10 Sexual Selection Flashcards
Alturism
Behaviour beneficial to others but costly to self
Hamiltons rule - fitness benefits can be gained (3)
- Directly through producing and raising own offspring
- Indirectly through helping to raise offspring related individuals (kin selection)
- Total fitness (inclusive fitness) = direct fitness + indirect fitness
Adaptive phenotypic plasticity
Property of a given genotype to produce different phenotypes depending on the different environmental conditions, thereby enhancing organisms life
Contains same genes but different expression of the genes, tailored to enhance survival For the environment encountered
Genetic systems that produce adaptive epigenetic variation
Ultimate plasticity (2)
- Brain system alter behaviour to maximise survival prospects
- Behaviour and learning —> associative learning (spotting patterns) / insight learning (experimental play to solve problems)
Natural selection
Adaptation to a constant challenge - favouring mutations that increase survival in the environemt
Also - adaptation to varying challenges - favouring mutations that alter gene expression to produce phenotypes that fit current status of a variable environment
What may selection cause
Complex cognition - learning and complex behaviour to maximise fitness in changing worlds
How is natural selection good?
Natural selection works on natural genetic and variations, and with constraints:
- Population size limits efficient of selection
- Poor fitness of intermediate form
- Next form not genetically pure
Efficacy of selection
- Evolution can proceed by genetic drift or selection
- Magnitude of drift it depends on population size
= large changes in small population size
Does complex design imply a designer?
Irreducible complexity - not necessarily rejected by particular case studies in which natural selection is a good explanation (is it confirmed when we can’t explain them?)
When does selection occur
variation in the phenotype / some of this variation is heritable / the phenotype is associated with the ability to secure mates
THEN the next generation will be biased towards individuals with higher ability to secure mates
Where sexual selection occurs the outcome varies by sex (females)
fewer potential offspring / invest more in outcome of each (fitness defined by mate quality / choosy about potential mates)
Not universal - different where males show parental care
Where sexual selection occurs the outcome varies by sex (males)
many potential offspring / invest little in each (fitness defined by mate quantity not quality / compete for access)
Not universal - different where males show parental care
Sexual selection criteria (females and males)
Females - Intersexual (choose makes based on phenotype)
Males - Intrasexual (compete for access for females) (where sexual selection is strong the males die young)
Post copulatory sexual selection definition
Where females mate with more than one male, she has sperm from more than one male in reproductive tract - sperm competition
Post copulatory sexual selection adaptations
Co-operative sperm behaviour
Post copulatory sexual selection (getting rid of sperm)
Cloacal pecking in dunnocks
Ebonly jewelwing
Post copulatory sexual selection prevention
Ejaculate plugs - preventing remating
Sperm size which prevents displacement
Intersexual sexual selection: female choice
Where is female choice most commonly found
Where females care for progeny and males don’t COMBINED WITH where males cant physically monopolize access to females
Intersexual sexual selection: female choice (direct benefits)
Female picks males who will provide for progeny
Nuptial gifts in insects
Good territory, provisioning
Intersexual sexual selection: female choice (indirect genetic benefits)
Exaggerated traits are a way of telling males with ‘good genes’ from ‘bad genes’
They represent ‘honest signals’ of quality (unlike non exaggerated traits)
Sexual conflict
Male adaptation to manipulate female to mate with him, to not relate with rivals
However female adaptation is to avoid manipulation and to remate
—> continuous evolutionay chases
Why does natural selection not act for ‘the good of the species’
Operates on genetic variation among individuals, so a trait can benefit the individual and not the whole species
Why Altruism Represents a ‘Problem to Be Solved’ in Evolution
If natural selection favors individual fitness, how could altruistic behaviors evolve? Why would individuals sacrifice their own survival or reproduction to help others?
Genetic mechanism underpinning plasticity
Controlled by genes that allow for the activation of different traits in response to environmental signals - don’t change the genetic code but influences how an organisms phenotype will develop in different environments
Flexibility that enables organisms to survive in a variety of conditions without needing genetic evolution in each generation
How does learning allow adaptation to variable environments
Allows organisms to adjust behaviours based on experience and past environmental conditions, enhancing survival in changing environments
Why natural selection cant create a ‘perfect organism’
- Genetic constraints - evolution is limited by genetic variation and some traits may not evolve because the necessary mutations are too rare
- Trade offs - adaptations in one context may reduce fitness in another
- Historic constraints - evolution builds on existing traits (past evolutionary shapes current adaptations)
Irreducible complexity definition
Idea that certain biological systems are too complex to have evolved through gradual evolutionary steps - suggests these systems require all parts to function and cant have evolved from simpler systems
Irreducible complexity debate
Complexity can arise through gradual modifications over time
Sexual vs Natural selection
Natural selection favors traits that enhance survival
Sexual selection favors traits that increase mating success, even if they reduce survival
Theories of female choice
- Good genes hypothesis - pick males with superior genetic quality
- Direct benefits - pick mates that provide immediate benefits such as protection or parental care
- Resource acquisition - select males who can provide better resources
