Evolution Flashcards
(250 cards)
1
Q
Two views of evolution
A
1) change in character traits of a population (Darwin, phenotypic change)
2) change in population allele frequencies (genotypic change)
2
Q
Gene
A
1) region of DNA that codes for a specific polypeptide
2) can be regulatory, act as switches for gene expression, of express given trait
3
Q
Genome
A
large recipe book in the form of amino acids (composed of genes)
4
Q
Locus
A
Physical location of specific gene on a chromosome
5
Q
Allele
A
Version of a specific gene at a given locus
6
Q
Causes of change in allele frequencies
A
1) Natural selection
2) Genetic drift
3) Gene flow
4) Mutation
All are microevolutionary processes
7
Q
Neutral theory
A
Kimura (1983)
1) Much of genetic variation is neutral, do not affect phenotype (occur by chance and not selection)
2) They either do not alter the product of genes OR affect non-coding regions of DNA
I.e. Traits may change, but they do not influence fitness
Evolutionary Biology pg. 17, 354
8
Q
Is neutral theory subject to natural selection?
A
No.
9
Q
Importance of neutral theory
A
Can look into ancestry through neutral mutations
10
Q
Hardy-Weinberg Equilibrium
A
In the absence of disturbance, gene frequencies will remain constant
If you know allele frequencies in one generation, you can predict genotype frequency in next generation
11
Q
Hardy-Weinberg Equilibrium assumptions
A
1) No evolution (no genetic drift, no gene flow, no natural selection, no mutation)
2) Random mating
12
Q
Genetic diversity
A
Number and relative frequency of alleles in a population
13
Q
What are the benefits of high genetic diversity
A
Ability to respond to change
14
Q
Natural Selection
A
1) Evaluates alleles on basis of fitness
2) Occurs when one phenotype has higher fitness
3) There are three types of natural selection, directional, stabilizing, disruptive
Evolutionary Biology p. 60
15
Q
Directional Selection
A
1) Allele frequencies change in one direction
2) Favors one extreme of trait distribution
3) Decreases genetic diversity
16
Q
Stabilizing Selection
A
1) Alleles associated with mean trait values increase
2) No change in average trait value
3) Decrease in genetic diversity over time
4) Increase in trait and gene frequency over time
17
Q
Disruptive Selection
A
1) Alleles associated with both extremes of a trait are favored
2) Distribution bifurcates
18
Q
Sexual Selection
A
When there is variation in mating success based on different characters
Evolutionary Biology p. 60
19
Q
Genetic Drift
A
1) Independent of fitness
2) Due to random chance
2) More likely in small populations
3) Leads to fixation and loss of alleles
4) Two causes: founder effect and genetic bottleneck
20
Q
Founder effect
A
1) Small number of individuals found a new population, and new population does not reflect the allele frequency of source population
2) Also called peripatric speciation
Evolutionary Biology p. 234
21
Q
Genetic bottleneck
A
Drastic and/or random reduction in population size (not due to differences in fitness)
22
Q
Gene Flow
A
1) Movement of alleles from one population to another (immigration/emigration-functionally)
2) Equalizes allele frequencies between populations
3) Can restore lost alleles
23
Q
Mutation
A
1) Production of new allele via damage or replication errors to DNA
2) Increases genetic diversity
3) Variable effect on fitness
24
Q
Inbreeding
A
1) NOT a microevolutionary process
2) Changes genotype frequency and phenotypic expression
2) Does NOT change allele frequency
3) Homozygous recessive genotypes often decrease fitness
25
Speciation
1) enough microevolutionary processes occur to create a new species
2) formation of a new species from an ancestral species
3) two components: reproductive isolation and genetic divergence
26
Species
1) Evolutionary independent population
2) Distinguished by common characteristics
3) Three functional distinct definitions: biological, morphological, phylogenetic
27
Biological Species Concept
1) Reproductively isolated populations
2) Member of a species can interbreed and produce viable offspring
3) Can only be applied to organisms that we can observe breeding (can't apply to fossils and extinct species or geographically isolated species, e.g. blue whales)
4) Hybridization is still allowed (not all or nothing)
Evolution p. 215
28
Morphological Species Concept
1) Based on differences in morphology
2) Widely applicable to fossils and both sexual and asexual organisms
3) Criteria is subjective and intra-specific variation can sometimes be greater than that of inter-specific (e.g. sexual dimorphism in buffleheads and zebras look different but can successfully interbreed)
29
Phylogenetic Species Concept
1) Based on ancestral analysis
2) Smallest identifiable group assigned species status (monophyletic group)
3) Can be applied widely
4) Unfortunately, there are only a few thorough phylogenies available
30
What is the relationship between reproductive isolation and genetic divergence
As isolation increases, so does divergence
31
Reproductively Isolating Mechanisms
1) How populations reproductively isolate
| 2) pre- and post-zygotic isolation
32
Pre-zygotic isolation
Pre-mating
1) Ecological Isolation (temporal isolation (Gryllus crickets reproducing at different times) or habitat isolation (soapberry bugs feeding on different plants))
2) Behavioral isolation (sexual isolation (female mate choice, song of finches) or pollinator isolation (plants are specialized to specific pollinator and there is no overlap))
Post-mating
1) Mechanical isolation (reproductive structures do not fit)
2) Copulatory isolation (female not stimulated by male-occurs in some fly species)
3) Gametic isolation (failure to fertilize, e.g. in larval spawning by abalone or corals).
Evolutionary Biology p. 221
33
Post-zygotic isolation
1) Extrinsic: hybrids are formed but have low fitness for environmental reasons
a) ecological inviability
b) behavioral sterility
2) Intrinsic (low hybrid fitness is independent of environmental context
a) hybrid inviability (reduced survival due to genetic incompatibility)
b) hybrid sterility (reduced production of viable gametes)
34
Mechanisms of speciation (5)
1) Allopatric speciation
2) Dispersal/colonization
3) Vicariance
4) Sympatric speciation
5) Polyploidy
35
Allopatric Speciation
1) Populations become geographically isolated
2) Gene flow ceases
3) Populations diverge genetically (via drift, selection, and mutations) making them separate species
4) Results from dispersal/colonization and vicariance
36
Dispersal/Colonization
1) Small number of individuals disperse to new habitat
2) Founder effect increases genetic drift
3) If new environment differs, selection may occur
4) Populations diverge genetically (via drift, selection, and mutations) making them separate species
4) Common on islands
5) Type of allopatric speciation
37
Vicariance
1) Large populations split into two or more sub-populations
2) Usually occurs due to emerging geographic barriers
3) New populations are genetically isolated (no gene flow)
4) Populations diverge genetically (via drift, selection, and mutations) making them separate species
5) Type of allopatric speciation
Evolutionary Biology p. 236
38
Sympatric Speciation
1) Speciation without geographic isolation
2) Occurs when natural selection overwhelms gene flow (via temporal and behavioral isolation and polyploidy; e.g. soapberry bugs, beak length correlates with fruit size, they mate where they eat)
3) Example: linkage disequilibrium between beak size and color, strong mate choice for same color, reinforces mating of same color and beak size, speciation occurs
4) Example, band-rumped storm petrel has split in sympatric populations with separate breeding seasons
Evolutionary Biology p. 238-40
39
Example of behavioral disruption of mating
1) Soapberry bugs specialize on different types of food (based on mouth morphology). As a result they occupy different plants and do not mate with bugs on other plants.
