Chapter 5 - Origin of Species

Question 1

Speciation

Answer 1

the process by which one species splits into two or more species

Question 2

Microevolution

Answer 2

changes in allele frequency in a population over time

Question 3

Macroevolution

Answer 3

refers to broad patterns of evolutionary change above the species level

Question 4

How do we define a species?

Answer 4

• a group of similar living things that ranks below the genus in scientific classification and is made up of individuals able to produce offspring with one another
• Used to be based just on physical similarity (morphology).
• Now use morphology, physiology, DNA, ecology.

Question 5

Biological Species Concept

Answer 5

states that a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring; they do not breed successfully with members of other such groups
i.e., they are reproductively isolated from other species.

Question 6

Reproductive barriers (isolating mechanisms)

Answer 6

Pre-zygotic Barriers
Post-zygotic Barriers

Question 7

Pre-zygotic Barriers

Answer 7

Habitat isolation
Temporal isolation
Behavioral isolation
Mechanical isolation
Gametic Isolation

Question 8

Post-zygotic Barriers

Answer 8

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

Question 9

Habitat isolation

Answer 9

populations live in different habitats and do not meet

Question 10

Temporal isolation

Answer 10

different breeding times, seasons

Question 11

Behavioral isolation

Answer 11

courtship or mating behaviors

Question 12

Mechanical isolation

Answer 12

sex organs are mechanically incompatible

Question 13

Gametic Isolation

Answer 13

gametes (egg and sperm) are incompatible

Question 14

Reduced Hybrid Viability

Answer 14

Genes of the different parent species may interact and impair the hybrid’s development or survival in its environment

Question 15

Reduced Hybrid Fertility

Answer 15

a common feature of reproductive barriers separating recently diverged species

Question 16

Hybrid breakdown

Answer 16

Some first-generation hybrids are fertile, but when they mate with each other or with either parent species, offspring of the next generation are feeble or sterile

Question 17

Limitations of the Biological Species Concept

Answer 17

• Cannot be applied to fossils or asexual organisms
• Hybridization sometimes observed in nature

Question 18

Morphological species concept

Answer 18

defines a species by structural features
- It applies to both sexual and asexual species but relies on subjective criteria

Question 19

Ecological species concept

Answer 19

defines a species in terms of its ecological niche

Question 20

How Does Speciation Occur?

Answer 20

Speciation will occur if environmental conditions are different, and populations are separated for long periods and developed their own unique characteristics.

Question 21

Speciation can occur in two ways:

Answer 21

1. Allopatric speciation
2. Sympatric speciation

Question 22

Allopatric speciation

Answer 22

geologic barrier divides a population, leaving each group to follow its own evolutionary path.

Question 23

Sympatric speciation

Answer 23

more common in plants, no geographic barrier. Isolation is due to accidents during cell division resulting in polyploid offspring.

Question 24

The Process of Allopatric Speciation

Answer 24

Geographical barrier arises
Separated populations may evolve independently through mutation, natural selection, and genetic drift
- Causes genetic divergence
Reproductive isolation may arise as a by-product of genetic divergence
- E.g., geographically isolated populations of mosquitofish have become reproductively isolated as a result of selection under different levels of predation

Question 25

Sympatric Speciation
Can occur if gene flow is reduced by factors including:

Answer 25

• Polyploidy
• Sexual selection
• Habitat differentiation

Question 26

Polyploidy

Answer 26

 involves a spontaneous doubling of chromosomes, also means random
 is a condition of having more than 2 complete sets of chromosomes
 the presence of extra sets of chromosomes due to accidents during cell division
 much more common in plants than in animals
 can produce new biological species in sympatry within a single generation

Question 27

Autopolyploid

Answer 27

individual has more than two sets of chromosomes that came from same parent of species

Question 28

Allopolyploid

Answer 28

individual that has more than 2 copies, but these copies come from different type of species.

Question 29

Sexual selection

Answer 29

 members of one sex choose mates of the other sex to mate with and compete with members of the same sex for access to members of the opposite sex.
 Sexual selection for mates of different colors has likely contributed to speciation in cichlid fish in Lake Victoria

Question 30

Habitat differentiation

Answer 30

 more types of habitat in the same quantity in geographical zones
 Sympatric speciation can also result from the appearance of new ecological niches
 E.g., North American maggot fly (Rhagoletis pomonella) can live on native hawthorn trees, as well as more recently introduced apple trees

Question 31

Hybrid Zones

Answer 31

where ranges overlap, and mating occurs

Question 32

Hybrid Zones
Three possibilities:

Answer 32

Reinforcement
Fusion
Stability

Question 33

Reinforcement

Answer 33

strengthens reproductive barriers if hybrids have reduced fitness

Question 34

Fusion

Answer 34

members of the two lineages mate together forming hybrids

Question 35

Stability

Answer 35

each lineage keeps its own range apart of each other save for some areas of overlap.

Question 36

Punctuated Equilibrium

Answer 36

is a theory that proposes that once a species appears in the fossil record, the population will become stable, showing little evolutionary change for most of its geological history

Question 37

Gradualism

Answer 37

is a hypothesis, a theory, or a tenet assuming that change comes about gradually or that variation is gradual in nature and happens over time as opposed to in large steps