cycle 7

Question 1

what is sex?

Answer 1

sex is the exchange of genetic material.

Question 2

How does sex work in sexual organisms

Answer 2

In sexually reproducing organisms, gametes fuse to generate new combinations of alleles in the off-spring

• typical of animals and plants, most eukaryotes
• for example in humans through sex and combination there are more than 10^600 allele combination, which is why no two humans are identical

Question 3

how does sex work in asexual organisms?

Answer 3

In asexually reproducing organisms, sex can happen by acquiring DNA from another organism or their environment
- typical in bacteria and archaea

Question 4

what is the name of sexual reproduction with two organisms?

Answer 4

Individuals have separate sexes and need a pair= dioecious (ie. two house)
E.g humans, lions

Question 5

what is the name of sexual reproduction with one organism?

Answer 5

Individuals are both sexes = monoecious (one house)

= hermaphrodites (animals)

Question 6

what is typical of sex in plants?

Answer 6

• plants are monoecious and each individual develops the reproductive tissue of both sexes

Question 7

what is atypical of sex in animals?

Answer 7

• hermaphrodites
• Simultaneous: simultaneously male and female
• E.g earthworms, individuals have ovaries and testes
• Sequential: starts as one sex and develops into another
• E.g bluehead wrasse, starts as female (yellow), if the dominant male dies, a female will become male
  E.g clownfish male can become female

Question 8

When sex changes occur how does an individual know when it should be female and when it should be male?

Answer 8

= size advantage model
- in protogyny start as female, since the small size has more eggs, but when size grow more reproductive success as male, so you transition
- protandry first male then female
(Gamete production is lower when a smaller female, but with time egg production ability gets bigger when female so you change.)

Question 9

explain the rarer types of sex occurring in ekaryotes? What type of species?

Answer 9

• Usually single celled eukaryotes called protist
• Have different mating types(at least 2+)
• Gametes of different mating types fuse
• Exchange nuclei between mating types

Question 10

Which type of reproduction does not involve sex?

Answer 10

• asexual reproduction
• the new individuals are clones and are genetically identical, this means there has been no sex and no exchange of genetic material
• Ex. pieces of potato plant, tuber can be planted and new individuals will grow
• Ex. strawberries produce runners that produce new roots and new individuals plants can grow that are exact copies

Question 11

What is asexual reproduction in animals?

Answer 11

• pathogenesis
  Methods
  1) offspring can develop from unfertilized diploid egg (are clones)
  2) meiosis can occur in DNA of haploid egg that will replicate and go from haploid to diploid egg (not clones)
• ex. hammerhead sharks

Question 12

How does asexual reproduction work in unicellular organisms?

Answer 12

• divide to reproduce
  ~occurs in bacteria and archaea via binary fission
  ~or in unicellular eukaryotes where they divide by mitosis
• produces clones

Question 13

how does sex in bacteria and archaea work?

Answer 13

• They reproduce asexually, but they can undergo genetic exchange between individuals: = SEX
• eg. bacterial conjugation occurs by transferring plasmids (circular bits of chromosomes inside cell) through conjugation into another cell), you can can also have DNA from other organism go into cell),or have DNA from virus grab DNA from bacteria and transfer DNA into another cell.

Question 14

What are the limitations of sex?

Answer 14

sex is costly, sex is risky, sex is inefficient

Question 15

why is sex risky?

Answer 15

• Finding a mate is time-consuming, takes resources

- In search exposed to predation, at higher risk of sexually transmitted disease

Question 16

why is sex costly?

Answer 16

• Only ½ of genetic material is inherited
• For every generation, sexual individuals pass on 2 times less of their genetic material
• Two fold cost of sex

Question 17

Why is sex inefficnet?

Answer 17

• Producing males reduces reproductive output
• Only females “grow” new off-spring, so males(only bring sperm) do not add to the population
• Asexual populations grow faster

Question 18

So if sex is risky, costly and inefficient why did sex evolve?

Answer 18

• must of been evolutionary benefits, sex introduces greater population variation, which in turn means there can be greater adaptability (ie. can adapt quicker to new environments), and make better combination of alleles)

Question 19

How does sex generate variation?

Answer 19

• sex generates the variation not possible through asexual reproduction
• get gene exchange, independent assortment of chromosomes, recombination, fusions of maternal and paternal chromosomes (get the new combination of alleles)
• thus offspring are genetically distinct from both parents

Question 20

What is the lottery model?

Answer 20

• sexual populations have greater diversity of offspring increased probability of some offspring surviving/having favourable phenotypes

Question 21

What are the advantages of sex and alleles?

Answer 21

• by lottery sex can bring beneficial alleles of different genes together
• Sex makes it easier to remove “bad” allele. If by lottery independent assortment brings all the bad alleles together this result in a very low fitness that is easily selected against and removed

Question 22

what is the summary explanation for why there is sex?

Answer 22

• life started out through asexual division
• most life forms engage in some form of sex, in many different ways, so it must be a good thing
• the benefits must have outweighed the costs for sex to have evolved
• generates diversity – better chance at lottery
• makes new and improved combinations of alleles
• generates genotypes of higher fitness more quickly
• makes it easier to remove “bad” alleles

Question 23

Do asexual organism have the ability to bring beneficial alleles together?

