Week 7-Evolution

Question 1

Evolution: where did this idea come
from?

Answer 1

■ Aristotle was the first to suggest some ideas about evolution
■ However, in general terms, evolution is a 19th century idea
■ Before 19th century people thought that adaptations were produced by divine
intervention. They did not think that there was a natural process that could produce anything that was so exquisitely designed as an eye.
■ Homology (Cuvier, 1830): this concept was
born before Darwin’s book. If a bat has 5 fingers in its wing, a human hand has 5 fingers, and the fin of a porpoise has 5 fingers it could be that we all shared a common ancestor.

Question 2

Evolution: Who’s Charles Darwin?

Answer 2

■ Went to South America at the age of 22 and made some observations such as:
– Marine iguanas are different from land iguanas
– Mockingbirds looked a little bit different in different islands
– Tortoises that ate plants near the ground had rounded shells and shorter necks. Tortoises on islands with tall shrubs had longer necks and shells
that bent upward, allowing them to stretch their necks
– Gave his collection of finches to British Museum and they noticed that they varied.

Question 3

What’s evolution and natural selection?

Answer 3

■ The environment cannot support an unlimited population growth.
■ Organisms are in constant competition not just for food but other resources too.
■ Organisms vary in traits.
■ In this example green beetles tend to get eaten by birds (they can spot them easily)
■ The surviving brown beetles will have brown baby beetles because this trait has a genetic basis
■ Brown colour becomes more common in population and eventually all beetles will become brown

Question 4

What are selection pressures?

Answer 4

Environmental factors that increase or decrease the likelihood that a particular combination of genes makes it to the next generation. Advantageous traits are selected disadvantageous traits are not.

Question 5

What is evolution about?

Answer 5

■ Evolution is not about survival of the fittest, it is about a design for reproductive success
■ It is all about how many children and grandchildren you have and whether you do it better than somebody else in that population
■ It is ALWAYS relative: it depends on what is happening in the population at that time.

Question 6

What is fast evolution+example?

Answer 6

Fast evolution: resistance to antibiotics: 6 months. It happens when populations are large and selection pressure is strong
– Big populations have lots of genetic variation
– Selective breeding: every time you try to change one trait you have a byproduct, you have an implicit selection going on, on other traits.
So although you may be realising a benefit in one, or a place, you are paying a cost in the others.

Question 7

What’s an example of slow evolution?

Answer 7

Coelacanth same for 150 million years

Question 8

What are the 4 big evolutionary principles?

Answer 8

1.Principle of natural design for gene replication
2.Superabundance
3.Natural Variation
4.Selection pressures

Question 9

What’s the principle of natural design for gene replication?

Answer 9

We are a constellation of genes that drive
physiological processes and behaviours. Evolution does not operate in individuals, rather evolution operates in genes. Genes need to make it to the next generation

Question 10

What’s superabundance?

Answer 10

Animals and plants produce more offspring than necessary.

Question 11

What’s natural variation?

Answer 11

Each offspring is somehow different

Question 12

What are types of selection pressures?

Answer 12

-Natural selection pressures: Organisms must ensure that the genes survive so they can make it to the next generation
-Selection pressure: predation, susceptibility to disease and toxins, dangerous environment

Question 13

What are adaptations?

Answer 13

How do organism respond to those pressures? (They are called adaptations)
Usually adaptations have a trade off price to pay…. The smaller the trade off the better the adaptation

Question 14

What’s an evolutionary trade off?

Answer 14

In evolution, organisms cannot invest in everything, so they either invest in one trait or another

Question 15

What’s a trade off?

Answer 15

-A situation where to gain some advantage, you have to pay a price.
-For instance big brains are certainly nice to have but they are costly in terms of the energy they
use up, make childbirth difficult, and are easily damaged.

Question 16

What’s sexual selection pressures?

Answer 16

Genes only make it to the next generation if they convince the individual who holds them to reproduce. (intersexual and intrasexual competition)

Question 17

What’s intersexual competition?

Answer 17

Attributes that females and males use to select mates. Members of the competitive sex show off for mates and the opposite sex chooses the best display. Some examples include dancing, singing, or showing bright colours.

Question 18

What’s intrasexual competition?

Answer 18

Occurs within a sex for access to mates, they are more pronounced among males. For example, the strength and size of the “horn” of horned beetles or antler size in deer.

Question 19

What do males and females look for in their mates?

