Speciation Chapter 26 Flashcards Preview

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Flashcards in Speciation Chapter 26 Deck (50):
1

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Describe the process of speciation.

Speciation occurs when populations of the same species become genetically isolated by lack of gene flow and then diverge from each other due to selection, genetic drift, or mutation

2

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Compare and contrast four different species concepts.

a

3

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Compare and contrast allopatric speciation and sympatric speciation.

b

4

Describe the possible outcomes of two divergent populations having secondary contact.

b

5

Explain the roles that gene flow, selection, genetic drift, and mutation play in the process of speciation (Freeman p 503).

If gene flow ends, allele frequencies in isolated populations are free to diverge—meaning that the populations begin to evolve independently of each other.
Divergence may occur as a result of mutation, natural selection, and genetic drift.

This genetic divergence may eventually lead to speciation, the creation of new species.

Usually, speciation creates two or more distinct species from a single ancestral group.

6

List the five types of prezygotic isolation.

temporal
habitat
behavioural
gametic
mechanical

7

List the two types of
Postzygotic isolation:

Hybrid viability
Hybrid sterility

8

Define the Biological species concept:

reproductive isolation b/t populations
Advantages: evolutionary independence
Disadvantages: not applicable to asexual or fossil species: difficult to assess if populations do not overlap

9

Explain the process of allopatric speciation by colonization

Colonization events often cause speciation because the physical separation reduces gene flow, and genetic drift via the founder effect causes the old and new populations to diverge rapidly.

10

Explain the process of allopatric speciation by vicariance.

Vicariance events are thought to be responsible for the origin of many modern species.

Physical isolation of populations via dispersal or vicariance produces genetic isolation, the first requirement of speciation.

When genetic isolation is accompanied by genetic divergence due to mutation, natural selection, and genetic drift, speciation results.

11

Design an experiment to determine if a new species can be created from a single existing species.

b

12

In general terms, explain the process of sympatric speciation.

natural selection can overcome gene flow and cause sympatric speciation.

Speciation may occur because even though populations are not physically isolated, they may be isolated by preferences for different habitats.

13

Discuss the example of sympatric speciation occurring between hawthorn flies and apple flies (Freeman p 510).

Apple maggot flies feed and mate on apple fruits
hawthorne flies feed and mate on hawthorne fruits
-found sympatrically, they do not generally interbreed.
genetically diverging

14

Explain how autopolyploidy could lead to sympatric speciation.

tetraploid (4n) maidenhair ferns
genetically isolated from wild-type populations
genetic drift and natural selection cause the wild-type and polyploid populations to diverge, speciation is then under way.

15

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Why is speciation by polyploidy so common in plants?

1. In plants, somatic cells that have undergone many rounds of mitosis can undergo meiosis and produce gametes. The multiple rounds of mitosis increase the likelihood of tetraploid daughter cells.

2. The ability of some plant species to self-fertilize makes it possible for diploid gametes to fuse and create genetically isolated tetraploid populations.

3. Hybridization between plant species is common, creating opportunities for speciation via formation of allopolyploids.

speciation by polyploidization is driven by chromosome-level mutations and occurs in sympatry
speciation by polyploidy is virtually instantaneous. It is fast, sympatric, and common.

16

Design an experiment to determine if a new species can be created from two existing species.

b

17

Design an experiment to determine if two populations of very similar appearing birds on two large islands are one or two species.

b

18

Define speciation

If gene flow ends, allele frequencies in isolated populations are free to diverge—meaning that the populations begin to evolve independently of each other.
Divergence may occur as a result of mutation, natural selection, and genetic drift.

This genetic divergence may eventually lead to speciation, the creation of new species.

Usually, speciation creates two or more distinct species from a single ancestral group

19

The _____________________ concept considers populations to be evolutionarily independent if they are reproductively isolated from each other:

biological species

they do not interbreed or they fail to produce viable, fertile offspring.
therefore, no gene flow occurs between these populations

20

define prezygotic

Prezygotic isolation occurs when individuals of different species are prevented from mating.

21

define postzygotic isolation

Postzygotic isolation occurs when individuals from different populations do mate, but the hybrid offspring produced have low fitness and do not survive or produce offspring.