2) Apple maggot exploits two different types of apples that have different peak fruiting times. Therefore the timing of emergence of adults differs resulting in reproductive isolation.
40
Example of allopatric speciation
1) Galapagos finches colonizing new islands and then undergoing speciation.
2) Turtles and the Isthmus of Panama.
41
Polyploidy
1) Special case of sympatric speciation
2) Usually caused by mutation that creates extra chromosome copy
3) Two types: autoploidy and alloploidy
42
Example of polyploidy
Allium (garlic and onion) species have evolved via polyploidy.
43
Autoploidy
Mutation doubles chromosome number, resulting in individuals that can only self-fertilize to produce viable offspring
44
Alloploidy
Two different species mate, there is a mutation in the offspring that doubles the chromosome number, allows for self-fertilization
45
Hybrids
1) Formed when isolated populations reconnect if sufficient genetic divergence has occurred through pre- and post-zygotic isolation
2) If viable hybrids form, they may have differential fitness than both parent species
46
Hybrid Zones
1) Areas of overlap where interbreeding of separate species occurs
2) If hybrid fitness is higher than either parent species, homogenization occurs
3) If hybrid fitness is is lower than either parent species the hybrid zone narrows and reinforcement of separate traits in parent species emerges
47
Hybrid zone with high hybrid fitness, description and example
1) Fusion occurs reproductive barriers are weakened, there is substantial gene flow between species, this can cause the parent species to become a single species over time.
2) Cichlid fish in Lake Victoria, as turbidity increases, less selection for male coloration from females so hybrid fitness
3) Hypothetical example: Two species of fish where females select for a blue and a red color morph. Waters become more turbid so color is more difficult to see. Hybridization occurs and the hybrids are better equipped to exploit resources in turbid environment and mate choice disintegrates due to turbidity. This would cause fusion of the two species.
48
Hybrid zone with low hybrid fitness, description and example
1) Reinforcement of barriers between species occurs and rate of hybridization decreases.
2) example European flycatchers. In sympatric species, females will never mate with other species, so female choice selects for divergence in male secondary sexual characteristics, so hybrids with intermediate characteristics have low fitness.
49
Macroevolution
dramatic and rapid evolution
50
Two views on the pace of evolution
1) gradualism
| 2) punctuated equilibrium
51
Gradualism
1) genetic change is continuous through time
2) these genetic changes lead to changes in phenotype and eventually to new species
3) predicts transitional forms (e.g. cetacean evolution)
52
Punctuated equilibrium
1) change occurs in short bursts
2) long periods of minimal change
3) few or no transitional forms
4) rapid appearance of new species
53
Orthologs
1) Genes that diverge from a common ancestral gene by phylogenetic splitting at the organismal level
_________ A_Species 2
A |
________X
| |_________ B_Species 2
|
---( )
| _____________ B_Species 1
| |
| ____X
B |_____________ A_Species 1
Evolutionary Biology p. 40
54
Paralogs
1) Genes that originate from an ancestral gene duplication
| Evolutionary Biology p. 40
55
Cambrian Explosion
1) Major radiation of multicellular animals, beginning of Paleozoic era (540 mya)
2) Within 40 million years almost all major animal phyla appear
56
Homeotic Genes
1) found in all multicellular organisms
2) control development (transcription)
3) can be specific to regions of the body
4) are turned on or off by regulatory genes
5) highly conserved (extreme selective pressure to maintain them, similar sequences in very different organisms)
57
Hox genes and complexity
1) More hox genes typically yields more complex organisms
2) Gene duplication mutations produce more Hox genes (these hox genes are paralogs)
3) influenced by heterochrony and heterotropy
58
Hox genes
Control development (growth and body region)
59
Heterochrony
difference in duration of expression, e.g. skull formation in chimps and humans (chimps have longer duration development of jaw bones)
60
Heterotropy
difference in location of expression
61
Example of heterochrony and heterotropy
1) Fin versus limb bud growth in vertebrates
2) both mouse limbs and fish fins form from limb buds in embryo
3) hoxd-11 and shh are genes that regulate direction of limb growth
4) hoxd-11 is expressed early in development, but there is differential expression of this gene later in development, leading to different shapes of limbs and fins
62
Phylogenetic trees
1) Series of branches (population), nodes (forks where ancestor splits), and tips (extinct and extant species) that trace phylogenetic relationships
2) Sister taxa occupy linked by nodes
63
Clade
Ancestor and all descendants (starts at node)
64
Ingroup
Member of clade
| Evolutionary Biology p. 36
65
Outgroup
1) Taxon with common ancestor that does not fit into clade
Importance: Give nearest reference point to understand clade
Evolutionary Biology p. 36
66
Monophyletic Group
Complete clade
67
Paraphyletic Group
Clade with erroneous omissions (common ancestor without all descendants)
68
Polyphyletic Group
Clade with erroneous inclusion (different common ancestors)
69
What can be used to create phylogenies
1) Fossil record
2) Comparative molecular biology (molecular clocks and orthologs)
3) Comparative anatomy and embryology
4) Biogeography
70
Molecular Clock
1) When differences in DNA sequences can be used as a marker for how much time has passed
2) Must be specific to character traits and taxa
Evolutionary Biology p. 42
71
Sympleisomorphy
Ancestral trait in cladistics
72
Snyapomorphy
1) Shared derived trait in cladistics (where nodes form)
2) Ingroups share synapomorphy
Evolutionary Biology p. 402
73
Problems with cladistics
1) Must select good, homologous traits for character matrix
2) Homoplasies can occur: when analagous traits are included in cladistics, as opposed to homologous traits
3) Many possible tree formations (but select tree with maximum parsimony)
74
Homoplasies
1) The independent evolution of a character or character state in different taxa
2) Trait is not inherited from a common ancestor
3) Convergent evolution, parallel evolution, and evolutionary reversal
4) E.g. wings are present in birds and bats but they are analogous, not homologous
Evolutionary Biology p. 47
75
Adaptive Radiation
1) Appear in phylogenies as polytomies
2) Rapid speciation events
3) Occurs as a result of colonization events, mass extinctions, morphological innovations
4) E.g., Galapagos finches
Evolutionary Biology p. 50
76
Polytomy
1) Node with multiple branches
| 2) Star phylogeny (indicative of adaptive radiation)
77
Colonization event
1) Habitat unoccupied by a competitor is colonized by a species
2) Colonizing species quickly radiates to exploit new resources
78
Mass extinction
1) Removes major competitors from the system
| 2) Allows surviving species to exploit resources that were previously occupied
79
Morphological innovation
Allows new resources to be exploited
80
Whale evolution
Order Cetartiodactyla, closest relative is hippo. All Cetartiodactyls have astralagus but cetaceans. Why? Most likely explanation is that the astralagus was lost in cetaceans (rather than lost for hippos and cetaceans, adn then regained in hippos) based on idea of maximum parsimony. Supported by discovery of ambulocetus (early cetacean without astralagus)
81
Timeline for life on earth
1) Eons: Hadean, Archaean, Proterozoic, Phanerozoic (includes Paleozoic, Mesozoic, Cenozoic eras)
2) PreCambrian includes Hadean, Archaean and Proterozoic.
