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Biology 2 - Test 2 > Evolution of Sex > Flashcards

Evolution of Sex Flashcards

1
Q

Modes of Reproduction

A

Asexual and Sexual

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2
Q

Asexual Reproduction

A

Amixis - No mixing

Mitotically based reproduction with no syngamy(fusion of gametes with reduced ploidy)

  1. Colonial
  2. Clonal
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3
Q

Amixis

A

No mixing

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4
Q

Syngamy

A

Fusion of gametes with reduced ploidy

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5
Q

Asexual Reproduction:

Colonial

A

Cell division adds to existing colony

- coral reefs

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6
Q

Asexual Reproduction:

Clonal

A

Reproduction with an individual not connected to you.

  1. Budding
  2. Polyembryony
  3. Apomixis
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7
Q

Asexual Reproduction:

Clonal - Budding

A

Vegetative reproduction
- seeds fall to ground and grow

  • hydra grows a second organism on its side that splits and goes on its own way.
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8
Q

Asexual Reproduction:

Clonal - Polyembryony

A

One fertilized egg develops into multiple individuals

  • Different morphologies but start as 1 embryo
  • armadillos
  • human twins
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9
Q

Asexual Reproduction:

Clonal - Apomixis

A

Single unfertilized egg develops into adult.

  • an egg never needs sperm to come in and fertilize.
  • typically there used to be reproduction but the female population decided to get rid of males.
  • males are unnecessary from a biological perspective
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10
Q

Sexual(mixis) Reproduction

A

Meiotic reduction of ploidy followed by syngamy.

  1. Automixis
  2. Amphimixis
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11
Q

Mixis

A

Mixing of genes

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12
Q

Sexual(mixis) Reproduction:

Automixis

A

Syngamy within the same parent

  • syngamy within mother fuse and creates a new offspring that is diploid
  • shuffled the genome still which means it is not a clone
  • being Asexual without partner BUT still sexual as you are shuffling your own genome.
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13
Q

Sexual(mixis) Reproduction:

Amphimixis

A

Syngamy between parents.

  • two sexes each produce a miotically reduced gamete which then come together in syngamy to produce diploid offspring.
  • Human reproduction
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14
Q

When did sex evolve?

A

Proterozoic Eon.

1.2 BYA.

Bacteria and Archaea did not engage in sexual reproduction.

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15
Q

How did sex evolve?

A

Unknown.

3 working models:

  1. DNA repair strategy(of single chromosome organisms)
  2. Selfish Genetic Elements
  3. Transformation(bacterial)
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16
Q

How did sex evolve?

DNA repair strategy(of single chromosome organisms)

A

Like crossing over except for DNA repair.

Holiday junction resolution.

Haploid genome

  • Grab another strand of DNA and borrow it to fix yours but some crossing over happens
17
Q

How did sex evolve?

Selfish genetic elements

A

Bacterial conjunction is one way in which sex began.

  • must have an F factor to create a “sex pilius”(grabs hold of another bacteria and wont let go)
  • In the process F factor leaves the plasmid copy so genetic material is swapping and the new plasmid containing bacteria can go on and repeat the process to others.
18
Q

How did sex evolve?

Transformation(bacterial)

A

Upon stressful conditions, bacteria incorporate foreign DNA into genome.

  • Stress induce bacteria to go through transformations.
  • grab “naked” DNA and insert randomly into genome to attempt to survive the stress via recombinant chromosome.
19
Q

Asexual VS Sexual reproduction

A

Asexual always chosen UNLESS stress forces Sexual.

20
Q

The Cost of Sex

A

Most common reproduction mode among animals but comes with significant costs compared to Asexuality.

  1. Cost of Males
  2. Cost of Meiosis
21
Q

The Cost of Sex:

Costs of Males

A

Asexual reproduction produces twice as many offspring as sex.

