Week 4: Questions

Question 1

Explain how the evolutionary history of our species explains each of these features:

The human testes hang outside of the body. The vas deferens or sperm duct in humans is 25 cm long, stretching up from the scrotum, curving around the pelvis, looping around the ureter, and then exiting the body at the tip of the penis.

Answer 1

Male mammals have developed an external scrotum to house the testes and keep them cooler than the rest of the body but for mammals, the testes form initially far from the scrotum just like how our nonmammalian ancestors did.

The testes descend from the top and because of this, the vas decerns loops over the ureter, the outlet tube from the bladder and settles into the circuitous route and this is due because of the legacy of early ancestors.

Question 2

Explain how the evolutionary history of our species explains each of these features:

Humans cannot produce Vitamin C and must include it in their diet to stay healthy.

Answer 2

Scurvy can happen by the lack of vitamin C in the diet. All herbal cures even from ancient times were rich in Vitamin C.

Vitamin C is made from a modified form of glucose in which the majority of mammals can produce but in humans, there is a mutation in the gene that renders the enzyme making it non-functional.

This deems this as a pseudogene.

Question 3

Explain how the evolutionary history of our species explains each of these features:

The human eye has a blind spot, caused by the fact that the optic nerve lies in front of the retina.

Answer 3

The developed over a long period of time in small steps and each step improved the eye’s ability.

The eye evolved overtime, but each new step was based on previous ones

It reflects historical constraints that led to what it is now

Question 4

Explain how the evolutionary history of our species explains each of these features:

Some humans can digest lactose as adults, while others are lactose intolerant

Answer 4

The mutation that allows lactase production to continue in adulthood is not common

Question 5

Two conditions are necessary and sufficient for natural selection to act on a population to produce evolutionary change:

Answer 5

Condition #1
There must be variation in a population with respect to a specific trait, and this variation must have a genetic (heritable) basis

Condition #2
Variant individuals must differ in the number of healthy, reproductive offspring that they produce.

Question 6

Explain how evidence from biogeography supports Darwin’s theory of evolution by natural selection.

Answer 6

Animals from the same continent were more related than those from the same habitat

A fossil species found in South America resembles current living species

This showed that species were evolving and as they gained traits that were better suitable to their habitat, they spread and moved to new parts of the continent

Question 7

Natural selection is based off three observable facts of nature:

Answer 7

1. Individuals in a population differ from one another (variation)
2. Variations are inherited (parents pass their variation to their offspring
3. In any population many more offspring are born to survive to adulthood

Certain individuals with particular variations have a greater chance of survival, therefore a greater chance of reproducing. When they reproduce, they pass their variations on to their offspring
The next generation would have a higher frequency of those variable traits and overtime, a species would become better adapted to its environment

Question 8

What variation is found in dairy farming populations with respect to the lactase persistence trait?

Answer 8

When animals who produce milk are domesticated, it is a easily accessible source of food

Those in dairy farming populations can often produce lactase so they can digest dairy since it becomes their main source of energy

Question 9

Does variation in which the lactase persistence trait have a genetic (heritable) basis?

Answer 9

Yes, those with a mutation (could produce lactase) could pass this on to their children so that they are able to consume dairy as well

Question 10

Do individuals in these populations who display lactose intolerance or the lactase persistence trait differ in the number of healthy, reproductive offspring that they produce? If so, how?

Answer 10

No because children are usually weaned off milk by a certain age anyway

Question 11

Name three other adaptations found in human populations. Explain why each trait is adaptive.

Answer 11

Morphological (i.e., a physical feature of the human body)

Adaptation of eye sockets to protect the eyes

Behavioural
Long-term parental care

Physiological (i.e., related to internal body systems such as circulation or digestion).
- Tanning of skin when exposed to the sun

Question 12

Why is it adaptive for human babies and infants to produce the enzyme lactase?

Answer 12

Because at that age, dairy is all they are able to consume to survive, so they need to be able to digest it

Question 13

Explain why it is advantageous for individuals living in populations that have domesticated dairy cows to be able to digest milk into adulthood

Answer 13

Since they have a source of dairy, that they can continue to use it as a food source throughout their life

Question 14

Do lactose-intolerant individuals have copies of a gene for the production of lactase, the enzyme responsible for digestion of lactose?