3) Cambrian (in Paleozoic era) yields large multicellular organisms
82
Hadean eon
1) Formation of earth
2) Cooling of earth, formation of oceans from rain
3) Idea of Primordial Soup (Miller), life formed from rich organic compounds
83
Archaean eon
1) Origin and radiation of prokaryotes
| 2) Photosynthesis begins and oxygen increases in atmosphere along with aerobic respiration
84
Proterozoic eon
1) Origin and radiation of eukaryotes
2) Larger cells with distinct nucleus and mitochondria (mitochondria came from a eukaryote that ingested bacteria and adopted aerobic respiration)
3) Chloroplasts appear
4) Simple multicellular organisms
85
Phanerozoic eon
1) Diversification of multicellular organisms
| 2) Broken up into 3 eras: Paleozoic (ancient animals), Mesozoic (dinosaurs), and Cenozoic (mammals)
86
Paleozoic era
1) era in the Phanerozoic eon
2) Ancient animals
3) Cambrian explosion
4) First vertebrates
5) Diversification of fish
6) Invasion of land
7) Extensive fern forests
8) First gymnosperms
9) Permian extinction
87
Proximate causes
Immediate, mechanical causes of biological phenomena, e.g. what causes a male bird to sing? Testosterone and other hormones, the syrinx, and the operation of certain centers in the brain.
88
Ultimate causes
Historical causes, especially via natural selection, e.g. what events led to birds singing? Past individuals who were inclined to sing were more successful in attracting mates.
89
Horizontal gene transfer
Transfer and change of genes from one taxon to another through non-reproductive means.
E.g. the evolution of mitochondria in cells when eukaryote consumed bacterium, aphids acquired gene for synthesizing carotenoids from fungi, viruses to humans
E.g., HGT between mitochondria and nucleus
Evolutionary Biology p. 38, 350
90
Vertical gene transfer
Transfer of genes through reproductive means, parent to offspring
91
Anagenesis
Evolutionary change of features within a single lineage (species)
Evolutionary Biology p. 33
92
Cladogenesis
1) Branching of a lineage into two or more descendant lineages.
2) Following cladogenesis, anagenesis occurs between each lineage causing divergence
Evolutionary Biology p. 33
93
Sister groups (phylogeny)
Two clades that originate from a common ancestor
| Evolutionary Biology p. 33
94
Homolog
Shared traits among taxa that share a common ancestor, e.g. forelimb skeletons of tetrapod vertebrates
Evolutionary Biology p. 35
95
Analog
Shared trait among non-related taxa, typically related to exploitation of similar niche or resource, e.g. wings in bats and birds
Evolutionary Biology p. 35
96
Hybrid speciation
When various phenotypic and DNA markers throughout the genome reveal two ancestral sources
Evolutionary Biology p. 38
97
Time of divergence between species
D=2rt, r=rate at which these genes evolve in given taxa
the factor 2 appears since this gene has diverged in two lineages
Evolutionary Biology p. 42
98
Evidence for evolution
1) hierarchical organization of life
2) homology
3) Embryologic similarities
4) Vestigial characteristics
5) Convergence
6) Suboptimal design
7) Geographic distributions
8) Intermediate forms
Evolutionary Biology p. 44
99
Mosaic evolution
1) Evolution of different characters at different rates within a lineage
2) It tells us that a species evolves not as a whole but piecemeal
3) Many of its features evolve more or less independently
4) Every species is a mosaic of plesiomorphic and apomorphic characters
Evolutionary Biology p. 44
100
Plesiomorphic
Ancestral
101
Apomorphic
Derived
102
Dollo's Law
1) Complex characters are unlikely to be regained once they are lost
2) Exceptions include aquatic larval stage in salamanders (was lost but then regained).
Evolutionary Biology p. 48
103
Adaptation
1) A characteristic that enhances the survival or reproduction of organisms that bear it, relative to alternative character states.
2) Adaptations have evolved by natural selection.
3) Adaptations have evolved for ideal situations for ancestral states, not current, "the future cannot cause material events in the present", no goals in biology
Evolutionary Biology p. 56
104
Example of adaptive evolution
Soapberry bugs have adapted rapidly to new food plants. The bugs feed on soapberry plants, but have adapted to new food sources by changing beak length to pierce different sized pods.
Evolutionary Biology p. 57
105
Evolutionary trade-offs of pleitropy
1) When natural selection on pleiotropic genes favors allele that has higher overall fitness, despite possible negative affects of second trait
2) Adapting to one condition means you are allocating energy to one specific task, which may draw away from other factors of development. For example, plants that have evolved in soil with high metal loads have evolved a tolerance to these metals, but with this tolerance comes depressed growth and development.
Evolutionary Biology p. 58
Evolutionary Biology p. 116
106
Culture
information capable of affecting individual's behavior that they acquire from other members of their species through teaching, imitation, and other forms of social transmission. E.g. humpback whale song, foraging in dolphins
107
Levels of selection
Selection can occur on the genic, individual, population, or species level.
Evolutionary Biology p. 62
108
Genic selection
1) Natural selection at level of gene.
2) Illustrated by transposable elements, which replicate and proliferate within the genome, regardless of whether or not they are good or bad to individual.
3) Transposable elements are among selfish genetic elements
Evolutionary Biology p. 62
109
Selfish genetic elements
Gene elements that are transmitted at higher rates than other parts of the genome, e.g. segregation distortion
Evolutionary Biology p. 62
110
Segregation distortion
1) When gene frequencies fall outside normal Mendelian expectations.
