KS3 · Biology

Competition between organisms

A woodland has only so many nuts, and two kinds of squirrel are eating them. One kind came to outcompete the other. How did that happen?

Biology · Competition

What is each one competing for?

Pick a feature or strategy, then pick the resource it helps the organism win.

Still to sort

Food (0)

Something an animal feeds on.

Shelter (territory) (0)

A group that wins enough has space to raise young without overcrowding. In a crowd, disease spreads more easily.

Mates (0)

Who gets chosen to mate with.

Water and minerals (0)

Taken in from the soil.

Light (0)

Needed for photosynthesis.

Pollinators (0)

Birds, bats or bees that transfer pollen.

Seed dispersers (0)

Animals that eat fruits and nuts, then deposit the seeds.

Space (0)

Room for roots, and light that isn't blocked by a neighbour.

10 of 10 still to sort.

Every habitat has only so much food, water, light and space, so living things struggle for them. Each feature below helps its owner win one of those resources. Which one?

Watch out: When everything is sorted, count the fights. You might be surprised.

Who competes for what?

Animals, plants, or both?

All living things need resources from their habitat, but a habitat only has so much of each one. That's why organisms are in competition. Tick which group or groups compete for each resource.

  • A Animals
  • B Plants
  1. Food
  2. Water
  3. Shelter (territory)
  4. Mates
  5. Light
  6. Minerals
  7. Space
  8. Pollinators
  9. Seed dispersers

Variation and competition

?

Reason it through

Why can a longer, thin beak help a hummingbird compete for food?

Link 1 of 4

First link · your turn

Do all hummingbirds have exactly the same beak?

2
Locked — reveal the link above first
3
Locked — reveal the link above first
4
Locked — reveal the link above first

Two sneaky ideas

Which of these is closest to what you think?

Be honest. Pick the idea that is closest to what you think right now, then say how sure you are.
How sure are you?

Worked case: red and grey squirrels

Why did the grey squirrel outcompete the red?

Grey squirrels were introduced to the UK from North America and outcompeted the native red squirrels. Join the factors with arrows (from cause to effect) to show how they combined. Then compare your web with the lesson's.

  1. Red and grey squirrels eat the same food (nuts and seeds)
  2. They share the same woodland habitat
  3. They compete for food and shelter
  4. Greys have more offspring
  5. The grey population can grow faster than the red
  6. Greys are immune to, or more likely to survive, squirrelpox; reds have a high death rate from it
  7. Greys outcompete reds (outcome)
Add a link

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WHAT YOU'VE LEARNED

A quick recap of today's lesson.

Winning isn't only about fighting. Let's find out what it is about.

What you need to know

  • Every habitat has limited resources, so organisms are in competition for them.
  • Animals compete for food, water, shelter (territory) and mates. Plants compete for light, water, minerals, space, pollinators and seed dispersers.
  • Competing isn't only fighting. Adaptations and strategies help organisms win resources, and a stag's fight is just one of them.
  • The fittest means the best adapted to the environment, not simply the strongest. Better adapted makes surviving and reproducing more likely, not certain.

The big picture

Every habitat has limited resources, so organisms are in competition for them. Animals and plants compete for different things and win them in many ways, fighting being only one. The fittest are the best adapted, which makes surviving and reproducing more likely, but never certain.

Key points

1Competition is the struggle between organisms for limited resources.
2Animals compete for food, water, shelter (territory) and mates; plants for light, water, minerals, space, pollinators and seed dispersers.
3Variation means some individuals compete more successfully than others, which can drive natural selection.
4Fighting is only one strategy. Others include a long, thin beak, scent and song, bright feathers, deep roots, many leaves, colourful flowers, good fruits and wind-scattered seeds.
5The fittest are the best adapted to their environment. That might be a lion's bite, a peacock's feathers or a lizard's camouflage.
6Better adapted organisms are more likely, not certain, to survive and reproduce, because random events mean less well adapted ones sometimes do too.

Worked example

Problem

Two plants grow in the same patch of soil. One has deep, far-reaching roots and the other has short roots. Explain why the deep-rooted plant is more likely to survive and reproduce.

⚠ Watch out

Thinking competition means fighting, and that the fittest are the strongest. Fighting is one strategy among many, and in science 'fittest' means best adapted to the environment. Also watch for 'always survives': better adapted only makes survival more likely.

🧠

Memory hook

Limited resources, many strategies, better chances. Only so much to go round, lots of ways to win it, and 'fittest' means best adapted, not strongest.

✓

Check yourself

Without looking back: pick one resource animals compete for and one feature that helps an animal win it. Then say why that feature makes the animal more likely, but not certain, to survive and reproduce.

Flashcards

(14)
What is competition, and why does it happen?
The struggle between organisms for limited resources. It happens because the resources in each habitat are limited, so individuals are in competition for them.
Name the resources animals compete for.
Food, water, shelter (territory) and mates.
Name the resources plants compete for.
Light, water, minerals, space, pollinators and seed dispersers.
Which resource is on both the animal list and the plant list?
Water.
Do organisms compete only by fighting?
No. Animals and plants have a variety of adaptations and strategies that help them compete. Fighting is only one.
How do stags and peacocks compete for mates?
Stags fight to show physical strength. Peacocks grow impressive features such as bright feathers; animals with the most impressive display are more likely to be chosen.
How can animals compete for shelter?
By being territorial, for example marking territory with scent or, in birds, using song to show it is claimed.
Why is a hummingbird with a long, thin beak more likely to survive and reproduce?
It can reach further into flowers, so it is more likely to drink more nectar.
How do leaves help a plant compete?
Leaves absorb light for photosynthesis. Many leaves, or leaves with a large surface area, absorb more light and make more glucose.
A plant's flowers lack colour and scent. Why is that a problem?
Pollinators are less likely to visit, so pollen is less likely to be transferred, and that transfer is necessary for plant reproduction.
How does wind-scattered seed help a dandelion?
New plants grow away from the parent, so they are less likely to be crowded or shaded by it.
What does 'the fittest' mean in science?
The best adapted, the best fit to their environment, not simply the strongest.
Do the best adapted organisms always survive and reproduce?
No. They are more likely to, but it is about chances, not certainty. Random events mean less well adapted organisms sometimes survive and reproduce.
Why did grey squirrels outcompete red squirrels in the UK?
They share food and habitat so compete for both; greys have more offspring so grow faster; and greys are immune to, or more likely to survive, squirrelpox, which kills reds at a high rate.

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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How this lesson was checked. This KS3 Biologylesson was published through Lightbulb Learning's human-designed editorial process — the educational standards, accuracy rules and publication checks it must pass were authored and approved by Philip Halpin. It passed subject-specific assessment, automated educational checks and technical publication verification before going live (publication checks completed 9 October 2026). Published pages are monitored, human spot-checking is ongoing across the lesson library, and anything found wrong is corrected or withdrawn. How our lessons are made and checked. Spotted a mistake? Email hello@lightbulblearning.co and we'll review it.