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BIOL1010/1011 > Evolution: Lecture 2 > Flashcards

Evolution: Lecture 2 Flashcards

1
Q

Examples of natural selection?

A
  • Drug resistance in pathogenic microorganisms (cause disease)
  • Pesticide resistance
  • Host-switching in insects (feed on plants and go from one to another)
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2
Q

Are these the only systems where we observe natural selection?

A

No, we can see many other systems that have natural selection in them.

  • These are just more convenient systems to study for biologists.
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3
Q

Why are they more convenient?

A

They are more convenient due to:

  • Strong selective pressure (more resistant populations)
  • Short generation times as they are easier for longevity (one biologist can carry out the entire study).
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4
Q

What is selective pressure?

A

A selective pressure is any reason for organisms with certain characters to have either a survival benefit or disadvantage.

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5
Q

Example of selective pressure?

A

People with darker skin have an advantage in the sun when compared to people with lighter skin.

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6
Q

What is warfarin and when was it done?

A

Warfarin is a rat poison (pesticide) that has been used since the 1950’s, being laced into rat baits.

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7
Q

What does Warfarin do?

A

Warfarin interferes with synthesis of
blood-clotting agents which causes bleeding which causes death.

  • A few days after exposure, there are no blood clotting factors left.
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8
Q

Effect of Warfarin?

A

A small cut or spontaneous bleed will cause the rat to bleed out and die.

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9
Q

What is Warfarin actually doing?

A

It is interfering with and enzyme that regenerates inactive K vitamins, which are used to produce blood clotting agents.

  • Vitamin K is used up then regenerated in the process of making blood clotting agents but they cannot work without the enzyme which is impacted by warfarin.
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10
Q

What is associated with warfarin resistance?

A

Mutation(s) in a gene that encodes VKORC1 are associated with warfarin resistance.

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11
Q

What does this mutation in VKORC1 actually do?

A

The mutation makes an amino acid change that blocks the effect of warfarin, therefore only a higher dose will do damage to the rat.

  • This is associated with increased warfarin resistance.
  • There is a lower chance of a resistant rat consuming a high enough dose to become sick.
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12
Q

How does resistance increase?

A

Resistance increases rapidly in populations after poisoning programs were introduced.

  • Poison works well at first but quickly resistance will increase.
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13
Q

Why does resistance increase so fast?

A

A much larger proportion can become tolerant because resistant rats can have more children (more fitness = more offspring).

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14
Q

What do we see from the graph showing poison resistance?

A

When the poison was introduced, the percentage of resistant rats climbed extremely quickly. After it was taken away, however, the percentage of resistant rats decreased once again.

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15
Q

Why did resistance go down after the poison was taken away?

A

It went down because it is less advantageous be resistant when there is no poison present in the environment.

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16
Q

Health of resistant rats vs. susceptible rats?

A

When there is no poison present, resistant rats are less healthy than the susceptible rats, who are extremely healthier.

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17
Q

How many effects are there to the mutation?

A

The mutation has two effects:

  1. relatively resistant to warfarin
  2. poor user of vitamin K
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18
Q

What features of natural selection does this example demonstrate?

A
  1. Editing rather than creative mechanism. The variation must simply be acted on not created
    – Needs variation to act on
  2. Contingent on time and place
    (adaptation to the particular environment). The gene variants that confer warfarin resistance happen to be disadvantageous when poison is not being used. This is why the percentage goes down after the poison is taken away.
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19
Q

What are soapberry bugs?

A

They are bugs with beaks that they insert into the fruit to extract food. Their typical fruit is from the balloon vine tree, accounting for their long beaks. Yet, in some areas, a tree with a flatter fruit (rain trees) became more common, leading to evolutionary change of smaller beaks in the bugs in that environment.

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20
Q

What was the change?

A

Populations living where the rain tree is have shorter beaks as they are able to get more nutrition on average. This means they are more fit and have a greater number of offspring. They are favoured in this environment. NATURAL SELECTION.

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21
Q

Evidence for Tree of Life and Descent with Modification?

A
  • Homology
  • Biogeography
  • Fossil Record
  • These serve the purpose of introducing observations about the world or things in it that have an immediate and ready explanation under the TOL for the pattern of evolution and don’t fit very well under other models/explanations.
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22
Q

What is Homology?

A

“Similarity resulting from common ancestry”

  • Observing features you see in two similar species: the explanation for seeing it is because they’re inherited from a common ancestor.
  • Different versions of the same thing or character historically
23
Q

How does homology make sense?

A

It makes sense under the Tree of Life. Having widespread homology supports a tree of life idea.

24
Q

What does it mean?

A

2 similar species who have similar or shared traits may have inherited them from a common ancestor?

25
Q

Examples of homology?