2) E.g. the t locus of the house mouse, in heterozygotes, t allele kills sperm carrying normal T allele, as a result, more than 90% of males carry t allele, but tt embryos are sterile and often die young.
3) Can lead to genetic conflict speciation
Evolutionary Biology p. 62, 229
111
Species selection
1) Selection among groups of organisms, when groups involved are species and there is a correlation between some characteristic and the rate or speciation or extinction.
2) Does not shape adaptation of organisms but shapes disparity between organisms of the world
3) E.g., Red Queen hypothesis and idea of sexual forms prevailing over asexual forms
Evolutionary Biology p. 65
112
Preadaptation/exaptation
A feature that fortuitously serves a new function, a feature co-opted for a new function
Evolutionary Biology p. 66
113
Complexity in evolution
A complex feature often serves an adaptive function
| Evolutionary Biology p. 68
114
Design in evolution
The function of a characteristic is often inferred from design
Evolutionary Biology p. 68
115
Lack of genetic variation
Lack of genetic variation often yields phylogentic constraints, e.g. seven cervical vertebrae of mammals and giraffes
Evolutionary Biology p. 72
116
Character displacement
Divergence of species as a consequence of their interaction, e.g. Galapagos finches
Evolutionary Biology p. 73
117
Evolution by selection and inheritance
If there is 1) a correlation between a phenotypic trait and the number of offspring that individuals leave to the next generation and 2) a correlation between the phenotype of a trait in parents and their offspring, then the trait will evolve
Evolutionary Biology p. 106
118
Absolute fitness
Number of zygotes produced over a lifetime, W=Pr(Survive)*E(offspring)
Evolutionary Biology p. 107
119
Selection
Increased fitness of a heritable trait, strength of selection is determined by fitness differences
Evolutionary Biology p. 107
120
Relative fitness
Absolute fitness divided by agreed upon fitness reference (which changes on a case by case basis)
Evolutionary Biology p. 108
121
Positive selection
When one allele has higher fitness than another, natural selection favors its spread through the population
Evolutionary Biology p. 108
122
Selective sweeps
Beneficial mutation spreads rapidly through population towards fixation
Evolutionary Biology p. 109
123
What metric measures selection
s, Selection coefficient (strength of selection)
124
Rate of adaptation (quantitative)
deltap = s*p*(1-p) where p*(1-p) is an indicator of the genetic variance in a population (high == high genetic variance, low = low genetic variance where there is fixation)
*Rate of evolution is proportional to the strength of selection and the amount of genetic variation.
Evolutionary Biology p. 110
125
Deleterious mutations
Mutations that decrease fitness, s would be negative and therefore rate of adaptation would be negative.
Evolutionary Biology p. 113
126
Why do deleterious mutations persist?
They occur at low frequencies (when they are caused by recessive genes), so only homozygote recessives experience decreased fitness making it harder for selection to act
Evolutionary Biology p. 113
127
Industrial melanism
Evolution of melanic forms in polluted urban environments, example of strong evolutionary selection
Evolutionary Biology p. 113
128
Parallel evolution
Two similar species sharing a common ancestor and independently evolving a similar trait
E.g., placental and marsupial gliders (flying squirrel and sugar glider)
Evolutionary Biology p. 114
129
Probability of mutation surviving and becoming fixed
Pr(fixation) = 2s (2 times the relative fitness advantage of mutant heterozygote relative to homozygote with original allele)
Evolutionary Biology p. 115
130
Side effects of natural selection
1) Result from genetic correlations
2) Evolutionary trade-offs
Evolutionary Biology p. 116
131
Genetic correlation
1) Occurs when two traits are inherited together
2) One cause is pleiotropy
Evolutionary Biology p. 116
132
Pleiotropy
When two traits are linked (e.g. height and foot size, nipple evolution in males as pleiotropic side effect of natural selection on females)
Evolutionary Biology p. 116
133
Linkage disequilibrium
When allele frequencies do not match expected frequencies based on Mendelian genetics, possibly because two genes are linked
Evolutionary Biology Ch. 4
134
Hitchhiking
1) A consequence of linkage disequilibrium
2) When an allele at one locus spreads by natural selection acting on a second locus that in linkage disequilibrium with the first
3) how much change in an allele's frequency will result from hitchhiking? s(sub a)*D, or selection of allele times linkage disequilibrium between two alleles (PAB-PA*PB)
Evolutionary Biology p. 117
135
Example of evolutionary trade-offs
1) Soay sheep horns, big horns == more mating success but shorter lifespan, vestigial horns == less mating success but longer lifespan, therefore heterozygote advantage wins out and heterozygotes have highest fitness (p. 117)
2) Sickle cell anemia and malaria
136
Polymorphisms
Genes that differ at certain site
| Evolutionary Biology p. 118
137
Fixation
1) When allele frequency goes to 1
2) When mutation becomes fixed, genetic variation at nearby region is also eliminated
3) Use the contrast between the patterns seen in DNA (with polymorphisms and fixation) to determine whether or not selection acted on standing genetic variation in loci that have recently experienced adaptive evolution.
Evolutionary Biology p. 118, 119
138
Balancing selection
1) Selection that maintains genetic variation with a population
2) Overdominance and frequency-dependent selection
Evolutionary Biology p. 120
3) Multiple niche polymorphism
Evolutionary Biology p. 123
139
Overdominance
1) Occurs when the heterozygote has higher fitness than both homozygotes
2) maintains genetic variation
3) e.g. malaria and sickle cell anemia
Evolutionary Biology p. 121
140
Polymorphic equilibrium
Both alleles are maintained
| Evolutionary Biology p. 121
141
Frequency-dependent selection
1) Occurs when the fitnesses of alleles change depending on their own frequencies (often, an allele gets a fitness advantage when rare)
3) E.g. Alpine elderflower orchid, half the plants have purple flowers and half have yellow flowers, bumblebees visit rare colors more frequently because orchids don't reward bees with nectar or pollen so the rare color had not yet been associated with orchids yet
142
Multiple niche polymorphism
1) When different genotypes specialize on different ecological niches
2) Each genotype is shielded from competition with other genotypes
3) E.g., many herbivorous insects have host races that specialize on different species of host plant. The pea aphid has host races adapted to different crop plants and each host selects for different alleles at several loci, which maintains polymorphism in the aphid
Evolutionary Biology p. 123-4
143
When does selection favor the most common genotype?
