The Formation of Species Flashcards
What is natural selection?
Natural selection is the effect of survival of the fittest within a population over time
What is microevolution?
Microevolution happens on a small scale within a single population. The changes would not result in the newer organisms being considered as different species
- Example: A species has a color or size change.
What is macroevolution?
Macroevolution refers to major evolutionary changes over time.
- Example: A whale is a descendent of a land animal.
- Results in the formation of a new species
What is a species?
A species is a group of organisms that may contain genotypic and phenotype variability and members have the potential to interbreed and produce viable and fertile offspring.
What is speciation?
Speciation is when two groups of a population begin to evolve in different ways. As time goes on, they become more and more different until they are no longer able to interbreed
What is the defining characteristic separating one species from the other?
Species are reproductively isolated. This is the key feature that defines a species from another.
- This criterion is not perfect, as some species can form mules, but they are not reproductively viable
What is allopatric speciation?
Allopatric speciation occurs when interbreeding is stopped between two populations of a species due to a geographic barrier and two different species emerge.
- Ex: Two squirrel populations on the opposite sides of a canyon, where the river is too vast to cross.
What is sympatric speciation?
Sympatric speciation occurs when different species emerge from the same population in the same geographic area. Gene flow is reduced due to the following:
- Polyploidy: A mistake in cell division results in an extra chromosomal set. Thus a plant can have a 4N chromosome number instead of a 2N chromosome number. These 4N plants can’t breed with 2N plants, but can breed with themselves or other 4N plants.
- Reproductive Isolations: Mutations occur where a subset of the species mates at a different time, or eat a different food source. When mating time happens, they only mate with their own population subset. (Apple maggot flies laying eggs in apples vs hawthorne fruit)
What is autopolyploidy?
Autopolyploidy is a subset of polyploidy:
- Organism has more than two sets of chromosomes all derived from a single species.
- Ex: AAAA
- Additional chromosal set that is identical to parent species.
- If plant X has a 2N = 10, a new species Y, arises as an autodiploid from X has a 2N = 20
What is allopolyploidy?
Autopolyploidy is a subset of polyploidy:
- Organism has more than 2 sets of chromosomes derived from different species
- Ex: AABB
Is speciation slow or fast?
Speciation can be slow or fast, and it can involve a few genes or many genes
What are the two models that deal with speciation?
The two models that deal with speciation are:
- Gradualism
- Punctuated Equilibrium
What is gradualism?
Gradualism is a speciation model:
- A common ancestor is involved which over a long period of time gave rise to current organisms
- Many small changes occurred during the process and some cases are well documented in the fossil record.
What is Punctuated Equilibrium?
Punctuated equilibrium is a speciation model:
- After a period of equilibrium, evolution is concentrated in very rapid events of speciation
- This is also well noted in the fossil record
- Studies are showing that this model is favored
What is coevolution?
Coevolution is the evolution of two or more species whose members exert selective pressures on one another. Ex:
- Predator-Prey relationships
- Host-Parasite relationships
- Mutualistic species (Some hummingbirds only like a specific flower and their bills are perfectly suited to grab the nectar from it, and as a result pass the pollen on to other flowers)
