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Evolution Flashcards

Evidence of evolution I evidence of evolution II the selection process I the selection process II origins of species

1
Q

what is the definition of evolution

A

descent with modification

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2
Q

what is the plural of genus

A

genera

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3
Q

what is palaeontology

A

the study of fossils

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4
Q

what is an adaptation

A

inherited characteristics of organisms that enhance their survival and reproduction in specific environments

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5
Q

what is natural selection

A

a process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits
the favourable traits are seen at a higher frequency in future generations

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6
Q

what is artificial selection

A

the process where humans select and breed organisms with desired traits

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7
Q

TRUE/FALSE individuals evolve

A

FALSE the population evolves over time

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8
Q

TRUE/FALSE evolution by natural selection can only occur when the individuals in the population differ in that trait

A

TRUE if all the individuals in a population were genetically identical for a trait then evolution by natural selection cannot occur

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9
Q

TRUE/FALSE a trait that is favourable in one place may be useless in another place

A

TRUE the traits favoured depends on the organisms environment

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10
Q

what is an example of ongoing evolution that dramatically effects humans

A

the evolution of drug resistant pathogens

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11
Q

how do resistant strains of bacteria emerge

A

some penicillin strains disrupt the cell wall of bacteria by deactivating their enzymes
bacteria became able to synthesise their cell walls using a different bacteria that penicillin couldn’t attack
these bacteria reproduced at higher rate compared to other bacteria and the resistant individuals become increasingly more common

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12
Q

how can bacteria become resistant to antibiotics so quickly

A

they can proliferate quickly and can exchange genetic material with members of their own species and other species (a resistant bacteria can pass the resistant gene to other bacteria making them resistant too)

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13
Q

natural selection is a process of ………………., not a creative mechanism

A

editing
a drug does not create a resistant pathogen it selects for resistant individuals that are already present in the population

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14
Q

what is homology

A

similarity resulting from common ancestry

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15
Q

what are homologous structures

A

e.g. the underlying skeletons of arms, forelegs, flippers

these structures are shared due to a presence in their common ancestor

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16
Q

how else can anatomical homologies be compared apart from comparing what is visible in adult organisms

A

we can compare early development of different organisms

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17
Q

what two structures do all vertebrate embryos have at some stage in their development

A

a tail behind the anus
pharyngeal aches
both of these develop into different structures in different species and can have very different functions

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18
Q

what are vestigial structures

A

leftover structures of marginal or no importance to the organism that served a function in the organisms ancestor

e. g. vestiges of leg bones in snakes
e. g. eye remnants in blind species

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19
Q

what molecular similarities suggest that all species descended from common ancestors

A

they all use the same genetic code and some genes have the same functions in different species

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20
Q

what is an evolutionary tree

A

a diagram that represents evolutionary relatedness among groups of organisms

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21
Q

what is convergent evolution

A

the independent evolution of similar features in different lineages

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22
Q

resemblance due to convergent evolution is referred to as ……………. instead of homologous

A

analogous

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23
Q

what is the difference between analogous and homologous

A

analogous features - similar function but no common ancestry
homologous features - common ancestry but not necessarily a similar function

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24
Q

where does the evidence of evolution come from

A

taxonomy
comparative anatomy
fossils and geology
biogeography

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25
Q

what is biogeography

A

the study of the geographic distribution of species

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26
Q

what does it mean if a plant or animal species is endemic

A

they are found nowhere else in the world

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27
Q

how do we categorise organisms

A

by comparing them with potential close relatives

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28
Q

what is phylogeny

A

the evolutionary history of a species or a group of species (phylogenetic tree)

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29
Q

what is systematics

A

a discipline focused on classifying organisms and determining their evolutionary relationships

