Final Exam Flashcards
Evolution by natural selection
Natural selection will lead to evolutionary change only if the phenotypic differences are due to genotypic differences
Natural Selection acts on individuals
Evolution occurs in populations
favorable traits persist
Basic tenents of natural selection
- variation exists
- heritability
- struggle for survival (reproductive potential and survival rates)
- Survival and reproduction are not random (favorable traits persist – AKA natural selection!)
Tinbergen’s 4 Questions
- Function
allows chick to get fed –> chick can survive and grow, eventually produce its own young - Causation
eyes detect yellow bill with red spot –> visual system perceives signal, motor system sends commands to muscles –> muscles move chick to peck red spot
WHAT ASPECTS TRIGGER RESPONSE? beak shape, spot orientation, color, etc.
head shape, size and color do not matter
cues: (1) color of spot, (2) contrast between spot and bill
- Development
chick performs behavior shortly after hatching, does it before seeing it –> innate - Evolutionary History
laughing gull: chick opens bill and closes it around parent, parent regurgitates to baby
shared trait suggest behavior was present in a common ancestor but red spot evolved after species diverged
Scientific Method
- Observe and describe (qualitative stage, what and why)
- Hypothesis (forming an educated guess)
- Prediction (IF…THEN)
- Test Experiment (quantitative stage)
- Drawing conclusions
Scientific Paper
AIM RD
Abstract - summary and key questions
Intro - literature review
Methods - experimental design and techniques
Results - quantitative report on findings
Discussion
Convergent v Divergent Evolution
divergent evolution and occurs when one species diverges into multiple descendant species
Convergent evolution occurs when species have different ancestral origins but have developed similar features
Phylogenetic Trees
Phylogenetic trees: the study of the evolutionary history and relationships among individuals or groups of organisms
Sister taxa
Node
Branch
Root
Advantages and Disadvantages of Sexual Reproduction
adv: genetic diversity increases survivability, adaptive to change
dis: costly to find mate
Differential Investments in Sexual Reproduction
Gamete production
Males produce many small, inexpensive sperm; reproduction limited by access to female’s eggs
Females produce few, large, energy-rich eggs
- provide care to embryos/young
- reproduction limited by access to resources and time
Operational Sex Ratios
Ratio of sexually active males to females
Heavily biased toward males (gamete production)
Effect on mating behavior
OSR IS BIASED TO WHOEVER HAS LOWER OSR
Differential Parental Investment
Expenditures of time and energy and risks taken by a parent to help existing offspring at the cost of reducing future opportunities to reproduce
Expenditure of time/energy/risk by one parent on current offspring reduces resources for future offspring
Investment in offspring = tradeoff between current and future reproduction
Differential Parental Investment: Difference between sexes in gamete size and other investment in offspring
Hyp: Differential parental investment ultimately leads to sex differences in behavior
Typical Sex Roles
Females focused on mate choice (quality)
Males focused on competition for mates (quantity)
Sex Role Reversal
Instances when males make larger parental investment or engage in other activities that cause the operational sex ratio to become reversed
More sexually selective, sexually active females than males
Ex: Pipefish
“pregnant fish”
- offer large pouch to store and carry eggs
- selective to large, ornamented females with larger clutches of eggs
Nuptial Gifts
Male gives gifts, if not, may have no chance to reproduce at all
Precondition for male reproductive success
Ex: Empid flies (Long-tailed Dance Fly)
- Heavily female-biased OSR because most males are off hunting for insects to bring back to swarm as a mating inducement
- Male enters swarm, bearing nuptial gift, and chooses among females advertising with large/patterned wings or decorated legs or inflated sacs on abdomen
Alternate Mating Tactics
Mating strategy used by males or females that differs from the prevailing strategy of the sex
ex: Iguanas: inseminate ‘old sperm’ without ejaculation
ex: Baboons form friendships with female; also can gang up on more dominant male
socially subordinate individuals compensate for inability to dominate others in their group
In species with conditional mating strategies, the ability of disadvantaged individual to switch to a different tactic
Conditional Mating Strategies
Conditional strategies evolve when selection favors behaviorally flexible individuals that can opt for the alternative tactic that provides them with the best possible outcome, given their standing with others
ex: Horned Scarab beetle – large horns or testes; as larvae, developmental mechanisms will determine future body size; “minor” male will sneak past big-horned male, his sperm will overpower
Siblicide
Faculatative
Obligate
Female Choice in Reproductive Behavior
Females discriminate mate choice; can enable males with favored hereditary characteristics to produce more successfully than others
NUPTIAL GIFTS
Ex: Chimpanzees: more likely to copulate with females if bring meat from killed smaller primate [utility]
Ex: Dung beetles – male presents dung ball to female, rolls away to distant burrow, female will accompany
Ex: black-tipped hanging fly – won’t accept unappetizing gift, will only allow male to copulate as long as she is eating
Ex: fireflies – based on duration of light flashes, indicative of spermatophore size; packets of protein
PARENTAL CARE
Ex: stickleback fish –> prefer males who shake bodies more frequently; indicates more fanning of eggs in nest, which sends oxygenated water over the eggs, increasing gas exchange and hatching success
Ex: stickleback fish –> prefer red bellies , longer fanning, carotenoids, healthier
NONMATERIAL BENEFITS
Ex: Japanese Damslefly –> prefer hotter males, territory in sun, eggs laid in warmer places to develop more quickly, indirectly helps offspring
Ex: Satin bowerbird –> ornamentation, although no material benefit
Male-Male Competition in Reproduction
Intrasexual selection
Competition for Mates:
Intrasexual: by intimidating, deterring, attacking same-sex rivals (males)
Mechanisms of Intra-Sexual Competition
- Scramble competition - race to get access to mates
- Endurance rivalry - maintain energetically costly activities for long time to get mates
- Contests - ability to fight get more mates; trait: anything that improves performance in fights
Scramble Competition
Resources and females are widely dispersed
Males simply try to find scarce receptive females before others do
Males who get to females first will gain mating access
Traits favored:
- well-developed senses/locomotor structures
- early search and swift mate location
mating success: most persistent, durable and perceptive; not most aggressive
ex: fireflies
ex: ground squirrels, will fertilize 75% of her ova, even if she meets again
superior spatial memory; ground squirrels return to places where they interacted with on-the-verge receptive females
Endurance Rivalry
Males that maintain energetically costly activity for longer have a HIGHER mating success
- Traits favored are the ability to remain reproductively active for long periods of time- eg long courtship or look for mates for a long time
Ex: Marsopial mouse
- for male, one short/intense single mating season
- go all out to father as many young as possible
- Male will mate for 6 hours at a time with as many females as he can
- Not one male is left alive at the end!