A
  • “Standard” anatomical homologies
  • Vestigal structures
  • Molecular homologies
26
Q

Examples of “standard” anatomical homologies?

A

Many mammals have a similar form (arm, fin, wing, leg in different animals) despite having different functions.

  • They are homologs of the same common ancestor.
  • Similar features stem from having the same common ancestor
27
Q

What are vestigial structures?

A

They are structures with little or no function, derived from more complex structures.

  • They come from a recent common ancestor who would have had the functional version.
28
Q

Example of vestigial structure?

A

Remnant hind-limb bones in whales
and some snakes.

29
Q

Functional structure in non-functional forms means?

A

Vestigial structures: a different version of the same homologs. Function was lost along the way from ancestor but a small nonfunctional form is transferred.

30
Q

Molecular Homologies?

A

Homologies at the biochemical level

31
Q

Example of molecular homologies?

A

The universal genetic code is shared by the vast majority of animals
& plants & protists & Bacteria & Archaea

  • We ALL have the same code
32
Q

What are pseudogenes?

A

They are molecular vestigial features:

One organism contains a code for an amino acid that is 95% similar to the functional version, but it does not encode for the right protein. Another similar species has the functional protein.

33
Q

What can we determine with pseudogenes?

A

If we went back to the ancestors between those two organisms, it probably had a common ancestor with the functional protein.

34
Q

Homologies and the Tree of Life?

A

Often, nested distributions amongst organisms, following classification based on other similarities fits a tree of life model.

  • In other words, we expect to see a tree of life that fits our nested distribution of homologies.
35
Q

What do we see when we look at many homologies at once?

A

When we look at many different homologies, we see a dominant pattern. That is not to say that it is absolute, but that it is the more common pattern.

36
Q

Analogous structures?

A

Species with similar functions, but no common underlying structure (similarity is not from common ancestry)

  • We can see this on the tree of life as well
37
Q

What causes analogous structures?

A

The outcome of Convergent Evolution is having analogous structures.

38
Q

What do we see from analogous structures?

A

We might think that they have a common ancestor, but:

  • this is unlikely, as the underlying structure is not similar
  • therefore, there is no common ancestor between them
39
Q

What would the analogous structures look like on the tree of life?

A

A case where the tree of life had two branches that evolved very similarly, but do not come from the same branch on the tree. These two species would be analogous, but not actually closely related.

40
Q

Example of analogous structures (wings)?

A
  • A moth and a hawk. Both have wings and are capable of flight, yet they have different types of wings. This means that they are not closely related.
41
Q

Example of analogous structures (flying squirrels)?

A

The North American flying squirrel and the Australian sugar glider both have a similar composition for their flight mechanism, yet they are very dissimilar in many other ways.

  • They are both much more similar to other organisms in their respective areas.
  • Therefore they are not very closely related, and more likely convergent evolution occurred in different branches of the tree.
42
Q

What is biogeography?

A

The geographic distribution of organisms

  • Some taxa (groups of similar species) are restricted to certain locations where they are endemic
  • Explanation: Descent from a common ancestor that lived in that location
43
Q

Example of biogeography?

A

Macropodiformes:

There are many different species of kangaroos in Australia and New Guinea. They are distributed over the area and not found elsewhere.

44
Q

Another example?

A

There are many different, very similar plants in Hawai’i that occur naturally. They are all related and seen on all the different islands.

45
Q

The fossil record?

A

Descent with modification predicts
‘transitional forms’ and the order of appearances by the fossil record.

46
Q

Advantage of the fossil record?

A

It allows us to look more directly at the past.

47
Q

What are transitional forms?

A

Forms with different aspects of different, older forms.

48
Q

Examples of transitional forms?

A

Good examples:

  • Groups with major adaptations
    associated with an ‘unusual lifestyle’

For instance:
– Whales (fully aquatic mammals)
– Birds (powered flight)

49
Q

Transitional forms in evolutionary progression?

A

We should see relatives of species B with species A’s features if they are related. This organism will be a transitional form.

50
Q

Whale transitional forms?

A

Older whales were more similar to land animals, progressing more as they began adapting to the fully aquatic lifestyle.

51
Q

Whale’s adaptations to being permanently aquatic?

A

Adaptations to being permanently aquatic:
* Lack hind-limbs
* Forelimbs lack distinct fingers
* Dorsal fin, caudal flukes
* Nostrils on top of head,….. etc.

52
Q

Order of appearance?

A

When fossil record is good, ‘descendant’ groups should appear later in time than the earliest of their proposed ancestral groups.

53
Q

Example of the order of appearance?

A

Whale example:

  • First aquatic whale-like forms: ~50 million years ago
  • First (eutherian) land mammals: ~80 million years ago

BIOL1010/1011 (22 decks)

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