1) Underdominance
| 2) Positive frequency-dependent selection
144
Underdominance
1) When heterozygotes have the lowest fitness
2) Eliminates genetic variation
3) E.g., Heterozygote sunflowers have lower fertility because their chromosomes fail to pair correctly during meiosis (because there are chromosomal differences within the same species as a result of inversions and translocations during evolution)
Evolutionary Biology p. 125
145
Positive frequency-dependent selection
1) Frequency dependence that favors most common
2) E.g., Heliconius butterflies are distasteful, and birds that eat a butterfly quickly learn to avoid it
Evolutionary Biology p. 126
146
Mean fitness
1) Average fitnesses of individuals within a population
2) Can be calculated when you know the fitnesses and frequencies of the three genotypes at a locus
Evolutionary Biology p. 126
147
The fundamental theorem of natural selection
1) Evolution through natural selection causes mean fitness to increase over time
2) Increases in mean fitness are related to genetic variance for fitness
Evolutionary Biology p. 126
148
Adaptive landscape
1) Tells us how the population will evolve
2) Mean fitness against allele frequency
3) A point is an individual and a population is a cloud of points
4) With overdominance, there is a peak at an intermediate allele frequency where polymorphic equilibrium will be maintained, regardless of starting point
5) With underdominance, there are two peaks at opposing allele frequencies
6) With positive selection, allele increases in frequency until a peak is reached
Evolutionary Biology p. 128
149
How are mutations dealt with in populations?
1) Mutation selection balance
2) Selection acts to remove deleterious mutations through purifying selection, however mutations are continually reintroduced leading to mutation selection balance.
Evolutionary Biology p. 130
150
Mutation load
1) how much a mutation influences the mean fitness of a population
2) very harmful mutations will only survive at low frequencies, yielding a minimal impact on mean fitness
3) very benign mutations will survive at higher frequencies, matching the mean fitness influence of harmful mutations
Evolutionary Biology p. 130
151
Sibling species versus sister species
1) Sibling species are almost identical in appearance but often have different ecology, behavior, chromosomes or genetic markers.
2) Sister species share a common ancestor and are one another's closest relatives
Evolutionary Biology p. 216
152
Parapatric speciation (desription and example)
1) Graded level of gene exchange among adjacent populations and sometimes between more or less distinct populations that are sympatric.
2) Anthoxanthum grass adapt to soil with different levels of contaminants, but this occurs on a cline so there is still some residual overlap between species.
3) Divergence of lizards on white sand and dark soil habitats, some mixing of genes
Evolutionary Biology p. 217
153
Dobzhansky-Muller incompatibilities
1) Incompatibilities can occur in hybrids without ever producing incompatibilities within a population
2) When a two different mutations form in two new species and go to fixation, and they combine for the first time in hybrids causing incompatibility
Evolutionary Biology p. 224
154
Haldane's rule
1) Hybrid sterility or hybrid variability is often limited to the heterogametic sex (e.g. males in humans)
2) Because males are XY in humans, there is no extra X to act as a back up should one chromosome be inherited incorrectly
3) Male hybrids are frequently sterile in mammals, reverse for birds
Evolutionary Biology p. 224
155
Ecological Speciation
1) Speciation can occur as a side effect of adaptation to different ecological circumstances
2) For example, two monkeyflower species colonized different elevations where natural selection favored flower traits that appeal to different pollinators, so exchange between the populations decreased substantially leading to speciation
Evolutionary Biology p. 227
156
Genetic conflict
1) When an allele increases its own transmission to the detriment of other alleles at the same or other loci
2) Can lead to speciation is mutation for "selfish" gene occurs in one population and not the other
Evolutionary Biology p. 228
157
Hybrid Speciation
1) When hybrid fitness differs from parents and allows hybrid to utilize new habitat (exploit different resources)
2) E.g. sunflowers, hybrids formed (no polyploidy), and lives in drier or saltier habitats, and there is genetic incompatibility with parent species
Evolutionary Biology p. 234
158
Introgression (definition and example)
1) When genes from one species are incorporated into genes from another species, which mat enhance adaptation
2) Heliconius butterflies are distasteful and aposematic and traits for coloration and distastefulness have spread through Heliconius butterfly species (even those that are distantly related).
159
Hermaphrodite
When each individual of a species has both male and female gonads
Evolutionary Biology p. 247
160
Anisogamy (definition and evolution)
1) Dimorphism in gamete size
2) Likely evolved because there are two ways that gametes can have high fitness:
a) being large and well-provisioned, which inhibits movement
b) being small and mobile, which enhances the ability to find a large immobile gamete
Evolutionary Biology p. 249
161
Reproductive assurance
1) Increased chance of successful reproduction when potential mates are rare or absent with hermaphroditism (favors this mode of sex)
Evolutionary Biology p. 249
162
Sexually antagonistic selection
1) When selection favors the expression of different traits based on sex
2) Leads to sexual dimorphism
3) Increase in trait's expression benefits one sex but harms the other
Evolutionary Biology p. 250
163
Darwin's hypothesis of sexual selection
1) Selection caused by competition for mates among individuals of the same sex
2) Certain traits evolve only be sexual selection, e.g. long-tailed widowbirds, females prefer longer tails
3) Secondary sexual characteristics that are selected decrease survival, e.g. tungara frog calls, the calls that are more attractive to females attract more predators
Evolutionary Biology p. 251-2
164
Why is sexual selection more intense on males than females?
1) Because males have many sperm, he is capable of fertilizing many eggs from many females, therefore, a trait that increases the number of mates he attracts is favored by selection and will spread
2) In contrast, a female can often fertilize all of her eggs with a single mate so there is no advantage for multiple matings
3) Called Bateman's principle, e.g. fruit flies showed that the number of offspring males sired increased in proportion to the females he mated with
Evolutionary Biology p. 253
165
Operational sex ratio
1) The relative number of males and females available to mate at any moment
2) Strongly influences the outcome of sexual selection
3) Typically more males are available than females (because females are not available when they are developing new eggs, carrying embryos, or caring for young), so females are often a limiting resource for males
4) Exceptions to this yield sex role reversal (females are sexually selected than males), e.g. the red phalarope where females are larger and more brightly colored than males because after mating the males show parental care, not females
Evolutionary Biology p. 254
166
Alternative mating strategies
1) Divergent ways that males of the same species acquire matings
2) E.g. Isopods have three morphs, alphas are largest and defend harems, betas look like females and slip past alphas, and gammas are the smallest that use stealth to sneak past alphas. This is maintained by negative frequency-dependent selection (good to be rare)
Evolutionary Biology p. 255
167
Sperm competition
1) A way that males interfere with each other's reproduction
2) Can prevent sperm from other males from fertilizing eggs (e.g. damselflies that have a small rake or scoop at the end of their penis)
3) Can make it more difficult for later males to fertilize mate's eggs (e.g. guarding females)
4) Can make more sperm (e.g. primates)
Evolutionary Biology p. 255-6
168
How does female choice evolve?