- Stress and exhaustion of search, furious mating, and aggressive encounters results in deathFemales breed a second or third year
Males stay all season without feeding, die of disease, parasites… after one season while females live to the next season
TRADE-OFF!!!! - live longer vs get more mates
This is favorable IF the probability to survive and reproduce in the next season is low anyway- then may as well get all you can in the first season
die of stomach ulcers, disease & parasites after one season
Sperm Competition
Competition among males with respect to the fertilization success of their sperm
The competition between males that determines whose sperm will fertilize a female’s eggs when both males’ sperm have been accepted by the female
ex: Black-winged damselfly –
male’s penis has lateral horns and spines that enable him to scrub out female’s sperm storage before passing on his own
- tries to win sperm competition by physically removing rival gametes from his mate’s body
- flies around copulating with different males
- females can copulate with different male
ex: Hens
- eject semen received by low-ranking roosters
traits favored: a. prevent rival sperm access, b.displace rival sperm
–
Sperm competition is LOW in chicken and quail. Males court females. Forced copulation is rare.
Sperm competition is HIGH in ducks and geese. Multiple males mate with one female. Forced copulation is common.
^sperm comp = ^forced copulation
Mate Guarding
Decrease odds of mate acquiring additional partner
Reduction of female copulating with other male, thereby diluting or removing sperm the guarder male has allocated
Ex: Milkweed beetle – stays mounted after copulation (30% liklihood of finding new partner for males, 50% for females)
Usually ends when female fertility period ends
Ex: Warblers
- false egg
- guarder males used false egg cue to stop mate guarding
- female warbler still fertile
- female warbler copulated with extra-pair partners, often fertilizing his sperm
Mating Systems
Monogamy - one female, one male
Polyandry - mating system in which female has several partners in breeding season
Polygyny - mating system in which male fertilizes the eggs of several partners in breeding season
Circumstances –> Strategy
Reversed Sexual Dimorphism
females larger than males
In scramble competition, males race to get access to receptive/ reproductively valuable females
Traits favored = well developed sense/locomotory organs, which can lead to SEXUALLY DIMORPHIC SENSE ORGANS - nervous system differences
Males may be able to smell/move more quickly to find females
Also favored = early search, swift mate location - males mature more quickly than females to get them faster - males will be SMALLER - LESS TIME TO DEVELOP -
REVERSED SEXUAL SIZE DIMORPHISM - females larger
ex: redback spider
- need to search for females
- strong FIRST MALE SPERM PRECEDENCE - male who gets to female first gets to father most of her children
- Paternity strongly biased towards the first male to mate
- Males mature EARLIER so they can start to search faster
- Males are SMALLER - the first male to reach a female will fertilize most of her eggs, so TRADE-OFF between size and speed!
males mature much earlier (and much smaller)than females, they can start the search early and try to beat their rivals
Sexual Selection v. “Other” Natural Selection
Sexual selection: traits favored because they increase success in competition over other potential mates
“Other” Natural Selection: traits favored because they increase LRS in ways not related to competition over mates
Sexual selection can often favor traits that decrease survival..
