Example of Divergent, Directional and stabilising selection
E.G Spadefoot toads
* 2 morphs 1) omnivore 2) carnivore -> separate feeding niches
Divergent S = mark recapture experiment showed less survival of intermediate morphs
Directional S = Carnivores shown to do better than omnivores
Stabilising S = Intermediate morphs selected for when other species are present and dominant
Example of heterozygote advantage
Sickle cell anaemia, heterozygote for gene means you are immune to malaria whereas homozygote Is detrimental
Frequency dependant selection
PFDS - Mullerian mimicry
NFDS - Batesian mimicry
NFDS - (Gigord et al 2001) -Negative frequency-dependent selection maintains a dramatic flower color polymorphism in the rewardless orchid ( purple selected for as bees perceive it as “novel” and are attracted to it)
Example of a steep + shallow CLINE
Steep CLINE = cryptic + conspicuous morphs of rock pocket mice, reasonable gene flow but high predation selection (wrong morph in wrong area = dead)
Shallow CLINE = Alpha
Primary Hybrid zone
Directed reading - ring species Linn et al
Secondary hybrid zone
- Postglacial recolonization in European hedgehogs,
Example of reinforcement , RCD and magic trait/ direct system
E.G. Pied flycatchers (+ collared) - normally live in allopatry, when in sympatry males (P) change their plumage to make It different to C’s (female preference for plumage also changes) - the gene that is adaptive is linked to mating preference
EXAMPLE OF
1) Reinforcement
2) Reproductive character displacement
3) Magic trait / direct system
Example of peripatric speciation + founder effect speciation
E.G. Paradise Kingfishers (New Guinea)
- small periphery population split off and colonised islands
- each different island has own species which are morphologically different
Example of habitat isolation , hybrid inviability , sexual isolation and cryptic isolation
E.G. Timema Cristinae ( stick insect)
- 2 different ecomorphs , specialised to 2 different host plants (demonstrate a level of reproductive isolation)
- hybrids inviable as camouflage ineffective
Example of sympatric speciation
E.G Howea palm
- thatch + curly palm
- 1 island , 6 hybrids ever found
- differing soil preference + phenology
Example of ecological character displacement
Inter species
E.G. Brook + ninespine stickleback
- when ninespines present, brooks show evidence of benthic living (stronger jaws + wider bodies)
Sexual selection vs Natural selection
E.G. Marine Iguanas of Galapagos
- male size is sexually selected for
- increase in size shown to have negative effect on male fitness (harder to maintain larger body in extreme conditions)
Examples of sexual selection being affected by : Food resources, predation , parasitism,
FR: Red crossbills - (10 ecotypes + minimal gene flow) females select based of feeding efficiency + strategies
Predation: Guppys, red spots attrative to females but increase predation
Parasitism: Common Yellow throat , females select for melanin based black marks (which are linked to immunity) , parasites can affect production of these black marks
Example of mutation accumulation
E.G. Huntingtons disease - caused by a dominant allele expressed at 30+ years old
Example of Antagonistic pleiotropy
E.G. gene that causes overproduction of sex hormones can cause cancer later on
Example of mullers ratchet
E.G. Chao et al. RNA virus
- created 20 lines of RNA virus , fored genetic drift by randomly sampling 1
- regrew a culture from that 1
- repeated for 20 generations
- fitness (growth rate) declined over generations
Example of Red-queen dynamics
E.g. Morra et al (2011)
- co evolved nematode with bacterial pathogen
- resulted in higher rate of outcrossing
- when population was made asexual = extinction
- sexual populations were able to respond to parasitism pressures
Costly sexual traits
1) Red deer antlers
2) Guppies bright tails + red spots
3) Macaw has large tails - aerodynamic costs
Example of more than 2 mating systems
Ciliates - no sexual selection
Example/evidence for sensory bias theory
Crested auklets
- put ornament on least auklet
- auklet showed significantly more courtship displays
Examples of female choosiness for : fecund males, parenting ability and resources
1) Lemon tetra fish , females select for male who have not recently spawned (pipefish is opposite way round)
2) Mottled sculpin
3) Female scorpion flys swap copulations for gifts (prey)
Example of fisherian run-away selection
e. g. Stalk eyed fly
- range of genetic dimorphism based on width of eyes
- experiment artificially selected flys from different lineages
- females from long stalk lineage always choose long eye stalk fly’s
Example of chase away selection
E.g. Drosophila , toxic male semen
- toxins in male semen reduce females lifespan
- females evolve resistance
- males evolve increasingly toxic semen ( kills other sperm + increases females egg laying rate)
Good genes model
Peacocks
Example of two-level selection + genome conflict
E.g. Y chromosome genes
- for y chromosome female s= useless
- y chromosome favours adaptations that bias sex allocation
- Autosomal + X chromosomes have their own optima, selected to oppose any hypothetical Y adaption for sex bias
Example of two-level selection + genome conflict
Mitochondria and host conflict
E.g. Yeast cells (petite) mutations
- defective mitochondria shorter so replicates faster
-selected for at mitochondrial level
- mutation has negative effects on yeast cell (impairs cellular growth)
clear genome conflict
Segregation distortion
Drosophila male SR gene
- however males with SR bred half as much
Example of antagonism herbivory behaviour + coevolution
1) Passiflora (passion flower) , vines have cytotoxins in them
2) Heliconius caterpillars , can detoxify and disable them for use against predators
Example of altruism
Beldings ground squirrels, call to alert for predators, singles them out
Examples of eusociality
naked mole rats
