Evolution
Physiological Mechanisms
Genetics, Development, Evolution
Ecology- study of interactions among organisms and their environments
Phenotypic variation in a population is due to: genotype and environment
Sometimes genetic differences among individuals have a greater influence on phenotypic variation in population, sometimes environmental differences that individuals experience have a greater influence
Heritability- the portion of phenotypic variation in a population due to genetic differences between individuals
Natural selection- one mechanism of evolution if three conditions are met THEN adaptive evolution occurs
- Phenotypic variation in the population
- Some of that variation is inherited
- Interaction with the environment: Traits that increase survival and reproductive of individuals increase in frequency
NATURAL SELECTION Those individuals with traits best suited to the local environment survive, grow and leave more fertile offspring
This leads to changes in genetic makeup of a population over generations and favorable characteristics accumulate over time
Relative frequency of genes change over time
natural selection acts on individual
evolution acts on population
Why aren’t organisms perfectly adapted to their environments?
-What is “perfection”?
-Organism currently not in an environment it evolved in
-Genetic constraints and lack of genetic variation-
-Gene flow
-Ecological trade-offs
Fitness
Fitness- an organisms ability to produce offspring, relative amount within population (compared to others in same population)
Infanticide- killing infants, happens in different kinds of species for different reasons (lions, langurs)
Why does this happen?
in 1960’s it was hypothesized it was for population control.. but this does not help the population; selection works on individual level not population level
Hypotheses to explain infanticide:
-The pathology hypothesis
-The population regulation hypothesis
-The quicker reproduction hypothesis
Scientific Method in a nutshell: 6 steps hypothesis testing
1.Observe and interesting pattern- male lions kill cubs
2.Determine question of interest- why do male lions commit infanticide?
3.Determine the hypotheses- Male kills infants to get female to come back into estrus sooner so he can now mate with her
4.Make predictions- if male kill infants to gain access to females, then the cubs he kills should not be related to him
5.Design, conduct, and analyze experiments- collect blood samples of cubs and male lions, test paternity
6.Evaluate the hypotheses
Females evolve to protect offspring, sometimes mating with multiple males at the same time so paternity is unknown
Altruism
States- periods of time something is happening
detritivores- organisms that eat dead things
ethogram- inventory of behaviors
Animals sacrificing- if you sacrifice yourself other animals that are related to you with same genes can live on and pass on genes
Altruism- is “self sacrificing” behavior, lowers helpers reproductive success while increasing reproducing success of others in species
How does altruism evolve?
50% of DNA is similar to parents, 50% of DNA is similar to sibling
Coefficient of relatedness= r
The probability any two individuals will share a copy of a particular gene
In diploid species, any given allele has a 50% chance of segregating into particular egg or sperm
Direct selection- acts on traits that promote success in personal reproduction
Direct fitness- a measure of personal reproduction (your own offspring that survive and reproduce)
Indirect selection (Kin Selection)- acts on traits that promote success in the reproduction of non-descendant relatives
Indirect fitness- a measure of the number of relatives that the altruist helps to survive and reproduce
Inclusive fitness- direct+ indirect fitness (a total measure of the genetic success of an individual)
Hamilton’s Rule:
Hamilton proposed that an altruistic gene will be favored by natural selection when indirect fitness gained by the altruist is greater than the direct fitness it loses as a result of its self-sacrificing behavior: r(b)B > r(c)C (x)= subscript
B- the extra number of relatives that exist thanks to the altruist’s actions
r(b)- the coefficient of relatedness between the altruist and the extra individuals
C- the number of offspring not produced by the altruist
r(c)- the coefficient of relatedness between parent and offspring
What are Hymenoptera? ant, bees, wasps
What are some main characteristics of Eusocial species? Males are unfertilized eggs
What factors led to the evolution of this extreme form of altruism?
Parthenogenesis- egg developed into adult without being fertilized= 100% related
Sampling
calculate # seconds engaged in each entry, sum up total seconds for behavior, # of occurrences of each event
Instantaneous (scan sampling)- watch one animal or groups of animals for pre set intervals, don’t need to be able to to identify individuals, useful for observing states only, can monitor large groups
count number of scans engaged in each behavior, divide by total number of scans
Communication
Behavioral interactions between animals involve communication (visual, auditory, chemical, electrosensory, mechanosensory) <- Signal Modalities
Communication can take place between
members of the same species- conspecifics
members of different species- heterospecifics
Animals communicate using signals
includes a sender of a signal and receiver of the signal which changes the behavior of the individual
For a signal to be adaptive both parties must benefit from the signal
Sometimes an eavesdropper can benefit from a signal being sent (bird seeing urine trail)
Many animals signal in more than one modality at a time (birds using visual and auditory)
Why do animals communicate?