SS:
ex: Red throat of frigate bird increases probability of mating successfully but increases risk of predation; Favored by sexual selection but OPPOSED by ‘other’ natural selection
O:
ex: Brood patch of bird increases chance of reproducing successfully, but not important in competition over mates; Favored by ‘other’ natural selection
SS and O:
ex: Many eyes of jumping spider increase chance of finding a mate, but also of capturing prey; Favored by other natural selection & sexual selection
Extra-Pair Copulation
A promiscuous mating behaviour in monogamous species
A mating by a male or female with someone other than his or her primary partner in a seemingly monogamous species
Ex: Collared Flycatcher
- use sperm storage system to bias male fertilization chances
- can be stored for long periods of time (1 month)
- slipping away to give advantage to male with larger white forehead patch
BENEFIT: gain ‘good genes’ lacking in bonded male, increasing fitness of offspring; extra-pair paternity only if flycatcher chooses; must have greater genetic quality (white patch), improving survivability and reproductive success of offspring; more common when male genetic quality is highly variable
COST: extra energy in reproducing
Ex: Warblers
- false egg
- guarder males used false egg cue to stop mate guarding
- female warbler still fertile
- female warbler copulated with extra-pair partners, often fertilizing his sperm
Males do so to have maximum mates
BENEFIT: due to having such low parental investment, it is evolutionarily adaptive for men to copulate with as many women as possible, as it will allow them to spread their genes with little risk of future investment; ex: house wren 2 mates=9 offspring, 1 mate=<6
COST:
Economics of Parental Investment
duration
amount
timing
quality
trade-off between current & future reproduction
benefits: increased survival& success of offspring
costs: decrease likelihood of successful future reproduction, physiological costs, opportunity costs(foraging & other matings)
parental care will only evolve if it results in a net fitness increase
K and r Selection
the selection of combinations of traits in an organism that trade off between quantity and quality of offspring
r = focus upon either increased quantity of offspring at the expense of individual parental investment
k = reduced quantity of offspring with a corresponding increased parental investment of K-strategists, varies widely, seemingly to promote success in particular environments
r-selected species are those that emphasize high growth rates, typically exploit less-crowded ecological niches, and produce many offspring, each of which has a relatively low probability of surviving to adulthood ex:dandelion
•Parents’ strategy: intelligent, autonomous, but expensive offspring•development of traits necessary for success after birth:•learning•physical abilities•development depends on food that is scarce/difficult to obtain
K-selected species display traits associated with living at densities close to carrying capacity and typically are strong competitors in such crowded niches that invest more heavily in fewer offspring, each of which has a relatively high probability of surviving to adulthood ex:elephant
K selection (carrying capacity): stable environments
•larger body size
•slower development
•longer lifespan
Key factor affecting success of offspring: intense intraspecific competition
Iteroparity -produce offspring in successive bouts - small # of young that receive intensive care - relatively low mortality rate of young
K-selection ex:
ex: old world monkeys 25% of life focused on r, brain size ability to work in complex groups
ex: black eagles juveniles fed by parents long after they could feed themselves fitness; hunting ability
r-Selection ex:
ex: salmon - single intense breeding event, die, many offspring
ex: redback spiders: thousands, no care, high mortality, spiderlings able to catch prey autonomously immediately
Factors Affecting with Sex Provides Most Parental Care
- Sex with higher initial investment
- Sex with lower cost/benefit ratio
care will evolve in the sex for which care yields greatest net fitness increasex
Parent-Offspring Conflict
when parents gain fitness by withholding parental care or resources from some offspring in order to invest in others now or later
- offspring desire greater investment than their parents provide
- parents try to allocate resources to ensure the maximum number of offspring survive
- conflict occurs when offspring want more resources than parent willing to give
will at some point prefer to invest in future not current
the evolutionary conflict arising from differences in optimal parental investment (PI) in an offspring from the standpoint of the parent and the offspring
o Natural selection favors different optimal for parent & offspring
o Everything parent gives offspring, it doesn’t keep for itself or other offspring
ex: red-mason bee – preferential to first offspring, females, more likely to survive, physiological conditon declines, foraging less good,
ex: burying beetle,
earwigs == earwigs respond to chemical cues of well-fed nymphs
Offspring-Offspring Conflict
siblicide
obligative
faculative
obligate vs. facultative siblicide
OBLIGATIVE ex: nazca booby (first chick always kills second, only 60% of first-laid eggs hatch, laying two eggs reduces complete nest failure by 16%);
FACULATIVE blue-footed booby (when siblicide occurs, first chick always kills second, only in food shortage, older
one only kills younger one when first-born weight drops to 75% of normal)
INSURANCE AGAINST FAILURE, INCREASES CHANCE OF REPRODUCTIVE SUCCESS
Operational Sex Ratio Process
Parental Investment (gamete production, other)
High (f) Low (m)
[few, energy-rich eggs] [many, low-energy sperm]
Potential Reproductive Rate (max number of offspring given unlimited access to opposite sex gametes)
Low (f) High (m)
Time-Out Period (time spent acquiring resources for gametes and caring for young)
High (f) Low (m)
Operational Sex Ration (OCR) Few active (f) Many active (m)
[Heavily biased toward males]
[Females have nothing to gain from copulating again –> many fewer sexually active females]
Siblicide
Fitness advantage enjoyed by offspring disposal of siblings
Faculatative
Obligate
Facultative occurs later on in development; after they have been born
Siblicide occurs as soon as it hatches,
EX: Black eagles
Ample resources —> it might not happen
Obligate will always happen
Insurance egg: lay egg to provide insurance that their efforts aren’t failed, response to a high risk situation; obligate, to make sure there is one at least
Extra reproductive hypothesis: faculatative siblicide, Extra one, bc may survive; dependent upon availability of resource, siblicide will not occur if enough is present
OBLIGATIVE ex: nazca booby (first chick always kills second, only 60% of first-laid eggs hatch, laying two eggs reduces complete nest failure by 16%);
FACULATIVE blue-footed booby (when siblicide occurs, first chick always kills second, only in food shortage, older
one only kills younger one when first-born weight drops to 75% of normal)
INSURANCE AGAINST FAILURE, INCREASES CHANCE OF REPRODUCTIVE SUCCESS
Brood Parasitism
Females of some bird species lay their eggs in other nests or the nests of other species that are smaller (usually closely related)
Brood parasitism — warbler and cookoo; supernormal stimuli; —> adapted that way to ensure the warbler’s fitness; cookoo will destroy magpie the nest
warbler may push out own eggs when trying to get rid of cuckoo
accept eggs at end of mating season, little time to renest
unable to remove/grasp large eggs
Push out the male they’re helping and take over the nest
Mormon Cricket
Ex of nuptial gift, female-biased OSR
Mormon cricket
Male gives female nutrient-rich spermatophore (nutrients to produce more eggs)
Refuses lightweight females
Katydid
Female katydid only competes to mate when food is scarce, making the male’s spermatophore especially valuable
Males especially choosy, females fight
OSR switches when food is no longer scarce
Dependent on pollen quantities
Low food condition: female-biased OSR,
Katydid
Female katydid only competes to mate when food is scarce, making the male’s spermatophore especially valuable
Males especially choosy, females fight
OSR switches when food is no longer scarce
Dependent on pollen quantities
Low food condition: female biased
- Higher
When parental investment is high for an organism
When parental investment is high for an organism
OSR is low
Fewer sexually active females
Ex: High P.I. for females
More sexually active males
Male-biased OSR
Hamilton’s Rule
Hamilton’s Rule [ inclusive fitness]
rB > C
indirect fitness > direct fitness
r=relatedness
B=benefit to recipient for altruistic behavior
C=cost of altruistic behavior
Natural Selection
Traits favored because they increase lifetime reproductive success (LRS)
Sexual Selection
within a species, the advantage some have over others to reproduce
Monogamy v. Promiscuity
Monogamous species tend to form lifelong breeding pairs, share a nest, guard against intruders together, and take care of offspring together
Promiscuous species tend to have low levels of social affiliation, do not mate with one specific partner, and usually only the females care for offspring
When parental investment is high for an organism
When parental investment is high for an organism
OSR is low
Fewer sexually active
Ex: High P.I. for females
More sexually active males
Male-biased OSR
OSR IS BIASED TOWARD WHOEVER HAS LOWER PI
however competes is the one with the bias
Eusociality
3 main components , examples
Many species of animals are eusocial, living in large colonies.
