DIVERGENT & CONVERGENT EVOLUTION
GENE FLOW & SPECIATION
=Divergent Evolution= Divergent evolution occurs when an ancestral group splits into two or more species (also called speciation). The resulting species will share many anatomical (structural) similarities because they have inherited them from a common ancestor. The relatively rapid divergence of a population into several species is called an ''adaptive radiation''. =Convergent Evolution= Some organisms possess similar anatomical structures, not because of any shared ancestry, but because they occupy a similar niche. These species have independently evolved similar features to serve a similar function. The similarities of these structures tend to be superficial and when they examined more closely they usually have some fundamental differences. [image:http://i.imgur.com/og0hOJU.png?1] For instance, aquatic carnivores such as dolphins and sharks appear to be quite similar. They both have flipper, a similar coloration and the same streamlined body shape. These similarities have evolved because of the similar selection pressures associated with their niche. However, their internal systems are actually very different. Dolphins are mammals and give birth to live young whereas sharks are a type of fish and that lays eggs. Dolphins have lungs whereas sharks have gills. [image:http://i.imgur.com/YAeLkTt.png?1] Another common example is the eyes of vertebrates (animals with a spine such as humans) and the octopus. These structures serve the same function and look very similar. However, they have actually evolved quite differently. In humans the blood vessels and nerves pass in front of the retina, creating a blind spot (4). In the octopus the blood vessels and nerves interface with the retina from behind. This is actually the "better" design as it means octopuses don't have a blind spot.
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