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30
Q

what is taxonomy

A

the study of naming and classification of organisms

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31
Q

what is a binomial

A

the 2 part Latin name of an organism

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32
Q

what is the first part of the binomial

A

the name of the genus

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33
Q

what is the second part of the binomial

A

the specific epithet and is unique for each species in a genus

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34
Q

what is the order of classification from specific to non specific

A 
species
genus
family
order
class
phylum
kingdom
domain
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35
Q

what is a taxon

A

the named taxonomic unit and any level of the hierarchy

e.g. panthera is the taxon of a leopard at genus level

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36
Q

what does a branch point in a phylogenetic tree represent

A

the common ancestor of two evolutional lineages diverging from it

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37
Q

what are sister taxa

A

groups of organisms that share an immediate common ancestor that is not shared by any other group
the members of a sister taxa are each others closest relatives

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38
Q

what does the root of a phylogenetic tree represent

A

the most recent common ancestor of all the of all the taxa in the tree

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39
Q

what data can systematists use to infer phylogeny

A

morphology
genes
biochemistry

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40
Q

when does convergent evolution occur

A

when similar environmental pressures and natural selection produce similar adaptations (analogs) in organisms from different evolutionary lineages

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41
Q

the more complex the two similar structures when comparing organisms the more likely the evolution was convergent/divergent

A

divergent - they shared a common ancestor

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42
Q

what are molecular homoplasies

A

coincidental matches in the DNA of two organisms

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43
Q

if more than 25% of DNA bases match it is likely that the organisms are homologous/analogous

A

homologous

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44
Q

what is cladistics

A

an approach to systematics in which organisms are placed into groups called clades based primarily on common descent

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45
Q

what is a clade

A

a group of species that includes an ancestral species of all its descendants
a clade is equivalent to a monophyletic group

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46
Q

what is a paraphyletic group

A

consists of ancestral species and some but no all of its descendants

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47
Q

what is a polyphyletic group

A

includes distantly related species but does not include their most recent ancestor

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48
Q

for mammals, the backbone is what

A

a shared ancestral character - a character that originated in the ancestor of the taxo

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49
Q

for mammals, hair is what

A

a shared derived character - an evolutionary novelty unique to a clade

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50
Q

what is an outgroup

A

a species or group of species from an evolutionary lineage that is closely related but not part of the group of species being studied

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51
Q

what is the ingroup

A

the group of species being studied

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52
Q

what is the principal of maximum parsimony

A

the simplest explanation that is consistent with the facts

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53
Q

what is the principal of maximum likelihood

A

identifies the tree most likely to have produced a given set of data based on probability

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54
Q

what 2 principle need to be used when creating a phylogenetic tree

A

maximum parsimony and maximum likelihood

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55
Q

what are gene families

A

groups of related genes within an organisms genome

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56
Q

what are the two types of homologous genes

A

orthologous and paralogous

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57
Q

what do orthologous genes result from

A

Orthologous genes are homologous genes that diverged after evolution gives rise to different species, an event known as speciation.
The genes generally maintain a similar function to that of the ancestral gene that they evolved from
e.g. cytochrome c has the same function in humans and dogs

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58
Q

what do paralogous genes result from

A

Paralogous genes are homologous genes that have diverged within one species. Unlike orthologous genes, a paralogous gene is a new gene that holds a new function. These genes arise during gene duplication where one copy of the gene receives a mutation that gives rise to a new gene with a new function, though the function is often related to the role of the ancestral gene.
e.g. this is how all the different olfactory receptor genes arose

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59
Q

what is a molecular clock

A

an approach for measuring the absolute time of evolutionary changed based on the observation that some genes appear to evolve at constant rates

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60
Q

what causes the difference in the speed that clock like mutations occur

A

the more neutral mutations the faster the change in the gene

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61
Q

what are the 3 domains

A

bacteria
archaea
eukaryotes

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62
Q

what is horizontal gene transfer

A

genes are transferred from one genome to another though different mechanisms

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63
Q

what is gradualism

A

profound changes can be the result of small changes over long periods of time

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64
Q

what is catastrophism

A

recurrent catastrophic events causing widespread extinction and resulting in sharp boundaries between fossil areas

