Final Flashcards
1
Q
Where does biological diversity come from?
A
evolution
2
Q
what is evolution?
A
a change in allele frequencies in a population over time
3
Q
how do we study evolution?
A
1) genetics (how does inheritance work, Mendel)
2) population and quantitive genetics (how do allele frequencies change over time and space?)
3) paleobiology (how do large-scale evolutionary changes affect organisms?)
4) integration of genetics and morphology (developmental patterns and evolutionary transitions)
4
Q
what are the required conditions for natural selection to occur?
A
evolution in response to natural selection is inevitable if:
1. there is variation in a trait
2. that variation is heritable
3. some variants survive and reproduce more than others
5
Q
where did the idea of evolution by natural selection come from - what ideas did it rely on?
A
Charles Darwin
relied on the ideas of Lyell (long evolutionary time period)
Malthus (survival of the fittest)
Lamarck (transmutation)
6
Q
Who was Alfred Russel Wallace?
A
came up with the theory of natural selection independently of Darwin, but later, spurring Darwin to publish his own work
7
Q
Who was Jean-Baptiste Lamarck?
A
proposed transmutation mechanism of inheritance (that species change over time
Lamarckism
species themselves must be capable of changing
8
Q
who was Thomas Malthus?
A
human population can increase faster than food supply, which leads to competition and survival of the fittest
there must be a pressure to force adaptation (ie. food)
9
Q
who was Charles Lyell?
A
landforms were not fixed but changed slowly as a result of geological processes that can be observed today
the earth is much older than believed and undergoing constancy change
timeframe for evolution is on the geologic time scale
10
Q
what is the link between existing variation within a population and the process of natural selection?
A
the existing variation in a population’s traits occurs. as a result of natural selection forcing the reproductive success of fit traits, which are then inherited in a population (causing said variation)
11
Q
why is heritable variation leading to differential fitness essential for evolution?
A
evolution cannot occur without heritability in natural selection.
12
Q
who is Georges Cuvier?
A
found that many species have gone extinct
some species survive, others go extinct
13
Q
what is Lamarckism?
A
acquired traits can be inherited and are lost through disuse
14
Q
what did On the Origin of Species state?
A
the struggle for existence firn limited resources = favourable variations tend to be preserved and unfavourable ones destroyed
15
Q
what were Darwin’s four postulates?
A
- Individuals within a species vary
- Some variation is inherited
- more offspring are produced than can survive and reproduce
- survival and reproduction are not random but related to phenotypic variation.
16
Q
what did Charles Darwin contribute?
A
natural selection is the mechanism by which biological evolution occurs
17
Q
what is adaptive radiation?
A
a process in which organisms diversify rapidly from an ancestral species into many new forms
ex. Darwin’s finches
18
Q
Natural selection can occur without ___, but evolution by natural selection cannot
A
Heritability
19
Q
What are Mendel’s genetic crosses?
A
he performed the test cross and the monohybrid cross
20
Q
what is a test cross?
A
cross homozygous recessive individual to determine if the other parent is homo or hetero dominant
Mendel used to check his monohybrid crosses
aa x A?
21
Q
what is a monohybrid cross?
A
two heterozygous parents come together for a single pair of genes
f2 produces a 3:1 phenotypic ratio and a 1:2:1 genotypic ratio
22
Q
how does meiosis determine the frequency and genotype of gametes of homozygous and heterozygous individuals?
A
the pair of alleles that control a character separate as gametes in meiosis
half of the gametes (haploid) carry one allele, and the other half carry the other allele
diploid organisms get one allele from each parent
23
Q
what is the difference between dominant and recessive alleles?
A
often, the dominant allele codes for a functional protein, whereas the recessive allele codes for a loss of function.
24
Q
What is incomplete dominance? how does this affect phenotypic ratios?
A
when the effects of the recessive allele can be seen in a heterozygote
intermediate phenotype
ex. a red and a white flower making a pink heterozygote
rather than being 3:1, F2 is now 1:2:1
25
what is co-dominance? how does this affect phenotypic ratios?
when both alleles have significant effects, making both alleles detectable in heterozygotes
both traits expressed
1:2:1
ex. blood types
26
what is blending inheritance?
theory of inheritance from the mid-1800s
offspring have traits that are intermediate to their parents
variation will be reduced over time
27
what did Gregor Mendel do?
tested the hypothesis of blending vs. particulate inheritance
used true-breeding variety of peas
many varieties of different characters
published Uber Pflazenhybriden
28
what were the objectives of Mendel's pea plant experiment? how did he conduct his experiments differently from others?
to determine whether statical patterns in occurrence of the contrasting trits persisted by means of crossing or blending
he...
