Chapter 24: The Origin of Species
Interactive Question 24.1
Name the type of reproductive barrier and whether it is pre- or postzygotic for the following examples.
Type of Barrier | Pre- or Post- | diat Example | bothof
a. reduced hybrid fertility | 造价员报考条件b. Post- | Two species of frogs are mated in the lab and produce viable, but sterile, offspring. |
c. gametic isolation | d. Pre- | Two species of a urchins relea gametes at the same time, but no cross fertilization occurs. |
e. mechanical isolation | f. Pre- | utsTwo orchid species with different length nectar tubes are pollinated by different moths. |
g. temporal isolation | h. Pre- | Two species of mayflies emerge during different weeks in spring |
i. hybrid breakdown | j. Post- | crazy babyTwo species of salamanders mate and produce offspring, but the hybrid’s offspring are sterile. |
k. behavioral isolation | l. Pre- | Two similar species of birds have different mating rituals |
m. reduced hybrid viability | n. Post- | Embryos of two species of mice bred in the lab usually abort |
o. habitat isolation | p. Pre- | Peepers breed in woodland ponds; leopard frogs reed in swamps |
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Interactive Question 24.2
Fill in the following table to review the five approaches that biologists have propod for conceptualizing a species.
Concept | Emphasis |
Biological | a. reproductive isolation |
b. morphological | Anatomical differences, most commonly ud |
c. ecological | Unique roles in specific environments |
d. paleontological | Morphologically discrete fossil species |
phylogenetic | e. evolutionary lineage leading to unique genetic history |
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Interactive Question 24.3
a. A new plant species B forms by autopolyploidy from species A, which had a chromosome number of 2n = 10. How many chromosomes would species B have?
a. 20 chromosomes
b. If species A were to hybridize by allopolyploidy with species C (2n = 14) and produce a new, fertile species, D, how many chromosomes would species D have?
a. 24 chromosomes
Interactive Question 24.4
a. Differentiate between allopatric and sympatric speciation
a. In allopatric speciation, a new species forms while geographically isolated from the parent population. In sympatric speciation, some reproductive barrier isolates the gene pool of a subgroup of a population within the same geographic range as the parent population
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b. How might reproductive barriers ari in each type of speciation?
a. Reproductive barriers may evolve as a by-product of the genetic change associated with the isolated population’s adaptation to a new environment, genetic drift, or xual lection. In sympatric speciation in plants, hybridization between cloly related species followed by mitotic or meiotic errors that produce fertile polyploids is a common mechanism. A change in resource u or xual lection may reproductively isolate a subt of an animal population
Interactive Question 24.5
What factors have contributed to the adaptive radiation of the thousands of endemic species of the Hawaiian Archipelago?
The Hawaiian Archipelago is a ries of relatively young, isolated, and physically diver islands who thousands of endemic species are example of adaptive radiation resulting
from multiple colonizations and allopatric and sympatric speciations
Interactive Question 24.6
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Compare the gradual and punctuated equilibrium models of evolution.
In the gradualism model of evolution, small changes accumulate within populations as a result of chance events and natural lection, leading to the gradual divergence of species. The punctuated equilibrium model holds that evolution occurs in spurts of relatively rapid change intersperd with long periods of stasis. A species changes most as it aris from an ancestral species and then undergoes little change for the rest of its existence.
Interactive Question 24.7
Give examples of reptilian structures that were exaptations for flight in birds.
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Feathers and wings may have first developed as structures for social displays, thermoregulation, and camouflage; light, honeycombed bones may have incread the agility of bipedal dinosaurs.
Interactive Question 24.8
a. Fetal skulls of humans and chimpanzees have similar shapes. The quite distinctive differences in adult skull shape results from different patterns of allometric growth .
b. A salamander species that retains its gills (a larval trait) when it is full grown and xually mature is an example of paedomorphosis .
surveillancec. The shorter feet of tree-dwelling salamanders may have resulted from an evolutionary have resulted from an evolutionary change in a regulatory gene that switches off growth of the foot sooner than in ground-dwelling salamanders. The three cas (a., b., and c.) are all examples of heterochrony .
