Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
The process of Science Does Predation Drive the evolution of Lizard horn length? One recent and particularly elegant demonstration of natural selection in action involved the flat-tailed horned lizard, a desert inhabitant of the American Southwest (see figure a) The lizard’s main predator, birds called shrikes, attack by biting a lizard’s neck just behind the skull, severing the spine. The shrike then carries the dead prey to a convenient place, such as a fence or a branch, impales it and eats it (see figure b). Kevin Young and colleagues at Utah State University and Indiana University made the observation that flat-tailed horned lizards defend against attack by thrusting their heads backward, stabbing the shrike bird with the spiked horns that protrude from the rear of the skull. This led the researchers to question whether longer horn length represented a survival advantage. Young’s hypothesis was that the longer horn’s did provide a survival advantage, and he formed the prediction that live horned lizards would have longer horn lengths than dead ones Young’s experiment was simple: he measured the length of rear horns and the tip-to tip spread distance of side horns from the skulls of 29 dead lizards (found where they had been impaled) and 155 live lizards. His results, shown in figure c, indicate that the average horn length of live lizards is about 10% longer than that of dead lizards. The researchers concluded that defensive behavior against predators is one factor driving natural selection of horn length among this lizard species. Examples of Natural Selection: Lizards 1. 2. 3. 4. What is/are the variation(s) in the population? What is/are the environmental challenge? Which trait is successful under which condition? How is this/are these an example(s) of Natural selection? Be sure to include how genetic variation is relevant Be sure to include how overproduction of offspring is relevant Be sure to include how struggle for existence is relevant Be sure to include how differential survival and reproduction is relevant Which example do I research? Assigned by your group number!!! A,2: Peppered moths of England (Tiger Book p290-291) 3,6: Snails in England (frog book p266) 4,5: Flat tailed horned lizards ( Your book p256) 7,8: Pesticide resistance (Your book p 244) Natural selection is a prominent force in nature: Snail Example Well over 100 cases of the effects of natural selection have been extensively documented. The land snails in the Figure belong to a single species, Cepoea nemoralis, found in woodlands and open fields throughout Europe. Their shells differ in color and in the presence or absence of stripes. The snails in the photograph are not usually found together. Snails with lightcolored, striped shells are found mainly in welllighted areas, whereas dark colored individuals lacking stripes are found in shady places. The shell color pattern camouflages the snails in their respective habitats, hiding them from birds that prey on snails. If a snail appears in an area where its color pattern does not conceal it, birds are more likely to find that snail than a camouflaged snail. Thus, snails whose shells match their environment are likely to survive and reproduce, passing along characteristics to their offspring, while those with uncamouflaged shells will likely be eaten. Examples of Natural Selection: snails 1. 2. 3. 4. What is/are the variation(s) in the population? What is/are the environmental challenge? Which trait is successful under which condition? How is this/are these an example(s) of Natural selection? Be sure to include how genetic variation is relevant Be sure to include how overproduction of offspring is relevant Be sure to include how struggle for existence is relevant Be sure to include how differential survival and reproduction is relevant