Vocabulary

predation interspecific competition symbiosis parasitism mutualism commensalism

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www.scilinks.org Topic: Predator/Prey Keyword: HM61205

^^Mi/'C National Science

Maintained by the IK I if'C National Science m Vftj. Teachers Association

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www.scilinks.org Topic: Predator/Prey Keyword: HM61205

figure 20-1

A rattlesnake has several adaptations that make it an effective predator.

figure 20-1

A rattlesnake has several adaptations that make it an effective predator.

(a) Green leaf mantid, Choeradodus rhombicollis

(b) Amazonian poison frog, Dendrobates ventrimaculatus figure 20-2

(a) Green leaf mantid, Choeradodus rhombicollis

(b) Amazonian poison frog, Dendrobates ventrimaculatus figure 20-2

Coloration is an adaptation in prey as well as predators. In (a), the mantid cannot readily be detected among the leaves. In (b), the frog's bright colors warn other organisms that the frog is toxic if eaten.

Materials 4.1 m white string, 4 stakes, 40 colored toothpicks, stopwatch or timer, meterstick

Modeling Predation

Materials 4.1 m white string, 4 stakes, 40 colored toothpicks, stopwatch or timer, meterstick

Procedure

1. Use the stakes and string to mark off a 1 m square in a grassy area.

2. One partner should scatter the toothpicks randomly throughout the square. The other partner will have 1 minute to pick up as many toothpicks as possible, one at a time. This procedure should be repeated until each team has performed five trials.

3. Record your team's results in a data table.

Analysis Toothpicks of which colors were picked up most often? Which toothpicks were picked up least often? How do you account for this difference?

Adaptations in Animal Prey

Animals may avoid being eaten by carnivores in different ways. Some organisms flee when a predator approaches. Others escape detection by hiding or by resembling an inedible object, as shown in Figure 20-2a. Some animals use deceptive markings, such as fake eyes or false heads, to startle a predator. Some animals have chemical defenses. Animals such as the frog shown in Figure 20-2b produce toxins and use bright colors to warn would-be predators of their toxicity.

In mimicry (MIM-ik-ree), one species closely resembles another species. For example, the harmless king snake is a mimic of the venomous coral snake, as shown in Figure 20-3. This form of mimicry is called Batesian mimicry. Another form of mimicry called Mullerian mimicry, exists when two or more dangerous or distasteful species look similar. For example, many kinds of bees and wasps have similar patterns of alternating yellow and black stripes. This kind of mimicry benefits each species involved because predators learn to avoid similar-looking individuals.

Adaptations in Plant Prey

Plants cannot run away from a predator, but many plants have evolved adaptations that protect them from being eaten. Physical defenses, such as sharp thorns, spines, sticky hairs, and tough leaves, can make plants more difficult to eat. Plants have also evolved a range of chemical defenses that are poisonous, irritating, or bad-tasting. These chemicals are often byproducts of the plants' metabolism and are called secondary compounds. Some examples of secondary compounds that provide a defensive function are strychnine (STRIK-nin), which is produced in plants of the genus Strychnos, and nicotine, which is produced by the tobacco plant. Poison ivy and poison oak produce an irritating chemical that causes an allergic reaction on some animals' skin.

(a) Scarlet king snake, Lampropeltis triangulum (b) Eastern coral snake, Micrurus fulvius figure 20-3

The king snake in (a) may avoid predators because of its mimicry of the color patterns of the coral snake in (b). A closer look reveals the differences: the king snake has a red snout and a black ring separating its red and yellow rings, and the coral snake has a black snout and adjacent red and yellow rings. The ring patterns of other species of coral snakes may differ from the patterns shown in the photo above.

(a) Scarlet king snake, Lampropeltis triangulum (b) Eastern coral snake, Micrurus fulvius

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