Examples: honeybees, termites, naked mole rats
Eusociality has three main components:
- Cooperative brood care
- Cohabiting, overlapping generations
- Division of labor, including non-reproductive castes (e.g. worker bees)
Bird Brood Patch
Brood patch of bird increases chance of reproducing successfully, but not important in competition over mates
Favored by ‘other’ natural selection
Jumping Spider
Many eyes of jumping spider
Increase chance of finding a mate, but also of capturing prey
Favored by other natural selection & sexual selection
Frigate Bird
Red throat of Frigate bird
Increases probability of mating successfully- but increases risk of predation
Favored by sexual selection - but OPPOSED by ‘other’ natural selection
Intersexual Selection, Intrasexual Selection
Mate Choice
Intersexual Selection: making themselves more attractive to opposite sex (females)
Competition for Mates:
Intrasexual: by intimidating, deterring, attacking same-sex rivals (males)
Facial Expression
- Universality
- Development
- Evolution
Facial expressions - universality, development, evolution
Function
“ Signal passive/aggressive feelings
“ Elicit positive/aggressive responses
Causation
“ Ver specific sets of muscles control facial expressions
Development
“ Begin smiling at faces around 40 days old
“ Use responsive smiling by 2 months of age
“ Study faces by the end of second month
“ Focuses on mouth movements at 5 months
===
Evolution Bearing teeth threat Half baring teeth- stops to end threat Submissive primate grimace Human smile
Human Sexual Attraction
Human sexual attraction - how it related to OSR
o Males are quantity based and females are quality based
Relationship between Human Attractiveness Features and Fitness
Relationships between human attractive features and fitness
Males are attracted to females with sloping jaw and full lips
Females are attracted to square jaw and prominent brow
o Both are attracted to symmetry
o Waist to hip ratio
“ 0.7 which is strongly correlated with health and fertility for women
“ 0.9 which is strongly correlated with health, fertility, and low cancers rates for men
Potential Human Innate Releasing Mechanisms
- Potential human innate releasing mechanisms - neoteny features
o People prefer babylike animals and things- ex. puppies, babies, kittens
o Large Round head, large round low eyes, short, stout limbs
o People would neotenized animal vs adult animal
o Mickey Mouse over the years
o Innate releasing mechanism neural network that is responsible for fixed action patterns or similar behavior sequences are produced by a neural network
Neoteny Features
Neotonization - the retention of juvenile features in the adult animal
Potential human innate releasing mechanisms - neoteny features
o People prefer babylike animals and things- ex. puppies, babies, kittens
o Large Round head, large round low eyes, short, stout limbs
o People would neotenized animal vs adult animal
o Mickey Mouse over the years
Innate releasing mechanism neural network that is responsible for fixed action patterns or similar behavior sequences are produced by a neural network
Healthy Mate Theory
Explanation for preferences by females for males whose appearance signals that they are unlikely to carry disease or parasites
Ex: Bower birds with high-quality bowers less likely to carry parasites in feathers
Good Genes Theory
Preferences for certain male ornaments and courtship displays enable families to choose partners whose jeans will help their offspring develop mechanisms to combat infection and disease
ex: cricket can evaluate strength of immune system through courtship display, cricket with song that conveys stronger IS
Ex: large plumage sign of health and free from parasites-hard to grow and maintain when p present due to physiological stress
Ex: peacocks with larger eyespots produced more offspring that survived better when released from captivity
Analogous Traits, Homologous Traits
ANALOGOUS: not related, similar traits due to similar environmental pressures
ex: sugar glider and flying squirrel
ex: vertebrate eye and cephlapod eye
Homology
traits that are similar to one another due to shared ancestry
ex: common structure of the vertebrate limb
divergent evolution from same origin
Genotype, Phenotype
Phenotype: physical and behavioral traits
Genotype:“blueprint” - genetic instructions present in an organism
Ethology
the scientific study of animal behavior, especially in the natural context
Comparative Approach
- comparing traits and environments across taxa in search of correlations that test hypotheses about adaptation
- if a behavior did arose from environmental pressure, then comparison of closely-related species subject to different pressures should yield different behavioral characteristics via divergent evolution
- if behavior
ex: gull mobbing
The “Natural” Experiment
Independent variable varies naturally and dependent variable is measured to see if vary A affects B
Phylogeny
the study of the evolutionary history and relationships among individuals or groups of organisms
Sign Stimulus
sensory cue that triggers the behavior
(red spot on bill)
ex: Red herring
Sign stimulus for chick = red spot on bright bil
lSign stimulus for parent gull = chick’s pecking on bill
Supernormal Stimulus
Tailfeather of widowbird
an exaggerated sign stimulus
(GIANT red spot on bright bill)
ex: Oystercatchers were willing to roll huge eggs into their nests to incubate
Fixed Action Pattern
(FAP) a stereotyped motor response that may be initiated by an environmental stimulus
Chick’s FAP = pecking parent’s bill
Parent’s FAP = regurgitating fish
Social Releasing Mechanism
sign stimulus that is emitted and received by the members of the same species