1) Direct benefits (e.g. katydids eat male spermatophore after insemination)
2) Pleiotropic effects (e.g. guppies are attracted to orange objects because they feed on orange fruit, and, as a side effect, are now attracted to orange males)
3) Good genes (e.g. three-spined sticklebacks prefer red males because it is an indicator of health)
4) Fisher's runaway (e.g. widowbird tails)
Evolutionary Biology p. 257
169
Direct benefits (female choice)
When males provide mates with resources that increase female survival and reproductive success (e.g. offspring care and food, katydids inseminate females with spermatophore with nutritional benefits for the female)
Evolutionary Biology p. 257
170
Pleiotropic effects (female choice)
1) When an allele that changes a female's mating preference will typically also change other things about her.
2) E.g. female guppies have a mating preference for males with more orange as males and females are attracted to the color orange (associated with their food)
3) Mating preferences that evolved by selection on pleiotropic effects are perceptual biases
Evolutionary Biology p. 258
171
Perceptual biases
When things females are attracted to are side effects of the sensory system that evolved for reasons other than mating, before male signals were even present
Evolutionary Biology p. 258
172
Good genes (female choice)
When some male traits (called indicator traits) are correlated with traits that increase lifetime fitness
E.g. three-spined stickleback females prefer red males, and red males increase immune system function making these males healthier.
Evolutionary Biology p. 258-9
173
Fisher's runaway
When combined forces of natural and sexual selection favor a trait, then that trait will become even more pronounced and preferences for that trait will continue to grow.
Evolutionary Biology p. 259
174
haplodiploid sex determintation
1) When females are diploid but males are haploid
2) Allows females to control the sex ratio through behavior, e.g. in flies, unfertilized eggs that are laid become males and eggs fertilized in vivo are females, female can adjust the sex ratio of offspring
Evolutionary Biology p. 260
175
Why does selection favor an equal sex ratio?
1) Results from the fact that every individual has one father and one mother
2) As a result, when there are fewer males, males will leave more offspring than females
3) Therefore, any mutation that causes females to produce more sons has an evolutionary advantage and will spread
4) This advantage disappears when the sex ratio reaches equal numbers of males and females
5) Can work in the opposite direction (favoring females)
Evolutionary Biology p. 261
176
Why are males "more expensive"?
The production of males in a sexual population reduces its reproductive potential by a factor of two
E.g. if in a sexual population each female produces two offspring, then only a portion of those offspring can produce further offspring (since some will be male), when compared to an asexual population where each female produces two offspring via parthenogenesis
Evolutionary Biology p. 263
177
Why is sex favored?
1) Males are expensive
2) Sexual reproduction gives rise to genetic variation (Red Queen Hypothesis)
E.g. mud snails that are exposed to higher densities of parasites have higher frequencies of sexually reproducing individuals
3) Selective interference is reduced
Evolutionary Biology p. 261,264,265
178
Selective interference (Hill-Robertson effect)
Because alleles are typically not independent of each other, fitness may be better with one given trait, but if that trait is linked to another trait that is being selected against it will not accumulate. Sexual reproduction reduces the likelihood of this happening.
Evolutionary Biology p. 265
179
Clonal interference
1) Type of selective interference
2) Happens when two or more beneficial mutations spread through a population at the same time, but the combination of those two mutations yields higher fitness than each mutation alone, but the combination of these alleles is not possible due to asexual reproduction
Evolutionary Biology p. 265
180
Ruby in the rubbish effect
1) Type of selective interference
2) The loss of beneficial mutations as a result of their linkage to deleterious mutations
3) OR a beneficial mutation goes to fixation, but due to linkage disequilibrium deleterious mutations hitchhike along with it
3) E.g., Seen in yeast
Evolutionary Biology p. 266-7
181
Muller's rachet
Irreversible accumulation of deleterious mutations in an asexual population
Evolutionary Biology p. 267
182
Why do hermaphrodites avoid reproducing with themselves (forego reproductive assurance?)
1) Because a downside of self-fertilization is inbreeding depression, which is the loss in fitness whose parents are close relatives
2) This is achieved through self-incompatibility or behavioral changes
Evolutionary Biology p. 269
183
How do new genes arise in eukaryotes?
1) Duplication is the most common mechanism
2) Duplications can be caused by:
a) unequal crossing over
b) replications slippage
c) retrotransposition
Evolutionary Biology p. 347
184
Unequal crossing over (gene duplication)
1) When recombination happens between different positions on chromosomes that are misaligned during meiosis
2) Therefore, in an individual's gametes this may cause an unequal distribution of gene copies
3) E.g. red and green opsin genes, should have two red and two green opsin (but can have one and one), but if unequal crossing over occurs and one gamete only has rep opsin, if that egg is fertilized the son will be colorblind because it is missing the green opsin (doesn't have protein to distinguish green and red)
Evolutionary Biology p. 347
(https://www.youtube.com/watch?v=tNZrhWhFVQw&t=124s)
185
Replication slippage (gene duplication)
1) When the DNA polymerase loses its place and copies a segment of chromosome twice
2) Happens during DNA replication
3) When it happens to the daughter strand, much more deleterious as it amplifies the repeats, when it happens in the mother strand, there is a shrinkage of the number of repeats in daughter strand
Evolutionary Biology p. 347
https://www.youtube.com/watch?v=nRPNJ1T-ggg
186
Retrotransposition (gene duplication)
1) When messenger RNA from a gene is reverse-transcribed to DNA, which is then integrated into the genome
2) After RNA is back-transcribed to DNA it is inserted in a random place in the genome
Evolutionary Biology p. 347
187
Copy number variation
1) When there is polymorphism in the number of copies of the gene that individuals carry
2) Leads to phenotypic differences
3) E.g. individuals with more AMY1 have more amylase in saliva
Evolutionary Biology p. 348
188
Types of nucleotide sequences
1) intron: removed by RNA splicing, is not expressed (INtervening sequences)
2) extron: bond to one another to form RNA (EXpressed sequences)
Evolutionary Biology p. 349
189
Exon shuffling
When mixtures of exons duplicated from genes with different functions can generate new genes with new functions
E.g., the jingwei locus in fruit flies: the first three exons of this gene are duplicates of the exons in the YMP gene, the fourth exon is the duplicate of Adh gene that was retrotransposed into an intron of YMP.
Evolutionary Biology p. 349
190
Three methods of creating new genes
1) gene duplication
2) de novo genes
3) Horizontal gene transfer
Evolutionary Biology p. 350
191
Whole genome duplication
1) Gene duplication on a massive scale
2) Occurs via tetraploidy
Evolutionary Biology p. 350
192
De novo genes
1) Genes that originate from noncoding DNA
E.g., many de novo genes in the testis of fruit flies
Evolutionary Biology p. 351
193
Gene family
1) A set of loci that arose by duplication and that code for proteins that typically have the same biochemical function
2) Typically made up of paralogs
Evolutionary Biology p. 351
194
What happens to a functioning duplicate that becomes fixed?