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65
Q

what is Uniformitarism

A

the same processes seen today that also acted in the past

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66
Q

what are the 5 causes of evolution

A 
natural selection 
non random mating
genetic drift
dene flow
mutation
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67
Q

for natural selection to occur what 3 conditions must be fulfilled

A

variation differential selection

inheritance

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68
Q

what is non-random mating/sexual selection

A

individuals with particular traits are more likely to mate

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69
Q

what is genetic drift

A

random changes in the frequency of traits due to chance factors
e.g. the founder effect and the bottleneck effect

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70
Q

what is the founder effect

A

A small group establishes a new population with a different gene pool

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71
Q

what is the bottleneck effect

A

A small fraction of the population survives that is no longer representative of the original population

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72
Q

what is gene flow

A

changes due to movement from one place to another

Gene flow is the transfer of alleles from one population to another population through immigration of individuals

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73
Q

how does natural selection work

A
  • Organisms differ from one another i.e. there is variation
  • These differences are heritable i.e. passed from generation to generation
  • Many more organisms are born than survive and reproduce (mortality)
  • Therefore, any variation that makes one offspring more successful than another will have a greater chance of being past to the next generation (survival of the fittest)
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74
Q

what is microevolution

A

small scale evolution - a change in allele frequencies in a population over generations

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75
Q

what 3 mechanisms cause allele frequency change

A

natural selection
genetic drift
gene flow

76
Q

phenotypic variation often reflects ………. variation

A

genetic

77
Q

how can gene variation be quantified at the whole gene level

A

the average percentage of loci that are heterozygous (two different alleles for a locus)

78
Q

why does nucleotide variation result in less phenotypic change than gene variation

A

many nucleotides occur within introns so are spliced from the mRNA
of those variations that occur in exons most of them do not result in an amino acid change. however when the amino acid changes this generally alter the protein causing genetic variation and 2 forms of the protein

79
Q

when does genetic variation result

A

it can originate from

  • gene duplication
  • mutation
  • other processes that produce new alleles and new genes
80
Q

genetic variations can be produced rapidly in organisms with short/long generation times

A

short

81
Q

what is a point mutation

A

a change in one base pair

82
Q

in diploid organisms harmful alleles that are dominant/recessive can be hidden from selection

A

recessive

83
Q

point mutations in noncoding regions generally results in …………… variation

A

neutral

84
Q

how does redundancy in the genetic code effect the outcome of a point mutation

A

even though a point mutation occurs the amino acid composition may not be changed due to wobble

85
Q

how can point mutations that alter an amino acid still be neutral

A

even if the amino acid was changed it still may not be significant enough that the shape and function of the protein changes

86
Q

how can mutations be passed to offspring

A

only mutations in cell lines that produce gametes can be passed to offspring

87
Q

in animals the majority of mutations that occur in somatic cells are/are not passed to offspring

A

are not

88
Q

give an examples of how gene duplication can occur

A

errors in meiosis such as unequal crossing over
slippage during DNA replication
activities of transposable elements

89
Q

how can small gene duplications that currently confer no effect cause harm in the future

A

they can persist over generations allowing mutations to accumulate
it results in an expanded genome with new genes that may take on new functions

90
Q

how did we develop 380 functional olfactory receptor genes

A

the olfactory gene duplicated many times and the duplicated genes developed new functions

91
Q

mutation rate in prokaryotes is higher/lower than in plants and animals

A

lower - but they have many more generations per unit time so mutations can quickly create genetic variation

92
Q

RNA has a higher/lower mutation rate than DNA

A

higher because it lacks the proofreading systems of DNA

93
Q

what mechanisms contribute to shuffling of alleles in sexual reproduction

A

crossing over
independent assortment
fertilisation

94
Q

does the presence of genetic variation guarantee that a population will evolve

A

no - more factors that influence evolution need to be present

95
Q

what is a population

A

a group of individuals in the same species that live in the same area and interbreed, producing fertile offspring

96
Q

what is a gene pool

A

all the copies of every type of allele at every locus in all members of the population

97
Q

when is an allele said to be fixed in the gene pool

A

if only one allele exists for a particular locus in a population and all individuals are homozygous for that allele

