In this Learning Pathway, we start learning how species respond to environmental change by exploring some basic ideas about ecology and evolution. We will consider these ideas:
- Niches. This reflects the idea that different species are adapted to different kinds of environments – we say that species have different niches. This is extremely important because it means (a) that species can only live in certain places, and (b) when the environment changes species may not be able to live where they do – for instance when the climate changes, or when forests have been cleared.
- Then we explore what happens to species when the environment changes. This is called ‘”the four ways”‘ because every response can be placed into four categories (tolerance, range shift, evolution or extinction). For every species on earth, the balance of the four ways describes the species’ past and determines its future, especially if one realises that humans are evolutionary agents.
- Then we consider one of these four ways in a little more detail. This is evolution. This is because evolution explains how we have come to have so many species, and what those species are like.
- Are the range of environmental conditions in which a species can exist.
We live in a period of dramatic climate change and other environmental change. What will this do to species? To understand how we can (or cannot) predict how species will respond, we need a little bit of theory to build our science around.
How the living organisms of the world will respond to environmental change pivots on the idea of the ecological niche. We all know that different parts of the world have different climates and landscapes and that different species live in these different regions (think polar bears in the Arctic and jaguars in the jungles of South America). These different species live in these different environments at least partly because they are adapted to their local environment. In that case, we then say that these different species have different niches. Niches are not places, they are the range of environmental conditions in which a species can exist.
What makes up the environment that defines a niche?
As we noted above niches represent the set of environments that a species can persist through the generations. The environment includes the physical environment, such as the climate, how much sun or shade there is, or for aquatic animals the chemical composition of the water they live in. However, it also includes all the other species that the species of concern interacts with.
Ecology: what is a niche?
One important part of the idea of the niche is that it is controlled by how the species exploits resources in its environment. If there are two species living together and exploiting the same resources, then one will usually be worse than the other at doing this – eventually, that species will disappear because the other species will outcompete it. However, species can live together because they exploit different resources or because they exploit the same resources in different ways. These species then have different niches, even though they occur in the same place.