Cycle 8 - Species and speciation

Question 1

Morphological species concept

Answer 1

Delineate species based on measurable, observable traits.
Can compare dead specimens.
Species - a distinct cluster of individuals in phenotypic space.

Question 2

Problems with MSC

Answer 2

Can’t distinguish different species with similar appearances.
Phenotypic variability is not consistent across different species.
Gives little info about evolutionary history.

Question 3

Biological species concept

Answer 3

Species - a group of interbreeding populations that are reproductively isolated from other groups.
Testable
Explains evolution

Question 4

Problems with BSC

Answer 4

Doesn’t apply to asexual organisms, shy organisms, extinct organisms

Question 5

Genetic cohesiveness

Answer 5

Populations of same species experience gene flow that mixes their genetic material

Question 6

Genetic distinctiveness

Answer 6

Because populations of a different species are reproductively isolated, they cannot exchange genetic material

Question 7

Phylogenetic Species Concept

Answer 7

Species - group of population with a recent evolutionary history
Assessed by evolutionary tree
Can be applied to all groups of organisms

Question 8

Problems with PSC

Answer 8

Cannot prove reproductive isolation
Molecular data not possible from most fossils

Question 9

Clinal Variation

Answer 9

Different environmental conditions favor different traits, leading to evolution within a species.

Question 10

Reproductive barriers

Answer 10

Something which prevents gene flow between populations.
They evolve to be different species.

Question 11

Ring species

Answer 11

Species whose geographical distribution forms a ring around uninhabitable terrain.

Question 12

Prezygotic Isolating Mechanisms

Answer 12

Any isolation that occurs before fertilization:
Ecological Isolation
Behavioral Isolation
Temporal Isolation
Mechanical Isolation
Gametic Isolation

Question 13

Ecological Isolation

Answer 13

May occupy same region but live in different habitats

Question 14

Behavioral Isolation

Answer 14

Mating signals not recognized by another

Question 15

Temporal Isolation

Answer 15

Mate at different times

Question 16

Mechanical Isolation

Answer 16

Differences in structure prevent interbreeding

Question 17

Gametic Isolation

Answer 17

Gametes not compatible, cannot fertilize

Question 18

Postzygotic Isolating Mechanisms

Answer 18

Occurs when the zygote produced is unable to survive until birth/reproduction age:
Hybrid Inviability
Hybrid sterility
Hybrid Breakdown

Question 19

Hybrid Inviability

Answer 19

Would have 2 sets of distinct genes/developmental instructions that are too different to allow development. Fertilization occurs but eventually die young.

Question 20

Hybrid sterility

Answer 20

Chromosomes cannot pair properly during meiosis, offspring survive but are sterile (cannot produce functional gametes).

Question 21

Hybrid Breakdown

Answer 21

First generation hybrids can produce viable gametes and offspring, but second generation offspring have low fitness, are sterile, or are unviable.

Question 22

Allopatric Speciation

Answer 22

Two populations are geographically separated by a physical, geographically barrier that individuals cannot cross.
Results in reproductive isolation and increased genetic divergence.

Question 23

Sympatric Speciation

Answer 23

Populations are not geographically or environmentally separated.
New species occur even in absence of geographic isolation.

Question 24

Secondary Contact

Answer 24

Populations interact again after being isolated.

Question 25

Fusion (resume interbreeding)

Answer 25

The two populations interbreed and produce fertile offspring.
Gene flow continues and they remain one species.
Decreases rate of speciation.

Question 26

Hybrid zone

Answer 26

Where individuals of previously separated populations interbreed but offspring typically have lower fitness as they are not well adapted to environments outside of hybrid zone.

Question 27

Reinforcement

Answer 27

When two species are back in contact and they cannot interbreed.
Increases the rate of speciation.

Question 28

Polyploidy mutations

Answer 28

Results in individuals with one or more extra copies of genetic material. Polyploidy individuals are forced to mate with each other causing divergence within population that leads to speciation.