Chapter 18

Question 1

what is a population?

Answer 1

a group of individuals of the SAME species living in a certain area

Question 2

what is a species?

Answer 2

individuals who are reproductively the same and yield viable offspring of the same kind

Question 3

what is a hybrid?/

Answer 3

from different species that can breed to produce offspring that are different from the parents and typically sterile

Question 4

what is the best way to determine what species an organism is and why?

Answer 4

DNA, bc appearances can be deceiving

Question 5

what are the 3 pillars of evolution?

Answer 5

1. species accumulate differences
2. descendants differ from their ancestors
3. new species arise from existing ones

Question 6

what is the biggest thing to remember about evolution and who evolves?

Answer 6

POPULATIONS evolve, NOT individual organisms

Question 7

list Darwin’s 3 postulates

Answer 7

1. all organisms reproduce in excess of the numbers that can actually survive= survival of the fittest
2. individual numbers of a species vary from one to another; some differences are more beneficial than others
3. some variants will survive and some will be destroyed (selected for vs. selected against)

Question 8

what was Darwin’s theory about the variation of species?

Answer 8

species will be modified in the direction of the most advantageous variants

Question 9

what was Darwin’s theory for how giraffes got long necks?

Answer 9

variation was present among the population, but longer necks were more suited to the present environment, so they survived and reproduced more

Question 10

what was Lamarck’s WRONG theory for how giraffes got long necks?

Answer 10

thought variation was acquired during life by individuals. like giraffes stretched their necks?? dumbass

Question 11

what are the 2 forms of evolution?

Answer 11

1. divergent

2. convergent

Question 12

what is divergent evolution? give an example

Answer 12

becoming less alike over time, like how all the different flowering plants evolved from a common ancestor

Question 13

what is convergent evolution? give an example

Answer 13

becoming more alike over time, like aquatic animals all evolving to have a streamlined body shape; the environment influenced the phenotype

Question 14

what 2 kinds of structures are evidence for evolution?

Answer 14

1. homologous structures

2. analogous structures

Question 15

what are homologous structures? give an example

Answer 15

come from common ancestral form; differs somewhat in form, similar function
ex.) the humerus in humans, dogs, birds, and whales

Question 16

what are analogous structures? give an example

Answer 16

similar form and function; different evolutionary origin’ only very DISTANTLY related, like way back to eukaryotic cells
ex.) wings of a bird (bones) vs. wings of an insect (no bones)

Question 17

what is speciation?

Answer 17

when 2 new populations diverge from the original population, takes thousands to millions of years, through an accumulation of differing phenotypes where individuals of the 2 new populations must be unable or unlikely to breed, hybrids likely sterile

Question 18

is speciation guaranteed?

Answer 18

no, there are many different factors involved, like environment

Question 19

what is gene flow?

Answer 19

exchange of genetic material among populations or within a population

Question 20

what does gene flow require?

Answer 20

interaction between individuals, duh

Question 21

what may gene flow do to speciation and why?

Answer 21

act as a barrier, bc as long as there is gene flow populations will tend to remain similar to each other

Question 22

what are the 2 kinds of speciation?

Answer 22

1. incipient speciation

2. sympatric speciation

Question 23

what is incipient speciation?

Answer 23

geographic separation of populations from a parent species, leading to subsequent evolution

Question 24

what is vacariance?

Answer 24

geographic separation of populations resulting in a pair of closely related species, basically the same thing as incipient speciation

Question 25

give an example of incipient speciation

Answer 25

northern owls vs mexican owls; very similar but geographically separated, gene flow stopped because of separation and differences accumulated

Question 26

what is sympatric speciation?

Answer 26

speciation within species remaining in one location

Question 27

how does sympatric speciation happen?

Answer 27

1. adaptive radiation and resource partitioning: spreading out reduces competition
2. changes in chromosome number: more or less than normal because of nondisjunction

Question 28

how did honeycreepers get so many different beak shapes?

Answer 28

began with a founder species; then adaptive radiation, sympatric speciation

Question 29

what is aneuploidy?

Answer 29

difference in chromosome number

Question 30

what is polyploidy?

Answer 30

increased number of chromosome pairs

Question 31

what is autopolyploidy?

Answer 31

offspring having 2 sets of chromosomes due to no cytokinesis, nondisjunction, in one species

Question 32

what is allopolyploidy?

Answer 32

different species with different diploid numbers of chromosomes, resulting in offspring with different chromosome numbers, almost like instant speciation

Question 33

what is gradual speciation?

Answer 33

species diverge at a slow, steady pace as traits change incrementally

Question 34

what is punctuated equilibrium?

Answer 34

species diverge quickly and then remain unchanged for long periods of time

Question 35

what is the hybrid zone?

Answer 35

the location where different species can come together to form hybrids

Question 36

what 3 different scenarios may occur over time in the hybrid zone?

Answer 36

1. reinforcement
2. fusion
3. stability

Question 37

what is reinforcement in the hybrid zone?

Answer 37

hybrids less fit than either purebred species and the two continue to diverge until hybridization can no longer occur

Question 38

what is fusion in the hybrid zone?

Answer 38

reproductive barriers weaken until the two species become one (hybrids must be fertile)

Question 39

what is stability in the hybrid zone?

Answer 39

fit hybrids continue to be produced

Question 40

what are the 2 kinds of reproductive isolating mechanisms that suppress speciation or hybridization?

Answer 40

1. pre-zygotic

2. post-zygotic

Question 41

list and describe the 5 kinds of pre-zygotic isolating barriers?

Answer 41

1. temporal: the two species reproduce at different times; like spring and summer
2. behavioral: like different mating calls between birds and insects
3. ecological: lions and tigers have different hunting territories, so no contact
4. physical: size differences ;-)
5. gamete incompatibility: certain sperm don’t contain right enzymes to penetrate the egg barrier of some other species

Question 42

what kind of pre-zygotic isolating barrier is 2 species of crickets with different soil preferences?

Answer 42

ecological

Question 43

what kind of pre-zygotic isolating barrier is 4 different male reproductive structures in fly species?

Answer 43

physical

Question 44

what kind of pre-zygotic isolating barrier is different flower shapes causing inability for hybridization?

Answer 44

physical

Question 45

what kind of pre-zygotic isolating barrier is thin vs. thick-lipped cichlid?

Answer 45

behavioral due to mating practices with their lip shape

Question 46

what is the post-zygotic isolating barrier?

Answer 46

hybrid inviability

Question 47

what 2 ways do hybrid inviability occur?

Answer 47

1. fertilization occurs but the embryo fails to develop

2. embryo successfully develops but resulting individual is sterile

Question 48

give an example of hybrid inviability

Answer 48

mules are sterile due to different chromosome numbers from horses and donkeys