Sexual advertisement and mate attraction
Parental care (begging, recognition)
Environmental information (predator alarms, food location)
Territory defense, conflict resolution
Social integration (contact calls)
Predator defense (warning colouration)
Selection acts on pre-existing traits
can’t anticipate future environment
moths can hear ultrasonic sounds, bats produce ultra sonic sounds and prey on moths, whistling male moths produce ultrasonic signals which attracts females
Sensory Exploitation
communication signals originate in actions that activate pre-existing sensory abilities of receivers
Sensory exploitation in African Cichlid fish:
Male with bright orange spots on the anal fin, a female may try to pick up what appear to be eggs on the fin; females attracted to male with spots as pre existing bias for fertilization
The sensory exploitation only benefits the signaler
bright spots and stripes in the color pattern of the spider Nephila pilipes attract prey to the predator at night
Sensory exploitation- or retention of ancestral trait?
male fish of fish who don’t have sword tails has one attached to him and he is sexually preferred
Why resolve conflicts with harmless threat displays instead of fighting?
less likely to die in a fight or get injured when threatening
Selection acts to keep signals honest (paper wasp dark patches on their face = strength)
Evolved display behaviors mean they don’t have to fight to the death
Signal Deception:
Male Photinus flies flash to attract females of their species, sometimes female of another species, Photuris responds to his signals and instead of mating with him, eats him
Why do some males do the wrong thing?
– Novel Environment Theory- not in an environment they evolved in, appear similar to maladaptations (mal = bad) doing something that is decreasing an animals fitness
– Net Benefit Theory- if you never respond to a signal than you’ll never get to mate
Adaptation- Benefit of the trait outweigh the cost of the trait (Does not have to be perfect) must contribute more to fitness on average compared to other alternative traits
illegitimate signalers are usually trying to fool a member of another species
Eavesdropping
birds signaling to other bird of same species but another predatorial species picks up the signal
eavesdropping influences the evolution of bird calls
Food and Predator Adaptation
An adaptation has to be better than alternative traits, not perfect
Cost vs benefits of fitness
Other reasons for maladaptations:
Pleiotropy- one gene causes multiple phenotypic effects (net benefit theory) (allele that codes for sickle cell anemia helps prevent malaria infection)
Genetic Drift- random changes in genotype of populations
Gene Flow- mixture of genotypes between two or more different populations
Agelenopsis aperta (In Texas):
Desert Grassland population- harsh environment, low predators = more aggressive
Riparian population- more favorable environment, high predators = more cautious
Agelenopsis aperta (In Arizona):
Riparian population much more aggressive and less cautious than predicted, gene flow from desert population to riparian responsible
Predator Defense
More beneficial to mob all types of hawks than to be selective
Convergent and Divergent evolution can be used to compare behaviors of different species
Confusion effect: group of zebras, can’t tell where one ends or begins so it’s hard to single out one, less likely to capture one
Dilution effect- probably of being eaten in a larger group decreases
Many eyes hypothesis- more eyes to watch for predators means less likely of successful attack on group
Selfish herd- animals in the center of the herd may be more inaccessible to predators
Game theory- the success of an individual depends on what it’s competitors are doing
Life dinner principle- if individual doesn’t go early enough they’ll go hungry, if individual goes too early they could be eaten
Distraction displays- (broken sing act) mother pretends to have broken wing to distract predator from nest and fly away before being eaten
Crypsis = camouflage- blending into the back ground
Aggressive mimicry- blending into background to not be seen by prey item, sit and wait
Aposematism- bright colors that show how toxic animals are (poison dart frogs)
Batesian mimicry- where a harmless species mimics a harmful one
Adaptations of prey tell lots of information on predator
Ratio of mimics can never get too high (normally around 10%) because predators will bring mimic ratio back down
Mullerian mimicry- two species that have toxins or are dangerous that mimic each other, amplifies signal and takes into account predators can learn
Why behave conspicuously?
