Cycle 7 Flashcards
Reproducing sexually generates new multilocus combinations of _____
alleles
Sexual reproduction does not create new alleles, that is _______’s job
mutation’s
But, sex (producing gametes through meiosis and fusing) can create new ______ of diploid genotypes
combinations
T/F Over the entire human genome, > 10^600 possible combinations of alleles
TRUE
________: Only reproduce asexually
Obligately asexual
Examples of obligately asexual
-Budding/binary fission
-Also in some vertebrates: unfertilized diploid eggs develop into clones of the mother
Importance in terms of genetic ______: offspring genetically distinct from either parent and (usually) from each other
variation
________: Can produce sexual sometimes, or asexually
Facultatively sexual
Example of Facultatively sexual:
In some trees: Asexual vegetative propagation or sexual reproduction
Sexually reproducing species may be _____ (equal sized gametes) or _______ (gametes either small & motile or large & immobile)
isogamous
anisogamous
Some species can ________ (fuse gametes from the same individual to make a zygote), others cannot
self-fertilize
Monoecy (hermaphrodism) can be ______ or _______
simultaneous or sequential
______ species may have no distinct ‘mating type’
Isogamous
Individuals can be _____ (separate sexes)
dioecious
In monoecious: Each individual can produce male and female gametes at the _____ time
same
Anisogamous species usually have ___ sexes
two
NOW: most multicellular organisms, especially animals, reproduce ______ at least some of the time.
sexually
Or ______ (hermaphrodites)
monoecious
________ on the y-axis and ___ on the x-axis - the slope is positive meaning the bigger you are the more successful you’re at reproduction
reproductive success, size
______: Each individual throughout their life can change sex
Once reach the threshold body size or age
sequential
When should an individual be male, and when should they be female? (In what conditions should selection favor being male vs female?)
Size advantage model of sex change
2 BYA: bacteria start exchanging genes (______)
parasex
Sometimes sex seems like a bad idea…
(3 reasons)
Cost of mating: finding a mate is time-consuming and often risky
Cost of males: in most sexual species, only females can “grow” the population
Cost of meiosis: only pass half of your alleles to offspring
Sex is ________ (many things can go wrong)
complicated
______: M to F
Protandry
______: F to M
Protogny
3.5 BYA: the first cells reproduced _______
asexually
Obligately ______ animals are rare and extinction-prone
asexual
Without sex, deleterious mutations _______ in the population
accumulate
1.2 BYA: ________ appears (specialized gametes, formed by meiosis, fuse to create a diploid zygote)
eukaryotic sex
______ are unlikely to be able to infect new (rare) host genotypes
Parasites
BUT bdelloid rotifers have been ________ for > 40 mya and still have not gone extinct
obligatory asexual
Why is sex so widespread?
One explanation for the persistence of sex:
Over the long term, sexual recombination benefits the population by getting rid of harmful ______
mutations
__________: keeping up with other species (much better supported)
Evolutionary arms races
______ principle: running to stay in the same place
Red Queen
___ “breaks the ratchet” by creating new genotypes:
Sex
Some have even more deleterious ______, but some (‘rubies in the rubbish’) have fewer
mutations
When is it advantageous to produce a diverse variety of offspring genotypes?
_________: more sex in unpredictable environments, less sex in stable environments (not well supported)
Lottery principle
Another explanation for the persistence of sex:
Immediate benefits in certain ________
environments
Reproducing sexually allows producing new and rare combinations of _____
alleles
In many animals, members of one sex (usually _____) have exaggerated and costly traits that may reduce survival.
males
_____ _____ favors traits that increase mating success
Sexual selection
Sexual Selection: That is, traits that improve the ability to attract or compete for ____
mates
Competing for access to mates, or, individuals of the choosy sex select mates in two ways: first ______ selection which is Direct competition
Intrasexual selection
_______ selection: Choice
Intersexual
Usually, but not always, males are the competing sex and females are the choosy sex… why? ______ places different selection pressures on males and females
Angiosamy
In The Mating Game: Which player will probably win the mating game?
The highest quality male
The highest quality female
The male with the lowest standards
The female with the highest standards
All the players have an equal shot of winning
The highest quality male
Which player will probably lose the mating game?
The lowest-quality male
The lowest-quality female
Tie between the lowest quality male and the lowest quality female
The player with the lowest standards
The mating game is so much fun that really, there are no losers
The lowest-quality male
When playing the Mating game, which sex has a higher fitness ON AVERAGE
Males
Females
Average fitness is equal for both sexes
Average fitness is equal for both sexes
When playing the Mating game, which sex has a higher POTENTIAL fitness?
Males
Females
Average fitness is equal for both sexes
Males (more variation/spread, more opportunity to contribute)
Not the same for females (because we are constrained by how many eggs we can produce): Increasing fitness for females by…
mating with good quality males rather than more mates
Why be choosy? (3)
-Direct benefits (attractive mates are good parents)
Food, territory, protection
-Indirect benefits (attractive mates have good genes)
Offspring survival
-Sexy sons/a taste of beautiful (attractive mates produce attractive offspring)
Selective forces on males and females
How can males best increase their fitness?
More mates for males
______ fitness is higher in males
Potential
On _____ the same fitness between sex
average
Males may have different _____ for long-term vs. short-term mates
standards
Females may have different _____ for long-term vs short-term mates
priorities
Sex differences in _______ and _______ determine which sex competes and which sex chooses
parental investment and potential fitness
What if both sexes invest heavily in parental care?
Sexual selection still happens, but both sexes compete
Mating preferences in humans?
What qualities are attractive in a partner?
Atratcve human: symmetry
