Karteikarten
Natural Selection
Karten in diesem Stapel (34)
- 1G.D. and Heterozygote 4G.D. decrease heterozygosity to decrease within a population over time
Wright-Fisher Model
Hetero. decrease by half in effective population size
NZ Snapper stuck in lake - 2G.D. and Divergence 6G.D. on island
Eg 2 islands with 10 inhabitants each
Begin - A1A2 heterozygous at neutral A locus
Mating randomly and no migration/mutation
= eventually islands fixed A1 or A2
SPECIATION
EG Galapogos Island - 3No Foresight - No Purpose 3No way to anticipate the future
Favours changes that are immediately beneficial
Evolution history if a lineage is contingent on genetic and environmental events - 4Natural Selection Depends On ... 2Relationship between phenotype and genotypes/fitness
= relation between fitness and genotype which determine whether or not evolutionary change occurs - 5Thomas Robert Malthus Principles of Population 4Population growth food supply
= famine or other checks on population
Zone of between resources and population = in which nat. sel. by resource limitation occurs
= in which less-fit forms are unable to survive - 6Fitness Ability of Individual (genotype) to survive (viability) and to reproduce (fertility) 2Viability - probability of survival to reproductive age.
Fertility - average number of offspring per individual that survive to reproductive maturity - 7Constraints to Natural Selection 2HALDANE 1932
"Could produce a 'race' with the intellect of Shakespeare and stature of Carnea, but could not produce a race of angel" - 8Absolute Fitness 1Average number of offspring (reproductive success) produced by individuals of a particular genotype
- 9Relative Fitness 1Average number of offspring produced by individuals of a particular genotype RELATIVE to other members of a population
- 10Coat Colour of Oldfield Mice Peromysus polionotus 3Light coated mice live on the beach
Grey/ dark coated inland
Variation within one population - 11Coat Colour of Oldfield Mice Genotype to Phenotype 4Mc1R melacortin - 1 receptor gene
Acts as a switch
Contact with alpha-MSH melanocyte stimulating hormone - produce eumelanin = dark coat
Contact with ASP agouti signal protein - produce phaeomelanin = light coat - 12Light Pocket Mice Dark Lava 460-98% survived probability of light phenotype to dark phenotype
Selection co-efficient
Larger = stronger action on nat. sel.
= alleles change faster - 13Frequency-Independent Selection 9Directional selection
OVERDOMINANCE - heteroygote advantage (balancing selection)
UNDERDOMINANCE - heterozygote disadvantgae
Lead to FIXATION or ELIMINATION
A1 dominant - initial increase in frequency most rapid
- pace slows once common in pop.
Co-do - dominant reaches fixation most rapidly
Recessive - takes much longer to increase in freq.
- Once common, fixation comes quickly - 14Overdominance 5Heterozygote advantage
Start at high/low freq., its freq. increases/decreases respectively
Reach intermediate freq. (doesn't depends on initial freq.) so long as both alleles in pop.
Hetero has higher fitness than homo.
Direction of nat. sel. relies on allele frequency in pop. - 15Heterozygote Advantage Example 4Sickle cell anaemia - Beta-haemoglobin locus
Homo = severe anemia
Hetero = middle anemia but parasite growth decreased
Homo = normal - 16Underdominance 4Heterozygote disadvantage
No real world example within species/scare
Practical implication of human autoimmune disease Lupus
Chromo. rearrangements decrease fertility at meiosis in mouse/models - 17Positive Frequency Dependent Selection 5Fitness associated with the trait (phenotype) increases as frequency of trait (genotype) increases in population
Allele above critical threshold = reach fixation
Allele below = lost from population
Eg geographical ranges of butterfly Heliconics spps
May favour genetic differentiation and long-term possibly speciation - 18Negative Frequency Dependent Selection (Inverse) 6Fitness associated with trait (phenotype) increasesd as the freq. of trait of trait (genotype) decrease in population
Balancing selection
Allele starts at high freq. = phenotype common
Low fitness = allele decline in freq.
Allele starts low freq. = phenotype rare - high fitness = increased freq.
