Name 3. The graph below shows the effect of hunting imposed on horn length in bighorn sheep populations over several years. a. What type of selection does it show? b. Propose an explanation for the change in horn length. c. What do you predict will happen to horn length if hunting stops? 4. What genetic evidence would support the occurrence of a strong selection event? 5. How have cane toads changed since they were introduced to Australia? Explain the impact that invasive cane toads have had on the evolution of Australian snakes. 6. Refer to section 10.6 Humans as Agents of Selection. Identify 2 unintended consequences of artificial selection by humans and describe examples for each.
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The graph shows a negative trend between year and mean horn length. This indicates that hunting is selecting against individuals with longer horns, as they are more likely to be targeted by hunters. This type of selection is called directional selection. Show more…
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Focus on the evolution of the horn size in the Bighorn sheep population from 1950 to present. Explain how selection was a factor in the evolution of horn size since 1950. The hunters chose to harvest the sheep with the larger horns. Only smaller horned sheep survived and reproduced, so, over time the population had smaller horn size. The female sheep chose the males with the largest horns, so only sheep with large horns reproduced. As a result, sheep currently have larger horns than 70 years ago. The mutation for smaller horns happened so the sheep would not be harvested by hunters, and now that mutation spread through the population. Selection was not a factor in the evolution of horn size since 1950.
Suman K.
Take, for example, a population of black furred and white furred rabbits living on a white iceberg. The rabbits are of the same species and able to mate. A pack of wolves found the population and quickly eliminated the black rabbits from the population, leaving only white rabbits. If all the black furred rabbits were eliminated, explain why black furred rabbits could show up again? 7. Identify the type of selection being described in the following scenarios. a. In the arctic larger polar bears where able to hunt larger animals and thus be able to eat more which helped them survive. Eventually the average size of polar bears increased in the population. This is an example of what type of natural selection? _________________________ b. When a particular species of fox was evolving, the foxes with the longer legs and larger bodies were able to run fast and jump over obstacles, and the foxes with shorter legs and smaller bodies were able to evade predators by hiding in burrows and rock crevices, the foxes with large bodies and short legs were not able to hide very well nor run very fast. The foxes with the longer legs and large bodies, and the foxes with the shorter legs and smaller bodies were both, on average, able to live longer than the short legged, large bodied foxes. What type of natural selection is happening in this group? _________________________ c. Peacocks use large, elaborate and colourful feathers to attract a mate. Generally speaking, the larger, more colourful and elaborate the display the better. But as the display gets larger and more elaborate it makes it more difficult for the bird to evade predators, the colourful display also attracts predators very easily. Peacocks with smaller, less elaborate displays are ignored by the peahens and do not mate. What type of natural selection is working on the peacock population? _________________________
Adi S.
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