Sexual Suicide
Redback spider
Transferring sperm –> blocks female’s sperm receptacles–> Somersault into mate’s jaws
- cannibalized males fertilized more sperm than non-c males did
- partly due to female being less likely to mate again promptly
- low likelihood of finding another mate
- male genitalic pedipalps become broken or nonfunctional in course of initial mating
- sexual suicide occurs when males have almost no chance of mating again
Relationship between sign stimulus and FAP
Sign stimulus: red spot on bill
FAP: peck
Sign stimulus: peck
FAP: regurgitate fish
Monogamy
One male, one female
ex: female satin bowerbirds
female-enforced: burying beetle: pushes male from perch when he begins to release pheremones
ex: yellow-eyed junco – cares for young while mother incubates second group
more likely to hatch with bi-parental incubation 97%, 75%
Polygamy
Male has several partners during breeding season
ex: digger bees – males copulate with several females, sometimes in a single morning
Polyandry
Female has several partners during breeding season
ex: sandpiper females copulate with 2-3 mates per breeding season
ex: honeybee – using sperm from a dozen or so, copulate in midair
Fertility Insurance Hypothesis
Genetic benefit to polyandrous females
extra-pair fertilizations could reduce risk of female having an infertile partner as a social mate
ex: red-winged blackbirds
eggs of polyandrous red-winged blackbirds more likely to hatch
eggs of monogamous red-winged blackbirds less likely to hatch
ex: poly v. mono prarie dogs
Genetic Compatibility Hypothesis
Female preference for males who possess genes complementary to their own, heterzygous
pseudoscorpion – refused to remate with lone partners, prefered new mates; chance of obtaining gen-comp sperm increases with number of partners
superb starlings – went looking for males less
Material Benefits Hypothesis
females gain material benefits (food presents, spermatophores)
ex: megachild bee – by mating with many mates, female megachild mates gain access to pollen and nectar in thise mates territories
ex: the spermatophores of highly polyandrous butterflies contain more protein than monogomous species
Sexual Dimorphism
males larger than females
ex: male elephant seals
- mating system is highly polygynous; a successful male is able to impregnate up to 50 females in one season
- males can grow to 14 ft & 5,000 lb. while the females grow to 11 ft and 1,400 lb
- body length
- Copulation frequency is related directly to success in male-male competition, i.e., social rank
- Pregnant females form dense aggregations called harems. The proximity of males to the female harem is determined by social rank, the higher ranking males being closest to the females
ex: Red deer
- Males take over harems by locking antlers & pushing other males
- Males with larger antlers breed more than do males with smaller antlers
- Males with larger antlers have lower survival rates than do males with smaller antlers. Weaponry confers mating advantage but survival cost.
Sandpiper mating
Polyandrous females
Monogomous males
excess males, abundant food, precocial young
Why females would be polyandrous
- FERTILITY INSURANCE HYPOTHESIS
Fertility Insurance Hypothesis: Genetic benefit to polyandrous females
extra-pair fertilizations could reduce risk of female having an infertile partner as a social mate
ex: red-winged blackbirds
eggs of polyandrous red-winged blackbirds more likely to hatch
eggs of monogamous red-winged blackbirds less likely to hatch
ex: poly v. mono prarie dogs
2. GENETIC COMPATIBILITY HYPOTHESIS
Genetic Compatibility Hypothesis
Female preference for males who possess genes complementary to their own, heterzygous
pseudoscorpion – refused to remate with lone partners, prefered new mates; chance of obtaining gen-comp sperm increases with number of partners
superb starlings – went looking for males with less heterozygocity
- MATERIAL GAINS HYPOTHESIS
ex: megachild bee – by mating with many mates, female megachild mates gain access to pollen and nectar in thise mates territories
Why females would be polyandrous
- FERTILITY INSURANCE HYPOTHESIS
Fertility Insurance Hypothesis: Genetic benefit to polyandrous females
extra-pair fertilizations could reduce risk of female having an infertile partner as a social mate
ex: red-winged blackbirds
eggs of polyandrous red-winged blackbirds more likely to hatch
eggs of monogamous red-winged blackbirds less likely to hatch
ex: poly v. mono prarie dogs
2. GENETIC COMPATIBILITY HYPOTHESIS
Genetic Compatibility Hypothesis
Female preference for males who possess genes complementary to their own, heterzygous
pseudoscorpion – refused to remate with lone partners, prefered new mates; chance of obtaining gen-comp sperm increases with number of partners
superb starlings – went looking for males with less heterozygocity
- MATERIAL GAINS HYPOTHESIS
ex: megachild bee – by mating with many mates, female megachild mates gain access to pollen and nectar in thise mates territories
Altricial
young born in relatively immature or helpless form - - require intense care
ex: meadowlark
Semelparity
reproductive strategies available to living organisms
semelparous = single reproductive episode before death
ex: salmon
iteroparous = multiple reproductive cycles over the course of its lifetime
ex: pig
Iteroparity
- produce offspring in successive bouts
- small # of young that receive intensive care
- relatively low mortality rate of young
Precocial
young can move about, feed themselves, and thermoregulate shortly after birth
ex: ruffled goose
Residual Reproductive Value (RRV)
• expected value of future reproduction
i.e., how many surviving offspring are you likely to have in the future?