Allele would eventually reach intermediate freq. of 2 polymorphs - 19Physical Constraints to Natural Selection 2Ratio between fibia diameter and mass
Fibia breaks down first when old limit on speed of horse by weight and strength of bone. - 20Convergent Evolution 3Harvestman and cellular spider
Convergent evolution of long thin legs
= Distribute weight over large surface - 21Negative Frequency Dependent Selection Feeding Behaviour 3Lake Tanganyika's scale eating cichlids
LHS/RHS feeding
Attack prey from behind - prey become more aware of one side
= switch between morphs - 22Negative Frequency Dependent Selection Fihser's Sex Ratio 3Sex ratio even in pop.
Chromo. sex determination (mammals/birds)
Each individual has mum and dad and contribute equally to ancestory of next gen = same average fitness - 23Negative Frequency Dependent Selection Fihser's Sex Ratio Explanation 9Less female births than males
= newborn female better mating than new male
= have more offspring (females)
= parents predispersed to have females
= allele for female producing tendencies spreads
= females become common
1:1 sex ration approached
= Advantage for female sex dies away
EVOLUTIONARY STABLE STRATEGY - 24Negative Frequency Dependent Selection Fihser's Sex Ratio Test 3Samoan butterfly species
99% female and 1% male after infection with Wolbachia bacterium
2001 = varience that could produce many more males than females - 25Negative Frequency Dependent Selection Host-parasites 5Host adapted and therefore resistant to parasites would have highest fitness
Parasite population 'rare type' = advantageous and would be epected to spread
Pare hosts adapted to increasingly common parasite have advantage over other hosts
= maintain polymorphism
= creat cycles of evolutionary change in host and parasite species - 26Co-evolution 4MUTUALISM - evolutionary changes in each species benefit other species
eg Humans and livestock
Antagonistic co-evo. - evolutionary changes in each species decreases fitness for other species
Evolutionary arms race - 27Predator-Prey Co-evolution 52 molluscs - one is predatory
Sinistrofulgar (prey) and Mercenaria (predator)
Different thickness of shell
If predatory mollusc has thinner shell = breaks trying to get in - 28Predator-Prey Co-evolution 52 molluscs - one is predatory
Sinistrofulgar (prey) and Mercenaria (predator)
Different thickness of shell
If predatory mollusc has thinner shell = breaks trying to get in - 29'Random' Selection 2Chance or randomness when cause of event can result in several outcomes
Can only specify probability/frequency of one/other outcome - 30Neutral Theory of Evolution 4MOTTO KUMURA - neutral theory of molecular evolution in 68
Most variance in a population is selectively neutral
Most changes in DNA or amino acid seq. over time and thus many molecular differences between populations related species are selectively neutral
Differences due to GENETIC DRIFT - 31Genetic Drift 5Process of random fluctuations in allele frequency due to sampling effect in finite populations
G.D. and nat.sel. - 2 important causes of allele substitution
G.D. in all natural populations as no such thing as an infinite population
NAT.SEL. = ADAPTATION
G.D. = NOT ADAPTATION - 32Genetic Drift and Natural Selection 3Alleles at all loci are potentially subject to random to random genetic drift but not nat. sel.
NEUTRALIST - SECTIONIST DEBATE - dispute about whether drift or selection is primary driver of evo. changes in sebset of mutations that reach high freq. in population
G.D. is 'null hypothesis' to explain population different against which evidence for nat.sel. may be tested - 33Consequence of Genetic Drift 3Finite pop. - allele freq fluctuate over time even without nat. sel.
Some alleles fixed, others lost and fraction of hetero in proportion decrease over time
Separate population diverse in term of allele freq. and in term of which alleles are present - 34Allele Freq. Fluctuate due to G.D. 7Manx Cat breed
Unsure what it was
Picked up with ears without pain like a rabiit
So said it was a cat-rabbit hybrid
long ears, no tail, longer hind legs than forelegs
Heterozygote lethal
Small population = founder effect (G.D. and human selection)
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- Beschreibung
- Degree Evolutionary Biology of Animals Karteikarten am Natural Selection, erstellt von katy.lynock am 23/05/2013.
- Erstellt von
- katy.lynock · Mai 2013
- Aktualisiert
- 26 Mai 2016
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