Organisms interact with other organisms and with their environment. Changing one part of an ecosystem changes others, sometimes in ways that are not obvious.
A food chain shows how energy passes from one organism to the next. It begins with a producer, usually a photosynthetic organism such as a plant or an alga, followed by consumers. The arrows show the direction the energy travels.
A food web is several food chains joined together, and it shows the real picture: most animals eat more than one thing. If one population changes, the others change too. Remove a predator and its prey may increase, which then reduces the prey’s own food supply.
Many crops depend on insects, so the plants and the insects are interdependent too.
Insects, especially bees, pollinate a large proportion of the crops people eat. Without pollination those plants set little or no fruit or seed.
A decline in insect populations, from habitat loss, pesticides or disease, is therefore a threat to the food supply and not only to wildlife.
Organisms are affected by their environment: temperature, water, light and the availability of food all limit where a species can live. They also change it, as trees do by shading the ground beneath them.
Some toxic materials are not broken down or excreted, so they build up inside an organism over its lifetime. This is bioaccumulation. Their concentration may then increase at higher trophic levels, because each predator eats many contaminated prey. This is biomagnification, and it is why birds of prey were badly affected by pesticides.
Back to Ecosystems practice ยท View all Ecosystems questions
