What are other examples of adaptations that prey organisms have evolved to help them escape predators? How might these adaptations have come about and how do these adaptations defend the prey from possible predators? Furthermore, if a new predator were to be introduced to the environment, would the adaptation remain effective in defending the prey organism? Be sure to connect your response to information we learned earlier this year and the biological themes.
Tuesday, April 6, 2010
Predation and Prey Adaptations
In Chapter 5, Coyne discusses how wild mice have developed different coloration depending on the color of the soil the mice live in in order to avoid predators (116). An experiment conducted by Donald Kaufman revealed that this adaptation successfully aided mice in avoiding predators such as owls and therefore being able to survive and reproduce. These results indicate that the coloration of the mice likely evolved through the forces of natural selection, resulting in coloration that concealed the prey organism from predators.
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Another example that may evolve from a prey organism is Batesian mimicry, which is when the prey's coloring mimics an unpalatable species's coloring to discourage predators. As Jerry Coyne mentioned, the new traits of organisms come from "Mutations-accidental changes in the sequence of DNA" (118). When a predator is present, it will usually kill the regular members of a species; however, this special "mutant" will have a new trait that allows it to escape being eaten by predators to survive and reproduce. In this case. The evolved mimicry would discourage predators from preying on the "mutant" due to recognition of associations between the appearance of the mutant to the experience of eating an unpalatable species.
ReplyDeleteIf a new predator was introduced into the system, then the new trait may not work. The new predator may not have any developed recognition for the mimicry to work. In this case, a new mutant may emerge with a trait that allows it to survive the predator and reproduce.
Like Frank said, Batesian mimicry is an excellent mechanism that allows organisms to fool many predators. One example of a mimic would be a king snake, which mimics the poisonous coral snake. Though both look alike, only one, the coral snake, is actually harmful (Mongabay.com).
ReplyDeleteAn adaptation that Coyne brings up that might help organisms escape predators are wings. Coyne presents that there are two theories about how wings evolved: the “gliding” theory and the “ground up” theory. Both theories relate to the adaptation of flight that helps the prey escape.
The “gliding” theory beings with an ancestral bird increasing the gene expression for muscle genes in the animal’s arms. Eventually, these arms would be muscular enough, and further down the evolutionary line, feathers develop, which help this later ancestor evolve. Feathers and strong arms help this animal escape predators already because the organism could stay off the ground for extended periods of time. Finally, an organism that would be able to flap its arms to fly would appear, and terrestrial predators would be helpless.
The “ground up” theory of how wings were developed supports that early organisms “hopped” to catch prey in tree tops. Later organisms would be able to run up steep slopes to escape from predators. Coyne gives the example of the partridge, a present day bird whose adult form could ascend 105 degree slopes by simply flapping their wings (46). Finally, along the evolutionary line, fully fledged wings would develop that would help the predator distance itself from predators (46).
One could even go as far as to say that learning how to fly or run steep slopes needs to be able to learn behaviors. Learned behaviors, as Campbell says, need to be learned during an infant’s sensitive period, the time when the infant could most easily learn things (1128-9). A young offspring has no experience in flying or ascending steeps slopes, but its parent does, and so the parent needs to be able to help the offspring fly (Wisegeek).
Both Henry and Frank provide suitable examples of the predator-prey relationship. Bartesian mimicry is indeed one of the most useful adaptations used by organisms to drive away the predators.
ReplyDeleteCamouflage is also a very useful adaptation related to the theme of evolution/natural selection. An example of this adaptations that prey organisms have evolved to help them escape from predators is the moth species. Due to the Industrial Revolution in England, the industrial wastes caused tree trunks to darken and lichen to die. This made it easy for the predators to detect the peppered moths.The peppered moth, Biston betularia [italicized], which was generally light colored adapted and became dark colored so as to camouflage as a tree trunk and prevent the predators from detecting the moths.If a new predator were introduced, the adaptation would definitely prevent the predators from seeing the moths like Coyne said, "Adaptation to the environment is inevitable if a species has the right kind of genetic variation" (117).
There are numerous mechanisms that organisms have developed in order to protect organisms from their predators. Among these are cryptic coloration (camouflage) and chemical defenses. Both of these evolutionary characteristics provide excellent defense against predators.
ReplyDeleteMantids are a species that have developed camouflage in order to disguise themselves against predators. Different species of mantids develop specific coloration in order to match their environment in terms of appearance. Figure 22.12 on page 459 in Campbell shows two species of mantids, one in Africa and one in Malaysia, that have evolved to perfectly match their environment. Also, Campbell writes "Over time, natural selection can increase the match between organisms and their environment" (Campbell 459). Organisms develop camouflage, through natural selection, in order to hide themselves from predators. If predators cannot identify their prey, the predators cannot eat their prey.
Another type of defense mechanism is the use of chemical defenses. Typically, organisms that have chemical defenses display aposematic coloration. Campbell writes, "Animals with effective chemical defenses often exhibit bright aposematic coloration" (Campbell 1201). Aposematic coloration is used to warn predators that the brightly colored organism has chemical defenses. This discourages predators from attacking their prey. Poison dart frogs are an example of an organism that has chemical defenses and uses aposematic coloration. Chemical defenses can acquired one of two ways. Organisms can either produce the toxins, such as the European fire salamander, or organisms can acquire the defense by "accumulating toxins from the plants they eat" (Campbell 1201).
