Download Which of the following is not necessary to demonstrate sympatric

1) Which of the following is not necessary to demonstrate sympatric speciation?
a. Sympatric Distribution
b. Monophyly (sister relationship between species)
c. Reproductive isolation
d. Islands of selection
e. History of allopatry unlikely
2) What is peripatric speciation?
a. Genetic polymorphism causes speciation within population
b. New niche is entered, speciation in adjacent niche
c. New niche is entered, speciation in isolated niche
d. Barrier forms, causing speciation in isolation locations
3) When did the KT extinction occur?
a. 3.8 billion years ago (bya)
b. 1.7 bya
c. 65 million years ago
d. 15 million years ago
4) Which is a trait that prokaryotes generally have?
a. Larger size
b. Commonly multicellular
c. Anaerobic
d. Both mitosis and meiosis
e. Presence of a cytoskeleton
5) Which is not an explanation for the Cambrian explosion?
a. Increase in oxygen content
b. Origin of hard parts
c. Evolution of eyes
d. Evolution of multicellular organisms
e. Genetic changes
6) Write two questions you had on the paper
Monday : Speciation
Prezygotic isolation, post-zygotic isolation
Allopatric: “separate place”= barrier forms
Peripatric “nearby place” = Moves to new location, speciates there, new range abuts old species range
Parapatric: “alongside place” = green warblers ring species that need specific call to mate
Sympatric: “same place” plants readily become polymorphic, so sympatric speciation more likely.
 Sympatric distribution
 History of allopatry unlikely
 Monophyletic sister taxa
 Reproductive isolation
 Pre-zygotic isolation
o Gamete recognition proteins are fastest evolving of any protein
 Examples
o Soapberry bug proboscis is length of balloon vine. Not good example because different
species on different plants
o Palms are a good example: mutation that caused reproduction time to be different
o Nicaraguan cichlids are a good example: mutation changed jaw morphology, diet,
habitat, then reproductive habits
Evolutionary processes involved in speciation
 Natural selection
 Sexual selection
 Genetic drift (not as important as the top two)
Natural selection process: Syntenic genes are the same in different species
Humans & chimps A gene (A & A’) are 3% different after 6my of divergence
Non-syntenic genes recombined to different locations
Recombined more, 4% different after 6my of divergence
Speciation in sticklebacks
 Three life history strategies: marine, limnetic (midwater freshwater, large gill rakers), benthic
 Species gets isolated in freshwater, becomes freshwater, then secondary invasion by marine
Freshwater cichlids in Lake Victoria have female sensory bias
Isolation
 Magnitude of prezygotic & postzygotic isolation increase with divergence time
 Among recently separated groups, prezygotic isolation is stronger than postzygotic
 Hybrid sterility is seen in the heterogametic sex
o IE drosophila females are viable, males sterile
o Dobzyhansky-Muller incompatability explains how new lineage can arise from one
individual with a mutation
 Allele gets fixed in one population in loci that it used to share with other
population, then the two species come back together and can not breed
22 the origin of life (Wednesday) :
Fst is conducted for each locus
 Higher Fst indicates directional locus
 Low (0) Fst indicates stabilizing selection in each population
Life
 reproducing
 Genotype & phenotype
 Metabolism
 Evolving
Problems in addressing origin of life
 Narrow time window
o Life evolved 3.8 bya
o Prokaryotes 3.5 bya
o Eukaryotes 2.1 bya
o Multicellular eukaryotes 1.5bya
Theories for evolution of life
 ET origin, not fully disproved
o Murchison meteorite contained 70 amino acids
 Chemical theory (inorganic molecules to organic via electricity)
o Experiment in 1953
Organic molecules to biological primers: combined in mud, sea foam
Protobionts: Heating and cooling mixtures of amino acids can form spherical proteinoids
 Mixtures of lipids and proteins can for liposomes, which can “reproduce” by budding
Natural selection would have acted to increase biochemical sophistication of protobionts
 DNA became repository of genetic information, more stable than RNA
 RNA then only does transcription, replication of DNA
Evidence of prokaryotic life 3.5 bya: stromatolites
 fossils abundant 3.5 bya
 Dominant lifeform on earth for over 2by