lower RRV = lower costs of parental investment
factors: age, health, time of season
Reciprocal Altruism (Reciprocity)
when an individual acts in a manner that temporarily reduces its fitness while increasing another organisms fitness
organism acts in a way that temporarily reduces fitness while increasing another organisms fitness expecting the organism to do the same at a later time
ex: baboons grooming one another
Mafia Hypothesis
Host parents would accept and raise parasitic young to protect against predation by parasitic species
ex: cuckoo will destroy magpie nest if gets rid of eggs
Direct Selection , Kin Selection
direct fitness: reproducing and rearing descendants, indirect fitness: assisting in rearing non-
descent kin
Direct selection- when a trait helps an organism sire successful offspring
indirect/kin selection- an organism’s trait benefits other relatives (nephews, cousins, etc.) who have non-zero coefficients of relatedness
Coefficient of Relatedness
in Hamilton’s Rule, r, is the coefficient of relatedness —> which is the probability that 2 organisms share identical alleles because of common ancestry
Hamilton’s Rule [ inclusive fitness]
rB > C
indirect fitness > direct fitness
r=relatedness
B=benefit to recipient for altruistic behavior
C=cost of altruistic behavior
Relatedness is the probability that two individuals share an allele due to recent common ancestry
R ranges from 0 to 1
Lifetime Reproductive Success
passing of genes from one generation to another in a successful manner
Monogamy
species tend to form lifelong breeding pairs, share a nest/home, guard against intruders together, and take care of offspring together
Bateman Effect
in most species, variability and reproductive success or reproductive variance is greater in male’s than females
Females invest more energy in producing offspring than males
Consistent with theory of parental investment. In most species the females are a limiting factor
Dopamine
dopamine is involved in the formation of attachments.
Oxytocin
Oxytocin and vasopressin have been shown to be involved in social recognition and pair bonding,
.hormone released by the pituitary gland involved in pair bonding
Oxt gene knocked out –> male cannot remember females; social amnesia ex: mouse
F more sensitive
Vassopressin
hormone involved in pair bonding and social recongition
Prairie voles are monogamous; cells in male prairie vole brain bind with hormone vassopressin; produced and released into bloodstream when copulates several times with given female –> rewarding sensation
less numerous v1a receptors in polygonous prarie voles
lacking DNA in polyn that encodes for v1a protein receptor
M more sensitive
Symbiosis
symbiosis- close and consistent interaction between different species “the living together of unlike organisms”
- COMPETITION
- interactions in which both species experience costs
ex: Cheetah and lions hunt for the same prey interacting in competition for gazelles and zebra - COMMENSALISM
- interactions in which one species benefits and the other has no benefit or cost- no fitness difference
ex: cattle egrets forage on insects that cattle disturb from the grass as they are grazing - MUTUALISM
- interactions that benefit both species- increase fitness of both
ex: oxpeckers remove ticks from animals that carry heavy tick loads and cannot remove them
- Food for the birds and parasite removal for the larger animals
- Oxpeckers spend more time foraging on impala ears and head than on other body parts because ticks are found at highest density on ears and head (74%of tick found)
- Impalas scratch and groom less often when oxpeckers are present, which allows them to spend time grazing and looking out for predators
Goby fish and blind shrimp depend on each other for food and shelterShrimp digs and maintainsburrow for both while gobywatches for predatorsShrimp’s digging stirs upfood for gobyShrimp keeps its antennaetouching the goby to know where burrow is and when predators arrive
Competition
symbiosis- close and consistent interaction between different species “the living together of unlike organisms”
- COMPETITION
- interactions in which both species experience costs
ex: Cheetah and lions hunt for the same prey interacting in competition for gazelles and zebra
Commensalism
symbiosis- close and consistent interaction between different species “the living together of unlike organisms”
- COMMENSALISM
- interactions in which one species benefits and the other has no benefit or cost- no fitness difference
ex: cattle egrets forage on insects that cattle disturb from the grass as they are grazing
ex: Clown fish position themselves in poisonous anemones to protect themselves from predators-anemone does not sting them ; Anemonefish secrete mucous on bodiesthat protect them against anemone toxin
Interspecific Mutualism, Intraspecific Mutualism
Interspecific mutualism- between species mutualism
Intraspecific mutualism- within species mutualism
symbiosis- close and consistent interaction between different species “the living together of unlike organisms”
- MUTUALISM
- interactions that benefit both species- increase fitness of both
ex: oxpeckers remove ticks from animals that carry heavy tick loads and cannot remove them
- Food for the birds and parasite removal for the larger animals
- Oxpeckers spend more time foraging on impala ears and head than on other body parts because ticks are found at highest density on ears and head (74%of tick found)
- Impalas scratch and groom less often when oxpeckers are present, which allows them to spend time grazing and looking out for predators
- gobi fish and blind shrimp
Goby fish and blind shrimpdepend on each other for food and shelterShrimp digs and maintainsburrow for both while gobywatches for predatorsShrimp’s digging stirs upfood for gobyShrimp keeps its antennaetouching the goby to know where burrow is and when predators arrive
Pilastro
Individual adjustment of sperm expenditure accords with sperm competition theory
Intro:
- sperm competition theory predicts that sperm expenditure should depend on the number of males competing to fertilize eggs - Risk model: sperm expenditure increases with competition between two males - compared to no competition - Intensity model: expenditure decreases with an increase in the simultaneous competition because of diminishing returns = strategic allocation of sperm among spawns - Fish are physically capable of controlling the sperm release but evidence in favor of the intensity model has not been generated - Study uses grass and black gobies in which there are territorial and sneaker males - thus there is a variable number of competitors naturally - Tested the risk and intensity models
Methods:
- Set up tank with a nest, territorial male, female, focal male and a range of sneaker males
- Manipulated the number of sneaker males competing for fertilization of one nest (0, 1, 2, 4 added males)
- Measured sperm expenditure of a focal sneaker male w/ varying number of competitors by sampling sperm in a standard amount of tank water
Results:
- Expenditure increases between 0 and 1 competitors but then decreases with increased # of competitors
Discussion:
- Results agree with theoretical predictions of risk and intensity sperm competition models
- Except that if the territorial male is considered one of the competitors, then the model predictions are off by one male
- Could be due to distance between males
- sneakers may not have perceived competition with territorial male
- Sperm allocation in spawning may be important because # of males changes over time - changing the chances being father!