1. used true breeding strains
2. focused on a single trait at a time
3. quantitative: counted the progeny
29
the results of Mendel's crosses support his three hypothesis
1. the genes that govern genetic characters are present in two copies in individuals
2. if different alleles are present in a pair of genes, one is dominant over the other
3. the two alleles of a gene segregate and enter games separately
30
the product rule in probability
when two or more events are independent, the probability that they will both occur is calculated using the product rule:
their individual probabilities are multiplied
the probability that A and B with BOTH occur = the probability of the event
31
what is Mendel's principle of segregation?
the pairs of alleles that control a character segregate in meiosis, as gametes are formed, with half of the gametes carrying one allele, and the other carrying the other allele.
32
the sum rule in probability
applies when several different events all give the same outcome
the probability that EITHER event A or B or C will occur = probability of event
A+B+C = probability of event
33
what is a dihybrid cross?
a cross between two individuals that are heterozygous for two pairs of alleles
Rr Yy x Rr Yy
this supported his theory of independent assortment
34
what is Mendel's principle of independent assortment
alleles of genes that govern two characters segregate independently dying the formation of gametes
35
what is a population?
an interbreeding group of individuals that belong to the same species and live within a restricted geographical area
36
what is population genetics?
the consequences of Mendelian genetics in a population
37
what assumptions have to be met for a Hardy-Weinberg equilibrium?
population allele frequencies do not change if:
1) the population is closed to migration from other populations (no gene flow)
2) the population size is infinite (no genetic drift)
3) no mutation is occurring in the population (no allele change between generations)
4) all genotypes in the population survive and reproduce equally well (natural selection does not affect alleles, same fitness)
5) individuals in the population mate randomly with respect to genotype (same fitness, random mating)
38
the location of a gene on a chromosome is...
a locus
39
what is the Hardy-Weinberg principle?
what would the genetic makeup of a population be at a particular locus if the population was not evolving?
40
what are the expected genotype frequencies under a Hardy-Weinberg population?
genotype: frequency:
AA p^2
Aa 2pq
aa q^2
41
because the gametes are haploid and mix randomly if there is no selection at the genotypic level, ________
all gametes go back to the gene pool
42
what did Sutton observe?
while studying meiosis and fertilization in 1903, he noticed:
1. chromosomes occur in pairs in diploid organisms
2. chromosomes of each pair separated in gametes
3. separation of each pair of chromosomes is independent of other pairs
43
segregation of ___ reflects the spertaion of ____ in meisosi
alleles
chromosomes
44
polymorphism
the existence of discrete variants of a character among individuals in a population
45
properties of complex traits
complex traits...
1. vary continuously (ie. height) (genetic nf environmental causes influences create continuous distribution)(ie. height in 1914 and now)
2. are polygenic (multiple genes for one trait)
46
what is a complex trait?
Complex traits, also known as quantitative traits, are traits that do not behave according to simple Mendelian inheritance laws.
ie. body size and length
47
is it possible for two individuals to have the same phenotype but different genotypes? the same genotype but different phenotypes?
Yes and yes
AA and Aa genotypes have the same phenotype
the same genotype can be expressed differently (epigenetics)
48
why is Hardy-Weinberg equilibrium a powerful test in evolution?
1. tells us when evolution is not occurring
2. departure from equilibrium suggests one or more assumptions have been violated
3. we can use it to predict genotype frequencies when we have less information about a population
*even if a population is not at HWE, this does not prove that it is evolving, we need to see a sustained change in allele frequencies
49
how do you test whether a population is in HWE?
1. calculate the allele frequencies, p and q
2. use the allele frequencies to calculate the genotype frequencies p^2, 2pq and q^2
3. calculate expected numbers under HWW
4. perform a Chi-Squared test
50
how do you calculate allele frequencies?
p = 2(AA) + Aa / 2(total observed)
q = 2(aa) +Aa / 2(total observed)
p + q = 1
51
how do we determine the expected numbers in a population?
multiply the genotype frequency by the total population to get your expected genotype number
ex.
