1
Q
Mutually beneficial (social behaviour)
A
Fitness gains for actor + recipient
2
Q
Selfishness (social behaviour)
A
Fitness gain for actor, loss for recipient
3
Q
Altruism (social behaviour)
A
Fitness gain for recipient, loss for actor
4
Q
Spite ((social behaviour)
A
Fitness loss for actor and recipient
5
Q
Components of inclusive fitness
A
Direct fitness + indirect fitness
6
Q
Direct fitness
A
Indiv’s direct contribution to next gen by reproduction (# of offspring)
7
Q
Indirect fitness
A
- Arises from additional reprod by relatives that results from actor’s actions
- Additional reprod that would NOT have achieved w/out assistance from actor
8
Q
Kin selection
A
Selection for + spread of alleles that increase indirect fitness
9
Q
Coefficients of relatedness for half-siblings, full siblings, and cousins
A
- Half-siblings = 1/2 * 1/2 = 1/4
- Full siblings = (1/2 * 1/2) + (1/2 * 1/2) = 1/2
- Cousins = 1/2 * 1/2 * 1/2 = 1/8
10
Q
r (coefficient of relatedness)
A
Gives probability that an allele in actor and allele in recipient at GIVEN LOCUS are identical by descent/arose by replication from ANCESTRAL COPY of an allele
11
Q
Hamilton’s Rule
A
- An allele for altruistic behaviour will spread if: B*r-C>0
- B = benefit to recipient (# of offspring), C = cost to actor (# of offspring), r = coefficient of relatedness
- Costs and benefits measured in terms of surviving offspring
12
Q
Adaptive value of spite
A
Highest when cost to actor is very low + damage to recipient is high, AND value of r b/w actor and recipient is low
13
Q
Type specimen
A
A single indiv (usually) that represents the entire species
14
Q
Typological/morphological species concept
A
Specimens considered to belong to same species if they “agree” morphologically w/ the “Type” of the species
15
Q
Problems with typological/morphological species concept
A
- Cryptic species (can’t be distinguished based on morphology alone)
- Phenotypic plasticity (morph. variation w/out genetic basis, envtally induced diffs
16
Q
Biological species concept
A
- Species = groups of interbreeding natural pops that are reprod. isolated from other such groups
17
Q
Why do individuals within a species resemble each other? (BSC)
A
Gene flow + interbreeding
18
Q
Evolutionary criterion for BSC
A
- Reprod. isolation + interbreeding
- Diff species cannot successfully made w/ each other
19
Q
Situations where BSC is not applicable
A
- Asexual taxa (oblig. parth, some proks)
- Fossil taxa (can’t test)
- Hybridization (diff species that produce viable offspring, e.g. polar bear + grizzly)
20
Q
Phylogenetic species concept
A
- Species = pop/group of pops that share common evolutionary fate through time
- Species are monophyletic groups (all descendants of single common ancestor) –> achieved via evolving diff synapomorphies
- Pops must have been evol. independent long enough for diagnostic traits to appear
21
Q
BSC vs PSC
A
BSC:
- Hard to test
- Cannot use on asexuals or hybridizing
- Cannot use on extinct species
PSC:
- Can apply to living + extinct
- Can be used on sexuals + asexuals
- Based on evol independence –> can be applied w/out difrect observations
- Tends to oversplit but more flexible than BSC
22
Q
Steps in allopatric speciation model
A
- Physical isolation of pops
- Genetic + ecological divergence of isolated pops
- Reprod isolation (BSC)
- Secondary contact (not always)
23
Q
Allopatric speciation
A
- Pops are physically isolated by barrier –> prevents gene flow b/w pops
- NO GENE FLOW
24
Q
Dispersal
A
- Rare dispersal event from 1 location to another –> fully isolated pops (no gene flow) –> founder effect
- Movement of organisms away from their point of origin
25
Vicariance
- Barrier forms b/w pops --> splitting them into 2 locations (fully isolated --> no gene flow)
- Splitting of faunas/floras (or pops) b/c of formation of a physical barrier
26
What drives divergence after isolation has occurred? (allopatric speciation)
- Mutation, genetic drift, bottle necks, viability + sexual + fecundity selection
- After allopatric isolation has occurred, these process can work independently in pops --> places them on separate evol. trajectories
27
Sympatric speciation
- Isolation + divergence occur at same place + time
- Occurs in presence of gene flow
28
Key features of sympatric speciation
Positive assortative mating + (driven by) disruptive selection
29
How does sympatric speciation work?
