Lesson 3 Essay Questions

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Lesson 3 Essay Questions: 1. Compare and contrast directional selection and disruptive selection and provide an example of each. Both directional and disruptive selection is a type of natural selection. Natural selection is the differential survival and/or reproduction of organisms as a function of their physical attributes. (phenotype) This results in evolution over many generations. Each mode of selection alters the mean or variance of a phenotypic trait in a population or species. These distributions can be represented in bell curves. Both selection processes can be influenced by human interaction. Directional Selection occurs when an extreme phenotype at one end of a population distribution is favored over all other…show more content…
Jaws are believed to evolved from the first pair of gill arches. The presence of jaws permits a predatory lifestyle. Early bony fishes or lobed finned fishes had lungs. Amphibians were the first group to have jointed appendages and to invade land. Amphibian means living both on land and in water. Besides the jointed limbs they have other features that are not seen in the fishes. Eyelids that keep the eye moist, sound producing larynx, and ears adapted to pick up sound waves. Amphibians have a great variety of reproductive strategies. This variety as well as the adaptations noted above made them successful colonizers of the land environment. Reptile are the next step in the evolutionary tree of chordates. The most outstanding adaptation of reptiles is that they have a means of reproduction suitable to a land existence, Fertilization is internal and the female lays leathery , flexible shelled eggs. The amniotic egg made development on land possible and eliminated the need for a water environment during development. Birds are considered feathered reptiles. They share a common ancestor with the crocodile. Nearly every anatomical feature of a bird can be related to its ability to fly. Birds lay a hard shelled amniotic egg rather than the leathery egg of other reptiles. Mammals are amniotes as well and share a common ancestor with the reptiles. However they represent a
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