Mimic shape of other animals and dance similar to other animals
Stotting Springbox- signal of unprofitability- stotting shows which springbox could be faster and shouldn’t be chased
Optimality Theory- net benefit vs cost is optimized as much as possible, highest benefit to cost is the only adaptation, benefits have to out weigh costs and will be maintained over a long period of time as they increase in number throughout population
Reto Zach’s observations of foraging crows- crows pick up whelks and drop them onto rocks so they smash and can be eaten
crows only picked up car
they flew up 5 meters before dropping
they kept trying until the whelk was broken, even if many flights were required
If crows are foraging optimally predictions:
large whelks should be more likely than small ones to shatter after a 5 meter drop
drops of less than 5 meters should have lower breakage rates
drops of more than 5 meters should not greatly improve the chances of opening a whelk
the probability of breaking should be independent of the number of drops
Optimal foraging theory predicts animals should behave in a way that:
maximizes benefits
minimizes costs
> so maximizes net energy gain
> the central assumption is:
the more net energy an individual gains = the greater reproductive success
Profitability of prey= energy gained per unit handling time
Alternative Foraging Strategies
genetically based strategies maintained by frequency dependent selection
conditional strategies based on environmental conditions
geographical separation and divergence
Frequency dependent selection- rare genotypes have higher fitness until they become less rare then a new rare genotype has higher fitness
Conditional Strategy- an inherited mechanism that give the individual the ability to be flexible
Evolution of Reproductive Behavior
Sexual selection- traits that lower survival, but enhance ability to mate are sexually selected traits
Bower buildings may be an indicator of brain size, traits may indicate genetic characteristics
Variance in reproductive success is greater for males than for females in satin bowerbird (females 1 or 2) (males up to 20)
Male and female gametes differ greatly in size
Eggs are bigger and more energetically costly
Sperm produced in higher numbers and are less costly
Operational sex ratio:
Actual sex ratio 50% males and 50% females in many sexually producing animals
Females aren’t looking to reproduce once pregnant, so more males are available to mate than females
Operational sex ratio based on males and females looking to mate so females can be picky as there are more males
Parental investment takes different forms, conventional sex roles females protecting offspring, males protecting offspring is non conventional
Differences between the sexes in sexual behavior may arise from fundamental differences in parental investment
Conventional sex roles lead to male-male competition and female mate choice
Sex role reversal
Males make larger parental investment, more sexually available females than males means competition among females and mate choice by males
Crickets produce spermatophores, energetically expensive for males to produce.. spermatophores in Amblycorypha alexanderi include protein piece that females eats while sperm fertilizes, extra protein created by males increases chance of offspring survival
Sexual selection involves trade offs
Species of beetle has certain amount of developmental tissue, if beetle has larger horn they have a small eye, large eye means small horn
Pecking order = dominance hierarchy
Options for subordinate males: female friendships bringing food to female friend, male friendships where they join and fight dominant male
Alternative mating tactics
Conditional strategy
Low ranking males can make the best of a bad situation
Higher fitness payoff by adopting an alternative then try to fight dominant opponents
Distinct genetically based strategies vs. conditional strategy?
If the 3 types represent 3 distinct strategies then:
the differences between them should be genetic and
the mean reproduction success of the 3 types should be equal
Sperm competition
some sperm:
swim faster, break into egg quicker
males can control sperm in females (dragonfly)
Mate guarding males- guarding so female can’t male with other male
Male spiders have mating plugs which are used to limit other males mating with female
Female mate choice leads to the evolution of nuptial gift giving (dung beetle uses dung ball, hanging fly offers a moth)
Sexual cannibalism
in some species, one sex (usually the female) consumes the other during sexual reproduction
Sexual suicide- the ultimate nuptial gift
What leads to extreme male ornamentation and courtship display?
Good Parent Theory:
Females prefer to mate with males that provide more portents care
Male courtship is linked to his parental abilities
Healthy mate or good genes
Bright colors can indicate good foraging ability, good health, stronger immune system (can help raise young, females avoid diseases and parasites if they choose them
Male inherited good traits from his father (so he can pass them to offspring)
Do male ornaments signal good genes?
Size of peacock tale size has positive correlation with how long chicks live for
Runaway Selection?
Female mate choice genes and genes for the preferred male attributes are inherited together
Daughters inherit the genes for the mate preference and sons inherit the preferred attribute (like bright tail in birds)
Males attract more females with the preference
The mate preference “takes on a life of its own”
Male needs to survive long enough to mate
Chase away selection theory (sensory exploitation):
Female has an attraction for male traits thats absent (preexisting bias)
Mutation produce a rudimentary male display trait
Female fitness declines -> female mating threshold increases -> male attraction declines -> exaggeration of male display -> (back to) female fitness declines
Sexual Conflict
Females resist matings, often have the control over which males get to mate
Males develop traits that enhance his ability to mate, even if it lowers female fitness
(forced copulations, infanticide, transfer of toxic compounds during mating)
Proximate and Ultimate Causation
Individuals that ate more sugary foods had more energetic benefits which gave them higher fitness, gene passed down to future generations
Causation (a way of explaining a sensation)
Proximate- short term, affected by genes and development (influence how mechanisms are created during development); neuronal-hormonal mechanisms control what animals do behaviorally
Ultimate- long term evolution adaptive benefits (affected by descent with modification from ancestral species) adaptive value of behavioral trait process of evolution by natural selection
Why are Prairie Voles monogamous (Microtus ochrogaster)?
