Cycle 7 Flashcards by Diya Vyas

Reproducing sexually generates new multilocus combinations of _____

alleles

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Sexual reproduction does not create new alleles, that is _______’s job

mutation’s

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But, sex (producing gametes through meiosis and fusing) can create new ______ of diploid genotypes

combinations

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T/F Over the entire human genome, > 10^600 possible combinations of alleles

TRUE

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________: Only reproduce asexually

Obligately asexual

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Examples of obligately asexual

-Budding/binary fission
-Also in some vertebrates: unfertilized diploid eggs develop into clones of the mother

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Importance in terms of genetic ______: offspring genetically distinct from either parent and (usually) from each other

variation

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________: Can produce sexual sometimes, or asexually

Facultatively sexual

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Example of Facultatively sexual:

In some trees: Asexual vegetative propagation or sexual reproduction

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Sexually reproducing species may be _____ (equal sized gametes) or _______ (gametes either small & motile or large & immobile)

isogamous
anisogamous

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Some species can ________ (fuse gametes from the same individual to make a zygote), others cannot

self-fertilize

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Monoecy (hermaphrodism) can be ______ or _______

simultaneous or sequential

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______ species may have no distinct ‘mating type’

Isogamous

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Individuals can be _____ (separate sexes)

dioecious

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In monoecious: Each individual can produce male and female gametes at the _____ time

same

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Anisogamous species usually have ___ sexes

two

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NOW: most multicellular organisms, especially animals, reproduce ______ at least some of the time.

sexually

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Or ______ (hermaphrodites)

monoecious

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________ 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

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______: Each individual throughout their life can change sex

Once reach the threshold body size or age

sequential

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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

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2 BYA: bacteria start exchanging genes (______)

parasex

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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

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Sex is ________ (many things can go wrong)

complicated

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______: 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