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