1) It may be lost by deletion or accumulation of loss of function mutations
2) It may retain its original function
3) It may undergo neofunctionalization
4) It may subfunctionalize
Evolutionary Biology p. 353
195
Neofunctionalization
Gene duplicate evolves a novel biological function
| Evolutionary Biology p. 352
196
Subfunctionalization
Gene duplicate carries out some role of the ancestral gene
| Evolutionary Biology p. 353
197
How does a gene die? (3 ways)
1) It can become a pseudogene (genetic skeleton)
2) It can undergo purifying selection
3) It can be deleted
Evolutionary Biology p. 353
198
Why are pseudogenes evolutionarily important?
Pseudogenes evolve quickly, which shows that mutations to functioning genes reduce fitness and are removed by purifying selection because pseudogenes are selectively neutral and therefore are free to drift to fixation
Evolutionary Biology p. 353
199
Gene trafficking
1) The movement of genes to new sites in the genome
2) When a functioning gene duplicate is established at a new location, its parental copy is sometimes lost by deletion, but the gene remains since it was moved to a new place in the genome
Evolutionary Biology p. 353
200
Nonsynonymous changes
Change protein in DNA
| Evolutionary Biology p. 354
201
Synonymous changes
Do not change protein in DNA
| Evolutionary Biology p. 354
202
dN/dS ratio
1) ratio of the fraction of sites that differ at nonsynonomous sites to the fraction of sites that differ at synonymous sites
2) =1, both mutations have the same change of genetic drift
3) <1 if most nonsynonymous mutations are deleterious and are removed by purifying selection
4) >1 if nonsynonymous mutations had a boos t from positive selection
Evolutionary Biology p. 355
203
Codon bias
When different codons that correspond to the same amino acid appear at different frequencies in the genome, favors accumulation of codons at A and T bases
Evolutionary Biology p. 356
204
Operon
Clusters of genes that are transcribed together into a single mRNA
Evolutionary Biology p. 357
205
Alternative splicing
1) Brings together different combinations of exons from the same locus
2) As a result, a single gene can produce more than one protein
3) Contributes to phenotypic plasticity
Evolutionary Biology p. 358
https://www.youtube.com/watch?v=xZwSmUNRBQQ
206
Karyotype
1) The number and structure of the chromosomes
2) Evolve when two chromosomes fuse, reducing the haploid chromosome number by one OR
2) Evolve by fission, increasing the number by 1
Evolutionary Biology p. 359
207
Inversions
1) Chromosomes with an inversion have the same genes as one without, but they are in different orders
2) Produced when a chromosome breaks at two places and the middle segment is reinserted backward
3) Breakpoints can disrupt a gene or alter its expression
4) Can benefit from meiotic drive, when inversion is heterozygous (paired with a chromosome that lacks the inversion), it is transmitted to the gamete more than 50 percent of the time, favors spread of inversion
5) Can benefit because of effects on recombinations. as heterozygous inversion blocks recombination of inverted region
4) Can benefit from random genetic drift
Evolutionary Biology p. 360
208
Genome Size and coding sequence (complexity)
1) Genome size doesn't really influence coding sequences for plants and animals
2) Increases coding sequences in prokaryotes and eukaryotes
Evolutionary Biology p. 362
209
Transposable elements
1) AKA Transposons
2) Short sequences of DNA that occur in many copies of the genome
3) Parasites that work on the molecular level
3) Reproduce simply because they can (no fitness benefit to host)
4) When host fights off TEs it is dead but remains in the genome
Evolutionary Biology p. 363
210
Gene duplication
1) Most common ways that new genes arise in eukaryotes
2) Occurs via unequal crossing over, replication slippage, and retrotransposition
3) A single gene locus in one ancestor is represented by two loci in descendent
Evolutionary Biology p. 40, 347
211
Parsimony
Simple rule of choosing the tree that requires the fewest evolutionary changes, namely the tree in which the fewest traits arise more than once or undergo reversal
Evolutionary Biology p. 403
212
Homoplasy
1) Independent evolution of similar traits via convergent evolution, parallel evolution, and evolutionary reversal
2) Creates problems for estimating phylogenies because the similarity is not caused by shared ancestry (shared ancestry == homology)
Evolutionary Biology p. 404
213
Evolutionary reversal
Return to an earlier, ancestral character state
| Evolutionary Biology p. 404
214
Parallel evolution
two or more lineages have changed in similar ways, so that the evolved descendants are as similar to each other as their ancestors were
215
Convergent evolution
convergent evolution occurs when descendants resemble each other more than their ancestors did with respect to some feature
216
Rate of nucleotide change in codons
1) Inconsequential nucleotides change (diverge) more rapidly
2) Order is third, first, second
3) Indicates that second nucleotide is most consequential
Evolutionary Biology p. 406
217
Incomplete lineage sorting (ILS)
1) When ancestral gene copies fail to coalesce in new species
2) Happens more frequently with short intervals between speciation events and large populations
Evolutionary Biology p. 406-8
https://biologos.org/articles/series/evolution-basics/incomplete-lineage-sorting
218
Why are phylogenies difficult to determine during a radiation?
1) Incomplete Lineage Sorting
2) Few new mutations are fixed in a short time span
3) Introgression
Evolutionary Biology p. 406
219
Ways to estimate phylogenies
1) Parsimony
2) Likelihood (What is the most likely observed DNA sequence in species)
3) Bayesian inference (Can be used to find most likely tree and substitution rate)
Evolutionary Biology p. 413-4
220
Tests for constancy
1) Plot sequence differences between pairs of species against time since divergence
2) Relative rate test where we can estimate the number of changes that have occurred assuming constant rate of change
Evolutionary Biology p. 417
221
Mutations and gene trees
1) If a mutation is beneficial, it will change a large area of the chromosome because of hitchhiking (reduced polymorphism)
2) If a mutation later becomes beneficial due to environmental change, less hitchhiking will occur and a small portion of the chromosome is impacted
3) Because fewer mutations have had time to accumulate on shallow gene trees, shallow gene trees are visible because they have reduced polymorphism
4) So, clues about whether adaptation resulted from new mutations versus standing genetic variation can be gleaned from the gene trees along a chromosome
5) E.g., Eda gene is based on standing genetic variation, gene tree even in newly adapted populations
Evolutionary Biology p. 417
222
Comparative method
1) Comparing sets of species to test hypotheses about adaptation
2) E.g., do two sets of genes typically evolve together? Could suggest that having one feature favors another or that both features are adaptations to the same environmental variable
Evolutionary Biology p. 422
223
Why is sex ratio female-biased in mammals and male-biased in birds?