98
Q

if a population is not evolving what happens to allele and genotype frequencies

A

they will remain constant from generation to generation (hardy-weinburg equilibrium)

99
Q

what 5 conditions must be met for a population to be in hardy-weinburg equilibrium

A
  1. no mutations - gene pool is not modified
  2. random mating
  3. no natural selection
  4. extremely large population size - genetic drift occurs in small populations
  5. no gene flow - no alleles moving in or out of populations
100
Q

an allele that confers resistance to an insecticide will increase/decrease in frequency in a population exposed to that insecticide

A

increase

101
Q

what is adaptive evolution

A

a process in which traits that enhance survival or reproduction tend to increase in frequency over time by natural selection

102
Q

genetic drift affects smaller/larger populations more

A

smaller

103
Q

what two circumstances can result in genetic drift

A

founder effect

bottleneck effect

104
Q

what is genetic drift

A

a process in which chance events cause unpredictable fluctuations in allele frequencies from one generation to the next

105
Q

how can genetic drift lead to a loss of genetic variation in a population

A

it can eliminate alleles from a population decreasing the variation

106
Q

how can genetic drift cause harmful alleles to become fixed

A

it happens by chance

107
Q

why does gene flow occur

A

either due to the movement of fertile individuals or their gametes

108
Q

how can gene flow result in 2 populations combining with a single gene pool

A

because alleles are transferred between populations, gene flow tend to reduce the genetic differences between populations

109
Q

is the outcome of natural selection random

A

no - it involves a chance event i.e. a mutation but the events that follow are not by chance

110
Q

what is relative fitness

A

the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals

111
Q

does selection act directly on the genotype or phenotype of an organism

A

it acts directly on the phenotype but indirectly on the genotype via how the genotype affects the phenotype

112
Q

what are the 3 types of selection depending on which phenotypes in the population are favoured

A

directional
stabilising
disruptive

113
Q

when does directional selection occur

A

when conditions favour individuals exhibiting one extreme of a phenotypic range (often occurs when a populations environment changes e.g. larger beak favoured for larger seeds)

114
Q

what is disruptive selection

A

when conditions favour both extremes both extremes of a phenotypic range over individuals with an intermediate phenotype (if there are very soft and very hard seeds available, intermediate beak is inefficient for both cases)

115
Q

what is stabilising selection

A

when conditions favour intermediate variants (e.g. birth weights - intermediate weights have higher chance of survival)

116
Q

what is the only evolutionary mechanism that consistently leads to adaptive evolution

A

natural selection

117
Q

what is sexual selection

A

a process in which certain individuals with inherited characteristics are more likely than other individuals of the same sex to obtain mates

118
Q

sexual selection can result in sexual dimorphism what is this

A

a difference in secondary sexual characteristics between males and females of the same species (e.g. size, colour behaviour)

119
Q

what is Intrasexual selection

A

selection within the same sex

individuals of one sex compete directly for mates of the opposite sex (e.g. male deer fighting)

120
Q

what is intersexual selection

A

also called mate choice (e.g. females prefer male traits that are corelated with good genes

121
Q

what is balancing selection

A

natural selection that maintains two or more phenotypic forms in a population
includes:
frequency dependent selection
heterozygote advantage

122
Q

what is heterozygote advantage

A

recessive alleles persist because they are hidden from selection
individuals that are heterozygous have more of an advantage than either homozygote and natural selection maintains heterozygosity

123
Q

what is frequency dependent selection

A

selection in which the fitness of a phenotype depends on how common the phenotype is in a population

124
Q

give an example of heterozygote advantage

A

heterozygotes for sickle cell anaemia are protected from malaria

125
Q

selection can act only on existing ……….