P^2 = 0.91 = total(0.91) = 1466.92 invidiuals expected to be AA
52
what is genetic drift?
changes in allele frequency due to random changes in populations
reduces genetic variation -- variation is lost more rapidly in smaller populations (bottlenecks and founder effects)
causes population divergence
53
what is inbreeding?
mating with relatives
affects genotype frequencies, but does not alter allele frequencies in itself
results in the fixation of homozygous individuals and elimination of heterozygosity
inbreeding depression results in reduced fitness
54
why are genetic drift and inbreeding important in small populations?
drift generally leads to reduced genetic diversity in small populations because rare alleles are often lost
the small size of the total gene pool will remain small regardless of how large the population becomes
inbreeding causes a disruptive selection, which fixates the homozygous genotypes and eliminates the heterozygous
55
what is disruptive selection?
both extreme phenotypes are favoured; intermediate phenotypes are selected against
56
what is balancing selction?
a type of natural selection in which more than one allele is actively maintained in a population. natural selection preserved balancing selection when:
1)heterozygotes have a relatively higher fitness
2) when different alleles are favoured in different environments
3) when the rarity of a phenotype provides a selective advantage
57
what is directional selection?
individuals of one extreme phenotype are favoured
58
what is sexual selection?
favours those individuals with specific traits that enhance their ability to mate with individuals of the other sex
often diminishes survival (ie. moose antlers)
encompasses intrasexual and intersexual selection
sexual asymmetry in energy investment in offspring means that females are more discriminatory with who they mate.
59
what is stabilizing selection?
individuals with intermediate phenotype are favoured, ec=xtreme phenotypes are selected against
60
from an evolutionary perspective, mating and survival will be random if the probability of occurring is NOT affected by an individual' _________
phenotype
61
what is a bottleneck?
tem[orary reduction in population size that cause drift, reduce genetic variation, and cause genetic differences between populations -- causing significant conservation implications
look at image
62
what is the founder effect?
a phenomenon in which a population that was established by just a few colonizing individuals has only a fraction of the genetic diversity of the population from which it was derived
see image
ex. expansion out of Africa
63
what are the types of non-random mating?
1. inbreeding (mating with relatives)
2. outbreeding (mating with individuals more distantly related)
3. assortative mating (individuals with similar genotypes and/or phenotypes mate with one another under a random mating pattern (eg. body size)
64
why does inbreeding depression result in lower fitness?
non-random mating changes genotype frequencies
selection acts of phenotypes
a greater proportion of your offspring will have lower fitness than expected with random mating
(rare, deleterious mutations are more common)
65
what is natural selection?
a predictable change in the frequency distribution of a trait between the parental and offspring generations as a result of three conditions:
1)individuals vary (in a population)
2) survival and reproduction is not random ("survival of the good enough")
3) variation is passed on to the offspring (inheritance)
66
what are the three patterns of natural selection?
-- directional selection
-- stabilizing selection
-- disruptive selection
67
___ is stronger in larger populations, whereas __ is weaker in larger populations
natural selection
drift
68
what is a male?
produce abundant, energetically cheap, and more motile sperm
69
what is a female?
produce few, energetically expensive and less motile eggs
70
what is sexual monomorphism?
when males and females of a species have no difference in phenotype.
71
what is sexual dimorphism?
when males and females of a species have distinctly different phenotypes
72
what are the agents of macroevolutionary change?
Gene flow -- change in allele frequencies as individuals join a population and reproduce. may introduce genetic variation from another population. unpredictable effect on fitness; may introduce beneficial or harmful alleles
genetic drift --- random changes in allele frequencies caused by change events. reduces genetic variation, especially in small populations; can eliminate rare alleles. unpredictable effect on fitness; often harmful because of loss of genetic diversity
natural selection --- differential survivorship or reproduction of individuals with different genotypes. one allele can replace another or allelic variation can be preserved. positive effect on fitness through the evolution of adaptations
mutation --- heritable change in DNA. introduces new genetic variation in a population; does not change allele frequency. unpredictable effect on fitness; most mutations in protein-coding genes reduce fitness.
73
what is microevolution?
changes in the frequency of a gene in a population.
74
how does the evolution of the trait mean occur?
when fitness varies positively or negatively with trait size
75
how does artificial selection on quantitative traits occur?
has an end goal, is very fast relative to natural selection
using directional selection to amplify to select for certain traits
76
what is an inbreeding depression?
a decline in the average fitness of inbred individuals in a population
77
what is intersexual selection?
selection based on interactions between males and females
males producing otherwise useless ornaments simply because females associate it with health and vigour
likely caused by sexual dimorphism
78
what is intrasexual selection?
selection based on interactions between members of the same sex
males use large body sizes, antlers, or tusks to intimidate, injure or kill rival males.
79
what is speciation?
the process of species formation (production of biodiversity)
combines the studies of ecology, evolution and genetics
80
what is the Morphological species concept?
the idea that individuals of a species share measurable that is that distinguish them from individuals of other species
not reliable, tell us little about the evolutionary or genetic processes
most traditional, simple to use
81
what is the Biological Species Concept?
the definition of species is based on the ability of populations to interbreed and produce fertile offspring
does not account for those who reproduce asexually or extinct organisms
Ernst mayr
82
what are the factors that cause genetic divergence between isolated populations?
