ch 22: Natural Selection

Question 1

Speciation

Answer 1

the evolution of a new species. How does this happen? 1 group splits into 2 new ones

Question 2

Theory must explain how…

Answer 2

Theory must explain how new species originate and develop through the subdivision and subsequent divergence of gene pools. The fossil record reveals the cumulative effects of speciation over vast tracts of time.

Question 3

Microevolution

Answer 3

consists of changes in allele frequency in a population over time

Question 4

Macroevolution

Answer 4

refers to broad patterns of evolutionary change above the species level, For example, the origin of new groups of organisms, such as mammals, from a series of speciation events

Question 5

Species

Answer 5

a population or group of populations whose members have the potential to inbreed in nature and produce viable, fertile offspring, but can’t produce viable offspring with members of other populations.

Question 6

Reproductive Isolation

Answer 6

barriers that prevent different organisms from different species from reproducing. Why can’t a rhino mate with a snake?

Question 7

Prezygotic barriers(3)

Answer 7

block fertilization from occurring by:

• Impeding different species from attempting to mate
• Preventing the successful completion of mating
• Hindering fertilization if mating is successful

Question 8

Habitat Isolation

Answer 8

Two species encounter each other rarely, or not at all, because they occupy different habitats, even though not isolated by physical barriers

Question 9

Behavioral Isolation

Answer 9

Courtship rituals and other behaviors unique to a species are effective barriers

Question 10

Temporal Isolation

Answer 10

Species that breed at different times of the day, different seasons, or different years cannot mix their gametes

Question 11

Mechanical Isolation

Answer 11

Morphological differences can prevent successful mating

Question 12

Gametic Isolation

Answer 12

The sperm of one species may not be able to fertilize eggs of another species

Question 13

Examples of Postzygotic Barriers(3)

Answer 13

Reduced Hybrid Viability (hybrid inviability)
Reduced Hybrid Fertility
Hybrid Breakdown

Question 14

Reduced Hybrid Viability (hybrid inviability)

Answer 14

Genes of the different parent species may interact and impair the hybrid’s development

Question 15

Reduced Hybrid Fertility

Answer 15

Even if hybrids are vigorous, they may be sterile, weaker

Question 16

Hybrid Breakdown

Answer 16

Some first-generation hybrids are fertile, but when they mate with another species or with either parent species, the offspring of the next generation are feeble or sterile

Question 17

Allopatric Speciation

Answer 17

gene flow is interrupted when a population is divided into geographically isolated subpopulations. New rivers, mountain ranges, lakes, etc. can split populations.

For example, the flightless cormorant of the Galápagos likely originated from a flying species on the mainland

Question 18

Sympatric Speciation

Answer 18

takes place in populations that live in the same geographic area.

• Polyploidy- common in plants, rare in animals, extra chromosomes
• Habitat differentiation
• Sexual selection

Question 19

Adaptive Radiation

Answer 19

the evolution of many diversely adaptive species from a common ancestor upon introduction to various new environments.

Question 20

Punctuated equilibrium

Answer 20

periods of little or no change are punctuated by the sudden change.

Question 21

The gradualism model

Answer 21

a slow, gradual descent from a common ancestor. Their morphology changes and they acquire new adaptations.

Question 22

Speciation Rates (3 of 3)

Answer 22

• In a survey of data from 84 groups of plants and animals, researchers found that
• The interval between speciation events ranged from 4,000 years (cichlids) to 40 million years (beetles)
• The average time between speciation events was 6.5 million years and was rarely less than 500,000 years

Question 23

Important Reminders!

Answer 23

• Individuals do not evolve!
• They do not struggle to survive
• They cannot change their genetic makeup in response to catastrophe
• Individuals live or die – if you live you reproduce and pass on your genes (adaptive heritable variations)
• ONLY POPULATIONS EVOLVE