Video Transcript
Complete the following. A blank ecosystem is more likely to
be affected by one species going extinct than blank ecosystem. (A) Marine, a terrestrial; (B)
primary, a secondary; (C) simple, a complex; or (D) plant, an animal.
Let’s first remember that an
ecosystem consists of a habitat and all of the organisms contained in that
habitat. So there wouldn’t be one ecosystem
classified as a plant ecosystem and another classified as an animal ecosystem. Ecosystems would contain both
plants and animals. So we can eliminate choice (D).
We may also remember that
extinction refers to a species no longer existing because all of the living members
of that species have died out, leaving no offspring. Ecosystems contain many interacting
species. And when one species in an
ecosystem becomes extinct, that is likely to affect other species in the ecosystem
that commonly had some type of interaction with the now-extinct species.
For example, one type of
interaction between species in an ecosystem is when one species relies on another
species for food. Let’s take, for example, a species
of bird that eats insects and primarily eats grasshoppers. If something happens to those
grasshoppers that causes them to die out and become extinct, then these birds will
no longer have access to that preferred food. The birds may be able to switch to
another type of food to survive, but it is likely they won’t have as much food as
they typically are able to get available to them.
As a result, the birds themselves
may begin to die more rapidly, from starvation, or may simply not reproduce as much
as they used to, because there is not much food available. In this way, the bird species
itself may become at risk of going extinct as well.
So we can see that one species
going extinct in an ecosystem can have big effects on other species in that
ecosystem. In a situation like we’ve
described, where there is one species that consumes, say, just one other species,
the loss of one species that another species relies on will greatly affect the other
species, perhaps even to the point of threatening that species with extinction as
well.
Fortunately, typically ecosystems
contain many more connections among species so that one species is often not
entirely reliant on the existence of one other species but instead can meet its
needs through interactions with a variety of species. This food web shows how species can
have multiple food sources and predators so that the extinction of one won’t as
greatly affect species that consume or are consumed by that species. Instead, if something happens to
the grasshoppers in this case, the birds can switch more easily to other food
sources, such as seeds and beetles, for example. In this way, the population sizes
of the birds, and all the other species, may be able to remain more or less the same
as before the extinction of the grasshoppers.
So, essentially, the more
connections that a species has with other species in the ecosystem, the more stable
the population of that species should be. We would call an ecosystem with
just a few interactions between species a simple ecosystem. And we would call an ecosystem with
more varied interactions among species a more complex ecosystem. So, as we have mentioned, a more
complex ecosystem with more varied interactions should be more stable and resistant
to change compared to a simple ecosystem.
If one species in a complex
ecosystem goes extinct, it will affect the ecosystem. But it won’t affect it as much as a
simple ecosystem would be affected. Therefore, the correct answer to
this question is (C): simple, a complex. A simple ecosystem is more likely
to be affected by one species going extinct than a complex ecosystem.