A

variations

126
Q

give an example of frequency dependent selection

A

fish with right mouths always attack from the left and so prey species begin to guard against this so the next year left mouth fish are favoured

127
Q

what is the result of speciation

A

one species splits into 2 or more species

128
Q

what is macroevolution

A

the broad pattern of evolution above the species level

e.g. new groups of organisms through a series of speciation events

129
Q

what is the biological species concept

A

a species is a group of populations whose members have the potential to interbreed in nature and produce viable fertile offspring

130
Q

…….………. occurs between different populations of a species and the ongoing exchange of alleles tends to hold populations together genetically

A

gene flow

131
Q

a reduction or lack of gene flow can play a key role in …….….

A

speciation

132
Q

what is reproductive isolation

A

the existence of barriers that impede members of 2 species from interbreeding and producing viable fertile offspring

133
Q

barriers block gene flow between the species and limit the formation of hybrids. what are hybrids

A

offspring that result from interspecific mating

134
Q

give examples of reproductive barriers

A 
prezygotic:
habitat isolation 
temporal isolation 
behavioural isolation 
mechanical isolation 
gametic isolation 
postzygotic:
reduced hybrid viability 
reduced hybrid fertility 
hybrid breakdown
135
Q

what are prezygotic barriers

A

they block fertilization from occurring

136
Q

what are postzygotic barriers

A

errors after the hybrid zygote is formed

137
Q

does the biological species concept apply to organisms that reproduce asexually all or most of the time

A

no

138
Q

species are designated by the absence of ……………….

A

gene flow

139
Q

what is the morphological species concept

A

distinguishes a species by body shape and other structural features

140
Q

can the morphological species concept be applied to organisms that reproduce sexually and organisms that reproduce asexually

A

yes

141
Q

what is the ecological species concept

A

it defines a species in terms of its ecological niche, the sum of how members of the species interact with the non-living and living parts of the environment

142
Q

can the ecological species concept accommodate sexual and asexual species

A

yes

143
Q

what is allopatric speciation

A

speciation that results when gene flow is interrupted when a population is divided into geographically isolated subpopulations

144
Q

give an example of allopatric speciation barriers

A
  • when water level in a lake subsides resulting in 2 or more smaller lakes that are home to separate populations
  • a river may change course and divide a population of animals that cannot cross it
145
Q

once geographic isolation has occurred the separated gene pools may …….

A

diverge

146
Q

describe the steps in allopatric speciation

A
  1. a population is separated into subpopulations by a geographical barrier
  2. different mutations arise in each subpopulation
  3. natural selection and genetic drift may alter allele frequencies in different ways in the subpopulations
  4. genetic divergence results and reproductive isolation may evolve
147
Q

reproductive isolation between 2 populations generally increases/decreases and the geographic distance between them increases

A

increases

148
Q

what is sympatric speciation

A

speciation that occurs in populations that live in the same area

149
Q

what is more common sympatric or allopatric speciation

A

allopatric - the ongoing gene flow in sympatric speciation makes it less common to occur

150
Q

sympatric speciation can occur if gene flow is reduced by factors such as:

A

polyploidy
sexual selection
habitat differentiation

151
Q

what is polyploidy

A

a chromosomal alteration in which the organism possesses more than 2 complete chromosome sets. it is the result of an accident in cell division

152
Q

polyploid is most common in animals/plants

A

plants

153
Q

what are the 2 forms of polyploidy

A

autopolyploid

allopolyploid

154
Q

what is an autopolyploid

A

an individual that has more than 2 chromosome sets that are all derived from the same species

155
Q

what is a tetraploid

A

an organism that has double the number of chromosomes due to failure of cell division

156
Q

can tetraploid organisms produce fertile offspring

A

yes but they are also tetraploid

they produce the offspring by self mating or by mating with other tetraploids

157
Q

why are tetraploids reproductively isolated from 2n plants of the original population

A

because the triploid (3n) offspring of such unions have reduced fertility

158
Q

how does an allopolyploid occur

A

when 2 different species interbreed and produce hybrid offspring and in subsequent generations a sterile hybrid can turn into a fertile polyploid called an allopolyploid

159
Q

why are most hybrids sterile

A

the set of chromosomes from one species cannot pair during meiosis with the set of chromosomes from the other species (they are not homologous with each other)

