Chapter 24: The Origin of Species

Question 1

What is speciation?

Answer 1

When one species splits into two or more species

Question 2

AGH What is the Morphological Species Concept?

Answer 2

• Species defined by their morphology (physical features)

Question 3

What are the advantages and disadvantages of the Morphological Species Concept?

Answer 3

Advantages:

• can be applied to asexual and sexual organisms
• useful even without knowing the extent of gene Flow

Disadvantages:
- It is subjective; what specific features distinguish two species?

Question 4

What is the Biological Species Concept?

Answer 4

• Species defined by their ability to produce viable, fertile offspring, but do not produce viable, fertile offspring with other groups
• considered two different species when gene flow is interrupted

Question 5

What are the advantages and disadvantages of the Biological Species Concept?

Answer 5

Advantages:
- based off of a single mechanism
> either they can or cannot reproduce
> it’s a simple differentiation between species such as a donkey and a horse

Disadvantages:

• not all species have been observed mating
• fossils can no longer mate, so it’s difficult to classify them using the Biological Species Concept
• bacteria do not mate, but they do swap genetic material, so they also cannot be classified using this concept

Question 6

What is the Ecological Species Concept?

Answer 6

• This concept is used to define species by their ecological niches (places) and their adaptations to that environment
• due to adapting in similar environments, they may have similar morphologies

Question 7

What are the advantages and disadvantages of the Ecological Species Concept?

Answer 7

Advantages:
- acknowledges the role the environment plays when constructing morphological development in organisms

Disadvantages:

• niches are assumed and not very accurate
• it’s difficult to draw the line between two different niches
• many taxa could have overlapping niches

Question 8

What is the Phylogenetic Species Concept?

Answer 8

• Species defined by their most recent common ancestor on a Phylogenetic tree

Question 9

What are the advantages and disadvantages of the Phylogenetic Species Concept?

Answer 9

Advantages:
- recognizes history and how evolution plays a part in connected species

Disadvantages:
- determining the degree of difference required to indicate separate species

Question 10

In the Biological Species Concept, species are designated by the _______ of gene flow.

Answer 10

absence

Question 11

Which Species Concept is most favorable among biologists?

Answer 11

Phylogenetic Species Concept

Question 12

What is reproductive isolation?

Answer 12

When barriers prevent two species from producing viable, fertile offspring.

Question 13

What are prezygotic barriers?

Answer 13

Barriers that occurred before a zygote was made

Question 14

What are postzygotic barriers?

Answer 14

Barriers that occur after a zygote has been made

Question 15

What are the 5 prezygotic barriers?

Answer 15

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

Question 16

What are the 3 postzygotic barriers?

Answer 16

1. Reduced Hybrid Viability
2. Reduced Hybrid Fertility
3. Hybrid Breakdown

Question 17

What is Habitat Isolation?

Answer 17

When two species occupy different habitats within the same area

• they hardly encounter each other
• therefore they do not mate and remain different species

E.g., some snakes live in the same area, but one species lives in the water and the other on land, therefore they do not reproduce

Question 18

What is Temporal Isolation?

Answer 18

When two species live in the same area, but mate at different times of the day, season or year.

• because they mate at different times of the day, season or year, they do not reproduce and remain separate species

Question 19

What is Behavioral Isolation?

Answer 19

When a species has a specific behavior/ritual that only the same species is attracted to.

E.g., male blue footed boobies do a certain movement with their feet to attract females for mating; no other species will respond to this gesture, which therefore keeps the blue footed boobies as their own species.

Question 20

What is Mechanical Isolation?

Answer 20

When two species attempt to mate, but their physical structures prevent them from doing so successfully.

E.g., there are two species of a snail (one who’s shell spirals clockwise and the other who’s shell spirals anti-clockwise). These two species of snails cannot align up their reproductive parts based on their shell design. Therefore, they remain as different species.

Question 21

What is Gametic Isolation?

Answer 21

When two species mate but the sperm is incapable of fertilizing the egg.

E.g., sea urchins release their sperm into the water in hopes to fertilize the eggs of a neighboring sea urchin, but if the neighboring sea urchin has different chemical qualities surrounding her eggs that reject the sperm, the species remain separate.

Question 22

What is Reduced Hybrid Viability?

Answer 22

When two species create an embryo, but the hybrid either dies young or does not complete development.

E.g., some species of lizards will hybridize and produce an offspring, but the hybrids fail to complete development and die (keeping the two species separate).

Question 23

What is Reduced Hybrid Fertility?

Answer 23

When two species create a viable offspring, but it is infertile.

E.g., a mule is viable (strong, healthy, and fully develops) but it cannot reproduce. As a result, horses and donkeys remain separate species.

Question 24

What is Hybrid Breakdown?

Answer 24

When the first-generation of hybrids is viable and fertile, but their attempt to mate and produce offspring fails as they are feeble and sterile (fertility is lost).

E.g., some species of plants will do this. Two will create a hybrid that is viable and strong, but when it tries to reproduce with the same species or with another hybrid it’s offspring are not viable or fertile.

Question 25

What is allopatric speciation?

Answer 25

When two species diverge because they became geographically isolated.

Question 26

What is sympatric speciation?

Answer 26

When two species diverge even though they have not been geographically separated.

Question 27

__________ speciation is the most important factor in reducing Gene Flow.

Answer 27

Allopatric

Question 28

What causes sympatric speciation?

Answer 28

• Polyploidy
• Habitat Differentiation
• Sexual Selection

Question 29

What is polyploidy?

Answer 29

When a new species diverges from an accidental extra set of chromosomes during Meiosis.

Question 30

What is an autopolyploid?

Answer 30

An individual with more than two sets of chromosomes derived from one species.

Most commonly happens in plants because plants can asexually reproduce.

Question 31

What is an allopolyploid?

Answer 31

An individual with multiple sets of chromosomes derived from different species

(When a hybrid is made and is fertile, but can only reproduce with other hybrids. The hybrid thus becomes a new species.)

Question 32

How does sexual selection correlate with sympatric speciation?

Answer 32

If females stop becoming attracted to a specific trait or behavior that half of the population does, the species will diverge.

E.g., for some fish, they look blue or orange depending on the lighting. If the females are attracted to blue fish, they will mate with the blue fish while the orange fish will mate with the orange, even though they were originally the same species. They will then diverge.

Question 33

What is Habitat Differentiation?

Answer 33

When species remain separate because they use their environment differently

Question 34

What is the punctuated model?

Answer 34

When a new species has a sudden distinct diversion from the parents and remains a different species.

Question 35

What is the gradual model?

Answer 35

When a species has minimal diversions from the parents and continues to gradually diverge until they are a completely new species.

Question 36

Can speciation occur with the change of a single allele? Explain.

Answer 36

Yes.

For example, the snail with the clockwise and anti-clockwise shells are separated by only one allele.

Question 37

Does sympatric or allopatric speciation occur most commonly?

Answer 37

Allopatric