Packer
Female African lions demonstrate a unique form ofplural breeding in which companions consistently produce similar numbers ofsurviving offspring. Consistent with theoretical predictions from models ofreproductive skew, female lions are unable to control each other’s reproductionbecause of high costs of fighting and low access to each other’s newborn cubs.A female also lacks incentives to reduce her companions’ reproduction, becauseher own survival and reproduction depend on group territoriality and synchro-nous breeding. Consequently, female relationships are highly symmetrical, andfemale lions are “free agents” who only contribute to communal care when theyhave cubs of their own.
Intro:
- Lion prides are well know to contain multiple breeding females
- All births of lions in the Serengeti National Park between 1963 and 1999 have been documented
- # of yearlings is measure of LRS
- Maternity is known in 80% of cases and attributed in the other cases
Methods:
- Measured the variance in LRS across females and compared that to a random model of LRS
- Measured time females spent alone before and after giving birth
- Measured who (owners vs rivals) got access to certain parts of carcass during feeding
- Measured cub survival as a function of pride size(# mothers) and other cubs’ ages
Results
Females have surprisingly little reproductive skew
Distribution of skews in real data is similar to the simulations of random skews
Females give birth in secrecy and keep young away from pridemates for a few weeks
Males that are larger supplant kill owners most often
Owners keep control less often
Females allow owners to keep the kill much more often
Cub survival rate increases with increased # mothers- pride size
Cub survival was highest when other cubs were same age - group rearing/nursing
Discussion
Females stay away from pride members when cubs are young and join in a creche rearing when cubs are older
Females show significantly lower reproductive skew than males
Despite significant weaponry, females do not fight for status or access to food
Cub survival is correlated with cooperative care among mothers
Smeltzer
receptor binding densities
Dopamine, oxyticin and vasopressin receptor binding in the medial prefrontal cortex of monogamous and promiscuous prairie voles
Intro:
Monogamous= prairie, pine voles; mating pairs form bonds
Promiscuous= montane, meadow voles; low levels of social affiliation
Oxytocin and vasopressin have been shown to be involved in social recognition and pair bonding while dopamine is involved in the formation of attachments
Females are more sensitive to oxytocin and males are more sensitive to vasopressin
Methods
- Comparisons between closely related species (prairie and montane voles)
- Receptor binding
o Uses radioactive form of the neurotransmitter or neuropeptide of interest to visualize the distribution of receptors in very thin slices of tissue
o Quantified using mean gray scale, which is basically how dark/dense the film is where the neurotransmitter binds to the receptor, compared to where the neurotransmitter does not bind to the receptor
“ Done on sexually naïve males and females
Results:
“ Prairie voles had lower densities of D1-like receptor binding and higher densities of D2 like receptor binding than meadow voles
“ Male prairie voles had the lowest desnity of D1-like receptors
“ Females had higher levels of oxytocin receptor binding than males and prairie voles had higher densities of oxytocin receptor binding than montane voles
Discussion:
“ The prairie vole has lots of receptors- what parts of the brain respond to vasopressin and oxytocin
Bshary
Bshary
Interspecific communicative and coordinated hunting between groupers and giant moray eels in the Red Sea
Introduction
“ True coordination in hunting requires that individuals play different roles during a hunt.
“ This has been demonstrated in some mammals and birds, but not fish.
“ The authors describe cooperative, interspecies hunting between two species of predatory fish in the Red Sea.
“ Grouper hunt in open water(pelagic zones) in day.
“ Moray eels hunt in reef crevices at night.
“ Hunting strategies are therefore complementary.
“ Hypothesis: groupers and moray eels hunt together and have greater success in shared hunts
“ Predictions: Two species spend more time near each other (duration and frequency) than is predicted by a random association model.
“ They signal each other to begin a hunt.
“ Prey catch rate is higher when grouper and eels are hunting together than when either is hunting separately.
Methods
“ Groupers were followed/observed for 406 hrs. The proportion of that time spent in association with Moray Eels was calculated and compared to chance.
“ Chance was calculated using Waser’s gas model, which predicts association durations based on independent movement.
“ Same was done for Moray Eels.
“ “Association” was defined by proximity of 10 m or fewer.
