U3L3

Question 1

Sympatric Speciation

Answer 1

occurs when a new species evolves from a single ancestral species while inhabiting the same geographic area.

Question 2

Allopatric Speciation

Answer 2

Occurs when a population is geographically divided into two or more isolated groups, typically due to a physical barrier like a mountain, river, or an event that isolates part of the population - leads to separate species

Question 3

Speciation

Answer 3

origin of new species, is at the focal
point of evolutionary theory

Question 4

Microevolution

Answer 4

consists of changes in allele
frequency in a population over time

Question 5

Macroevolution

Answer 5

refers to broad patterns of
evolutionary change above the species level

Question 6

biological species concept

Answer 6

states a species is a group whose members have the potential to interbreed in nature and produce viable, fertile offspring
* They do not breed successfully with other populations
* Gene flow between populations holds a species together genetically

Question 7

Reproductive isolation

Answer 7

existence of biological factors (barriers) that impede two species from producing viable, fertile offspring

Question 8

Hybrids

Answer 8

offspring of crosses between different species

Question 9

Prezygotic barriers

Answer 9

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 10

Postzygotic barriers

Answer 10

prevent the hybrid zygote from developing into a viable, fertile adult:
– Reduced hybrid viability
– Reduced hybrid fertility
– Hybrid breakdown

Question 11

Limitations of the Biological Species
Concept

Answer 11

cannot be applied to fossils or
asexual organisms (including all prokaryotes). The biological species concept emphasizes absence of gene
flow but gene flow can occur between distinct species (grolar bear)

Question 12

morphological species concept

Answer 12

defines a species by structural features
– It applies to sexual and asexual species but relies on subjective criteria

Question 13

Ecological species concept

Answer 13

views a species in terms of its ecological niche (role and position of an organism within its environment)
– It applies to sexual and asexual species and emphasizes the role of disruptive selection

Question 14

phylogenetic species concept

Answer 14

defines a species as the smallest group of individuals on a phylogenetic tree
– It applies to sexual and asexual species, but it can be difficult to determine the degree of difference required for separate species

Question 15

Speciation can occur in two ways

Answer 15

Allopatric speciation
Sympatric speciation

Question 16

Regions with more geographical barriers have less or more species than regions with fewer geographical behaviors?

Answer 16

more

Question 17

Sympatric speciation can occur if gene flow is reduced by factors including:

Answer 17

Polyploidy
Sexual selection
Habitat differentiation

Question 18

Polyploidy

Answer 18

The presence of extra chromosome sets due to accidents during cell division

Question 19

autopolyploid

Answer 19

an individual with more than two chromosome sets, derived from a single species

Question 20

allopolyploid

Answer 20

a species with multiple sets of chromosomes derived from different species

Question 21

A 4n (68 chromosomes) plant is crossed with a 2n plant (34
chromosomes). What would be the chromosome number in
the resultant offspring?

Answer 21

68/2 = 34 - undergoes meiosis
34/2 = 17 - undergoes meiosis
34+17 = 51

Question 22

Sexual selection can drive

Answer 22

sympatric speciation

Question 23

In allopatric speciation, geographic isolation restricts

Answer 23

gene flow between populations

Question 24

Sympatric speciation can result from

Answer 24

polyploidy, natural selection, or
sexual selection

Question 25

hybrid zone

Answer 25

region in which members of different species mate and produce hybrids. Hybrids result from mating between species with incomplete reproductive barriers

Question 26

Hybrids often have….. compared to parent species

Answer 26

reduced fitness

Question 27

Reinforcement: Strengthening
Reproductive Barriers

Answer 27

When hybrids are less fit than parent species. Reinforcement of reproductive barriers may occur through strong selection for prezygotic barriers
* Over time, the rate of hybridization decreases
* Where reinforcement occurs, reproductive barriers should be stronger for sympatric than allopatric species

Question 28

Fusion: Weakening Reproductive
Barriers

Answer 28

hybrids are as fit as parents, there can be substantial gene flow between species
* If gene flow is great enough, the parent species can fuse into
a single species

Question 29

Stability: Continued Formation of
Hybrid Individuals

Answer 29

Extensive gene flow from outside hybrid zone can overwhelm selection for increased reproductive isolation
inside hybrid zone

Question 30

Hybrid zones can lead to

Answer 30

1. Reinforcement
2. Fusion
3. Stability

Question 31

punctuated equilibria

Answer 31

periods of apparent stasis punctuated by sudden change

Question 32

2 models of speciation

Answer 32

Punctual model: Rapid evolution leading to final result
Gradual model: Evolution through small steps

Question 33

Types of prezygotic barriers

Answer 33

Habitat isolation: 2 species that occupy different habitats within the same area may encounter each other rarely
Temporal isolation: Species that breed during different times, seasons or years
Behavioural isolation: Courtship rituals that attract mates - mate recognition (ex: blue footed bird has a specific script to follow)
Mechanical isolation: Mating is attempted but morphological differences prevent its successful completion - biological differences that does not complete mating

Question 34

Types of post zygotic barriers

Answer 34

Gametic isolation: Sperm of one species may not be able to fertilize the eggs of another species
Reduced hybrid viability: Genes of different parent species may interact in ways that impair the hybrid’s development or survival
Reduced Hybrid fertility: If the chromosomes of two parent species differ in number or structure, hybrids may fail to produce normal gametes leading to infertile offsprings
Hybrid break down: Some first generations hybrids are viable and fertile but when they mate with another or a parent species, offsprings tend to be sterile.

Question 35

Possible outcomes for a hybrid zone

Answer 35

Reinforcement, fusion, stability