- Offspring of mating between individuals at each extreme (upper x lower) of a character have lower fitness --> eliminated
- As such, positive assortative mating at upper and lower extremes is selected for (disruptive selection)
30
Incipient species
Lineages that have ALMOST completed speciation (e.g. apply maggot fly host shift induced by apples ripening earlier than hawthorn fruits)
31
Ecological provocation of sympatric speciation
In envts occupied by few species + posses vacant ecological niches --> results in ecological opportunities for diversification
32
Resource polymorphism
- Individuals within a pop begin to exploit + specialize on different food resources
- Positive assortative mating + disruptive selection drive process to speciation
- e.g. feeding polymorphism resulted in evol of limnetic + benthic stickleback fishes
33
Sexual selection promoting speciation
- e.g. Hawaiian crickets --> pulses (in their songs) very conservative within species but very different b/w species
- Unbreakable correlation b/w male pulse rate + female preference for pulse rate
- Whenever a pop evolves a different male pulse rate, immediately female pref changes in lockstep, driving pop divergence (normally female pref drives male change)
34
Interaction b/ envtal characteristics + sexual selection --> promotes speciation
e.g. Cichlids (fish)
- Red and blue males, females have red or blue sensitive opsins
- In clear water, greater and very distinct colour pref by females
- In turbid water, largest frequency is no pref
35
Isolation via chromosomal change
- Polyploidization can result in instantaneous speciation (vital in diversification of plants)
- Addition/deletion of single chromosome will normally also result in reprod. isolation
- Even single mutation can result in complete isolation (left + right handed Japanese snails)
36
Secondary contact
Two groups that have diverged allopatrically come back into contact
37
Two types of reproductive isolation (barriers)
- Prezygotic --> prevent zygote formation
- Postzygotic --> zygote formed, but has issues
38
Prezygotic isolating barriers
- Ecological isolation --> mate at diff location/time
- Behavioural isolation --> different mating calls
- Mechanical isolation --> genitals don't work together
39
Postzygotic isolating barriers
- Zygotic, embryonic, or larval mortality
- Hybrid inviability (dies)
- Hybrid sterility (can't make gametes)
40
When can hybridization occur?
Can occur when recently diverged species come into secondary contact
41
Hybrid zones
- Geog. contact zone where interbreeding occurs + freq of hybrids can be high
- Hybridization results in formations of hybrid zones
42
3 outcomes of hybridization
1. Hybrids have lower fitness vs parental lineages --> results in reinforcement + character displacement --> short lived hybrid zone
2. Hybrids have equal fitness to parental species --> the 2 lineages interbreed + potentially merge into single lineage (introgressive hybridization)
3. Hybrids have higher fitness vs parental lineage --> hybrids can displace both parental species or possibly form new species
43
Intogressive hybridization
Hybrids fitness = parental species fitness --> the 2 species interbreed + merge into single lineage
44
Reinforcement + character displacement
- If secondary contact results in hybridization AND hybrids have lower fitness than parentals --> reinforcement --> involves assortative mating --> results in evol of prezygotic isolating barriers
- Also results in character displacement --> disruptive selection that increases difference b/w the 2 parental lineages
45
Hybridization resulting in 3rd new species being formed
- Happens occasionally
- Known in sunflowers + numerous other plants
- Also known in fishes + amphibians
46
Biogeography
- Science devoted to documentation spatial patterns of biodiversity
- Study of geog. distribution of orgs (incl. species + higher lvl taxa such as genera + families), in both past + present (+ their relationships)
47
Zoogeography
Animal geography
48
Phytogeography
Plant geography
49
Historical biogeography
Reconstruction of origin, dispersal, + extinction of taxa, as well as biotas
50
What results in biogeog. patterns (geog distribution of genetic lineages)
Dispersal + vicariance
51
Consequences of the formation of the Isthmus of Panama (collision of Caribbean + Pacific tectonic plates --> land lifted)
1. The Great American Exchange (more moved to SA, than NA)
2. Marine vicariance --> geminates (pairs of diverged species due to allopatric speciation (barrier))
52
Why was the Great American Exchange somewhat onesided?