Selection and Adaptation:
Mate guarding ensures that males will sire all of the female’s offspring (Ultimate Cause) could be because it’s related to other monogamous species
Hormonal/Nervous system mechanisms:
vasopressin (V1a) receptors, when bound with vasopressin gives positive neurological rewards which is triggered when around females
avpr1a gene codes for V1a protein receptor (NOT SEPARATE EXPLANATIONS, INTEGRATED)
Proximate and Ultimate causes are interconnected (history that leads to adaptations and genes that survived to the present and develop in young)
Dialect differences in different regions White-crowned Sparrows live in
Genetic differences (may affect neural mechanisms)
Environmental differences (experience and learning in young males)
How to tell?
Some raised in isolation (only twittered) (twittered isn’t a crystalized sound; tweet is a crystalized sound)
Some listened to tapes of adult male songs at 10-50 days
Start singing at 150 days and have a full song by 200 days
Sang dialect that they heard regardless of which nest they came from
supports environmental learning hypothesis
GENES AREN’T IRRELEVANT- genes are needed to hear, learn, and repeat song
Proximate mechanisms include neurophysiology and genetic activity:
Part of brain where song memories are stored
Part of brain that controls sound production
Neural mechanisms involved in song matching
key sensory (environmental) inputs-> gene activity-> changes in biochemistry-> alters neurophysiological mechanisms (song control system)-> learning
ZENK gene activity protein production in the brain of zebra finch after it hears the song of it’s species is very active in gene expression
Song only occurs in 3 of the 23 orders of birds
Why learn to sing?
What are the disadvantages of learning to sing?
What are possible advantages of learning to sing?
Repertoire matching allows neighbor recognition, the territorial success of a male depends on how many song types he shares
Same song can lead to aggression, singing repertoire is neighbor
Females can get information about his developmental history and suitability to a particular habitat
Females choose males who can copy their tutors
Development of Behavior
Nature-Nurture “controversy”
What is wrong with the view of nature versus nurture
The development of an organism is an interactive process
As an organism develops:
genetic information interacts with changing internal and external environment
genes are turned on or off by signals
signals are internal/cellular/chemical or external environmental stimuli
these interactions alter the assembly of the organism, its neural networks as well as other aspects of its physiological/anatomical systems
DNA does not function in the absence of an environmental context
Gene activity varies in the brains of nurse bees and foragers
Environmental factors are critical for every element of gene expression within organisms, Environment supplied molecular building blocks such as bases present in RNA and amino acids of proteins which are essential if the DNA information is to be used to make mRNA and proteins
Once an environmental stimulus causes gene expression, there is a new cellular environment which causes a new gene to be expressed (continuous cycle)
“DNA is both inherited and environmentally responsive” Gene Robinson
Polygenic- multiple genes are displayed with single behavior
Learning is the result of gene-environment interactions
Learning takes place in a brain that has already experienced environmental interactions
Genes construct learning systems and are responsive to sensory stimuli
Environment and genetic differences can cause behavioral differences amongst individuals
How would you test for genetic differences in behavior?
Use individuals without experience
A single gene can have effects on behavior and be the starting point for a cascade of effects
Human Behavior
Can evolutionary theory be applied to human behavior?
Cultural vs. Biological evolution
Biology and Psychology are a big portion of human behavior which used to be classified in a similar fashion
Psychoneural monism- mind and body are not separate entities
Francis Galton:
Associated the ideas of heredity and instinct with dangerous political thought
Care for sick and needy led to procreation of less fit
Coined eugenics- meaning “well born”
Thought state should intervene to modify human mating choices
Franz Boas and the Triumph of Culture:
culture became enshrined as the central concept of explaining the social behavior of humans, turning tide from racist ideas in anthropology
Edward O. Wilson:
Sociobiology
Evolutionary Psychology
Environment of Evolutionary adaptedness
Module based compatibilities in the brain
Nearly all sociobiologysts and evolutionary psychologists now assert the psychic unity of mankind
Racial and between group differences in behavior are largely attributeable to the influentce of culture (interaction of shared genes and cultural environment)
Asserts the existence of human universals, some cultures may amplify or suppress different unverisersals
Evolution psychology vs human behavioral
What is the modular brain concept?
Different components of the brain manage different Hormones and control different acts
We often act in ways that are caused by module reactions that aren’t conscious to us
Evolutionary psychology model
Environment of evolutionary adaptedness- mechanisms sculpted during the past will not necessarily appear adaptive today
Domain specific mental modules- problem solving models
Behavioral adaptation vs cognitive adaptation (NOT THE SAME THING)
Don’t need to be aware or conscious of the behavior’s function to engage in it
Humans were not “designed” to understand the casual processes that created their own psychology