Evolution and Genetics of Animal Species

Question 1

What is the Red Queen Hypothesis?

Answer 1

• Species are in a constant struggle against each other
• Continual extinction and replacement
• Regarding adaptations - the environment can be thought of as constantly deteriorating
• Adaptations that are beneficial at one time will not be in another
• Fitness will deteriorate when the balance of pressures change

Question 2

Name 4 different genetic systems

Answer 2

• Sexual reproduction
• Parthenogenesis
• Simultaneous hermaphroditism
• Protandrous sequential hermaphroditism

Question 3

Give examples of how sex is “costly”

Answer 3

• Reproductive interference

- Death and disease

Question 4

Give an example of the benefits of sex. How is this dependent on timescale?

Answer 4

• Strong selective pressures maintain recombination
• Can see benefits relatively quickly
• Selective forces such as these could increase the frequency of an allele that elicits higher recombination relative to one that elicits low recombination

Question 5

The main hypothesis as to why separate sexes developed so as to avoid self-fertilisation, which can lead to low fitness offspring, which are exposed to deleterious alleles. What is the name of this?

Answer 5

Inbreeding depression

Question 6

Briefly describe sex determination in clownfish

Answer 6

• Group tends to be one breeding pair & 4 non-breeders
• The breeding female is dominant
• If the female of the breeding pair dies or disappears, the breeding male becomes female
• Males and non-breeders possess bisexual gonads with co-existing mature testicular and immature ovarian tissues, whereas the gonads of females contain only ovarian tissues
• Female fish are born XX, male fish are born XY but can change sex.

Question 7

What are the three different levels of selection?

Answer 7

• Individual level natural selection; occurs because some individuals have higher fitness than others
• Group selection; defined as the evolution of certain traits because they decrease the chance of a population going extinct
• Kin selection; evolution of traits because they are passed on by relatives of individuals who express the traits

Question 8

What is the Wynne Edwards theory?

Answer 8

• Animals that helped, or failed to mate, did so for the “benefit” of the group, therefore such behaviours increased “survivorship” of groups whose members acted selflessly
• Selection occurs at GROUP level

Question 9

Why invoke group selection?

Answer 9

• Animals should behave selfishly & maximise reproduction - Darwin
• But some traits not explained by individual level selection

Question 10

Briefly describe Kin selection

Answer 10

• Sexually reproducing organisms do NOT produce replicas of themselves, but transmit part of their genome to offspring
• Gene copies are not only shared between parents & offspring but also with RELATIVES by descent
• An individual may act altruistically, even at great risk to itself if, by helping relatives, helps increase its alleles in gene pool & hence inclusive fitness of helpers

Question 11

What is inclusive fitness?

Answer 11

Number of individuals’ alleles passed onto future generations