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Biology 207 > Chapter 18 > Flashcards

Chapter 18 Flashcards

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1
Q

Speciation

A

The process of species formation.

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2
Q

Biological Species Concept

A

The definition of species based on the ability of populations to interbreed and produce fertile offspring.

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3
Q

Phylogenetic Species Concept

A

The definition of a species as a group of organisms bound by a unique ancestry(shared derived characters).

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4
Q

Ecological Species Concept

A

The definition of a species as a group of organisms that share a distinct ecological niche.

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5
Q

Scientific Name

A

A two-part name identifying the genus to which a species belongs and designating a particular species within that genus.

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6
Q

Describe androdioecous organisms.

A

They exist as natural populations of functional males and hermaphrodites but include no true females.

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7
Q

Describe gyonetic species.

A

Have only females.

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8
Q

What is the biggest issue with the Biological Species Concept?

Provide examples of when it does not accurately describe species.

A

Although the definition can work for species that reproduce sexually, it does not deal as well with the many species that reproduce asexually. By their approach to reproduction, whole groups of organisms in the biological kingdom sit outside the “conventional” definition of species. Thus, patterns of reproduction can blur the definition of species.

Androdioceous organisms, gyonetic species, hybridization.

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9
Q

Hybridization

A

When two species interbreed and produce fertile offspring.

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10
Q

What contributes to the genetic cohesiveness and genetic distinctiveness of species?

A

The Biological Species Concept defines species in terms of population genetics and evolutionary theory in a static world. The definition alludes to the genetic cohesiveness of species. Populations of the same species are said to experience gene flow that mixes their genetic material and could be the “glue” holding a species together. The second part of this concept emphasizes the genetic distinctness of each species. Because populations of different species are reproductively isolated, they cannot exchange genetic information. In fact, the process of speciation is frequently defined as the evolution of reproductive isolation between populations.

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11
Q

Binomial

A

Relating to or consisting of two names or terms.

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12
Q

Morphological Species Concept

A

The concept that all individuals of a species share measurable traits that distinguish them from individuals of other species.

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13
Q

Natural History

A

The branch of biology that examines the form and variety of organisms in their natural environments.

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14
Q

Identify three different factors that can influence gene flow within populations.

A

Ecology, habitat availability, and behaviour.

Ecology - Ex: Rats being found wherever humans are found.

Habitat Availability - Ex: Snails being transported by birds to new habitats.

Behaviour - Ex; Mice being able to interbreed but choosing not to.

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15
Q

Subspecies

A

A taxonomic subdivision of a species identified when geographically separated populations of a species exhibit dramatic, easily recognized phenotypic variation.

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16
Q

Describe the breeding and offspring characteristics of subspecies.

A

Individuals from different subspecies usually interbreed where their geographic distributions meet, and their offspring often exhibit intermediate phenotypes.

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17
Q

Ring Species

A

A species with a geographic distribution that forms a ring around uninhabitable terrain.

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18
Q

How does gene flow occur in ring species?

A

Adjacent populations of ring species can exchange genetic material directly, but gene flow between distant populations occurs only through intermediary populations.

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19
Q

Cline aka Clinal Variation

How does it occur?

A

A pattern of smooth variation in a characteristic over a large, environmentally diverse area.

Usually results from gene flow between adjacent populations that are each adapting to slightly different conditions.

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20
Q

Reproductive Isolating Mechanism

A

A biological characteristic that prevents the gene pools of two species from mixing even when they are sympatric.

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21
Q

Sympatric

A

Occupying the same spaces at the same time.

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22
Q

Prezygotic Isolating Mechanism

A

A reproductive isolating mechanism that acts prior to the production of a zygote, or fertilized egg.

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23
Q

Postzygotic Isolating Mechanism

A

A reproductive isolating mechanism that acts after zygote formation.

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24
Q

What are the prezygotic isolating mechanisms?

A

Ecological isolation,

Temporal isolation,

Behavioural isolation,

Mechanical isolation, and

Gametic isolation.

