Lectures 9-15 Notes

What are factors of microevolution?

- Natural Selection
- Genetic Drift
- Mutation
- Migration

What were some doubts of researchers?

- how and why do species diverge and diversify?
- explain patterns of variation?
- how do we have so many species?

What are key questions of speciation?

- what ecological and genetic conditions are required?
- how does reproductive isolation evolve?
- how many genes are evolved?
- is adaptive evolution required?

What is "the species problem"? What are the different concepts?

- how to define a species
- taxonomic and biological
- taxonomic: phonetic, genetic, ecological, phylogenetic
- recognition, cohesion, Darwinian, evolutionary

How is a species defined?

- phenotypic similarity by Carl Linnaeus
- genetic similarity

What is Sympatric?

- easy to identify within region

What is Allopatric?

- gradual differences between regions

What are the two main species concepts? What do they represent?

- taxonomic and biological
- taxonomic: measurable differences
- biological: infertility among individuals

What was Darwins idea of similarity between species? What was he influenced by?

- taxonomic
- individuals that resemble e/o, similar in phenotype
- influence by domestication & seeing varieties to become distinct species

What is the Biological Species Concept

- Ernst Mayr
- species can interbreed and exchange genes
- descent w modification leading to biodiversity

What question does the BSC raise?

how does evolution lead to a single population that can interbreed and produce two different species that cannot?

What are some highlights of the BSC concept?

- geographic isolation is not sufficient
- isolation is not absolute; potential for hybridization
- possibility of interbreeding in wild
- does not apply to bacteria, asexuals, self-fertilizing, fossils

Where does speciation occur? (geographic speciation)

allopatric
- when a population separates and occupy different areas
- they evolve due to genetic drift
- when combined again, distinctive, won't interbreed, barriers

sympatric
- gene flow which fights differentiation
- genes evolves greater and greater until species in same area do not interbreed

Which is more common allopatric or sympatric? Why?

- allopatric
- more common
- easier to evolve

What causes reproductive isolation?

- pre-zygotic barriers
- post-zygotic barriers

What are pre-zygotic barriers?

- finding mate & mating
- fertilization

What are post-zygotic barriers?

- development & growth
- survival and reproduction
- reproduction of offspring, growth, survival

What do pre-zygotic barriers do? What are the different types?

- prevent mating and fertilization; no zygote
- geographical, ecological
- temporal, behavioural (mate recognition)
- mechanical (genital structure)
- cellular (sperm-egg compatibility)

What type of Isolation occurs in Apple Maggot Flies? Why?

- habitat and temporal
- bc of host shift from berries to apples
- different timing of fly mating on apples (preferred host plant)
- reduced gene flow by 94% in sympatry (same region)

What type of Isolation occurred in Abalone?

- species don't have right sperm lysin protein to dissolve VERL egg to fertilize it
- molecular "lock and key"

What do post-zygotic barriers do? How is it caused? What are the two different types?

- prevent functioning of zygotes once formed
- by combinations of genes w low fitness in hybrids
- intrinsic & extrinsic

What does intrinsic mean?

- inviability, sterility, abnormal development
- genetically; die prematurely

What does extrinsic mean?

- ecological mismatch of hybrid phenotype
- lower fitness

How to intrinsic and extrinsic abnormalities arise?

- not favoured by NS
- byproduct of evolution acting separately in diff populations

What are examples of Intrinsic Post-Zygotic Isolation? Are they sterile or fertile?

Mule
- male donkey (62)
- female horse (64)

Hinny
- female donkey
- male horse

- both are sterile

What is genetic distance the measure of?

- degree of genetic differentiation between samples

What does the value 1 mean of post zygotic isolation? What does value of 0 mean?

- 1 means hybrids are sterile/inviable
- 0 means that they interbreed freely

What does this graph tell us?

- more fly pairs are genetically differentiated
- more likely they are to be reproductively isolated
- accumulation of intrinsic genetic incompatibilities

What is an example of a Extrinsic Hybrid? What occurred in these species?

- mullein mimicry in butterflies
- hybrids formed intermediate wing morphs
- have different colour patterns on wings
- higher predation risk
- lower mating
- lower fitness overall

What does research aim to determine?

- biotic & abiotic agents of selection
- speciation genes

What can you get through adaptation?

- mutations in diff populations results in diff material in diff populations due to selective pressures

What is adaptive evolution responsible for? why? What response do they have to?

- ecological speciation?
- adaptation by diff pops. can lead to RI and speciation, rapid divergence
- evolutionary response to diff selective pressures

Example of Adaptation in Freshwater Stick-back Fish?

- glaciation caused colonization by marine fish
- loss in bony plates (defence armour)

What does sickle-back bones protect them from?

