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80 Nature

4 LAVA FIELD

A volcanic eruption dramatically changed this

ecosystem in Hawaii. The cooled, hard lava

field is a hostile environment for living things,

yet one pioneer plant has managed to grow

on a tiny patch of soil blown in by the wind.

WHY DO ECOSYSTEMS CHANGE?

Ecosystems are continually changing, often

very slowly, sometimes very fast. A forest fire,

for example, can wipe out an ecosystem without

warning. Even so, a new community slowly begins to

form. First, short-lived pioneer plants arrive, along with

the animals that eat them. These are gradually replaced by

larger plants, such as trees, and their associated animals.

Eventually, a stable mix of species is established.

WHAT IS AN ECOSYSTEM?

From a tiny puddle to a vast forest, an ecosystem

consists of a living community, its environment,

and all their interactions. A community is a group

of animals, plants, and micro-organisms that live

together in the same area, or habitat. Its environment

includes sunlight, rainfall, and shelter.

Lava flow

from volcano

destroyed the

old ecosystem

1 WETLAND ECOSYSTEM

A great blue heron devours a fish, and the sunlight stimulates plant

growth. These are just two of the many complex interactions that make

up this wetland ecosystem in Florida, USA.

WHAT IS BIODIVERSITY?

Coral reefs have high biodiversity because they

contain large numbers of different species. Deserts

have low biodiversity because they have far fewer

species. Humans have reduced biodiversity in many

ecosystems by harmful activities, such as overfishing.

CORAL REEF IN THE RED SEA, EGYPT 1

Found in shallow tropical seas, coral reefs teem with

life. Corals are tiny animals whose chalky skeletons

form the rocky reef. This ecosystem provides food

and shelter for fish and other species.

Ecology

All living things have complex

relationships with other species and

with their environment. The study of

these interactions is called ecology.

Ecology looks at the. FOOD CHAIN

that links the eater to the eaten. It

also shows how vital chemicals are

recycled by. NUTRIENT CYCLES.

Crevices provide

shelter for eels,

crabs, and

octopuses

Anthias fish feeding

on plankton

Coral grows

slowly and is

easily destroyed

Fish of many

different species

feed and breed on

the reef

Fish provides heron

with the energy

to survive

Pioneer plant probably

grew from a spore

blown in the wind

bably

ecology