Chapter 14 - Speciation Flashcards
What are ring species?
Different populations of a species that can interbreed with one another to form a sort of ring, but that doesn’t go all the way around, meaning that there is a reproductive barrier at some point.
Examples are certain breeds of seagulls and salamenders.
What is a species?
A group of populations that have the potential to interbreed in nature and produce viable offspring, which are reproductively isolated from other such groups.
What causes speciation?
Reproductive isolation or a block to gene flow.
This can be caused by mutation, non-random mating, selection or genetic drift.
What are the pre-zygotic isolation mechanisms?
Ecological (ex. lions and tigers). They can interbreed, but just don’t live in the same locations.
Behavioral (ex. songbirds). They could interbreed but do not because of behavioral differences.
Temporal (ex. leopard frog and wood frog). They could interbreed but do not because their mating seasons do not overlap.
Mechanical (ex. snails). They could interbreed but do not because one species is counter-clockwise and the other is clockwise.
Gametic barrier: mating occurs but no gamete fusion.
What are examples of post-zygotic isolation?
Reduced hybrid viability (ex. Grolar)
Reduced hybrid fertility (ex. mule)
Hybrid breakdown (ex. F1 rice plant is very small and unsuccessful)
What is reinforcement?
When hybrids are at a selective disadvantage, and so so sympatric species evolve to improve pre-zygotic isolating mechanisms such as mechanical isolation to prevent hybrid production.
An example is with Blue Phlox flowers becoming red when they are sympatric with another species.
What are allopatry and sympatry?
Sympatry: at the same time and place.
Allopatry: separated by time and space.
What factors can cause sympatric speciation?
- Polyploidy
- Chromosomal structural changes
- Mutation that isolates a population
- Disruptive selection
- Sexual selection
How many mass extinctions are there?
5 have happened, and the 6th one is currently happening because of humans.
What is polyploidy?
When organisms have more than 2 sets of chromosomes. (ex. instead of 3n they can be 5n or even 84n). This can be caused by errors in meiosis among other things.
What are the 3 possible outcomes of hybridization?
- Reinforcement (hybrids cease to be formed)
- Fusion (the two species fuse)
- Stability (continued production of hybrid individuals)
