10.4.2 Allopatric Speciation Flashcards Preview

AP Biology > 10.4.2 Allopatric Speciation > Flashcards

Flashcards in 10.4.2 Allopatric Speciation Deck (12)
Loading flashcards...
1
Q

allopatric speciation

A

• Usually physical isolation (geographic barriers) precedes genetic isolation.
• Allopatric speciation can result from geographical isolation. Allopatric speciation is a type of speciation that can occur when a geographical barrier separates a splinter population from the original population.
• After geographical isolation, three sequential events may lead to allopatric speciation:
1. the founder effect
2. the continuation of genetic drift
3. selection pressure of the new environment
• An example of allopatric speciation is shown by the distribution of marsupial and placental mammals in relation to continental drift.

2
Q

Some geographical disturbances that may cause physical isolation include:

A
  • forest fire
    · earthquake
    · formation of a canyon
    · continental drift
3
Q

founder effect

A
  • This event is a form of genetic drift that occurs when the splinter group has some gene frequencies that differ from the main group, particularly if it is a small
    population.
  • In the illustration on the left, a splinter group of marbles leaves the original population to form a new population. The gene frequency, represented by marble color, is different in the splinter group versus the original population.
4
Q

The continuation of genetic drift:

A
  • As the population of the splinter group grows, genetic drift will continue. This drift will result in increased genotypic and phenotypic differences, many of which are nonadaptive. Although some of these changes may be adaptive and spread through the population quickly, the majority will be nonadaptive changes, causing variations in appearance that do not affect the success of the population.
5
Q

Selection pressures of the new environment:

A
  • The selection pressure in the new environment may be different from the previous environment. This difference can result in a shift in the gene frequencies away from those of the parent population.
6
Q

note

A
  • An example of allopatric speciation is shown by the
    distribution of marsupial and placental mammals in relation to continental drift.
  • The marsupials—the kangaroo, for example—are a taxonomic group of mammals characterized by embryonic development in a pouch. A placental mammal develops in a uterus.
  • Marsupials originated when the continents were still joined in a landmass called Pangaea. The breakup of Pangaea geographically isolated the marsupials of Australia. The Australian marsupials had a gene pool that was no longer representative of the original marsupial population. As the Australian marsupials of Australia populated the continent, genetic drift continued, resulting in greater genetic differences
    between them and the parent population. Environmental
    conditions created selection pressure, resulting in new
    species.
  • Meanwhile, placental mammals evolved from the marsupials in North America. The placental mammals underwent a similar radiation of species. Although both taxonomic groups arose from marsupial ancestors, the marsupials and placentals have many developmental and anatomical differences.
7
Q

True or false?
A geographical isolation event that leads to the creation of two very large subpopulations will not lead to allopatric speciation.

A
  • false
8
Q

__________ is when physical isolation resulting from a geographic barrier brings about genetic isolation of two populations of the same species.

A
  • Allopatric speciation
9
Q

Allopatric speciation depends on the physical separation of populations to allow for the development of genetic isolation (speciation). What is it about the physical barrier that is important?

A
  • It prevents intermating between individuals in the two populations.
10
Q

The reason that Australia is inhabited by many marsupials and no placentals is that

A
  • when Pangaea broke up there were only marsupials on Australia and they radiated outward filling all the ecological niches
11
Q

During allopatric speciation, a splinter goup is separated from the parent population by a geographic boundary. Genetic drift will produce many genotypic and phenotypic changes in the splinter group, all of which are adaptive.

A
  • false
12
Q

What kinds of places are good for studying genetic drift?

A
  • islands

Decks in AP Biology Class (383):