Greg Hurst Flashcards
Mutation importance
Large effect mutations are commonly lethal so removed by natural selection
Most selection acts on mutations of small effect
Some large mutations can be important eg endosymbiosis
Mutations in microbial genomes
Widespread transfer of whole genes between microbes giving functions eg antibiotic resistance
Population genetics
Mathematical model of natural selection Genetic basis Selection coefficients Sex and recombination Hardy weinburg
Egoist - individual selection
Darwin’s opinion
Selection is to maximise individual survival
More reproduction per individual
Traits of individuals make them better competitors and therefore they survive and reproduce by coincidence this may be for the good of the species
Altruist - group selection
For the good of the species so species success is maximised eg lemmings commuting suicide when population become too large
However this may be due to coincidence as lemmings disperse more when population is high and have accidents on the way
Altruism
Helping relatives - indirectly helping siblings raise offspring you’re also passing on your genes as you share 50% DNA with your sibling or directly by helping your own offspring
Give now receive later - reciprocity eg monkeys grooming each other
3 types of mutation
Neutral
Deleterious
Advantageous
How do neutral mutations effect genetic diversity
They don’t effect phenotype and are usually in introns or they can affect the phenotype but giving the same properties to the protein
The frequency may increase or decrease randomly as they are not selected for or against
Genetic drift
Will either be fixed or lost
Genetic drift has a bigger effect in small populations
How can something get common
Genetic bottleneck
Founder effect
Why hasn’t natural selection led to everyone having the same advantageous genes
Evolutionary lag - as soon as one problem is solved the problem changes
The environment changes to quickly for selection to keep up
Convolution produces cycles eg parasites benefit from a host but the host does not so the host selects against so the parasite mutates again and so the host has to also
Balanced polymorphisms -
segregational variation - when the best phenotype involves two alleles together and so is maintained heterozygote advantage
Environmental variation and genetic diversity - lactose requires lactase in humans in some this doesn’t persist to adulthood
Mutations stick in some species but not others
Frequency dependent selection - some traits are good when rare and less when common eg common features of a species are more easily preyed on whereas rare types can survive
Sexual selection
Fitness differences associated with acquisition of mates
When does sexual selection occur
Variation in phenotype
Some variation is heritable
Phenotype is associated with ability to secure mates
Next gen will be biased towards individuals with higher ability to secure a mate
Two forms of sexual selection
Intersexual - female choice
Intrasexual - Male competition
Intrasexual
Within the sex Large males Armaments Guard access to females Male - Male competition eg stags have large bodies and armaments Sexual dimorphism
Sperm competition - co operative sperm or cloacal pecking
Intersexual
Female choice
Quality
Females may choose based on appearance - arbitrary
Direct benefits - food and territory a nuptial gift
Genetic benefits - if the Male has exaggerated traits eg very long tails shows an ‘honest signal’ in some birds
Darwin’s postulates
All life is related in a tree
- species split into two called speciation
- intermediate transitional forms between tax’s must have existed in the past
- some clades have gone extinct
Divergent / divergent evolution
When one species splits into two new species due to reproductive isolation and different environments etc
Punctuated equilibrium
Some species histories are characterised by long periods of stasis followed by sudden changes into new forms called punctuations
Hox genes
Transcription factors that alter the expression of other genes
Development of complex form if they mutate they move around morphological segments of insects
Is there a tape of life ?
Blind watchmaker view - evolution has no goal or pathway
External events are opportunities for new dominant lines
Not predictable
Programme of life - we are alone in the universe and evolution can be predicted
Eg biotic interactions such as O2 levels at 2400 Mya was 5%
Plate tectonic movement
Copes rule
Body mass continues to increase until mass extinction this reduces predation risk
Convergent evolution
If there is a common selection pressure in different taxa the same character is derived independently eg birds and mammals have a 4 chamber heart but not related
Same morphologies but derived independently
Analogues not homologues
Petrification
Death in water Sedimentation Burial and pressure Bone structures found Sometimes carbon containing structures such as leaf prints