-- genetic drift
-- bottleneck and founder effect
--- mutation
--differential selection
83
what is the Phylogenetic Species Concept?
uses both morphological and genetic sequence data, a phylogenetic tree can be constructed for the organism of interest
84
what is the reproductive isolation mechanism?
a variety of biological characteristics that prevent individuals of a different species from mating and producing successful progeny
reduces interspecific mating and hybrid species production
operate at different times during the reproductive process, namely or post-zygotic
85
what is prezygotic isolation mechanisms
reproductive isolation mechanisms that exert their effects before fertilization and production of a zygote
86
what is postzygotic isolation mechanism
reproductive isolation mechanisms that operate after fertilization and zygote formation
87
what are the prezygotic mechanisms?
--ecological isolation
--temporal isolation
--behavioural isolation
--mechanical isolation
--gametic isolation
88
how does ecological isolation work?
the species live in different habitats
89
how does temporal isolation work?
the species breed at different times
90
how does behavioural isolation work?
the species cannot communicate
91
how does mechanical isolation work?
the species cannot physically mate (ex.. different genitalia, pollinator isolation)
92
how does gametic isolation work?
species have nonmatching receptors on gametes, so zygotes do not form
ex. coral sprawling, genetic incompatibility systems in plats, pollen tubes cannot grow
93
what are the postzygotic mechanisms?
--hybrid inviability
--hybrid sterility
--hybrid breakdown
94
how does hybrid inviability work?
hybrid offspring do not complete the development
not particularly healthy, rittled with health defects throughout life.
95
how does hybrid sterility work?
hybrid offspring cannot produce gametes.
96
how does hybrid breakdown work?
the hybrid offspring have reduced survival or fertility
97
what are the modes of speciation?
allopatric and sympatric
98
what is allopatric speciation?
when a physical barrier divides a geographic range (vicariance event)
gene flow ceases and separate populations evolve independently
over time, different alleles become fixed because of mutation, drift or selection.
provided sufficient time has elapsed fro significant divergence to take place
if the barrier is removed and populations come back into contact, they may remain distinct
interbreeding prevented by prezygotic and/or post-zygoic mechanisms
99
what is peripatric speciation?
the ancestral population seeds a small peripheral population
allopatric speciation where dispersal with a small new population occurs
divergence occurs over time, but most of the change occurs in the small population
100
what is sympatric speciation?
there is no geographical barrier to gene flow, instead reproductive isolation evolves between distinct subgroups that arise within one population
101
how does sympatric speciation occur?
stages:
1) polymorphism that affects fitness
2) matings between the two forms are discouraged (prezygotic) or disadvantageous (postzygotic)
102
what is autopolyploidization?
--polyploidy (one or more extra copies of a chromosome) can cause sudden speciation
-- if 2n gamete is fertilized with another 2n gamete, autopolyploid occurs
--autopolyploids can only mate with other autopolyploids = reproductive isolation
103
what is allopolyploidization?
similar to allopolyploidization, but involves the mating between two closely related species
104
what is Bateman's principle
male reproductive success should increase with multiple mating, whereas female reproductive success should not, has long been used to explain sex differences in behaviour.
105
what are phylogenies?
--branching diagram that shows the relationships between species, often according to the time since a common ancestor
106
what is a sister group?
two species (or groups of species) that share a common ancestor not shared by any other species or group
107
what is a node?
each branching point on. a phylogenetic tree
108
what is a clade?
all of the branches that emerge from a node
109
what is a phylogram?
a phylogenetic tree where the branch lengths represent the amount of inferred evolutionary change/time
branching + evolutionary time
110
what is a cladogram?
a phylogenetic tree where all the branches are simular length
just branches
111
what is a monophyletic group?
includes a common ancestor and all of its descendants
112
what is a paraphyletic group?
includes a common ancestor and some, but not all of its decendants
113
what is a polyphyletic group?
does not include the common ancestor
114
how are phylogenies inferred?
using character that are shared between a species
the characters used vary among, but not within species and have a genetic basis:
-morphology
-chromosomal
--molecular
115
what are characters vs character states?
the evidence consists of a number of characters, each with a number of discrete character states.
ex. flower colour (character) has blue and yellow states
can be for two reasons:
homologies and homoplasies
116
what are homologous characters?
homologies are shared because of common ancestry
ie wing bones of birds and bats
117
what are analogous characters?
homoplasies are simular in appearance but not in origin
Shared because of convergent evolution.
ie. the wings of birds and bats
118
how are homologies recognized?
