FITTING IT ALL TOGETHER

We have seen how different plants and animals are connected to each other through food chains. But very few things are part of a single food chain.

Let's look again at the food chain in Chapter 1. This chain connected kelp, sea urchins, and sea otters. Sea urchins eat kelp. But other animals, such as sea snails and crabs, do too. So kelp is part of more than one food chain. At the other end of the chain, the sea otter eats more than sea urchins. It also eats clams and other kinds of food. As with the kelp, sea otters are part of other food chains. Kelp, sea urchins, and sea otters are part of a food web. Each food web involves many plants and animals.

The kelp, sea urchins, and sea otters that we met at the start of the book are part of a large, complex food web.

Think about the food chains and webs in different places. Clearly some places can support a richer mix of living things than others. The diversity (richness) of an area in a region depends on which plants can live there. And which plants can live there depends on the climate.

Woodlands grow where the climate is not too cold, and not too dry. In this kind of climate, large numbers of plants can grow.

A region's climate is its average weather. Places with a warm climate get more of the Sun's energy each year. More plants grow in these areas. Rainfall also affects which plants can grow. Desert areas are dry. They cannot support many plants. So these areas are less rich in life.

The amount of plant life that can grow in an environment is called the productivity of that environment.

Deserts are areas where the climate is very dry. Without water, the land can support very few plants.

Simple Webs

There are many different food webs in the world. Some are simple and include only a few species.

Desert food chains are often simple. Desert plants such as cactuses are the desert producers.

Although deserts have few plants, they can still support primary and secondary consumers.

A simple food web is found in the Antarctic Ocean. There, shrimplike krill eat plant and animal plankton. Fish, seabirds, penguins, seals, and whales eat the krill. Then, top predators such as toothed whales eat seals, penguins, and squid.

In the Antarctic, no plants can live on the land. All the animals that live in the Antarctic rely on plant plankton living in the ocean.

Jaguars are among the top predators in the South American rainforest. The rainforest is the richest food web on Earth.

The Richest Webs

In productive environments, food webs are complex. Thousands of living things exist within a small area.

In the rainforest, trees are not the only producers. There are other plants such as ferns, climbing vines, and plants called epiphytes. The roots of epiphytes grow in the air.

Insects are the biggest primary consumers in the rainforest. There are millions of them. On one project, a scientist found nearly a thousand kinds of beetles. And this was on just nineteen rainforest trees!

Secondary consumers include other insects, birds, snakes, lizards, and mammals such as anteaters and sloths. The top predators are jaguars, caimans, and eagles. The connections between all these living things are complex.