Chapter 22: Species and Speciation

Question 1

define speciation

Answer 1

the process that produces new and distinct forms of life (essentially, development of reproductive isolation between populations)

Question 2

define species

Answer 2

the fundamental evolutionary unit (no one definition has yet satisfied all naturalists)

Question 3

what must a species be capable of doing?

Answer 3

must be fluid and capable of changing, giving rise to new species through evolution

Question 4

what is the Biological Species Concept? (BSC) by Ernst Mayr?

Answer 4

“species are groups of actually or potentially interbreeding populations that are reproductively isolated from other such groups”

Question 5

what are the main problems with the BSC?

Answer 5

-Difficult to apply in real world
• Cannot be applied to asexual or extinct
organisms
• Does not account for genetic exchange in ring
species
• Does not account for hybridization in plants

Question 6

what is the morphospecies concept?

Answer 6

members of the same species usually look alike

Question 7

what is the main problem with the morphospecies concept?

Answer 7

members of the same species may look very different phenotypically (polymorphisms) or different species may look very similar

Question 8

define ring species

Answer 8

when some species in a population cannot exchange genetic material directly, but they may do so indirectly (ex. some species are geographically isolated from one another, but others are not)
-share genetic material indirectly

Question 9

define hybridization

Answer 9

interbreeding between species (occurs in many plants)

Question 10

define ecological niche

Answer 10

the complete description of the role the species plays in its environment (habitat requirements, food, water, needs, etc.)

Question 11

Ecological Species Concept (ESC)

Answer 11

there is a one to one correspondence between a species and its niche
holds that it is impossible for two species to coexist in the same location if their niches are two similar because competition between them for resources will eventually lead to the extinction of one of them

Question 12

Evolutionary Species Concept (EvSC)

Answer 12

the idea that members of a species all share a common ancestry and a common fate

• requires that all members of a species are descended from a single common ancestor
• this is limited mostly to asexual species

Question 13

define reproductive isolation

Answer 13

the inability to produce viable fertile offspring

Question 14

what are the 2 categories of factors that cause reproductive isolation?

Answer 14

• pre zygotic (act before fertilization)

- post zygotic (act after fertilization)

Question 15

what are 3 pre-zygotic reproductive barriers?

Answer 15

• behavioral (songs, rituals, etc)
• physical
• temporal (time)
• ecological

Question 16

what is a post zygotic reproductive barrier?

Answer 16

genetic incompatibility

Question 17

what does it mean to be “partially reproductively isolated”?

Answer 17

when two populations are not yet two different species, but the genetic differences between them are enough so that the hybrid offspring have reduced viability/fertility

Question 18

define “allopatric”

Answer 18

“different place”

-physical separation

Question 19

define subspecies

Answer 19

a result of a partial genetic divergence of a singular species

Question 20

what are the two ways species become allopatric?

Answer 20

1. dispersal

2. vicariance

Question 21

define dispersal

Answer 21

when some individuals colonize a distant place (such as an island) far from the main source population

Question 22

define vicariance

Answer 22

when a geographic barrier arises within a single population, separating it into two or more isolated populations

Question 23

define peripatric speciation

Answer 23

(type of allopatric speciation) in this model, a few individuals from the mainland population disperse to a new location remote from the original population and evolve separately
-can be intentional or accidental

Question 24

does genetic divergence occur faster in smaller island populations, or in larger mainland populations?

Answer 24

faster in smaller island populations!

• genetic drift is more pronounced in smaller populations
• environment may differ than that of the mainland, driving natural selection

Question 25

define adaptive radiation

Answer 25

a bout of unusually rapid evolutionary diversification in which natural selection accelerates the rates of both speciation and adaptation
-occurs when there are many ecological opportunities available for exploitation

Question 26

define co-speciation

Answer 26

when organisms speciate in response to each
other…one changes a bit and the other one changes in
response to the first

Question 27

sympatric speciation

Answer 27

the process through which new species evolve from a single ancestral species while inhabiting the same geographic region

Question 28

define instantaneous speciation

Answer 28

(type of sympatric speciation) occurs in a single generation

-caused by hybridization between two species in which the offspring are reproductively isolated from both parents

Question 29

define tetraploid

Answer 29

double diploid 
(4 genomes rather than 2)

Question 30

define polyploidy

Answer 30

multiple chromosome sets in plants

Question 31

can speciation occur without natural selection?

Answer 31

YES, it can occur in the presence or absence of natural selection
-natural selection does not always lead to speciation (sometimes it does, sometimes it doesn’t)

Question 32

in what way is natural selection NOT a contributor to speciation?

Answer 32

in the case of genetic drift

Question 33

in what way could natural selection be a contributor to speciation?

Answer 33

• sympatric speciation
• allopatric speciation and adaptive radiation
• reinforcement of reproductive isolation

Question 34

define reinforcement of reproductive isolation (reinforcement)

Answer 34

process by which diverging populations undergo natural selection in favor of enhanced pre-zygotic isolation to prevent the production of less fit hybrid offspring