1) Significant trend for XY species to have female bias and ZW species to have male bias
2) Genes on Y and W chromosomes tend to degenerate increasing male mortality in XY determination and female mortality in ZW determination
Evolutionary Biology p. 424
224
Crown group
Living members of a group
| Evolutionary Biology p. 426
225
Stem group
Extinct members of a group
| Evolutionary Biology p. 426
226
Cryogenian period
1) 720-635 Mya
2) Earliest Eukaryotes
3) In the Proterozoic Era
Evolutionary Biology p. 434
227
Ediacaran period
1) 635-541 Mya
2) Ediacaran fauna fossils
3) Inferred lineages of sponges, cnidarians, bilaterians
4) In the Proterozoic Era
Evolutionary Biology p. 434
228
Cambrian period
1) 541-485 Mya
2) Marked by Cambrian explosion
3) Jawless fish and diverse algae
4) In the Paleozoic Era
Evolutionary Biology p. 434
229
Ordovician period
1) 485-443 Mya
2) Diversification of many phyla
3) In the Paleozoic Era
Evolutionary Biology p. 434
230
Silurian period
1) 443-419 Mya
2) Origin of jawed fish, small terrestrial vascular plants, arthropods
3) In the Paleozoic Era
Evolutionary Biology p. 434
231
Devonian period
1) 419-359 Mya
2) Diversification of bony fish, trilobites
3) Origin of ammonoids, tetrapods, insects, ferns, seed plants
4) Amount of terrestrial biomass greatly increased
5) In the Paleozoic Era
Evolutionary Biology p. 434
232
Carboniferous period
1) 359-299 Mya
2) Formation of Gondwana in southern hemisphere
3) Forests form
4) In the Paleozoic Era
Evolutionary Biology p. 434
233
Permian period
1) 299-252 Mya
2) Formation of Pangaea
3) Glaciation and low sea level
4) Major mass extinctions, particularly of marine life
5) In the Paleozoic Era
Evolutionary Biology p. 434
234
Triassic period
1) 252-201 Mya
2) Continents separate
3) Marine diversity increases
4) Gymnosperms dominant
5) First dinosaurs (reptilian diversification)
6) Transitional mammalian forms
7) In the Mesozoic Era
Evolutionary Biology p. 434
235
Jurassic period
1) 201-145 Mya
2) Angiosperms evolve
3) Marine revolution
4) In the Mesozoic Era
Evolutionary Biology p. 434
236
Cretaceous period
1) 145-33.9 Mya
2) Continents mostly separated
3) Mass extinction of dinosaurs (except theropods) and last ammonoids
4) In the Mesozoic Era
Evolutionary Biology p. 434
237
Paleogene period
1) 33.9-5.33 Mya
2) Radiation of mammals, birds, snakes, angiosperms, pollinating insects, teleost fish
3) Marine mammals begin to evolve in Eocene
4) In the Cenozoic Era
Evolutionary Biology p. 434
238
Neogene period
1) 5.33-0.012 Mya
2) Cool, dry climate
3) Grasslands spread
4) Modern families of mammals and birds
5) First apes
6) In the Cenozoic Era
Evolutionary Biology p. 434
239
Quaternary period
1) 0.012 Mya-current
2) Continents in modern positions
3) Repeated glaciations and sea level shifts
4) Extinctions of large mammals and birds (due to climate change and human hunting)
5) Evolution of homo sapiens
6) Rise of agriculture and civilizations
7) In the Cenozoic Era
Evolutionary Biology p. 434
240
Early earth
1) Water vapor and little oxygen
2) Oceans formed
Evolutionary Biology p. 435
241
Emergence of life
1) Simple organic molecules were produced by abiotic chemical reactions, forming last universal common ancestor (LUCA)
2) Simple molecules formed polymers to replicate
3) Evolution by natural selection could occur due to replication
4) Photosynthesis evolves in cyanobacteria and introduces oxygen to atmosphere (Archaean)
5) Origin of Eukaryotes (Archaean)
6)
Evolutionary Biology p. 436
242
Six major transitions in history of evolution
1) Separate replicators (genes) and formation of cell membranes --> genome within a cell, yields large, complex genomes evolve
2) Separate unicells --> symbiotic unicell yields symbiotic organelle and nuclear genomes with gene transfer between them
3) Asexual unicells --> sexual unicells yields evolution of meioisis and sexual reproduction
4) Unicells --> multicellular organisms yields evolution of cell and tissue differentiation and of somatic v. germ cells
5) Multicellular organisms --> eusocial societies yields evolution of reproductive and nonreproductive castes
6) Separate species --> interspecific mutualistic associations yields evolution of physically conjoined partners
Evolutionary Biology p. 437
243
Human evolution
Afarensis --> Africanus --> Erecturs --> Sapiens
| Evolutionary Biology p. 555
244
Neanderthals
1) Although we did not evolve from Neanderthals, homo sapiens hybridized with them (and Devonians) likely forming melanesians
Evolutionary Biology p. 555
245
Genetic diversity in human evolution
1) Most genetic diversity in South Africa because as people emigrated outward, this lowered the population size causing lower nucleotide diversity and more linkage disequilibrium
Evolutionary Biology p. 556
246
Social brain hypothesis
1) Living in complex social groups selects for large brains, specifically enlarged neocortex
2) Good evidence for this, as mean group size increases so does neocortex size (relative to body weight)
Evolutionary Biology p. 558
247
Are humans still evolving?
1) Yes
2) E.g. strong directional selection favoring lower cholesterol levels
3) E.g., stabilizing selection acted on females, women with average height had the largest number of children over a lifetime, while taller males are favored (directional).
Evolutionary Biology p. 565
248
How did diet and agriculture alter human evolution?
1) Humans evolved a higher metabolic rate and larger energy budget than any other primate (because we started to eat meat and needed to hunt for food --> endurance)
2) Lactase persistence developed independently several times where livestock were domesticated
3) SLC22A4 carries a mutation that increases absorption of the amino acid ergothioneine, present only at low levels today in diet, but ancestral people with this gene had a fitness benefit
249
Memes
1) Cultural mutations
2) Change in cultural elements via horizontal transmission
Evolutionary Biology p. 567
250
Marine mammal evolution
1) Presence of Pakicetidae, Ambulocetidae, and Remingtonocetidae in Tethys seaway in Eocene (in Paleogene, in Cenozoic era)
2) Presence of Basilosauridae represented pelagic species judging from spread to temperate and Antarctic latitudes in Eocene (in Paleogene, in Cenozoic era)
3) Archeocete diversity declined in the late Eocene, giving rise to Neoceti in the Oligocene, giving rise to mysticetes and odontocetes
4) Cetacean diversity increased in the Miocene into the Pliocene
5) Delphinids radiated from the late Miocene into the Pliocene
