section 2

Question 1

In some species natural selection can maintain a

Answer 1

sexual dimorphism, which is a difference in appearance between males and females.

Question 2

sexual selection

Answer 2

a type of natural selection resulting from variation in the ability to obtain mates

Question 3

In intrasexual selection,

Answer 3

the members of one sex compete among themselves for access to the opposite sex; mate choice plays no part in deciding the winner.

Question 4

In intersexual selection,

Answer 4

members of one sex choose their mates from among multiple members of the opposite sex.

Question 5

Why do males usually show the greatest effects of sexual selection?

Answer 5

In most animal species, females spend more time and energy rearing each offspring than do males. Because of this high investment in reproduction, females tend to be selective about their mates. Males are typically less choosy and must compete for access to females.

Question 6

In asexually reproducing organisms such as bacteria, each mutated cell

Answer 6

gives rise to mutant offspring (if the mutation does not prevent reproduction).

Question 7

In a multicellular organism, a mutation

Answer 7

can pass to the next generation only if it arises in a germ cell (i.e., one that will give rise to gametes)

Question 8

genetic drift

Answer 8

a change in allele frequencies that occurs purely by chance. Tends to eliminate alleles from a population.

Question 9

Founder Effect

Answer 9

which occurs when a small group of individuals leaves its home population and establishes a new, isolated settlement.

Question 10

Population bottleneck

Answer 10

occurs when a population drops rapidly over a short period, causing the loss of many alleles that were present in the larger ancestral population

Question 11

gene flow

Answer 11

movement of alleles between populations

Question 12

1.What are some ways that mutations affect an organism’s phenotype?

Answer 12

Mutations introduce new alleles, which may or may not alter the phenotype of an organism.

Question 13

2.Under what conditions does a mutation in one organism pass to subsequent generations?

Answer 13

• if it is a mutation that can be inherited
• in sexually producing organisms, it must be present in a gamete-producing cell. Mutations in somatic cells will not be passed on
• in asexually reproducers, it is transmitted to all its offspring

Question 14

macroevolution

Answer 14

describes large-scale evolutionary change

Question 15

species

Answer 15

distinct types of organsims

Question 16

Swedish botanist Carolus Linnaeus

Answer 16

defined species as “all examples of creatures that were alike in minute detail of body structure”

• first investigator to give every species a two-word name.
• devised a hierarchical system for classifying species.

Question 17

Linnaeus’s system did not

Answer 17

-consider the role of evolutionary relationships.(thought that each species was created separately and could not change. Therefore, species could not appear or disappear, nor were they related to one another)

Question 18

Harvard biologist Ernst Mayr

Answer 18

defined a biological species as a population, or group of populations, whose members can interbreed and produce fertile offspring.

Question 19

Speciation

Answer 19

• the formation of new species

- occurs when members of a population can no longer successfully interbreed.

Question 20

prezygotic reproductive isolation affect

Answer 20

the ability of two species to combine gametes and form a zygote.

Question 21

Prezygotic reproductive barriers include:

Answer 21

• Ecological (habitat) isolation
• Temporal isolation
• Behavioral isolation
• Mechanical isolation
• Gametic isolation

Question 22

Ecological (habitat) isolation

Answer 22

A difference in habitat preference can separate two populations in the same geographic area.

Question 23

Temporal Isolation

Answer 23

Two species that share a habitat will not mate if they are active at different times of day or reach reproductive maturity at different times of year.

Question 24

Behavioral Isolation

Answer 24

may prevent two closely related species from mating. Any variation in the ritual from one group to another could prevent them from being attracted to one another

Question 25

Mechanical isolation

Answer 25

Any change in the shape of the gamete-delivering or -receiving structures may prevent groups from interbreeding. Parts don’t fit.

Question 26

Gametic Isolation

Answer 26

If a sperm cannot fertilize an egg cell, then no reproduction will occur

Question 27

postzygotic reproductive isolation

Answer 27

separation of species due to selection against the hybrid offspring,

Question 28

Postzygotic reproductive barriers include:

Answer 28

• Hybrid inviability
• Hybrid infertility (sterility)
• hybrid breakdown

Question 29

Hybrid inviability

Answer 29

A hybrid embryo may die before reaching reproductive maturity, typically because the genes of its parents are incompatible.

Question 30

Hybrid infertility (sterility)

Answer 30

Some hybrids are infertile. A familiar example is the mule.

Question 31

Hybrid Breakdown

Answer 31

When the hybrids reproduce their offspring may have abnormalities that reduce their fitness.

Question 32

In allopatric speciation

Answer 32

formation of new species after a physical barrier separates a population into groups that cannot interbreed

Question 33

In Parapatric speciation

Answer 33

formation of a new species when part of a population enters a habitat bordering the parent species’ range, and the two groups become reproductively isolated.

Question 34

In sympatric speciation

Answer 34

formation of a new species within the boundaries of a parent species

Question 35

In plants, a common mechanism of _______ speciation is ________.

Answer 35

• sympatric

- polyploidy: occurs when the number of sets of chromosomes increases.

Question 36

How can polyploidy contribute to sympatric speciation?

Answer 36

Polyploidy results in a plant with an increased set of chromosomes. The plants with the increased chromosomes can no longer cross-pollinate with the original plant population even if they are in the same location.

Question 37

Why is it sometimes difficult to determine whether speciation is allopatric, parapatric, or sympatric?

Answer 37

1) the 3 speciation mechanisms represent points along a continuum of reproductive isolation (instantaneous to long term)
2) it is often difficult to recognize what constitutes a barrier to a species
3) the size of the barrier needed varies with the range over which the gametes spread.

Question 38

2.What types of information provide the clues that scientists use in investigating evolutionary relationships?

Answer 38

Fossils, molecular techniques such as sequencing of proteins of dna, and biogeographical studies.

Question 39

Biogeography

Answer 39

study of the distribution patters of species across the planet

Question 40

According to the theory of plate tectonics,

Answer 40

the Earth’s surface consists of several plates that move in response to forces acting deep within the planet

Question 41

vestigial structure

Answer 41

has no apparent function in one species, but homologous to a functional structure in another species.

Question 42

homologous structures

Answer 42

similar in structure or position because of common ancestry.

Question 43

analogous structure

Answer 43

similar in function, but not in structure because of convergent evolution, not common ancestry.

Question 44

convergent evolution

Answer 44

evolution of similar adaptations in organisms that do not share the same evolutionary lineage.