Evolution Lecture 2

Question 1

Natural selection in action examples and why are they easy to study?

Answer 1

Drug resistance in pathogenic microorganisms, Pesticide resistance, Host-switching in insects. Because they can reproduce often and have strong selective pressure and short generation times.

Question 2

Selective pressure

Answer 2

An evolutionary force that increases or decreases the reproductive success of a population, which drives natural selection.

Question 3

If you are resistant then you have what?

Answer 3

A higher fitness and have more offspring.

Question 4

How does drug resistance work?

Answer 4

A drug does not create resistance pathogens, it selects for resistant individuals already in the population.

Question 5

How does Warfarin work in rats?

Answer 5

The rat poison interferes with the synthesis of blood-clotting agents. So if they get a cut, they will bled to death. Rats use vitamin K to make blood clots but it gets used up in the process. But rats have an enzyme (vitamin K epoxide reductase) to reconvert the vitamin K back into its active form, and the cycle starts again. But the warfarin blocks enzyme so the vitamin K remains in its active form.

Question 6

How do rats resist warfarin?

Answer 6

It’s a mutation in a gene that encodes the enzyme. The rats with this gene have more kids and the resistance increases rapidly in populations after poisoning programs introduced. Warfarin will work very well for a while at killing rats, then isn’t anymore.

Question 7

What happened when they stopped using warfarin?

Answer 7

The amount of rats with resistance to warfarin will go down because that variant doesn’t convert vitamin k very well so they are malnourished, meaning it’s a disadvantage to have that gene with the poison.

Question 8

Why did the resistant gene spike so quickly?

Answer 8

Because there were probably rats that already had the gene from other populations.

Question 9

Artificial system

Answer 9

When the human changes the environment.

Question 10

Artificial selection

Answer 10

When the human interferes with the breeding process.

Question 11

Soapberry bug example?

Answer 11

Soapberry bugs feed on fruit in southern Florida of original host species. These fruits are bigger, so the bugs have longer beaks to get the seeds from fruits. Then a flatter introduced fruit in central Florida becomes very common. It is difficult for the longer beaked bugs to get the seeds out of this fruit so the shorter beak is now favoured and the average beak length in population falls.

Question 12

What is the soapberry bug a good example of?

Answer 12

Directional selection

Question 13

What do the soapberry bug and drug resistance how about natural selection?

Answer 13

It’s editing rather than creating mechanism, so it needs the variation to act on.

Species that produce new generations in short periods of time, evolution by natural selection can occur rapidly.

Contingent on time and place (adaptation to the particular environment).

Question 14

Evidence for a tree-of-life, and descent with modification?

Answer 14

Homology, Biogeography, Fossil record

Question 15

Homology

Answer 15

Similarity resulting from common ancestry. It’s different versions of the same thing. Homologs are features that you see in two similar organisms, two species because they share a common ancestor.

Question 16

Forelimbs of mammals example?

Answer 16

The human, cat, whale, and bat all have similar structure despite it being used very differently. This shows how they are homologues from the same ancestor.

Question 17

Vestigial structures

Answer 17

Structures with little or no function, derived from more complex structures. In two species they have the same complex structure but only in one it’s used as it’s supposed to. The common ancestor would have the functional one and the function for it got lost for one species (but the remnant of the structure is there).

Question 18

Example of vestigial structures?

Answer 18

Remnant hind-limb bones in whales and some snakes. They have pelvic bonds despite not having hind limbs, this shows how they are descendants of mammals that had hind limbs.

Question 19

Molecular homologies

Answer 19

Homologies at the biochemical level, like proteins and DNA.

Question 20

Universal genetic code example?

Answer 20

Almost all species on earth use it, so it is very very likely that the first species on earth used it. This proves that there is only one tree of life.

Question 21

Pseudogenes Example?

Answer 21

They are molecular vestigial features. They are in genomes. It’s a false gene that can’t code a correct protein but it has too many mutations in it. So it’s present but not helpful. It’s 95% identical to the sequence of another gene somewhere that encodes a protein. Its common ancestor has the protein that works.

Question 22

Nested distributions

Answer 22

Often, nested distributions amongst organisms,
following classification based on other similarities. It’s a dominant pattern. One box is inside the other one, having a dominant pattern, rather than occurring at pattern. The most recent common ancestor has restricted distributions because not many species have it.

Question 23

Analogus structures

Answer 23

It’s the reverse of homology. Similar functions,
but no common underlying structure (similarity not from common ancestry). Similar feature arise at 2 different times.

Question 24

An example of analogous structures?

Answer 24

An eagle and dragonfly both have wings both these two structures are very different from each other. Same with sugar gliders and flying squirrels.

Question 25

Convergent evolution

Answer 25

The independent evolution of similar features in species of different periods or epochs in time.

Question 26

Biogeography

Answer 26

The geographic distribution of organisms. Some taxa (groups of similar species) are restricted to certain locations (endemic). Explanation: Descent from a common ancestor that lived in that location.

Question 27

Endemic and example?

Answer 27

Native and restricted to a certain place. Like how all species of kangaroos live on Australia this means that first species of kangaroo lived in Australia where it’s too far away to get to somewheres else.

Question 28

The Fossil Record

Answer 28

Descent with modification predicts ‘transitional forms’. Order of appearance in fossil record. It’s a more direct way of looking at past life. It’s very accurate. We can expect to see certain thing from the fossil record.

Question 29

Transitional forms

Answer 29

Any fossilized remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group.

Question 30

Examples of transitional forms?

Answer 30

Groups with major adaptations associated with an ‘unusual lifestyle’. Birds (powered flight). Whales (fully aquatic mammals) different from most mammals. The differences are there adaptations so they could live in the water.