Results
“ Individuals of the two species interact more than predicted by chance
“ Individuals of the two species remain in close proximity during a hunt
“ Groupers signal eels to initiate a shared hunt with headshakes and body/fin quivering
“ Groupers that are not hungry do not signal to eels.
“ Fed fish were never observed signaling.
“ Hunt success for grouper was higher than expected when with eel, lower when without eel.
Discussion
“ This is the first demonstration of interspecific coordinated hunting in fish.
“ Both species hunt with normal strategies that happen to complement each other.
“ Possible that swallowing prey whole is key to success of relationship because competition over prey is minimized - no option for fighting or cheating.
Gelstein
Gelstein et al. (2011) Human tears contain a chemosignal
Introduction:
“ Darwin suggested that tears evolved as an emotional signal
“ Other theories suggest that tears evolved as a eye-protecting adaptation, a mechanism for removing toxins from the eyes
“ Tears are composed on proteins, enzymes, lipids, metabolytes and electrolytes
“ But human emotional tears differ in chemical composition from reflexive eye-protective tears
“ Hypothesis: human tears convey a chemosignal between humans
Methods
“ 1.Tested whether men could smell the difference between human emotional
“ tears collected from women and saline.
“ 2. Tested whether sniffing tears influences perception
“ Had men sniff jar of tears or saline and rate intensity, pleasantness and familiarity.
“ Placed pads containing tears below men’s noses and had men view emotionally -ambiguous pictures of women’s faces and rate sadness and sexual attraction.
“ Subjects also filled out a questionnaire that assessed empathy
Results
“ 1.Perception of tears and
o saline did not differ.
“ 2.Subjects rated sadness of
o pictures the same while sniffing tears and saline
“ 3. Subjects rated faces as less sexually attractive while sniffing tears than while sniffing saline
“ 4.Sniffing tears while watching a sad film resulted in reports of lower sexual arousal than while sniffing saline and watching a sad film.
“ 5. Subjects’ salivary testosterone levels decreased after sniffing tears and watching a sad film but not after sniffing saline and watching a sad film.
“ 6. In functional MRI, BOLD activity in brain regions related to sexual arousal was significantly lower in subjects who sniffed tears and watched sad films than in subjects who sniffed saline and watched sad films.
Discussion
” Tears as a chemosignal inhibit sexual arousal between male and female humans.
“ In Western culture, exposure to tears generally occurs in close proximity. Hence, the effects observed here are relevant to human behavior.
“ It is possible that tears in mammals in addition to humans serve as a chemosignals.
“ Are there signals in men’s tears, children’s tears?
Why Sex?
A female-only lizard species gives birth without having had sex; each egg has a complete set of her mother’s genes
If a female-only species can thrive, are males necessary?
The biological imperative to pass on genes
Studying asexual and sexual reproduction in Sonoran minnows to demonstrate the value of males
- sexually reproducing fish are more resistant to infestation with parasites
- The Red Queen theory: when a species stops evolving, it is doomed
- The evolutionary advantages of genetic variability among offspring
Descriptions of sperm and eggs: quantity versus quality
At a deep biological level, males and females want different things
Darwin’s theory of natural selection explained traits that improved species’ survival, but not extravagances like the peacock’s tail
- Why are ornaments typically seen on males?
- Ornaments as an indication of good genes
- Male competition and female choice, as seen in peacock mate selection
- In some species, females choose good behavioral traits or good genes
- Monogamy as a social solution to a biological dilemma
- female needs the male’s help, but the male will stay home only if he believes the chicks he’s helping to raise are his own
- Female songbirds cheating on mates to give offspring better genes
- Jacana birds and the reversal of male-female roles
- -> So many chicks are lost to crocodiles that females leave their eggs for the males to raise, and go off to reproduce again
- Gender roles determined by who competes for mates and who cares for young
- Chimpanzee society is patriarchal and violent
- Bonobo society is peaceful, due to female solidarity
- Exploring how a change in feeding ecology influenced chimpanzee and bonobo differences
- Implications for early humans, and humans today
- Evolutionary psychologists’ provocative theories about humans and our drive to reproduce
- Research into human scent and genetic compatibility
- Mate selection and the evolutionary roots of attractiveness
- Did brains evolve, in part, to attract mates?
- Humans have gone beyond the biological urge, and will raise children that do not share our genes
Genitalia – effect from sperm competition
Sperm competition is LOW in chicken and quail. Males court females.
Forced copulation is rare. Sperm competition is HIGH in ducks and geese. Multiple males mate with one female. Forced copulation is common.
Differences in sperm competition and forced copulation have led to very DIFFERENT genitalia in these groups.
==>Males have long spiraled phalluses to deliver sperm and displace rival sperm.Females have vaginal tracts spiraled in opposite direction and blind pouches to make insemination difficult and to control which male fertilizes her eggs.
Why live in groups
- Predator defense (“selfish herd”)
- Increase foraging by sharing information
- Protection from the elements
- Reproductive opportunities - mates are around!
- Cooperative childcare, hunting
Costs
- Conspicuous to predators
- Resource competition
- Transmission of disease
- Social stress
- Increased brood parasitism, threats, infanticide
Types of Social Interactions
Primarily same-sex
- Social dominance, agonistic behavior, affiliative behavior
Primarily opposite-sex
- Pair-bonding, Mating
Parent-offspring
- Pup retrieval, Licking and grooming
Antagonistic behavior
Syrian Hamsters
- Solitary species
- Highly aggressive
- Flank marking behavior
Social dominance
Major urinary protein
mouse social hierarchies
dominant males produce more
Hormones
Oxytocin and vasopressin = social recognition and pair bonding
f- oxy, vaso- males
dopamine = formation of attachments.
