Unit 2 Lecture 9

Question 1

What percentage of people worldwide is lactose intolerant?

Answer 1

70%

Question 2

How do we digest lactate (milk)?

Answer 2

We have an enzyme called lactase which is what digests milk

70% of adults stop producing this enzyme so they are unable to drink milk

Question 3

What is Culture-Gene Hypothesis

Answer 3

Our cultural changes (famine) led to evolutionary changes in our genes (and vise versa)
- If adults could digest milk, it could help during famine… but only in cultures that had domesticated cattle
- This advantage could lead to more intensive hoarding

Question 4

What does Selective Sweep Mean?

Answer 4

Linked genes increase in frequency together when selection happens faster than recombination
- refers to a process by which a new advantageous mutation eliminates or reduces variation in linked neutral sites as it increases in frequency in the population (Nielsen et al., 2005). This phenomenon is also called “genetic hitchhiking”

Question 5

What are the two genetic variants responsible for lactose tolerance?

Answer 5

1. G>C-14010 common in Saudi Arabia, Middle East, and Africa
2. C>T-13910 common in Europe and parts of Asia

Question 6

Were people in the past lactose tolerant or intolerant?

Answer 6

intolerant, bones showed this from over 6,500 years ago

Question 7

Hotspots of lactose tolerance matches up with what?

Answer 7

Cattle domestication

Question 8

Why do we think lactose tolerance started to persist (specifically in Europe)

Answer 8

There was negative selection against lactose intolerance during times of famine

Question 9

What was the general study of cliff swallow?

Answer 9

Cliff swallows either had large wings (less mobile) or small wings (more mobile and able to maneuver past cars)

Question 10

Originally in 1984, the individuals who were getting killed by cars had _____ wings and over time they got ______

Answer 10

Short; Shorter

Question 11

What accounts for the decreased number of road kills over time?

Answer 11

Selection removed individuals who had lower wing loadings (less maneuverable)
- We did not create this selection; it happened on accident/naturally

Question 12

What is an example of humans as agents of selection

Answer 12

Selection on different parts of B. Oleracea has resulted in different foods:
- Flowers –> broccoli and cauliflower
- Buds –> brussel sprouts
- Leaves –> cabbage and kale
- Stems –> Kohirabi

Question 13

Name more examples of humans as agents of selection

Answer 13

We have selected for all of these:
1. Wheat and rice the plant will normally shatter when the plants are ready and scatter through the wing
- humans selected for plants similar to wheat and rice that didn’t shatter so they could control it more
2. Tomatoes
3. Corn
4. Sunflower

Question 14

Explain the study of the resistance to insecticides by houseflies

Answer 14

Humans caused evolution of resistance of insecticides
- (in the graph) the red lines show the first introduction of a particular insecticide and the end of the use of the insecticide
- Triangle represents the first population of houseflies were resistance, and R shows when more of the population was resistant
We continually had to swap out and use different insecticides over the course of 40 years due to the houseflies developing a resistance to them

Question 15

Explain the study of EPSPS enzyme leading to roundup resistance

Answer 15

This enzyme was widespread in plants so researchers assumed it would be a good target
- They had their herbicide target this enzyme and made crops that were resistant to this herbicide (worked at first)
- Farmers started seeing these weeds coming back in their fields evolved a mutation to this EPSPS mutation that made it resistant to the herbicide

Question 16

Explain the study with the creation of BT

Answer 16

• Crops with Bt gene make their own pesticides so when bugs try to eat the crops , the bugs would die
• In fields that are BT free, those bugs who are not resistant to it are more fit and proliferate
• In fields that have BT crops, those bugs are resistant to it and are more fit and proliferate

Question 17

Explain the Cane Toad study

Answer 17

Cane toads were introduced to Australia in 1930s to get rid of the pest desiccating the cane field
- Someone got 100 toads and set them free and now there are billions of frogs, and there are still a lot of pests because the frogs never ate them
- Soon there was a selection of larger snakes with smaller gape sizes so they are able to eat cane toads that aren’t too large (since they’re toxic)

Question 18

Why are male horns getting shorter and shorter?

Answer 18

Because of trophy hunting we keep killing the rams with bigger horns, making a selection for smaller horns now

Question 19

How is the male horns study an example of negative selection differential ? Heritability > 0

Answer 19

-Because horn size is decreasing even though larger horn size is normally selected for
- If horn length were not heritable, it would not matter that we are removing the largest individuals from the population because they would not be passing genes for horn length on so we wouldn’t be seeing this decrease in horn length

Question 20

How has cod fishing influenced their history?

Answer 20

They are reaching sexual maturity at younger ages and younger sizes
- they are not going to be as reproductively successful as larger fish, because of this the population is declining