NA had --> moved to SA:
- Better migrators
- Better survivors (+ speciators)
- Better competitors (potentially due to NA fauna contact w/ Asian fauna)
Little effect on birds + animals that don't fossilize
53
"Law" of Geminate Species/Jordan's "Law"
- Not considered a scientific law today since sympatric speciation exists
- "Given any species in any region, the nearest related species is not to be found in the same region nor in a remote region, but in a neighboring district separated from the first by a barrier of some sort/at least by a belt of country, the breadth of which gives the effect of a barrier"
- Importance of allopatric speciation as a conseq. of barrier formation
54
Geminates (sister species) across Isthmus of Panama
Aquatic species
- Fishes, crabs, sea urchins, shrimp, gastropods (snails), isopods (crustaceans), ostracodes (crustaceans), + many other orgs
55
Isthmus of Panama + molecular clocks
- Sequence DNA --> count # of diffs/total nucleotides = sequence divergence
- Allows for calibration of rate of sequence divergence
- Calibrated by studying sequence divergence in geminates at the isthmus
56
What differing impacts did formation of Isthmus of Panama have on terrestrial vs marine ecosystems?
- Terrestrial --> dispersal (movement away from point of origin)
- Marine --> vicariance (splitting due to formation of physical barrier)
57
Biogeographic patterns + provinces
- Biogeog. provinces: Identified regions that possess unique faunal + floral assemblages
- Biogeographers interested in understanding historical events that resulted in these patterns
58
Endemic
Restricted to specific place or region; species found in 1 place and 1 place only
59
Fish biogeog. provinces of NA + latitudinal gradient in species diversity
- Correspond to drainage basins in NA
- Less species + less endemics in northern vs southern provinces
- Less diversity in northern NA vs southern NA
60
What was the major vicariance event for fish NA?
- Re-colonization of northern NA aquatic habitats after Pleistocene Glaciations
61
Glaciation refuge areas in NA
- Along the edges of the glacier where there was no ice
- Beringia (Alaska-ish), Pacific, Missourian, Mississippian, Atlantic, northeast of Hudson's Bay
- Contained isolated pops --> diverged allopatrically (become genetically distinct lineages within same species
62
Aquatic dispersal corridors
- Proglacial lakes
- All connected w/ each other at diff points in time --> species could disperse + re-colonize NA
- Isolated lineages came into contact --> genetic mixture
63
Phylogeography
- Study of geog. distribution of genetic variation within species
- Usually conducted by DNA seq. representatives of a sample of a species over its entire geog. range --> det how genetic variation changes over entire region
- Provides important insights into process of allopatric divergence (e.g being isolated in diff glaciation refuges) + dispersal after that
- Also provides evidence that different taxa have been affected by the same vicariance events in very similar ways (e.g. recolonization)
64
How does glacier formation occur?
Precipitation of snow > melting
65
Phylogeographic patterns in fish
Show that Lake Trout dispersed from the glacier refuges to recolonize NA
- Dispersed from 2 separate Beringian refuges, Mississippi, Atlantic, + Missouri refuges
- Not much dispersal from small Northeastern refuge
66
Latitudinal gradient of species diversity
- Species diversity increases from the poles to the equator
- # of endemics sharply decreases as you go north
67
Rapoport's Rule
- The range/area occupied by species tends to increase w/ increasing latitude
- Species w/ more northern distribution have larger range than southern distribution
68
Why does the lattitudinal diversity gradient exist?
No perfect explanation
- Historical factors: e.g. glaciations
- Ecological factors: e.g. climate
- Evolutionary factors: rates of speciation/extinction --> higher in arctic vs tropical b/c lots of empty ecological niches in north
69
What is life?