Henry, Frank, and Athena, the goddess of wisdom, are all right about Batesian mimicry being a very effective mechanism for organisms to defend against predators. On page 1201, Campbell cites the green parrot snake and hawkmoth larva as being in a Batesian mimicry complex with one another (Campbell 1201). The harmless hawkmoth alters its appearance to mimic the features of the harmful green parrot snake, which deters predators. Henry also presents an interesting point in the development of flight to defend against predators. It is interesting that flight appears to have developed in order to catch prey in treetops, but flight eventually turned into a mechanism to flee from predators.
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ReplyDeleteAnother useful adaptation that allows organisms to avoid being preyed upon is the development of shells or sharp spines. Animals such as turtles or porcupines have physical features that make them a very undesirable meal. Porcupines make it very difficult for predators to eat them because of their extremely sharp quills. Similarly, predators would have a tough time trying to get to a turtle through its protective shell. (About.com) This defensive mechanism would relate to the theme of structure and function. The structure of the sharp points of quills or the hard shells of turtles, function to make it very difficult for a predator to prey upon that particular organism. In addition to animals using defense mechanisms plants such as acacia trees use "hollow thorns that house stinging ants" (Campbell 1203). These ants deter any herbivores from preying upon the acacia's vegetation.
ReplyDeleteMr. Powers briefly mentioned one kind of chemical defense. In addition to creating toxins that would either cause an organism to taste bad or kill whatever predator ate it, animals such as the skunk produce chemicals that when released result in a not so pleasant aroma that an attacker will never forget.
Eric Hennings
Yes. The preys’ adaptations help the organisms to survive and reproduce. What about the predators? The adaptations to the preys’ defenses such as camouflage and armor are required so that the predator can also survive and reproduce. Without the ability to seize and consume prey, the predator starves and will not live to reproduce. As a result, predators have developed their own adaptations to acquire prey. "Most predators have acute senses that enable them to locate and identify potential prey. In addition, many predators have adaptations such as claws, teeth, fangs, stingers, or poison that help them catch and subdue the organism on which they feed"(Campbell 1201).
ReplyDeleteFor example Eric Hennings said that the sharp quills protect porcupines from predation. As a result of the development of such an exceptional defense, the predators developed new tactics to bypass the defenses. Weasels, bobcats, timber wolves, and wolverines are porcupines’ natural predators. They quickly attack and flip over the porcupines onto its unprotected belly and feast upon its flesh. (http://www.wildlifedepartment.com/species/porcupine.htm)
Predators are always a daily threat to animals and having ways to avoid the predators are always a natural selection to these organisms because then the organisms have a higher chance of surviving and reproducing. "Natural selection [changes] the genetic composition of a population [and] enhances the survival and reproduction" (Coyne 117). There are many ways to avoid predators like cryptic coloration as explained by Athena, Batesian mimicry as explained by Henry and Frank, and wings as explained by Michael. All of these adaptions to escape predators are a natural selection because these qualities help them survive and reproduce better.
ReplyDeleteJust like batesian mimicry helps prey avoid predators because the predator think the prey dangerous when the prey is actually harmless, mullerian mimicry also help keep predators away. Mullerian mimicry is when two harmful species mimic each other. Each specie "gains an advantage because the more [harmful] prey there are, the more quickly and effectively predators adapt, avoiding any prey with that particular appearance" (Campbell 1201-1202). An example of a mullerian mimicry is with the cuckoo bee and yellow jacket. Both bees look like each other and both a very dangerous because of the bees' sting. As a result predators of the bees avoid any prey with that kind of appearance (Campbell 1201-1202). The mullerian mimicry is natural selection to the bees since because both bees are dangerous, predators will not eat anything that looks similarly to them. Because they are not being eaten, the bees are able to survive longer and reproduce.
Another adaption that helps animals escape from predators is being nocturnal. Being nocturnal means that the animals sleeps during the day and functions during the night. Larger animals that are predators are not nocturnal so during the night time they are sleeping and not hunting for prey. For preys that are nocturnal, they are avoiding the predators at night time. Being nocturnal is a natural selection because the preys are avoiding being eaten in the night time and are able to survive and reproduce better. An example of a nocturnal prey is mice. The mice are able to avoid their predators like cats, eagles, and hawks (http://www.enchantedlearning.com/coloring/nocturnal.shtml).
The ability to escape from predators relates to the theme interdependence with nature. In any of the adaption previously stated, the prey had to depend on other organisms or its environment to escape the predator. With both types of mimicry, the prey had to depend on another organism that it looked like. When an animal is able to camouflage, the animals need to depend on its surroundings to camouflage with. A more obvious example of this theme is that the predator is dependent on the prey for food so the predator could survive.
The prompt also relates to theme Continuity and Change. The DNA for being able to camouflage, mimic other species, or having aposematic coloration is being transferred from one generation of organisms to another generation of organisms. If the genetic material was changing and didn’t carry the genes to be able to escape and hide from predators, then the organisms probably wouldn’t survive and would get eaten from the predators.