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Lecture 9

PSY352H5 Lecture Notes - Lecture 9: Genetic Recombination, Secondary Sex Characteristic, Vasopressin


Department
Psychology
Course Code
PSY352H5
Professor
Robert Gerlai
Lecture
9

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Friday, March 28, 2014
Lecture on Reproduction
REPRODUCTIVE BEHAVIOUR: PASSING ON YOUR GENES
-Reproductive behaviours are perhaps the most important from an evolutionary sense,
there is very strong selection pressure
they directly affect fitness, fitness is the number of offsprings produced that reach
sexual maturity, given the crucial importance of reproductive success, reproductive
behaviours are under strong selection pressure
-Why are there two genders and why do we have sex at all?
evolution is not about the population, but about what is good for an individual!
variability comes with costs, some of the species are not as good as you, so why
do you want to pair with someone else? The environment is not the same, it
changes all the time so your characteristics may not be always the best - so if you
just reproduce yourself you will lock your genetic make up without possible
adaptation. However, we need to acknowledge that evolution does not have any
future goal, it is only about what is the best for an individual in the present.
If all offsprings are identical without any change they can die out because it would
not be able to adapt to the environment. So if there is variability among offsprings,
at least some of them will be able to survive
your offsprings do carry your genes, but not only your genes, and that is what allow
them do be able to adapt to the changing environment
variability is advantage from the evolutionary perspective
sex is costly: energy and time to find the right mate, competition among members
of the same gender, it takes a lot of effort and time to reproduce and while the
animal is mating is not able to pay attention to predators or to find food, so bringing
new offsprings is very costly —> so we see how it is very important
-There must be some evolutionary advantage behind sexual reproduction
genetic recombination: increased genetic variance and increased flexibility (ex.
better adaptation to environmental change)
-Strong selection pressure on reproductive behaviours: it is very important from the
evolutionary perspective and that is why those behaviours are very fixed and complex
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Friday, March 28, 2014
reduced genetic variance in reproductive behaviour
reduced phenotypical variability making reproductive behavioural responses more
uniform (fewer surprises when encountering opposite gender)
species-specific behaviour
fixed action patterns
-Mate selection and courtship:
proper identification of the correct species: for us it is easy to choose the right
specie, but for animals it is little bit hard, when we think about fishes, there are
billion of different species and how do they know to identify the right specie? It is
critical because if the specie is not correct it will result in some mutations
selection of the best “fittest” mate: once you choose the best mate possible you are
also guaranteeing good fitness for your offsprings
synchronization of partners is crucial for reproduction, you need to persuade the
mate to mate which you and it depends on many factors such as season, food…
-Mating Systems of reproductive strategies, there are several different ones:
monogamy (1 male and 1 female): monogamy is quite rare in animal kingdom
polygamy (1 partner with many): more frequent in the animal kingdom
-polygyny (1 male with many females): this is the most frequent, most dominant
form of reproduction
-polyandry (1 female many males)
-polygynandry (many males with many females)
-Gender dependent differences in reproductive strategies
parental investment theory
-female and male appear to have highly different reproductive strategies
-many species, including our own, the female seems to be more choosy than
male, female prefers to wait, prefers to select the best male, often refuses
advances from the other males, and once they choose the are more faithful
-on the other hand, males are less choosy, they want to mate with as many
females as possible and as often as possible, and are less faithful
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Friday, March 28, 2014
-PARENTAL INVESTMENT THEORY: where do these differences come from?
ANISOGAMY:
-female’s investment is large: egg is costly to make (it is very complex cell,
including cytoplasms and stuffs), fry, chick, pup, baby….all require large
“investment” including a lot of energy and time from mother, mother is trapped in
pregnancy, and then in caring about offsprings and cannot only leave from baby
-male’s investment is small: sperm is less costly to make (small cell without
cytoplasm), male can walk away from offspring (no biological costs)
-so that is why female and male have very different reproductive strategies
-Inequality in costs of reproduction means gender dependent differential selection
if female posses genetic predisposition to choose wrong male that is not enough fit,
then they work against their own fitness, so that is why they wait longer to choose
the correct male —> females has to make sure her offsprings gets the best genes
on the other hand, males do not need to care, male only needs to make sure his
genes are past to the largest number of offsprings
-Gender dependent differential selection leads to gender specific reproductive
strategies:
the best way females can maximize their reproductive success is to get the best
male genome for their offspring: do not rush, throughly search for the best male
on the other hand the best way males can maximize their reproductive success is
to inseminate as many eggs as possible: sperm is cheap
-Most typical result of the different gender specific reproductive strategies:
so that is why the polygyny (one dominant male with many females) is the most
popular among animal kingdom —> those decisions are of course not an conscious
decisions, those are instincts, and the particular male appears better for female.
Female does not care if male reproduce with more females because they just care
about the best male possible
on the other hand there is strong male-male competition, males cannot tolerate
other males around
females tend to be less colourful, less conspicuous, generally those are males who
are more colourful, have better feather and that is because large selective pressure
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