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25
Q

What are the postzygotic isolating mechanisms?

A

Hybrid inviability,

Hybrid sterility, and

Hybrid breakdown.

26
Q

Ecological Isolation

A

A prezygotic reproductive isolating mechanism in which species that live in the same geographic region occupy different habitats.

For example, lions living in grasslands and tigers living deep in the forest so they don’t mate.

27
Q

Temporal Isolation

A

A prezygotic reproductive isolating mechanism in which species live in the same habitat but breed at different times of day or different times of year so don’t mate.

28
Q

Behavioural Isolation

A

A prezygotic reproductive isolating mechanism in which two species do not mate because of differences in courtship behaviour; also known as ethological isolation.

29
Q

Mechanical Isolation

A

A prezygotic reproductive isolating mechanism caused by differences in the structure of reproductive organs or other body parts.

30
Q

Gametic Isolation

A

A prezygotic reproductive isolating mechanism caused by incompatibility between the sperm of one species and the eggs of another; may prevent fertilization.

31
Q

Hybrid Inviability

A

A postzygotic reproductive isolating mechanism in which a hybrid individual has a low probability of survival to reproductive age because hybrid individuals have two sets of developmental instructions, one from each parent, which may not interact properly for the successful completion of embryonic development.

32
Q

Hybrid Sterility

A

A postzygotic reproductive isolating mechanism in which hybrid offspring cannot form functional gametes often as a result of the parent species differing in the number or structure of their chromosomes, which cannot pair properly during meiosis.

33
Q

Hybrid Breakdown

A

A postzygotic reproductive isolating mechanism in which hybrids are capable of reproducing, but their offspring have either reduced fertility or reduced viability.

34
Q

Source Population

A

In metapopulation analyses, a population that is either stable or increasing in size.

35
Q

What are the two stages of allopatric speciation?

A

First, two populations become geographically separated, preventing gene flow between them. Then, as the populations experience distinct mutations as well as different patterns of natural selection and genetic drift, they may accumulate genetic differences that isolate them reproductively.

36
Q

Allopatric Speciation

A

The evolution of reproductive isolating mechanisms between two populations that are geographically separated.

37
Q

Species Cluster

A

A group of closely related species recently descended from a common ancestor.

For example, when migrating to another island.

38
Q

Hybrid Zone

A

A geographic area where the hybrid offspring of two divergent populations or species are common. For example, when event causing allopatric speciation is removed and two populations come back into contact and some are able to reproduce because prezygotic isolation is incomplete.

39
Q

Reinforcement

A

The enhancement of reproductive isolation that had begun to develop while populations were geographically separated which occurs when natural selection will favour individuals that mate only with members of their own population.

40
Q

Parapatric Speciation

A

Isolation may occur in a situation where a single species is distributed across a discontinuity in environmental conditions, such as a major change in soil type. Although organisms from both sides of the discontinuity can interbreed freely, natural selection may favour different alleles on either side, limiting gene flow. In such cases, parapatric speciation, speciation arising between adjacent populations, may occur if hybrid offspring have low relative fitness.

41
Q

Sympatric Speciation

A

Speciation that occurs without the geographic isolation of populations potentially as a result of changes in diet, behaviour, or chromosomes that could effect reproductive isolation.

42
Q

Host Race

A

A population of insects that may be reproductively isolated from other populations of the same species as a consequence of their adaptation to feed on a specific host plant species.

43
Q

What are the three modes of speciation based on the geographic relationship of populations as they become reproductively isolated?

A
  1. allopatric speciation (allo = different; patria = homeland)
  2. parapatric speciation (para = beside), and
  3. sympatric speciation (sym = together).
44
Q

What three genetic mechanisms can lead to reproductive isolation?

A

Genetic divergence between allopatric populations,

polyploidy in sympatric populations, and

chromosome alterations, which occur independently of the geographic distributions of populations.

45
Q

How does genetic divergence between allopatric populations lead to reproductive isolation?

A

Gene flow is absent.

