer adapted to where it lives'.

Pin down the finish line

So when is a species actually extinct?

A species of frog once lived right across a region. Now there are only a handful left, all in a single pond.

Is the frog species extinct? Pick the idea closest to what you think right now.

Yes — there are so few left that it counts as extinct.Yes — it has gone from almost everywhere it used to live.No — some individuals of the species are still alive.It will be extinct the moment the frogs stop breeding.

How sure are you?

I'm sureI think soI'm guessing

Yes — there are so few left that it counts as extinct.

This is a common misconception

Very few is still not none. Those frogs in the pond are alive, so the species is not extinct. Extinction only happens when there are no individuals of the species left alive at all.

Yes — it has gone from almost everywhere it used to live.

This is a common misconception

Disappearing from most of its old home doesn't make a species extinct. While individuals are alive somewhere — even in one pond — the species still exists.

No — some individuals of the species are still alive.

This matches the evidence

Exactly. Extinct means there are no individuals of the species still alive. A handful in one pond is a species in trouble, but it is not extinct.

It will be extinct the moment the frogs stop breeding.

This is a common misconception

Losing somewhere to breed can help drive a species towards extinction — you'll see that next. But while any individuals are still alive, the species is not extinct yet.

Extinct means zero: no individuals of the species left alive. Rare isn't extinct. Gone from one place isn't extinct.

Exam line: Say it exactly: 'a species is extinct when there are no individuals of that species still alive'.

Predict, then check

Think about what a habitat actually does for the species that lives in it.

A species' habitat is still there — same place, same size. But it has changed, and it no longer gives the species anywhere to breed. Could this species still become extinct?

Sort the factors

Environmental change, human activity — or both?

This lesson names some factors as environmental change and some as human activity. Place each one: in one group, in both, or in neither.

A Environmental change
B Human activity

Climate change
Drought
An ice age
Hunting
An asteroid striking the Earth
Volcanic activity
New predators
New diseases

Your turn

Write it, then mark it

Describe three factors that may contribute to the extinction of a species. [3 marks]

Your answer

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The mark scheme

A new predator (1 mark)
A new disease or pathogen (1 mark)
Competition for food or mates (1 mark)
Environmental change, e.g. drought — no longer adapted (1 mark)
Habitat destroyed or changed (1 mark)
Its food organisms die out (1 mark)
A catastrophic event, e.g. volcanic activity (1 mark)
Human activity, e.g. hunting (1 mark)

Model answer

First, a new disease could arrive and drive the species to extinction. Second, the species could lose out to other organisms in competition for mates. Third, an ice age could come, and the species may no longer be adapted to where it lives.

Up to three marks — one for each different factor. Tick one point per factor you described, and stop at three.

Exam line: Use three DIFFERENT factors, and say what each one does: 'its habitat changes, so it no longer has anywhere to breed'.

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

What it really means for a species to be gone — and the different routes that can take it there.

What you need to know

A species is extinct when there are no individuals of it still alive.
New predators, new diseases, or competition with other organisms for food or mates can drive a species to extinction.
Environmental change — such as climate change, drought or an ice age — can leave a species no longer adapted to where it lives.
Habitat loss, losing the organisms it feeds on, a single catastrophic natural event, and human activity (hunting, or climate change caused by people) can all contribute too.

The big picture

A species is extinct when there are no individuals of it left alive. Several factors can drive a species to extinction — new predators, new diseases, competition, environmental change, habitat loss, losing the organisms it feeds on, a catastrophic natural event and human activity — and some of them work through another factor on the way.

Key points

1Extinct = no individuals of the species left alive. Very few is not none.

2Some routes are one step: new predators, new diseases, competition for food or mates, hunting, or a catastrophic event such as an asteroid strike.

3Some routes carry a 'so': environmental change, so no longer adapted; habitat destroyed or changed, so no shelter, food or breeding site.

4One extinction can lead to another: if the organisms a species feeds on become extinct, it can die out too.

5Climate change appears twice: it is an environmental change, and people can cause it.

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Worked example

Problem

A species of beetle feeds only on the leaves of one type of plant. People cause climate change, and the conditions where the plant grows change. Describe how this could lead to the beetle species becoming extinct.

⚠ Watch out

Calling a species extinct when only a few are left, or when it has disappeared from one place. Extinct means none are left alive — while even one individual survives, the species is not extinct.

🧠

Memory hook

Extinct means ZERO, not few. Then, for every factor, ask: does it go straight there, or through a stop on the way?

✓

Check yourself

Cover the page. In one sentence each, explain how (a) people and (b) the loss of the organisms a species feeds on can help drive a species to extinction.

Flashcards

(11)

What does it mean when a species is extinct?

There are no individuals of the species still alive.

Name two new arrivals that can drive a species to extinction.

New predators and new diseases (pathogens).

A species can be driven to extinction by competition with other organisms. What two things can they compete for?

Food and mates.

What can a drought or an ice age do to a species that may lead to its extinction?

Leave it no longer adapted to where it lives.

Give three examples of environmental change.

Any three of: climate change, global warming, drought, an ice age.

What three things can a changed habitat stop giving a species?

Shelter, food and somewhere to breed.

Does a habitat have to be destroyed before it can drive a species to extinction?

No. It may still be there but have changed, so it no longer gives shelter, food or somewhere to breed.

A predator feeds on one prey species. If that prey species becomes extinct, what can happen to the predator?

It can die out too — it has lost the organisms it feeds on.

Give two examples of a single catastrophic natural event that can cause extinction.

Volcanic activity, and an asteroid striking the Earth.

Name two ways human activity can contribute to extinction.

Hunting, and climate change caused by people.

Why does climate change count as both an environmental factor and a human one?

It is an environmental change, and people can cause it.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

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What can drive a species to extinction?

So when is a species actually extinct?

Environmental change, human activity — or both?

Write it, then mark it

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