 Colonial structures formed by photosynthesizing cyanobacteria
Once oxygen reached a particular level, explosion of life
Origin and early evolution of eukaryotes
 Universal gene-exchange pool hypothesis
o Archae, bacteria, eukarya evolved after lateral gene transfer ceased
 Endosymbiotic hypothesis
o DNA of mitochondria is similar to DNA of bacteria
o Cells now require ATP, enslave mitochondria
 Very few eukaryotes do not need mitochondria, like yeast
o Chloroplast were bacteria, enslaved by eukaryotes
Lecture 23: Cambrian Explosion (Friday)
Precambrian: 4.6 bya to 543 mya
Difference between prokaryotes and eukaryotes
 Larger cell size
 Nucleus & organelle
 Aerobic
 Cilia & flagella with tubulin rather than flagellin protein
 Linear DNA molecules complexed with histones
 Commonly being multicellular
 Both mitosis & meiosis
 Presence of a cytoskeleton
1.9 to 1.3 bya general trend towards increasing size of fossils
Wolbachia is a bacterial parasite used to understand the evolution of mitochondria
 Kills male drosophila, makes them sterile
Fossil record bias
 Geographic bias: sedimentary rock. Poor understanding in terrestrial, particularly tropical
o Most fossils are shallow coastal, lake
 Taxonomic bias
o Most of fossil record is marine species possessing shells
 Marine organisms only represent 10% of all species
 Temporal bias
o Old rocks are much rarer than new rocks
Ediacaran Fauna: before Cambrian explosion
 Dates to 560 mya
 Soft-bodied and non-burrowing
All but one of 35 phyla (not bryozoans) appear in Cambrian explosion (10-25my)
 New modes of locomotion: swimming, burrowing, climbing
 Diversity of body plans is astonishing
What caused the Cambrian explosion
 Increase in oxygen content of seawater
o Allowed organisms to achieve increased sizes and metabolic rates
o Large size is a prerequisite for evolution of predators
 Origin of hard parts
o Protection from predators
 Evolution of eyes
o First appear in trilobies 543 mya
 Genetic changes
o
Diversification of homeotic genes (small genes with large effects, expressed during
development. Moving base pair can change body plan)
Adaptive radiation: early branchs are short, later branches are long
 Occurs at edge of species ranges
 Facilitated by lack of predators and competitors
 May involve general adaptations (flight)
Punctuated equilibrium: proposed to account for “gaps” in fossil record
 Burst of speciation co-occur with rapid speciation
 After species form , the exhibit “stasis”
Mass extinctions
 When extinction rates are well above normal background extinction
 K-T extinction 65 mya, dinos died
 But we have not lost a single phylum…
Savolainen, V., Anstett, M.C., Lexer, C., Hutton, I., Clarkson, J.J., Norup, M.V., Powell, M.P.,
Springate, D., Salamin, N. and Baker, W.J., 2006. Sympatric speciation in palms on an oceanic
island. Nature, 441(7090), pp.210-213.
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Sympatric speciation must demonstrate monophyletic group, reproductive isolation, and
unlikely allopatry
Two species of palms diverged after island was formed
Disjunction in flowering time correlated with soil preference
Few genetic loci are more divergent between two species
Lord Howe Island is ideal to study sympatric speciation because it is been long isolated, is of
known age, and is small so geographic isolation cannot occur (at what scale??)
Palms on Lord Howe are of 4 species, 3 endemic genera
Howea is a monophyletic group, with H. forsteriana flowering before H. belmoreana
o Flowering separated by 6 weeks
o H. forsteriana is protrandrous, male flowers 2 weeks before females receptive
 On volcanic substrates, synchronous. Calcareous, protandrous
o H. belmoreana is synchronous
o H. forsteriana is found on basic calcareous substrates, H. belmoreana found on neutral
& acidic soils
o Both species are wind-pollinated
Most loci between the two species have low Fst, small number of loci have high Fst
o Very different from allopatric speciation, where genetic differences accumulate through
the genome
Hypothesized sequence of events
o H. forsteriana diverged by colonizing calcareous substrates.
o Lack of protandry on volcanic soils implies there is physiological cost of substrate type
 Flowering time is a plastic trait
o Unlikely that both species are truly isolated, as on small island & wind-pollinated