Answer 23

• to start all organisms have decent fitness, but have unique genetic variations:
• beneficial variants (1,2,3) cannot be combined together in asexual reproduction… = clonal interference
• unless there is sex: you can Exchange 1 and 2, Exchange again 1+2 hybrid and 3 then generate offspring that have most beneficial combination

Question 24

What is sexual selection in animals?

Answer 24

• Struggle for mates
• Traits favoured are those that increase mating success, increase individual fitness
• Can result in exaggerated traits that can reduce survival
  Ex. lions big with big mane

Question 25

what is intersexual selection?

Answer 25

• one sex chooses= mate choice
• animals it is usually females that chooses mates based on display and physical traits from males
• males compete to gain female’s attention

Question 26

What are examples of traits that have evolved due to intersexual selection?
what are the displays/ornamentation animals can have?

Answer 26

• elaborate courtship displays/calls
• Ornamentation
• Ex. peahens vs peacocks, the male peacocks have very elaborate feathers. Cumbersome since not as agile
• Bowerbirds: make display nests. Cumbersome because time consuming and only built to attract woman
• Peacock spider: have mating dance

Question 27

Which sex chooses?

Answer 27

• Sex that invest more parental care is usually the chooser
• sex that has relatively fewer contributions to the next generation is choosier
• Why? must be selective to ensure quality of off-spring
• Thus females are usually the “choosier” sex

Question 28

what is intrasexual selection?

Answer 28

• individuals of one sex compete amongst themselves for mates of the opposite sex
• Ex. fighting of elk (antlers bonking) or stag beetles

Question 29

what are the results of intrasexual selection?

Answer 29

• Males monopolize access to females
• Do this by outcompeting rivals or controlling a resource that is important to females, eg. food, territory, thus enabling direct control of females
• Ex. bowerbirds have intraselection as well since they are trying to outperform and outcompete other males

Question 30

How do females have intraselction?

Answer 30

• Females can compete with each other too
  for territory, for access to mates, for resources
• Nature of competition different

Question 31

what is sperm competition?

Answer 31

• A more discrete type if competition
• swimming speed – fastest sperm to get to the egg
• scrapers - scrape out sperm deposited by other males
  Ex. dragonflies, male can mate with females again and scrape out other men’s sperm. Now only his sperm is there
• mating plugs - after mating, leave a plug to prevent other males from mating
  Ex. moths

Question 32

What are the results of the mating game?

Answer 32

• male of highest fitness wins the mating game and produces the most offspring
• Male lowest fitness loses the game and has no offspring
• Males have higher potential fitness
• Females, have minimal deviation from mean with highest fitness only having slightly more offspring. This is because females are removed from the mating game when rearing offspring. So the other females of lower fitness have opportunities to mate
• Average fitness is the same for both sexes
• males and females have difference in choice and strategy

Question 33

conclusion on males from mating game

Answer 33

• reproduction is mainly limited by access to females
• individual fitness can vary widely
• higher potential fitness

Question 34

conclusions on female from the mating game

Answer 34

• have limited gametes, must spend time growing and rearing offspring
• must choose mates wisely(limited opportunities) to maximize the quality of their offspring
• individual fitness often closer to the mean

Question 35

What are the benefits of being choosy with reproduction?

Answer 35

Direct benefits
- attractive individuals are good parents (ie. more chance offspring survives)
- can gain food, territory, protection for offspring
E.g giving nuptial gift of fly for female to eat
Indirect benefits
- attractive individuals have good alleles (lower chance of parasites)
- improve survival or attractiveness of offspring

Question 36

what is sexual dimorphism?

Answer 36

• when sexual selection gets very strong
• different sexes have distinct differences in size or appearance
• oftentimes males will get bigger and brighter in colour

Question 37

why are males usually more affected by sexual dimorphism?

Answer 37

• dimorphism is impacted by the relative role in parental care
• males will oftentimes have lower parental investment

Question 38

why do females usually provide the most parental care? And what are the results?

Answer 38

• when rearing offspring females become unavailable for reproduction, (less opportunities)
• male competition for females is high
• males under stronger sexual selection
• ex. grizzly bear

Question 39

What happens when males provide the most parental care?

Answer 39

• availability of males is limited, males can be choosy
• females under stronger sexual selection
  (will become more showy)
• Ex. male seahorse, females deposit fertilized eggs in male pouch, and he is the one that gives birth to the babies,
• ex. red phalaropes (females big and red, since they defend territory while the males care for offspring)

Question 40

What happens when both sexes invest heavily in parental care?

Answer 40

• this is biparental care
• males and females removed from seeking additional mating opportunities (spend time caring for offspring)
• both sexes compete for mates, both sexes choosy
• sexual selection acts on both sexes, little to no dimorphism
• Ex. humans and emperor penguins

Question 41

IS there sexual dimorphism in humans? what is selected for?

Answer 41

• still some sexual dimorphism
• What traits are selected? Is it beauty, intelligence, wealth, parenting skills? Difference in choices long term vs short term?