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Level 3 Biology > Speciation definitions > Flashcards

Speciation definitions Flashcards

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1
Q

Population

A

A group of organisms of the same species living in the same area.

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2
Q

Genetic drift

A

Allele frequencies in a population change due to chance.

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3
Q

Natural selection

A

Individuals with favorable adaptations will survive and reproduce, passing on their successful alleles. Environmental factors (biotic and abiotic) act as selecting agents of successful phenotypes.

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4
Q

Gene pool

A

The range of different alleles present in a population.

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5
Q

Emigration

A

The numbers of individuals leaving the population.

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6
Q

Immigration

A

The number if individuals entering the population.

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7
Q

Founders effect

A

A few individuals carrying their alleles enter a new territory and begin a new population.

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8
Q

Gene flow

A

The movement of alleles into or out of a population due to the movement of fertile individuals.

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9
Q

Adaptations

A

Any structural, physiological or behavioral characteristics of an organism that allows it to occupy a specific ecological niche and so improve its chances of survival.

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10
Q

Species

A

A group of organisms that normally interbreed in nature to produce fertile offspring and belong to the same gene pool.

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11
Q

Mate selection

A

Individuals choose breeding partners with desirable phenotypes.

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12
Q

Mutation

A

A random and permanent change in the base sequence of the DNA.

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13
Q

Genetic variation

A

The collection of available genes(alleles) possessed by all of the interbreeding individuals in the population.

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14
Q

Bottleneck

A

The effect of having only a few individuals left after a catastrophe to breed the next generations.

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15
Q

Charles Darwin

A

The person who proposed a theory of evolution based on natural selection.

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16
Q

Allele frequency

A

The percentage of alleles present in a gene pool

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17
Q

Acquired Characteristics

A

Phenotypes that have been shaped by the environment

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18
Q

Selective breeding

A

When people select the individuals that will breed in a population

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19
Q

Allopatric species

A

Similar species that are geographically separated

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20
Q

Sympatric species

A

A species previously diverged from a common ancestor, and exist in the same area but are reproductively isolated

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21
Q

Reproductive isolating mechanism (RIM)

A

A barrier that prevents two organisms from different species from mating and producing fertile offspring / prevents successful interbreeding / prevents gene flow

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22
Q

Prezygotic RIM

A

Mechanisms that prevent successful fusing of gametes and therefore the formation of a zygote

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23
Q

Geographical isolation

A

When physical barriers separate populations so they cannot come in contact to reproduce and so there is no gene flow

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24
Q

Ecological isolation

A

Individuals of a species live in the same geographical area but differences in habitat/ecological niches results in them rarely coming into contact. so they so not reproduce and so there is no gene flow between them

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25
Q

Temporal isolation

A

differences in the timing of their behavior e.g. mating is prevented because the two species breed at different times of the year or day, therefore, there is no gene flow

26
Q

Structural/mechanical isolation

A

Structural shape means that mating is not possible. E.g., Insects’ genitalia may be shaped in a specific way to prevent hybridization. Therefore, there is no gene flow

27
Q

Behavioral isolation

A

Results from differences in behavior, usually different courtship rituals, so the courtship rituals are not recognized and so mating will not occur; or one species might be nocturnal and the other diurnal so they do not come into contact

28
Q

Speciation

A

The formation of different species from a common ancestor/ancestral species

29
Q

Hybrid

A

An infertile offspring produced by the reproduction of two different species

30
Q

Postzygotic RIM

A

The zygote forms but mechanisms prevent the development of the zygote into a fertile offspring

31
Q

Hybrid sterility

A

Offspring of two different species is often sterile. Usually because offspring has an odd chromosome number- Pairing of chromosome at meiosis to create gametes can’t occur with an odd number or due to the chromosomes not being homologous pairs ——Post-zygotic RIM

32
Q

Hybrid inviability

A

Genetic incompatibility means that even if a zygote forms from two different species it won’t divide properly because of unmatched chromosome numbers resulting in the zygote dying ——Post-zygotic RIM

33
Q

Hybrid breakdown

A

The first generation is fertile (usually with reduced viability and fertility) but the following generations are infertile because of genetic incompatibility ——Post-zygotic RIM

34
Q

Deme

A

A local population that has no or limited gene flow with members of other populations of the same species

35
Q

Gamete Isolation

A

Due to incompatibility of gametes-sperm may not be able to fertilize the egg of another species because the egg’s surface has the incorrect chemical receptors for the sperm to find and attach to it, sperm cannot penetrate the surface of the egg, sperm cannot survive the chemical environment of the female reproductive system

36
Q

Hybrid Vigour

A

Occurs as a result of polyploidy when offspring from two very inbred parents (homozygous for many genes) of the same species are stronger and healthier than the parents