22

Prezygotic Isolation
define and give an example of reproductive isolation - temporal process and example

populations are isolated because they breed at different times
Example: Bishop pines and monterey pines release their pollen at different times of the year

23

Prezygotic Isolation
define and give an example of reproductive isolation - habitat process and give an example

populations are isolted because they breed in different habitats
Example: parasites that begin to exploit new host are isolated from their original population

24

Prezygotic Isolation
define and give an example of reproductive isolation - behavioural process and give an example

populations do not interbreed because their courtship displays differ
Example: To attract male fireflies, female fireflies give species specific sequence of flashes

25

Prezygotic Isolation
define and give an example of reproductive isolation - gametic process and give an example

Matings fail because eggs and sperm are incompatable
Example - sea urchins - a protein called bindin allosa sperm to penetrate eggs. Differences in the amino acid sequence of bindin cause matings to fail between closely related populations

26

Prezygotic Isolation
define and give an example of reproductive isolation - mechanical process and give an example

Matings fail because male and female reproductive structures are incompatible
Example: in alpine skypilots (a flowering plant), the length of the floral tube varies. Bees can pollinate in populations with long tubes

27

Postzygotic Isolation
define and give an example of reproductive isolation - Hybrid viability and give an example

Hybrid offspring do not develop normally and die as embryos
Example - when ring-necked doves mate with rock doves, fewer than 6 percent of eggs hatch

28

Postzygotic Isolation
define and give an example of reproductive isolation - Hybrid sterility and give an example

Hybrid offspring mature but are sterile as adults

Example: A male horse can mate with a female donkey to produce a sturdy and long lived mule. However the mule is sterile

29

Define the Morphspecies concept:

morphospecies concept, biologists identify evolutionarily independent lineages by differences in morphological features.
idea = distinguishing features likely if populations independent isolated from gene flow.

disadvantages:
cannot identify cryptic species differ in non-morphological traits.
The features used to distinguish species under this concept are subjective.

30

Define the Ecological species concept:

The ecological species concept defines a species = a set of organisms exploiting a single set of resources, same range of environmental tolerances, and facing same predators and parasites.

Emphasis of natural selection
useful: ID bacteria, archea, asexual eukaryotes

31

Define the Phylogenetic species concept:

phylogenetic species concept is based on reconstructing the evolutionary history of populations.

Disadvantages:
Phylogenies are currently available = tiny subset of populations
Critics point -> lead to recognition more species than either of the other species concepts.

32

define Monophyletic group

On phylogenetic trees, an ancestral population plus all of its descendants is called a monophyletic group or clade.

33

Monophyletic groups are identified by ______________, homologous traits inherited from a common ancestor that are unique to certain populations or lineages.

synapomorphies

34

define allopatric speciation by dispersal

Dispersal occurs when a population moves to a new habitat, colonizes it, and forms a new population.

35

___________ occurs when a physical barrier splits a widespread population into subgroups that are physically isolated from each other.

Vicariance

36

Populations or species that live in the same geographic region (close enough to mate) live in __________

sympatry

37

mutation that results in ___________—the condition of having more than two sets of chromosomes—can cause speciation, particularly in plants.

polyploidy

38

define autopolyploid

Mutations that result in a doubling of chromosome number produce autopolyploid individuals.
In these individuals, the chromosomes all come from the same species.

39

define allopolypoid

Allopolyploid individuals are created when parents that belong to different species produce an offspring in which chromosome number doubles.

40

Explain how allopolyploidy could lead to sympatric speciation.

New tetraploid species may be created when two diploid species hybridize.
When diploid gametes fuse during self-fertilization, a tetraploid individual results.
diploid plant species have closely related polyploid species, supporting the claim that speciation by polyploidy is important in plants.

41

What happens when isolated populations come into contact

prezygotic isolation does not exist, populations may successfully interbreed.

Gene flow then occurs and may erase distinctions between the two populations.

Other possible outcomes are reinforcement, development of hybrid zones, and speciation by hybridization.

42

Selection for traits that isolate populations reproductively is called ____________

reinforcement.

43

define the characteristics of reinforcement of divergence

Sympatric species living in the same area are seldom willing to mate with one another.

Allopatric species living in different areas are often willing to mate with one another.

This is the pattern expected by reinforcement.

44

Briefly discuss the five possible outcomes when isolated populations come into contact again:

a) Fusion of the populations:
b) Reinforcement of divergence:
c) Hybrid zone formation:
d) Extinction of one population:
e) Speciation by hybridization:

45

geographic area where interbreeding between two populations occurs and hybrid offspring are common is called a ____________.

hybrid zone
example of this is seen with warblers
Hybridization often leads to extinction but sometimes leads to the origination of a new species

46

define fusion of the populations

to populations interbreed when the same species come into contact

47

define reinforcement of divergence

If hybrid offspring have low fitness, natural selection favours the evolution of traits that prevent interbreeding b/t populations
Example: fruit fly species in same geographical areas

48

define hybrid zone formation

there is a well definedgeographical area where hybridization occurs. This area may move ove time or be stable
Example: hrmit and townsend's warblers

49

define extinction of one population

if one population or species is a better competitor for shared resources, then the poorer competitor may be driven to extinction
Example: townstend's warblers may be driving hermit warblers to extinction

50

define creation of new species

if the combination of genes in hybrid offspring allows them to occupy distinct habitats or use novel resources, they may form new species
Example: sunflowers gave rise to new species with unique characteristics