Competition Corner

Competition Corner

No living thing survives alone. In every habitat, organisms **compete** for what they need, **depend** on each other, and are shaped by their surroundings. Where resources are limited, the best competitors survive, reproduce and pass on their genes.

Plant rivalry

Pick the THREE things that **plants** compete with each other for.

• Light
• Water
• Mineral ions
• Mates
• Territory

Interdependence

Species also **depend on each other** for food, shelter, pollination and seed dispersal. This is **interdependence**: remove one species and others are affected. A **stable community** is one where the species and environmental factors are in **balance**, so population sizes stay roughly constant.

What stays steady?

In one woodland the numbers of oak trees, squirrels and owls have barely changed in thirty years. Why do ecologists call this a **stable community**?

• Its species and abiotic factors are in balance, so population sizes stay roughly constant
• Its organisms have stopped competing with one another for limited resources
• One species has outcompeted the others and now dominates the wood
• Every population in it is growing steadily year on year

Two kinds of factor

The factors that shape where organisms live come in two kinds. Either kind can change, and either kind changes the community when it does.

Living or non-living?

A pond is monitored through the year. Pick the THREE **abiotic** factors the team recorded.

• Dissolved oxygen level
• Water temperature
• Light intensity at the surface
• Amount of algae available to eat
• The arrival of a heron

Spot the abiotic factor

In this description of a rock pool, tap the phrase that names an **abiotic** factor.

• By midday the pool is busy:
• limpets grazing the algae
• ,
• the water warmed to 22°C by the sun
• , and
• a crab hunting the smaller shrimp
• .

When a factor changes

A long drought lowers the soil moisture in a meadow. Which answer best explains the effect on the community?

• Grasses grow poorly with less water, so rabbits that graze them have less food and their numbers fall
• Populations fall, because droughts and low population sizes tend to happen together
• Nothing changes, because moisture is abiotic and only biotic factors affect populations
• Every species in the meadow dies out, because all living things need water to survive

Knock-on effects

Mink arrive at a riverbank where water voles graze the bankside plants. Put the knock-on effects into the order they follow.

• Mink arrive at the riverbank
• The mink hunt the water voles
• The water vole population falls
• The bankside plants the voles grazed grow more thickly

Built to survive

**Adaptations** are features that help an organism survive in its environment. There are three types, plus one special group of organisms.

Classify the adaptation

Name the type

A body feature is a _____ adaptation; a way of behaving is a _____ adaptation; an internal process is a _____ adaptation.

In the exam

Habitat mastered. Grade-9 habits for this topic: • **Plants** compete for light/space/water/minerals; **animals** for food/mates/territory. • Treat an **abiotic or biotic** factor as the **cause** of where things live. Give the mechanism, not just a correlation. • Classify adaptations precisely: **structural** is a body feature, **behavioural** is an action, **functional** is an internal process.

Explain the Arctic fox

The Arctic fox has thick white fur, a small body with short ears, and it buries surplus food in summer to dig up in winter. Explain how each of these helps it survive, naming the TYPE of adaptation each one is.

• Take each of the three in turn and label it structural, behavioural or functional.
• Say what each one DOES for the fox, not just what it is.
• Remember that body size and shape change how much heat an animal loses.
• The white fur earns two marks if you give both of its jobs.
• Finish with the survival payoff: what would happen to a fox without them.