- from predation in marine environments

What happens to stickleback fish in freshwater?

- loss of bony plates increases (too costly to produce)
- greater winter survival
- earlier breeding (essential to develop)
- gene that is responsible for amount of bony plates

What will happen of hybrids of freshwater fish?

- grow slower
- selective disadvantage
- greater predation = fitness disadvantage

What are the Answers to the Doubts?

- diverge genetically as result of mutation, GD, NS
- become reproductively isolated

What does microevolution allow?

- speciation to occur
- populations adapting independently

What is Adaptive Radiation?

- ecological and phenotypic diversity as result of speciation
- originates from single CA
- many different species
- exploitation of range of habitats and resources
- rapid diversification

What are 4 features of Adaptive Radiation?

1) recent common ancestry from species
2) phenotype-environemt correlation
3) trait utility
4) rapid speciation

What is an example of adaptive radiation in Hawaiian Honey Creepers?

- inhabit diff ecological niches as they colonize islands

What causes Adaptive Radiation?

1) ecological opputunity
- more resources
- less competitors
- oceanic islands

2) origin of key innovation
- organisms that evolved phenotypic innovation

3) high rates of speciation the clade
- comparing island to mainland clade
- Darwin's finches & Hawaiian Honey Creepers radiated on mainland
- mockingbirds did not

- species have expanded in number of species in mainland

What is hybridization?

- exchange of genes between species
- result of interspecies mating
- rare in mammals, common in plants
- result in complex patterns of variation
- significant for speciation and polyploidy

What is polyploidy? What are different types?

- organisms with 2+ sets of homologous chromosomes
- number of chromosomes copies it has
- allopolyploidy & autopolyploidy

What is allopolyploidy?
(AA x A*A* = AA A*A*)

- duplicated karyotypes between species
- common type of polyploidy
- from different sources
- tetraploid organism has 2 copies of chromosomes
- plants and food we eat

What is autopolyploidy?
(AA = AA AA)

- duplicated karyotypes from one species
- arises through non-disjunction & meiosis
- by oneself

What is the significance of polyploidy?

reproductively isolated from diploid parents
- sympatric speciation
exhibit novel phenotypes
- allows exploitation of new habitats
show hybrid vigour due to heterozygosity, allopolyploids
origin for 50% of flowering plants
- crops and invasive species

What are novel phenotypes?

phenotype that is concerned with its unique visual appearance compared to parents

What is Speciation Continuum?

- populations: some barriers
- ecotypes: strong barriers, morph and genotypic concepts
- btw: intrinsic post zygotic barriers
- species: near complete RI, biological concept applies
- btw: sterile F1 hybrids, allopolyploids still possible
- lineages: F1 hybrids don't form, phylogenetic concept

- speciation is not unidirectional process
- strength of RI increases
- intrinsic post-zygotic isolation increases
- likelihood of reversal decreases

When did Darwin begin writing in his notebook and what did he write?

- July 1837
- "The Transmutation of Species"
- "I think" & first evolutionary tree

What does this image represent? What does genetic distinctions do?

- how organisms are related through process of speciation
- how they accumulate reproductive isolation btw one another
- how they become genetically distinct

- lock in genetic differences = incapable of transferring that gene btw populations = rise to diverse organisms

Who is Carl Linnaeus?

- father of taxonomy
- binomial nomenclature
- system of classifications

What is the order of the system of classifications?

- kingdoms
- phyla
- classes
- orders
- family
- genera
- species

What are the three purposes of biological classification?

- shared information
- predictive power
- interpretation of origins & evolutionary history

What are taxon? What are the 7 different types in order?

- single taxonomic unit
- kingdoms
- phyla
- classes
- order
- family
- genera
- species

What is taxonomy?

- theory & practice of classification & naming

What is systematics?

- study of biodiversity and evolutionary relationships among organisms

What are the different components of a phylogenetic tree?

- outgroup taxon
- ingroup taxa
- terminal nodes
- terminal branches
- internal nodes
- internal branches

What are outgrip taxon?

- organism that is less related than all the other species

What are terminal nodes?

- taxa (organisms or group of organisms)

What are terminal branches?

- accumulated evolutionary time

What are internal nodes?

- common ancestors
- speciation

What are internal branches?

- accumulated evolutionary change

What are in-group taxa?

- all taxa disclosing the outgroup

What does this image represent?

- grey nodes are common ancestors & speciation events
- green is ancestral characters
- black are derived characters which differentiate organisms

Why conduct phylogenetic analysis?

- history of life
- large-scale patterns of evolution
- times traits evolve, how fast, what conditions
- pratical interpretations: when did parasites spread?
- which flu strain is successful?
- driver mutations of SARS?

What does this image represent?

