Lecture 6: Speciation

Question 1

Use the biological species concept to define what a species is

Answer 1

The Biological Species Concept defines species as individuals in popluations that can breed and produce fertile offspring. So, a species can mate with each other and their offspring are fertile.

Question 2

What is temporal isolation? Is it a prezygotic or postzygotic barrier?

Answer 2

Temporal isolation is a prezygotic barrier and it is when two species don’t reproduce because of different timing.

Question 3

What are the two types of reproductive isolation?

Answer 3

Prezygotic barriers: prevent fertilization from taking place
Postzygotic barriers: Mating occures, but the viability or fertility of offspring is reduced

Question 4

What is behavioral isolation? Is it a prezygotic or postzygotic barrier?

Answer 4

Behavioral isolation is a prezygotic barrier. This occurs when a potential mate does not “act” properly so there is no mating.

Ex: Wrong dance, wrong song, nuptial gifts

Question 5

What is behavioral isolation? Is it a prezygotic or postzygotic barrier?

Answer 5

Behavioral isolation is a prezygotic barrier. This occurs when a potential mate does not “act” properly so there is no mating.

Ex: Wrong dance, wrong song, nuptial gifts

Question 6

What is mechanical isolation? Is it a prezygotic or postzygotic barrier?

Answer 6

Mechanical isolation is a prezygotic barrier and it occurs when the genitalia are incompatible.
(They literally CANNOT mate)

Ex: Plants pollinated by different bees

Question 7

What is Gametic isolation? Is it a prezygotic or postzygotic barrier?

Answer 7

Gametic isolation is a prezygotic barrier and it occurs when male sperm does not fertilize the egg. Usually, the egg has a receptorthat only notices the right kind of sperm.

Question 8

What is habitat isolation? Is it a prezygotic or postzygotic barrier?

Red legged frogs vs Bullfrogs?

Answer 8

Habitat isolation is a prezygotic barrier and it occurs when populations are isolated because they breed in different habitats.

Ex: Red-legged frog breeds in fast moving streams, Bullfrogs breed in ponds

Question 9

What is Hybrid inviability? Is it a prezygotic or postzygotic barrier?

Sheep and goats?

Answer 9

Hybrid inviability is when the offspring die before they are even born.

Ex: Sheep and goats have different numbers of chromosomes so the development of their fertilized egg is impossible.

Question 10

What is Hybrid sterility? Is it a prezygotic or postzygotic barrier?

Mules?

Answer 10

Hybrid sterility is when the offspring cannot reproduce.

Ex: Donkeys and Horses can mate and produce a mule, but the mules are infertile.

Question 11

What is the morphospecies concept?

How is this helpful to paleontologists?

Answer 11

The morphospecies concept is that species that look different are different species (literally).

Paleontologists cannot observe mating patterns in their fossils, so they can make predictions based on appearance alone.

Question 11

What is the morphospecies concept?

How is this helpful to paleontologists?

Answer 11

The morphospecies concept is that species that look different are different species (literally).

Paleontologists cannot observe mating patterns in their fossils, so they can make predictions based on appearance alone.

Question 12

What is the Phylogenetic species concept?

Answer 12

Phylogenetic species concept identifies species based on phylogenies.

Question 13

What is vicariance and how is it different from dispersal?

Answer 13

A vicariance event is when a population is split by some sort of physical splitting of a habitat such as a river or earthquake.

Dispersal is when a group of individuals move to another location.

Question 14

What is allopatric speciation and what are its steps?

Answer 14

Allopatric speciation is speciation that occurs in the presence of geographical isolation.
1. Separation by vicariance or dispersal
2. Mutations (induces variation)
3. Natural selection - different environments could mean NS acts differently
4. Genetic drift
5. Reproductive isolation - if they cant mate and produce fertile offspring they are now two separate species

Question 15

How do trumpeter birds and snapping shrimp represent vicariance?

Question 16

What is sympatric speciation?

Answer 16

Sympatric speciation is speciation that occurs in the absence of a geographical barrier.

Question 17

What is sympatric speciation due to ecological niche?

Hawthorn and apple flies?

Killer whales?

Answer 17

Sympatric speciation can still occur when there is divergent selection.

The hawthorn and apple flies eat different fruitsand therefore mate on differnet trees. This limits gene flow.

Killer whales can be split into transient and resident groups and differ in their food choice and size of groups travelled in.

Question 18

What is internal sympatric speciation?

Answer 18

This refers to chromosomal mutations that cause a reproductive barrier

Question 19

What are the 5 cases that occur when isolated populations come back into contact?

Sunflowers (Helianthus)?

Answer 19

1. Fusion of populations: They come back together and breed like normal
2. Extinction (of one): One of the populations has become a better competitor for resources and drives the other to extinction
3. Reinforcement: They interbreed (like fusion) but their offspring have low fitness
4. Hybrid zone formation: Regions where populations are in contact and have fertile and viable hybrids
5. Speciation: The hybrids themselves become separate species

Sunflowers: Separate species can make a hybrid that itself constitutes a species