Topic 1 Evolution: Speciation

Question 1

• Speciation is the formation of new species. When gene flow ceases, or is interrupted, between two sections of a population, speciation begins.

Answer 1

Note

Question 2

• A group of individuals capable of interbreeding.

Answer 2

Species

Question 3

• This speciation occurs when the population is divided by a geographic barrier. Interbreeding between two resulting populations is prevented as a result. The gene frequencies in the population can now diverge due to natural selection, mutation, and genetic drift. If the gene pool sufficiently diverges, the separated populations will not interbreed when the barrier is removed. If they cannot interbreed, that means a new species has formed. This form of speciation happens through:

Answer 3

Allopatric Speciation

Question 4

a. Dispersal

b. Vicariance

Answer 4

Types of Allopatric Speciation

Question 5

• The group is isolated by being physically removed from the original location of the larger group

Answer 5

a. Dispersal

Question 6

• The group is isolated by a geographic barrier but is in the same overall location of the larger group

Answer 6

b. Vicariance

Question 7

• This is the formation of new species without the presence of geographic barriers. This can occur in a few different ways:

Answer 7

Sympatric Speciation

Question 8

1. Balanced Polymorphism

2. Polyploidy

Answer 8

Types of Sympatric Speciation

Question 9

• Natural selection due to polymorphism. Example: A population of insects has different colors. One color can camouflage to different substrates, but the insects in other colors cannot and will be eaten. Only insects with the advantageous color will mate as they are the ones that survive. The insects with this specific advantageous color are now isolated from other subpopulations

Answer 9

1. Balanced Polymorphism

Question 10

• Possessing more than the normal two sets of chromosomes, such as 3n or 4n, is considered polyploidy. This can lead to reproductive isolation, such as in plants. For example, nondisjunction of a 2n plant species could occur during meiosis, resulting in gametes that are still diploid instead of haploid. These diploid gametes could self-pollinate or reproduce with other gametes that have the same diploid number to form a 4n zygote, but the diploid gametes cannot reproduce with the normal 1n gametes. This new 4n zygote would be reproductively isolated from the original 2n species, and thus speciation can occur. In plants, the polyploidy can be further categorized into:

Answer 10

2. Polyploidy

Question 11

a. Autopolyploidy

b. Allopolyploidy

Answer 11

Types of Polyploidy

Question 12

• When an organism has more than two sets of chromosomes, both of which are from the same parental species

Answer 12

a. Autopolyploidy

Question 13

• When a organism has more than two sets of chromosomes, but they come from different species

Answer 13

b. Allopolyploidy

Question 14

• Two different closely related species mate and produce a hybrid along a geographic boundary called a hybrid zone

Answer 14

Hybridization

Question 15

• Hybridization can result in more genetic variation. This means the hybrid can live beyond the range of either parents.

Answer 15

Note

Question 16

• The rapid evolution of many species from a single ancestor. This occurs when an ancestral species is introduced to an area where diverse geographic and ecological conditions are available for colonization.

Answer 16

Adaptive Radiation