  • 2 partners to create 1 offspring
  • Asexual population grows exponentially
  • males create a disadvantage in the ratio of offspring produced
22
Q

The Cost of Sex:

Costs of Meiosis

A
  • recombination breaks apart co-adapted gene complexes

- co-adapted genes work well together in certain environments and meiosis destroys this

23
Q

Why Did Sex Evolve?(and how its currently maintained)

A

Advantages

  1. DNA Repair
  2. Purge Deleterious Mutations
  3. Promote Genetic Variation
24
Q

Why Did Sex Evolve?(and how its currently maintained):

DNA Repair

A
  • Allows the repair of damaged DNA by using one of the two chromosomes as a template
  • Damage occurs at a rate of 1,000 to 1,000,000 molecular lesions per cell per day.
  • Double stranded breaks are bad
25
Why Did Sex Evolve?(and how its currently maintained): Purge Deleterious Mutations
1. Muller's Ratchet - as asexual individuals multiply, deleterious(harmful) mutations accumulate. - over time this creates an unfit individual. - Sex allows deleterious mutations to be removed from the genome. - Must get rid of increasingly deleterious mutations - fit individuals outcompete those with deleterious mutations and thus removes them from the population.
26
Why Did Sex Evolve?(and how its currently maintained): Promote Genetic Variation
Similar to Muller's Ratchet. 1. Increases the rate of adaptive evolution. 2. Increases offspring diversity to exploit/defend against temporally heterogeneous environments. 3. Increases offspring diversity to exploit spatially heterogeneous environments. 4. Allows progeny to either escape of escalate an antagonistic co-evolutionary dynamic(Red Queen Hypothesis)
27
Why Did Sex Evolve?(and how its currently maintained): Purge Deleterious Mutations Muller's Ratchet
as asexual individuals multiply, deleterious(harmful) mutations accumulate. - over time this creates an unfit individual.
28
Why Did Sex Evolve?(and how its currently maintained): Promote Genetic Variation: Increase rate of adaptive evolution
Brings together beneficial alleles in fewer geneations. - genes A, B, and C come together much quicker than Asexual reproduction.
29
Why Did Sex Evolve?(and how its currently maintained): Promote Genetic Variation: Increases offspring diversity to exploit/defend against temporally heterogeneous environments.
Tomorrow is a mystery. - produce more offspring than the environment can handle to increase diversity. - those fit for tomorrows environment will flourish while the unfit die off. - Asexual are either really fit or really unfit for an environment AND can not adapt quickly enough to change.
30
Why Did Sex Evolve?(and how its currently maintained): Promote Genetic Variation: Increases offspring diversity to exploit spatially heterogeneous environments.
Entangled Bank - so much competition of species requires development of specific niche to survive. - Sex allows this diversification to happen where Asexual does not. - Sex has a greater "Niche Breadth"(ways to exploit a niche) than Asexual.
31
Why Did Sex Evolve?(and how its currently maintained): Promote Genetic Variation: (Red Queen Hypothesis) Allows progeny to either escape of escalate an antagonistic co-evolutionary dynamic
- it takes all the evolution we can do to keep everything else at bay - to stay ontop you keep evolving or die - Stable limit cycle - fluctuation of parasite VS host as the constant recombination of alleles swings the fight in favor of one and then the other as they adapt to each other - Co-evolutionary dynamic Example: - Snails reproduce Asexual without parasites as it is more efficient(more offspring). - When parasites present, snails produce Sexually to recombine the genome and produce offspring who can survive the parasites. - Escape the weaknesses the parasites are exploiting.
32
Entangled Bank
so much competition of species requires development of specific niche to survive.
33
Niche Breadth
Sex has a greater "Niche Breadth"(ways to exploit a niche) than Asexual. = higher likelihood of survival
34
Eukaryotes tend to be _______.
The vast majority are Sexual.
35
Persistence of Sex
- Asexuality is great in the short term but terrible in the long term due to environment instability. - Stressful Situations force the necessity for sex.
36
Persistence of Sex: Why do Asexual lineages continue to erupt from Sexual lineages?
- Asexuality is great in the short term but terrible in the long term due to environment instability. - Stable environments promote Asexuality - Produce offspring quickly and exploit the niche - BUT if the environment changes the entire species goes extinct.
37
Persistence of Sex: Stressful Situations
Sexual reproduction happens to hope one of the offspring will survive the stress. - you don't have the genome to survive so you adapt
38
How do you force something to go from Asexual to Sexual reproduction?
Take away its food. Imminent death = great necessity to change ASAP.
39
"Best Man Hypothesis"
Asexual progeny have a higher mean fitness in one environment. however, environments are temporally unpredictable. Thus, progeny diversity is highly adaptive. Asexual higher in one environment. Sexual greater survival in variety of environments.

Biology 2 - Test 2 (14 decks)

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