That which has a genotype + phenotype, and is capable of evolution
- This definition includes viruses
70
SSU rRNA
A conserved gene
71
Cenancestor
- = LUCA
72
LUCA vs IDA
LUCA/cenancestor is NOT same entity as the Initial Darwinian Ancestor
- LUCA/cenancestor = most recent common ancestor of all extant organisms
- IDA = first living thing/primordial form --> first thing that crept out of primordial soup
73
Challenges det phylogeny of early cellular life
- No outgroup to use in rooting the tree of life
- Estimating a root is still a hot area in research
- Different genes point to different relatedness b/w bacteria, archaea, and eukarya (incl. a polytomy - 3 branches off a single point)
- The issue lies in lateral gene transfer
74
Lateral gene transfer
- Certain bacteria have archaeal tRNA synthetase genes --> picked up from an archaean + incorporated into self
75
Reticulate evolution
- Cenancestor --> think of as not really a single organism, rather a community that did LOTS of lateral gene transfer --> 3 domains emerged out of primordial soup
- Non-bifurcating evolution, net-like evolution
76
Lokiarchaeota
- More in common w/ eukaryotes than w/ any other archaea
- Some defining features of eukaryotes (e.g. cytoskeleton) could have been present in last ancestor shared by eukaryotes + archaea
77
Types of fossils
- Compression + impression --> dies + falls into sediment, leaving an impression --> becomes rock
- Permineralized --> dies + falls into watery envt w/ sediment --> tissue replaced/coated w/ dissolved solutes that eventually harder
- Casts + molds --> falls into wet sediment, dies --> decomp --> leaves empty space --> area around it hardens
- Unaltered remains --> tree sap --> amber
- Trace fossils --> trace of org that existed in past --> burrows, tracks, etc.
78
Taphonomy
Study of fossilization process
79
3 major types of bias in fossil record
- Geographic
- Taxonomic
- Temporal
80
Geographic bias in fossil record
- Fossilization occurs much more readily in wet envts vs dry
- Most fossils we have are marine
81
Taxonomic bias in fossil record
- Result of hard parts (shells, bones, etc) vs soft (worms)
- We have more hard org fossils than soft
82
Temporal bias in fossil record
- Older rocks destroyed w/ fossils in them
- Rocks are constantly created + destroyed
- We have more new fossils than old fossils
83
Paleontology
Study of fossils
84
Geological time scale
- Eons > eras > periods > epochs
- Phanerozoic eon has visible life --> divided into Paleozoic (ancient life), Mesozoic (middle life), and Cenozoic (recent life) eras
85
First examples of multi-cellular life
- Ediacaran Fauna, end of Proterozoic (before Phanerozoic eon)
- Entirely soft-bodied orgs
- Radial symmetry, small marine life (size of a quarter), filter feeders/could absorb nutrients in H2O column
86
Radial vs bilateral symmetry
- Radial = can be divided at any point through center into multiple halves --> like slices of a pie
- Bilateral = can only bisect on 1 plane into 2 equal halves
87
The Cambrian Explosion
- One of greatest diversification events in history of life
- Almost all of currently recognized animal phyla appear within about 40 m.y. during Cambrian
- Major morphological innovations appeared --> much larger body size, fast-moving predators, radiation of bilateral symmetry
88
The Burgess Shale
- Formed in series of underwater mud slides --> instantly killed lots of shallow water orgs
- 505 mya
- Tremendous diversity of animal forms --> some difficult to classify --> "the problematica"
89
Mass vs background extinction
- Only 4% of all extinctions occurring during the mass extinctions
- 96% occurred b/c of background extinctions
- Background extinctions = steady rate of extinctions over Earth's history
90
How many mass extinctions were there?
The Big 5
- Ordovician --> major climate change (cooling then warming)
- Devonian --> global cooling
- Permian --> massive volcanism; largest --> "The Great Dying"
- Triassic --> massive volcanism
- Cretaceous --> meteorite impact (killed dinos)
91
6th mass extinction?
- Due to human activity
- Tropical deforestation, degradation of landscape for agriculture
- Rate of extinction is 100-1000x greater than background extinction
BIOL 359
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