Predation l v21 jqb s1

Predation Douglas Wilkin, Ph.D. Jean Brainard, Ph.D.

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Printed: October 29, 2013

AUTHORS Douglas Wilkin, Ph.D. Jean Brainard, Ph.D.

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C ONCEPT

Concept 1. Predation

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Predation

• Describe predation and its effects on population size and evolution.

What may be the most common way different species interact?

Biomes as different as deserts and wetlands share something very important. All biomes have populations of interacting species. Species interact in the same basic ways in all biomes. For example, all biomes have some species that prey on others for food.

Predation

Predation is a relationship in which members of one species (the predator) consume members of another species (the prey). The lions and buffalo in Figure 1.1 are classic examples of predators and prey. In addition to the lions, there is another predator in this figure. Can you spot it? The other predator is the buffalo. Like the lion, it consumes prey species, in this case species of grass. However, unlike the lions, the buffalo does not kill its prey. Predator-prey relationships such as these account for most energy transfers in food chains and food webs.

Predation and Population

A predator-prey relationship tends to keep the populations of both species in balance. This is shown by the graph in Figure 1.2. As the prey population increases, there is more food for predators. So, after a slight lag, the predator population increases as well. As the number of predators increases, more prey are captured. As a result, the prey population starts to decrease. What happens to the predator population then?

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FIGURE 1.1 Predators and Their Prey. Two lions feed on the carcass of a South African cape buffalo.

FIGURE 1.2 Predator-Prey Population Dynamics. As the prey population increases, why does the predator population also increase?

Keystone Species

Some predator species are known as keystone species. A keystone species is one that plays an especially important role in its community. Major changes in the numbers of a keystone species affect the populations of many other species in the community. For example, some sea star species are keystone species in coral reef communities. The sea stars prey on mussels and sea urchins, which have no other natural predators. If sea stars were removed from a 2

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Concept 1. Predation

coral reef community, mussel and sea urchin populations would have explosive growth. This, in turn, would drive out most other species. In the end, the coral reef community would be destroyed.

Adaptations to Predation

Both predators and prey have adaptations to predation that evolve through natural selection. Predator adaptations help them capture prey. Prey adaptations help them avoid predators. A common adaptation in both predator and prey is camouflage. Several examples are shown in Figure 1.3. Camouflage in prey helps them hide from predators.

Camouflage in predators helps them sneak up on prey.

FIGURE 1.3 Camouflage in Predator and Prey Species. Can you see the crab in the photo on the left? It is camouflaged with algae. The preying mantis in the middle photo looks just like the dead leaves in the background. Can you tell where one zebra ends and another one begins? This may confuse a predator and give the zebras a chance to run away.

Summary

• Predation is a relationship in which members of one species (the predator) consume members of another species (the prey).

• A predator-prey relationship keeps the populations of both species in balance.

Practice

Use this resource to answer the questions that follow.

• http://www.hippocampus.org/Biology → Biology for AP* → Search: Ecological Interactions 1.

2.

3.

4.

Define intraspecific competition.

Describe predator-prey interactions.

What is mimicry? Give an example.

Give an example of an example of camouflage.

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www.ck12.org Review

1. Describe the relationship between a predator population and the population of its prey.

2. What is a keystone species? Give an example.

References 1. Luca Galuzzi - www.galuzzi.it. . CC-BY-SA 2.5 2. CK-12 Foundation. . CC-BY-NC-SA 3.0 3. Crab: Mila Zinkova; Mantis: Adrian Pingstone; Zebra: Pharaoh Hound, Fir0002. . Crab: CC-BY-SA 3.0; Mantis: Public Domain; Zebra: CC-BY 2.5

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