Food chain and Extinction |
If an animal at the bottum of the food chain goes extinct,
will animals above it go extinct too?
If the predator animal preys only on that one prey animal, and that prey
animal goes extinct then the predator will go extinct also. But there are
few predators that prey on only one animal.
The answer depends on if the animals that feed on the newly-extinct
animal can find a new feed source. Animals that only have one source
of food are more at risk for extinction than animals that have
multiple sources or can adapt to new sources.
Hope this helps,
The answer to this question is, it depends. Generally, animals that are at the top of the food chain can survive off of many different food sources. Take people for instance. If cows were to go extinct, we would still be able to eat chicken or pigs or fish, and of course we also have the ability to live off of plants. To answer your question, you have to evaluate if the animals above the one that went extinct were dependent solely on the animal that went extinct and if they have the ability to adapt. The following questions will help you determine if an animal high on the food chain would go extinct:
1. Is the animal that goes extinct a food source for other animals?
2. If the extinct animal is a food source for other animals, is it the only food source?
3. If the extinct animal is the only food source for another animal, would the other animal be able to adapt and find a new food source? This might happen either through finding a new animal to eat in the same area, or the animals can migrate to a new area where they find a new food source.
Even if you can figure out the answers to these three questions, there are still other situations that might occur that would eliminate a second animal from becoming extinct. For instance, let us say that the animal that went extinct was eating all of a specific plant in the area. Let us also say that the extinct animals drove out another similar species because they were eating all of these plants and crowding out the secondary species. Once the animal became extinct and the plants grew back, that secondary species might come back and provide a food source for the animals above it on the food chain.
As you can see, there are a lot of what-if scenarios and it really comes down to the specific animal and ecosystem that one is speaking about.
If an animal (or plant or bacteria) near the bottom of a food chain or food web goes extinct or even becomes threatened or endangered it can have major impact on specific species and even entire ecosystems.
Organisms can adapt (and eventually evolve) to reduce the impact of the extinction of its food supply, but if it cannot adapt quickly enough it may also face extinction.
Right now this is occurring in our oceans where krill populations are decreasing and the whales that rely on the krill as their main food source are changing migratory patterns in order to adapt.
It can definitely happen. You're describing "coextinction." It can happen when a host goes extinct, leaving a specific parasite nothing to feed on (it is claimed that a mite went extinct along with the Passenger Pigeon, for example). It can also happen when a predator relies on a specific prey, as you describe. The Haast's Eagle in New Zealand went extinct when humans caused the Moa (a large flightless bird) to go extinct. Some pollination pairs are quite specific and thus susceptible to coextinction. For example you may have read that Darwin observed that some species of flowers were only pollinated by a single species of moth or hummingbird, but I'm not aware of any cases where this type of coextinction has been observed by humans.
For most animals that are not as highly specific about what they eat, coextinction is not a great risk. Furthermore, it's possible for a species to die out without going extinct. This is called extirpation. For example if all Blue Whales died out in the north Pacific, you'd consider this extirpation, but not extinction, because you'd still have Blue Whales in the north Atlantic.
We often still hear about the “food chain”. The problem is that food chains grossly oversimplify predator-prey relationships. They are much too rigid and linear. For example, species A consumes species B, which in turn consumes species C. Each species represents a tropic (or feeding) level. Think of it as a pyramid, with species C at the bottom, B in the middle, and A at the top.
If species C goes extinct, it is assumed that a domino effect will occur, with species B and A also going extinct. It stands to reason that removing the concrete foundation from a house will cause it to collapse. Then again, the false assumption is that species B will only consume species C.
Fortunately, nature has built in safeties. Food webs are a better representation of predator-prey relationships. In this case, there are multiple food sources (choices) for a given organism. If one gets eliminated from the mix, there are fallbacks to fill the void. Humans rarely subsist on one type of food, and neither do other animals (although they do exhibit preferences like we do). Most animals are generalists, meaning they aren’t particularly choosy when faced with starvation.
However, in some cases organisms are specialists. They have tightly coevolved relationships with other organisms. Think of it as a package deal – like mutualism and symbiosis. They will outright refuse to eat (or associate) with anything else, even when starvation is imminent.
The idea of the food chain applies here to an extent. If one partner goes extinct, the other will also typically follow. Compared to the broader food web, these disruptions are highly localized. The redundancy of the food web ensures that these extinctions will not domino to other trophic levels.
An offshoot of your original question is to look at the relationships from a broader ecological perspective. Organisms known as keystone species are vital to the stability of their community. Their extinction can have an indirect impact on other species in the food web, largely due to how they shape the environment (to make it suitable for others).
Yes, James, I am sure it has happened.
Sorry I don't have examples ready in mind.
But it doesn't necessarily happen every time.
There are many small animals and plants, so
the higher predators often have more than one food source.
Then losing one source makes life harder but not impossible.
Then predator populations decline but maybe no species among them goes extinct.
I guess this is one of the reasons we value diversity in the ecosystems,
and adaptability in each species.
The other way around happens too.
Sometimes a food animal at the base of the ecosystem
declines in number but isn't extinct,
and that can pinch a higher species which does go extinct.
There are higher species that have slowly evolved into a weak position,
and their extinction can happen at times which are only slightly special.
Such as the previous paragraph.
And then there are a few great disasters which create such stress
that many robust creatures go extinct,
and only certain lucky species survive.
Fortunately that kind of disaster seems to be very rare.
Not necessarily. It depends upon how adaptable the animals/plants are.
First, you need to watch out how you define "top" and "bottom" of a food
chain. How general is the definition? For example, you might consider some
sort of plant as being at the "bottom" of a food chain, but many animals
higher in the food chain can thrive on a "vege" diet, picking up necessary
proteins from alternative animal protein. At the other extreme, some animals
have very specific dietary needs, pandas for example. Those animals might
not be able to survive without a specific food source. Some parasites have
very specific dietary requirements, others are very flexible. So it's hard
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Update: June 2012