Lecture 6 - Biological Species Concept

Question 1

What is the heterozygote advantage?

Answer 1

Heterozygotes have a greater fitness than either homozygote.

Question 2

What is frequency-dependent selection?

Answer 2

It is when fitness depends on how common the phenotype is in a population.

Question 3

What are 5 constraints of evolution?

Answer 3

1. Laws of physics, thermodynamics, and gravity
2. Sources of genetic variation
3. Adaptation is opportunistic
4. Trade-offs in traits
5. Environmental change

Question 4

What is the biological species concept?

Answer 4

Species are considered groups of actually or potentially interbreeding populations, which are reproductively isolated from one another.

Question 5

What are 4 difficulties we face when it comes to defining species?

Answer 5

1. Cannot evaluate the reproductive isolation of fossils
2. Local variation
3. Asexual reproducers
4. Hybrids

Question 6

What are the 5 types of PRE-zygotic reproductive isolation?

Answer 6

1. Habitat isolation
2. Temporal isolation
3. Behavioral isolation
4. Mechanical isolation
5. Gametic isolation

Question 7

What are the 3 types of POST-zygotic isolation?

Answer 7

1. Reduced hybrid viability
2. Reduced hybrid fertility
3. Hybrid breakdown

Question 8

What is the difference between allopatric and sympatric speciation?

Answer 8

Allopatric speciation is when a species is separated by a geographic barrier that reproductively isolates them through natural selection or genetic drift. Speciation occurs in populations that still live in the same geographic area.

Question 9

What are the causes of sympatric speciation?

Answer 9

A mutation or polymorphism creates a phenotype that is attractive causing assortative mating or sexual selection. It can also be caused by habitat differentiation of polyploidy.

Question 10

What is polyploidy?

Answer 10

A chromosomal alteration where an organism has 2 complete chromosome sets due to a cell division error.

Question 11

What is autopolyploidy?

Answer 11

Nondisjunction, a cell division error within a species, doubles chromosomes, reproductively isolating the individual.

Question 12

What is allopolyploidy?

Answer 12

Two species with different amounts of chromosomes interbreed and an error doubles most alleles after a sterile hybrid forms.

Question 13

What are 3 reasons that polyploidy is an successful speciation method in plants?

Answer 13

1. It happens nearly instantaneously
2. It provides higher genetic diversity
3. It leads to reduced inbreeding depression