160
Q

how can an infertile hybrid reproduce

A

it may be able to asexually propagate itself

161
Q

allopolyploids are fertile when mating with each other but can they mate with their parent species

A

no

162
Q

why do allopolyploids and autopolyploids represent new species

A

because in both cases there is a reproductive barrier preventing gene flow

163
Q

describe the gametes of tetraploid organisms

A

diploid

164
Q

give examples of polyploid plants

A

potato, tobacco, wheat

165
Q

how can polyploids be generated in the lab

A

by using chemicals that promote errors in meiosis and mitosis

166
Q

how can sympatric speciation be driven by sexual selection

A

e.g. mate choice based on male breeding colouration can act as a reproductive barrier that keeps the gene pools of the 2 species separate

167
Q

how can sympatric speciation occur from habitat differentiation

A

can happen when a subpopulation exploits a habitat or resource not used by the parent population

168
Q

give examples of processes that produce genetic changes that result in allopatric speciation

A

natural selection under different environmental conditions
genetic drift
sexual selection

169
Q

what is a hybrid zone

A

a region in which members of different species meet and mate producing at least some offspring of mixed ancestry

170
Q

when do hybrid zones form

A

when 2 species lacking complete barriers to reproduction come into contact

171
Q

what can alter the location of a hybrid zone

A

changes in environmental conditions such as temperature

172
Q

how can a hybrid zone be a source of novel genetic variation that improves the ability of one or more species to cope with changing environmental conditions

A

an allele found in only one parent species is transferred to hybrid individuals. it is then passed to the other parent species when the hybrids breed with the second parent species

173
Q

if the hybrids don’t become reproductively isolated and form a new species from the parent species, what are the other possible outcomes for the hybrid zone over time

A

reinforcement barriers
fusion of species
stability

174
Q

hybrids are often less/more fit than members of their parent species

A

less

175
Q

what is reinforcement

A

when hybrid are less fit than the parent species natural selection should strengthen prezygotic barriers, reducing thee formation of unfit hybrids (it involves reinforcement of the barriers)

176
Q

if reinforcement is occurring then barriers to reproduction between species should be stronger for sympatric/allopatric populations

A

sympatric

177
Q

what is fusion

A

the weakening of reproductive barriers - reverse speciation -hybridizing species fuse into a single species

178
Q

what is stability

A

continued production of hybrid individuals

179
Q

what are the 5 steps in hybrid zone formation and outcome

A
  1. populations of a species are connected by gene flow
  2. a barrier to gene flow is established
  3. the populations begin to diverge
  4. gene flow is re-established in a hybrid zone
  5. reinforcement/fusion/stability
180
Q

what is punctuated equilibria

A

in the fossil records, long periods of stasis in which a species undergoes little or no morphological change interrupted by brief periods of sudden change

181
Q

a punctuated pattern indicates that a species occurred rapidly/slowly

A

rapidly

182
Q

what is the difference between punctuated and gradual speciation

A

punctuated - new species change most as they branch from parent species then change little for the rest of their existence
gradual - species diverge from one another more slowly and steadily over time

183
Q

are there specific traits that cause reproductive isolation

A

yes - scientists are researching which genes influence the formation of new species e.g. the gene that controls snail shell spiral can change the spiral direction preventing mating

184
Q

what can happen as speciation occurs over and over again

A

differences accumulate and become more pronounced eventually leading to the formation of new groups of organisms that differ greatly from their ancestors (e.g. origin of whales (cetacean) from terrestrial mammals)

185
Q

what does the time between speciation event include

A
  1. the length of time that it takes for populations of newly formed species to begin diverging reproductively from one another (can take ages)
  2. the time it takes for speciation to be completed once divergence begins (can be fast or slow)
186
Q

what are the 2 types of barrier

A

geographic - allopatric

temporal (behavioural) - sympatric

187
Q

what is co-speciation

A

when the speciation of one species due to a geographic barrier causes the speciation of another species

B (19 decks)

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