37
Q

Stabilizing Selection

A

Occurs in a population when intermediate phenotypes have the highest fitness, rather than those at one or both extremes. e.g. Human birth weight. (reduces genetic variation)

38
Q

Disruptive Selection

A

Occurs in a population when two more phenotype have higher fitness than the intermediate phenotypes. Disruptive selection can lead to speciation. e.g. Darwin’s finches beak shape with the selection pressure of differing food sources

39
Q

Directional Selection

A

When a phenotype towards one end of the range is favored over other phenotypes, causing the allele frequency to shift in the direction of that phenotype over time. e.g. peppered moth with the selection pressure of predation

40
Q

Divergent Evolution

A

The diversification/splitting of a common ancestral species into two or more species that develop different phenotypes due to becoming specialized to occupy different ecological niches with different selection pressures. e.g. gecko and NZ wren

41
Q

Adaptive Radiation

A

A type of divergent evolution that occurs when a common ancestral species rapidly evolves into a large number of new species due to the availability of many new ecological niches with different selection pressures. e.g. Darwin’s finches and ratites

42
Q

Convergent evolution

A

When two or more distantly related species evolve similar features/traits (analogous structures) in response to similar niche requirements and therefore a similar selection pressures. e.g. wings in insects, birds, bats

43
Q

Coevolution

A

Where over time, two unrelated species develop specific adaptations to enable their existence in the presence of the other organism as they exert selection pressures on each other, and any change in one species acts as a selection pressure that causes/leads reciprocal changes in the other species. e.g. pollinators-plants, predators-prey, herbivores-plants

44
Q

Punctuated Equilibrium

A

Long periods of stasis followed by rapid periods of change/speciation. These rapid changes may be triggered by sudden changes in the environment causing rapid changes in selection pressure that act on genetic variation already present in the species. Punctuated equilibrium can be seen in the fossil record as species disappear and new species appear

45
Q

Gradualism

A

States that evolutionary processes proceed slowly but continuously, so populations of an ancestral species slowly diverge from one another as the environment undergoes slow changes by accumulating adaptations as low intensity selection pressures are acting upon them, and eventually the accumulation of changes result in speciation occurring. Gradualism, we see a gradual change (in morphology/ many intermediate forms) due to the selection pressures remaining fairly constant, as even though mutation still randomly occur , no major change in form is selected for

46
Q

Extinction

A

Important natural process for evolution as provides vacant niches for other species that may evolve to occupy

47
Q

Homologous Structures

A

Structures in different species that are inherited from a common ancestor. The features similar in structure and origin but differ in function. The similarity in structure indicates common ancestry; which difference in function indicate adaption to different selection pressures in different environments. Evidence for divergent evolution

48
Q

Analogous Structures

A

Structures in different species that are not inherited from a common ancestor but have the same function and so similar form due to similar environmental selection pressure in different areas. Evidence for convergent evolution

49
Q

Fossil Record

A

Shows the change in structures and form over time, with the oldest fossils showing the most primitive features. Transitional forms toward the present day structures/species can be followed through sedimentary rock strata (layers) of different ages. Sudden disappearance and appearance of species evidence for punctuated equilibrium. Transitional forms evidence for gradualism

50
Q

Biogeography

A

Involves investigating the evolutionary relationships of species based on knowledge of how the geography of Earth has changed over time and influenced the distribution of living species today

51
Q

Genetic Distance

A

A measure of the genetic divergence between species, or between populations within a species. Populations/species with many similar alleles/genes have small genetic distances. This indicates that they are closely related and have a recent common ancestor

52
Q

Polyploidy

A

The presence of more than two complete sets in somatic cells (3n+). Polyploidy is a form of instant sympatric speciation

53
Q

Autopolyploidy

A

Polyploidy involving one species

54
Q

Allopolyploidy

A

Polyploidy occurring after the hybridization of two species

55
Q

Endemic species

A

Species that are found in one place and no where else

56
Q

Cline

A

A measurable gradient in a single characteristic of a species across its geographical range

57
Q

Ring species

A

Two populations that don’t interbreed live in the same region and connected by a geographical ring of populations that can interbreed

58
Q

Non-disjunction

A

A pair of homologous chromosomes has failed to separate or segregate at anaphase so that both chromosomes of the pair pass to the same daughter cell

59
Q

Evolution

A

Gradual process by which the present diversity of plants & animals arose from earliest and most primitive organism

60
Q

Subspecies

A

Groups that are very different from each other but still can interbreed

61
Q

Instant speciation

A

Speciation resulting from polyploidy

Level 3 Biology (3 decks)

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