Answer 14

Yes, but they have a T instead of C on the chromosome, which causes them to not be able to digest dairy

Question 15

Figure 9.2 illustrates geographic variation in lactose intolerance. Why have both lactose persistence and lactose intolerance persisted in modern human populations?

Answer 15

In certain places around the world, animals were domesticated so they consumed dairy and built up a tolerance of it, passing this gene on to their offspring. Meanwhile, in other areas domestication did not occur so they never had to build an immunity to lactase or passed it onto their offspring

Question 16

Refer to Figure 9.19
What was the medium ground finch population on Daphne Major in 1975, before the drought? What was the medium ground finch population in 1978, after the drought?

Answer 16

1400 before, 250 after

Question 17

Refer to Figure 9.21
What was the range of beak depth of medium ground finches on Daphne Major in 1976? In 1978?

Answer 17

9.4mm in 1976, 10.1mm in 1978

Question 18

Refer to Figure 9.22
Describe the findings presented in this graph in your own words

Answer 18

As the parents’ beak depth increased, the offsprings’ beak depth increased

Question 19

Explain how this graph illustrates how the two conditions necessary for natural selection to act on the medium ground finch population to produce evolutionary change in beak depth were met on Daphne Major during the drought

Answer 19

Condition 1: there was a variation before the drought and whichever type of beak a finch had, they passed it onto their offspring

Condition 2: those with larger beaks survived because they could eat the seeds available and they were able to pass this trait on to their offspring

Question 20

Distinguish between the meaning of physical fitness and the biological term of evolutionary fitness

Answer 20

Biological fitness is the number of allele (forms of genes) an organism passes on to the next generation, while physical fitness is an individual’s ability to ensure physically challenging activities

Question 21

Explain why selection may favour behaviours that increase the survival of an individual’s close relatives, as well as behaviours that directly increase the number of healthy offspring that an individual produces.

Answer 21

In order to increase reproductive success of those who carry the same genes as us (kin selection)

Question 22

Be sure that you understand why random events such as mutation and genetic drift cause evolutionary change but do not produce adaptation of an organism to its environment.

Answer 22

These mutations are neutral so natural selection does not act upon them.

Question 23

How will natural selection act on a feature associated with a harmful mutation?

Answer 23

It will reduce the frequency of it

Question 24

On a feature associated with a beneficial mutation?

Answer 24

It will increase the frequency of it

Question 25

On a feature associated with a neutral mutation?

Answer 25

It will not act on it, but overtime its frequency will randomly change (genetic drift)

Question 26

Explain why the moose populations on Newfoundland and the Canadian mainland likely differ due to the founder effect

Answer 26

The moose moved from one location to another and started their own population and this probably continued across the province

Question 27

Are these differences adaptive, i.e., are Newfoundland moose especially well adapted to life on ‘the rock’ due to the founder effect? Explain your answer

Answer 27

Yes because an entire population started from a different genetic makeup and overtime most likely evolved based on its habitat

Question 28

Which species of snapping shrimp is most closely related to Species P4?

Answer 28

C4

Question 29

Which pair of species is most closely related: (C3 and C4) or (C1 and C2)? Explain your answer.

Answer 29

C1 and C2 because they share the same

Question 30

Explain why two sister species of snapping shrimp in the Caribbean and Pacific Oceans are more closely related than two species that live close beside each other in the same ocean

Answer 30

Because they evolved from the same ancestor, whereas the other ones may have come from somewhere else

Question 31

The moose of Newfoundland are the same species as mainland moose, but the two populations are genetically isolated. Are they isolated due to a new geographical feature or due to dispersal?

Answer 31

Dispersal because a small number of them migrated to a new habitat and formed a new population

Question 32

Why would natural selection lead to genetic divergence between two isolated populations living in very different conditions?

Answer 32

They would each evolve and gain traits that are suited to their environment, therefore their genetic makeup will vary

Question 33

What outcome would you expect for two populations that had been in similar environments?

Answer 33

They will interbreed and the populations will merge (no speciation)

Question 34

In different environments?

Answer 34

They will interbreed and speciation will occur, or they will produce a hybrid who is sterile/not adapted to either environments and will die young