- how life has taken advantage of resources all over the planet

Are these phylogenetic trees related?
Why?

- yes
- show same relationship

Are these phylogenetic trees related? Why?

- no
- btw chimpanzee and gorilla, implies they have more recent CA

What are monophyletic groups?

- includes all species from same CA
- single ancestor gave rise to all species in this taxon
- derived from same CA
- more preferred; links names to history

What are paraphyletic groups?

- contains some but not all species from same CA
- taxon whose members are from 2+ ancestral forms not common to all the others
- non-evolutionary grouping of species

What can be said about phylogenies as forensic record?

- species that share recent CA are similar
- descent w modification

Why is there no such thing as reptiles anymore?

- because crocodiles and turtles fall under a different taxa then other reptiles
- crocodiles are more related to bursts then other reptiles

What is a critical step in reconstruction of phylogenetic history?

- identification & distinction of ancestral & derived traits

What is an ancestral trait?

- trait shared w CA

What is a derived trait?

- trait that differed from ancestral trait in lineage

What is homology? Example?

- similar traits due to shared ancestry
- humans and fish are homologous structures

What is homoplasy?

- similar traits as result of convergent evolution
- similar but evolved to be independent of one another

What is convergent evolution? Example?

- independant evolution of structures tha ressemble e/o
- preform similar roles due to shared ecology
- organisms evolve similar traits due to environment conditions

- different Cacti in the desert that look similar because they aim to prevent water loss
- similar morphology

- Cichlid Fishes
- evolutionary radiations in both lakes
- similar in form; convergence in feeding stratgeies

Why is molecular biology relevant to evolution and phylogeny?

- life is related through descent w modification
- common genetic code; evidence life is related
- relationships are in DNA and proteins
- mice, rates, flies, worms tell us stuff about humans

How do we infer relationships btw species from DNA sequences?

- DNA sequences can be derived and compared for diff species
- assessed for change sin nucleotides
- infer relationships in phylogeny

What are key innovations of phylogenetic trees?

- novel trait resulting in Adaptive Radiation
- carriers can exploit new resources or habitats
- rapid diversification
- how traits evolve and originate

What is the diversification equation? What does it mean?

- diversification = speciation - extinction
- new species - reproductive isolation
- innovation can increase speciation
- or decrease extinction

Why do some groups have more species than others? Example? What leads beetles and moths having more species?

- replication of "sister group" comparisons; analyze
- herbivory; convergent evolution btw insects and plants
- coevolution btw them drives rate of speciation in herbivores

What are other features of greater diversification?

- more sexual selection
- animal pollination
- increase dispersal
- increase range size; less RI
- lower likelihood of extinction

What was Lamarck's View?

- all organisms have inherent tendency to become more complex
- it will increase over time
- he was wrong

Have any Lineages evolved greater complexity?

- only some
- bacteria to archaea to eukaryotes

What are some complexity transitions that have occurred previously? (7)

- cells
- chromosomes
- genetic code
- sexual reproduction
- multicellularity
- colonies (non reproductive castes)

What does this image represent? Explain it.

- events that lead to major changes in inheritance
- indépendant organisms merged
- lead to high complexity & speciation through division of labour

What is division of labour? How does it relate to molecular cell biology?

- separation of a task, which each part is preformed by a different organism
- aerobic prokaryote becomes mitochondria: ATP production
- photosynthetic prokaryote becomes chloroplast
- which have their own genomes diff from the rest of the cell

What is the Unit of Selection? Example?

- phenotypic traits that increase fitness of individuals (may not benefit all species)
- example: sexual selection for colouration; increase predation
- traits that are good for species but reduce fitness of individuals
are not favoured by individual selection

When is Cooperation "Adaptive"? (2) Example?

1) High Relatedness
- helping relatives spread via NS
- example: birds helping parent feed other birds
2) Reciprocal Alturism
- organsims encounter e/o often
- cooperation can lead to high fitness
- may be costly to you but benefits others

When does cooperation break down?

- example: selection for cheaters

Why are genes the target of selection?

because genes are the unit of inheritance
- Richard Dawkins

What is a Form Cooperation?

- selection on individual organisms
- organisms work together for common/mutual benefits

What are genomes composed of?

- unrelated genes and alleles that have been inherited from diff places

What three things ensure that genes are mostly passed on independently?

- segregation
- recombination
- random mating

How do genes persist?

by improving fitness of a group: humans or animals
- group: genomes and body

What are to problems to consider about cooperation?

1) how do high levels of organization stay cooperative?
2) what is the extent of cooperation break down?
- genomic conflict

How do genomes stay cooperative?

- prevent competition within individuals
- prevents evolution
- aligning fitness interest
- ensure genes succeed by increasing fitness of organisms