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Speciation

Problems

Types of Speciation

Adaptive Radiation

Problem : Describe the difference between anagenesis and cladogenesis.

Anagenesis involves evolution within a single lineage. Cladogenesis, on the other hand, involves evolution in a branching pattern, with many new species evolving from a single parent species.

Problem : A flowering plant usually produces seeds that are diploid, or carry two copies of each chromosome. In one generation, however, this plant produces several seeds that have four copies of each chromosome (tetraploid). These seed germinate and mate with each other to create more tetraploid offspring. What type of speciation is this?

This is an example of sympatric speciation.

Problem : A population of geese exists in which 70% of individuals have dark feathers and the remaining 30% have white feathers. Due to the interruption of their nesting grounds by human development, the population becomes split into two populations. By chance, one population now has 90% white-feathered individuals and the other has 90% dark-feathered individuals. Over time, these two populations become different species, on of entirely white-feathered geese and the other of entirely dark-feathered geese. What kind of speciation is acting?

These two populations have undergone allopatric speciation, with the founder effect acting on feather color.

Problem : A population of grass plants lives at the edge of a mining area. Close to the mining area, the soil has become infused with a high concentration of metals, making it more difficult for plants to grow there. The grass plants that grow in these areas develop more slowly than those that grow farther away from the mines and they flower later in the season. As a result, two populations of grasses arise: those that are far away from the mines and bloom early in the season, and those that are close to the mines and bloom later in the season. These two populations experience temporal reproductive isolation and evolve into different species. What type of speciation is acting?

This is an example of parapatric speciation.

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