Most postzygotic isolating mechanisms probably develop as accidental by-products of mutation, genetic drift, and natural selection.

Natural selection cannot directly promote the evolution of reproductive isolating mechanisms between allopatric populations. Individuals in allopatric populations do not encounter one another and therefore have no opportunity to produce hybrids. In the absence of hybrids, natural selection cannot select against the matings that would have produced them. Natural selection may foster adaptive changes that create postzygotic reproductive isolation between populations after they reestablish contact. If postzygotic isolating mechanisms reduce the fitness of hybrids, natural selection can reinforce the evolution of prezygotic isolating mechanisms.

In cases of postzygotic reproductive isolation, mutations in a few gene loci may establish reproductive isolation.

Many traits that now function as prezygotic isolating mechanisms may originally have evolved in response to sexual selection.

46
Q

Polyploid

A

An individual with one or more extra copies of the entire haploid complement of chromosomes.

47
Q

How can polyploidy occur?

A

Polyploid individuals can arise from chromosome duplications within a single species (autopolyploidy) or through hybridization of different species (allopolyploidy).

48
Q

Autopolyploidy

A

The genetic condition of having more than two sets of chromosomes from the same parent species - a diploid (2n) individual may produce tetraploid (4n) offspring, each with four complete chromosome sets.

49
Q

Unreduced Gamete

A

A gamete that contains the same number of chromosomes as a somatic cell.

50
Q

Somatic Cell

A

Any of the cells of an organism’s body other than reproductive cells.

51
Q

How does autopolyploidy occur?

A

Through an error in either mitosis or meiosis, so that gametes spontaneously receive the same number of chromosomes as a somatic cell. Again, unreduced gametes do not have reduced chromosome numbers compared with somatic cells.

52
Q

Mitosis

A

Nuclear division that produces daughter nuclei that are exact genetic copies of the parental nucleus.

53
Q

Meiosis

A

The division of diploid cells to haploid progeny, consisting of two sequential rounds of nuclear and cellular division.

54
Q

Meiosis I

A

The first division of the meiotic cell cycle in which homologous chromosomes pair and undergo an exchange of chromosome segments, and then the homologous chromosomes separate, resulting in two cells, each with the haploid number of chromosomes and with each chromosome still consisting of two chromatids.

55
Q

Meiosis II

A

The second division of the meiotic cell cycle in which the sister chromatids in each of the two cells produced by meiosis I separate and segregate into different cells, resulting in four cells each with the haploid number of chromosomes.

56
Q

Haploid

A

An organism or cell with only one copy of each type of chromosome in its nuclei.

57
Q

Diploid

A

An organism or cell with two copies of each type of chromosome in its nucleus.

58
Q

Allopolyploidy

A

Two closely related species hybridize and subsequently form polyploid offspring.

59
Q

How does speciation arise via allopolyploidy?

A

When two parent species have diverged sufficiently, their hybrid offspring are sterile because chromosomes from the two parents do not pair properly during meiosis. However, if chromosome numbers double in the interspecific hybrid, the chromosome complement of the gametes is also doubled, producing homologous chromosomes that can pair during meiosis. The hybrid can establish a population of a new polyploid species provided that it can produce polyploid gametes. The route to a new polyploid species can be through self-fertilization or fertilization with other doubled hybrids.

60
Q

Evolutionary Divergence

A

A process whereby natural selection or genetic drift causes populations to become more different over time.

61
Q

How do chromosome rearrangements promote speciation?

A

Chromosome rearrangements inhibit chromosome pairing and recombination during meiosis. Therefore, new genetic variations favoured by natural selection would be conserved within the rearranged segments. These variations accumulate over time, contributing to genetic divergence between populations with the rearrangement and those without it. Chromosome rearrangements can be a trigger for speciation. Once a chromosome rearrangement becomes established within a population, that population will diverge more rapidly from populations lacking the rearrangement than if the rearrangement did not exist. The genetic divergence eventually causes reproductive isolation.

Biology 207 (8 decks)

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