1) strutural simularity
2) relations between parts
3) embryotic development
119
what are synapomorphies?
a shared derived character state found in two or more species
serve as markers for monophyletic lineages
an apomorphy found in two or more organisms
120
what is the principle of parsimony?
the phylogeny requiring the fewest evolutionary changes is the best estimate of the true phylogeny = most parsimonious
helps identify homologous characters and infer their ancestral and derived states
121
what are distance methods in phylogeny reconstruction?
construct phylogenetic trees from DNA sequence data, where the overall proportion of bases that differ between two species is calculated
we can estimate degrees of relatedness from comparisons in DNA sequences. (descendants from an ancient common ancestor = more time) (DNA sequences differences reflect time since common ancestor)
122
what is macroevolution?
evolution that occurs on a scale that transcends the boundaries of a single species.
123
what is adaptive radiation?
the rapid evolution of new species occupying new ecological niches
124
what is anagenesis?
speciation wherein the ancestor species is wholly replaced by a new species (evolution within lineage)
125
what is cladogenesis?
a parent species splits into two species
126
what is graduated equilibrium?
slow and steady gradual evolution that results in anagenesis
127
what is punctuated equilibrium?
rare and rapid (on a geologic time scale) events of branching speciation, resulting in cladogenesis
128
how old is the earth?
4.6 billion years old
129
when did unicelluar prokaryotes emerge?
3.2 - 3.4 billion years ago, from northern Canada, south Africa and Australia
many are found in stromatolites (biofilm traps sediment), which decline in abundance 500 million years ago
130
when did multicellular life emerge?
2.1 billion years ago
131
when did complex multicellular animals emerge?
650 million years ago?
132
what was Earth's early atmosphere like?
little oxygen, didn't exist in a molecular state, reduced atmosphere
oxidation was prevented by the removal of oxygen and other oxidizing gases or vapours
the input of energy turned these gases into a primordial soup
133
what is the Urey Miller experiment?
the experiment simulated the early Earth conditions and tested the chemical origin of life
2% of carbon was in amino acids 13 to 22 used in living cells
still, there's debate about earth's original atmosphere and reducing molecules present
134
which communities provide a model for early evolution of life?
vent communities
no light doesn't mean no photosynthesis. they use chemolithotrophy from various food sources (hydrogen sulphide) to create electrochemical potential and the hydrogen ion gradient.
135
in what periods did the great oxygenation event occur?
the archaean and the proterozoic
136
what occurred in the Archaean-Proterozoic periods?
transition from prokaryotes, eukaryotes, to multicellularity
the great oxygenation event
137
how do cyanobacteria obtain their energy?
photosynthesis
138
what is the great oxygenation event?
due to cyanobacteria producing gaseous oxygen as a byproduct of photosynthesis, the atmosphere converted the atmosphere from reducing to oxidizing
a dramatic change in the composition of life forms by stimulating biodiversity and leading to the near extinction of oxygen-intolerant organisms
139
what is endosymbiosis?
origin of key eukaryotic organelles, as a result, of symbiosis between separate single-cell organisms
archaea engulfed bacteria
140
what is the evidence for endosymbiosis?
-organelles are membrane-bound
-organelles have their own DNA (separate from nucleus)
-mitochondrial DNA is similar to bacteria/chloroplast DNA
-reproduction: mitochondria replicate by binary fission
141
what happened in the Paleozoic era?
Cambrian explosion
invasion of land
appearance of gymnosperms
major groups of tetrapods
142
what is the Ediacaran period? what happened?
pre-Cambrian, laid the groundwork for the Cambrian explosion and tetrapods
a lot of weird forms of animals are now extinct
640 mya
143
what is the Cambrian explosion?
-- the rapid appearance of many groups of organisms about 530 million years ago
--preceded by the appearance of shell parts
--evidence of arthropods (insects, shellfish) and echinoderms (sea urchins) and a large number of extinct forms
-- eyes, heads, mouths, and legs appear.
144
why was the cambiran explosion an explosion of life?
-- genetic diversity likely present
--increasing CO2 levels from eukaryotic algae
-- the evolution of grazing (reduction of algal mats because of the formation of mouths)
-- shift in ocean chemistry favouring the production of calcium carbonate (shells and bones)
145
what is mass extinction
the rate of extinction greatly exceeds the rate of speciation (more than 75% of known species in a geologically short time)
periodic
146
why are mass extinctions significant to evolution?
niches are cleared/ ecological opportunities available (wipes the slate clean)
leaves 'dead clades walking' - low diversity remnants of once diverse lineages
adaptive radiation replenishes the planet
