chapter 24 (but actually): speciation

Question 1

genetic isolation

Answer 1

occurs when a barrier to gene flow isolates two populations within a species (alleles no longer exchanged)

Question 2

genetic divergence

Answer 2

occurs when mutation, natural selection, and genetic drift occur in each of the isolated populations- populations evolve independently of each other

Question 3

three most common criteria used to identify species

Answer 3

• biological species concept
• morphospecies concept
• phylogenetic species concept

Question 4

main criteria for identifying species according to biological species concept

Answer 4

• reproductive isolation
• logical because these populations have no gene flow

Question 5

mechanisms that stop gene flow between populations

Answer 5

prezygotic isolation, post zygotic isolation

Question 6

prezygotic isolation

Answer 6

prevents individuals from different species from mating successfully

Question 7

postzygotic isolation

Answer 7

the hybrid offspring of matings between members of different species either dont survive or dont reproduce

Question 8

prezygotic isolation types

Answer 8

temporal, habitat, behavioral, mechanical, gametic barrier

Question 9

post zygotic isolation types

Answer 9

hybrid inviability and hybrid sterility

Question 10

temporal isolation

Answer 10

populations breed at different times (like different seasons)

Question 11

habitat isolation

Answer 11

populations isolated bc they breed in different habitats

Question 12

behavioral isolation

Answer 12

different courtship displays prevent interbreeding of populations (songbirds)

Question 13

mechanical isolation

Answer 13

male and female reproductive structures are incompatible

Question 14

gametic barrier

Answer 14

eggs and sperm are incompatible

Question 15

hybrid inviability

Answer 15

offspring do not develop normally and die during early development

Question 16

hybrid sterility

Answer 16

offspring are mature but sterile as adults

Question 17

disadvantages of biological species concept

Answer 17

• cannot be evaluated in fossils or asexual reproduction
• difficult to apply when closely related populations dont overlap geographically

Question 18

morphospecies concept

Answer 18

• independent lineages identified by differences in size, shape, other features
• applies to sexual, asexual, and fossil species

Question 19

disadvantages of morphospecies concept

Answer 19

• may lead to naming two or more species when it is one polymorphic species
• cannot identify cryptic species
• morphological features are subjective

Question 20

phylogenetic species concept

Answer 20

• identifies based on evolutionary history of populations
• can be applied to fossil, sexual, or asexual populations

Question 21

monophyletic group

Answer 21

• consists of an ancestral population, all of its descendants, and only those descendants
• can use the one snip test - imagine cutting a branch with scissors, everything that would come off is a monophyletic group

Question 22

synapmorphy

Answer 22

a trait found in certain groups of organisms and their common ancestor but is missing from more distant ancestors

Question 23

taxonomy

Answer 23

practice of describing, naming, classifying species

Question 24

allopatry

Answer 24

populations that are geographically separated

Question 25

two ways allopatric speciation can start

Answer 25

dispersal - movement of individuals from one place to another vicariance - physical splitting of a habitat

Question 26

example of vicariance

Answer 26

new physical barrier like mountain range or river splitting the geographic range of a species

Question 27

sympatry

Answer 27

populations that live in the same geographic area - makes interbreeding possible

Question 28

what types of factors can initiate the process of sympatric speciation

Answer 28

extrinsic factors (disruptive selection for extreme phenotypes), intrinsic factors (chromosomal mutations)

Question 29

disruptive selection

Answer 29

- favors extreme phenotypes (like high or low number of gill rakers) - if it persists, subsets of the population can be genetically isolated and diverge - leads to speciation

Question 30

mFAS gene

Answer 30

- affects ecological divergence and mate choice in australian fruit flies - codes for fatty acid synthase - makes external cuticles of flies more resistant to drying out

Question 31

polyploidy

Answer 31

possessing more than two complete sets of chromosomes - caused by an error in mitosis or meiosis

Question 32

autopolyploid

Answer 32

"same-many-form" individuals produced when a mutation results in a doubling of chromosome number and the chromosomes all come from the same species

Question 33

allopolyploid

Answer 33

"different-many-form" individuals created when parents of different species mate and an error in mitosis occurs - results in viable, nonsterile offspring with two full sets of chromosomes

Question 34

why is polyploidy successful in plants

Answer 34

- higher levels of heterozygosity - can tolerate higher levels of self-fertilization - genes on duplicated chromosomes can diverge independently

Question 35

secondary contact of two populations can produce what outcomes

Answer 35

fusion of the populations, extinction of one population, reinforcement of divergence, founding of hybrid zones, or formation of new species

Question 36

fitness of hybrid offspring - reinforcement of divergence

Answer 36

offspring will have lower fitness than parents bc they arent adapted well to either habitat- also may fail to develop normally / be infertile

Question 37

reinforcement

Answer 37

natural selection for traits that prevent interbreeding among populations

Question 38

hybrid zome

Answer 38

- geographic area where interbreeding occurs and hybrid offspring are common - can be long or short lived, narrow or wide, can move over time or be stable in one place

Question 39

mtDNA

Answer 39

- offspring receive via the mitochondria from the egg during fertilization - used to determine parentage of a hybrid individual