Answer 19

Men look for indicators of fertility AND Females look for good genes and resources.

Question 20

What are social or group selection pressure?

Answer 20

Organisms who are better able to get along with the group have greater chances to reproduce. Cooperative wolves are more likely to reproduce.

In a group, selfish individuals beat altruistic individuals. But, groups of altruistic individuals beat groups of selfish individuals.

Question 21

What’s Environment of evolutionary
adaptiveness (EEA) and what were the selection pressures at that time?

Answer 21

The environment when we evolved

Behaviours or traits that occur universally in all cultures are good candidates for evolutionary adaptations:
- Ability to infer others’ emotions
- Discern kin from non-kin
- Identify and prefer healthier mates
- Cooperate with others

Question 22

How is the EEA significantly different from modern society?

Answer 22

The ancestors of modern humans lived in smaller groups, had more cohesive cultures, and had more stable and rich contexts for identity and meaning.

Question 23

What can we think about human evolution?

Answer 23

-Evolution does NOT proceed in a single line
-We have little reason to claim evolutionary supremacy
-Evolution does not only proceed slowly and gradually: a sudden change in the environment or a mutation can accelerate evolution: lactose tolerance
-Only a few products of evolution have survived to present day. Fewer than 1% of all known species are still alive

Question 24

How are not all existing behaviours or structures adaptive?

Answer 24

-There can be non-adaptive evolutionary by products: SPANDRELS
-A belly button is not good for catching food, detecting predators, avoiding snakes, locating good habitats, or choosing mates.
-It does not seem to be involved directly or indirectly in the solution to an adaptive problem.
-By-products (spandrels) of large brains could be: religion, reading, writing, fine arts, the norms of commerce, and the practices of war.

Question 25

Why can humans compete with other species?

Answer 25

-Agile hands: tools
-Colour vision: opportunities and dangers, mastery of fire
-Bipedalism: Walk long distances, carry tools and food
-Linguistic abilities: pass information make plans form complex civilisations
LARGE BRAIN

Question 26

Why is absolute brain size is not a good measure of intelligence and what is an alternative way to look at brain/body weight ratio?

Answer 26

a) Larger animals tend to have larger brains
b) Super clever people (Einstein for instance) do not have heavier brains

Question 27

What does a human brain have or do that no other brain does?

Answer 27

-In the past it was thought that all mammalian brains, including the human brain, were made in the same way, with a number of neurons that was always proportional to the size of the brain.
-This means that two brains of the same size should have similar numbers of neurones.
If neurons are the functional information processing units of the brain, then the owners of these two brains should have similar cognitive abilities.
-This is an indication that the “all brains are made the same way” scenario is not quite right

Question 28

Give an example of a trade-off

Answer 28

-A large brain requires a large skull
-Upright posture (bipedalism) limits the size of the birth canal: Another trade-of

Question 29

What are the consequences of being born with an immature brain?

Answer 29

Reptiles: can fend for themselves since birth
Birds: need parental care, cannot be born more
mature because there are only limited resources in the egg
Mammals: need parental care to allow the nervous system to develop after birth

Question 30

Why do we not need solely specialised circuits at birth?

Answer 30

-Slowing of the brain development process allowing more time for growth (Neoteny, extended youth)
-Young mammals, and particularly young humans are guaranteed to be exposed to adults from who they can learn from (apprenticeship)
-This means that at birth we don’t need a brain that consists of solely specialised circuits of neurones that perform specialised tasks (a lizard definitively needs these circuits)

Question 31

What’s mate bonding?

Answer 31

-Genes have to convince their carriers to mate so they can make it to the next generation
-Promiscuity is a great solution and indeed this is what happens: most vertebrate species mate promiscuously.
-Most mammals tend to form mating bonds
Why?
-Female mammals give birth to relatively small numbers of helpless, slow-developing young
-As a result, it is adaptive for the males of many mammalian species to stay with the females that are carrying their offspring and promote their successful development.

Question 32

Mating bonds: What’s Polygyny?

Answer 32

Is the most prevalent in mammals
One male forms mating bonds with more than one female. It evolved because males’ investment in offspring compared to females is minimal. Father can sire many many offspring.

Females are SUPER choosy because of their investment she will choose the fittest male. This strategy evolved in species where females make a far greater contribution to reproduction and
parenting than males

Question 33

Mating bonds: What’s Polyandry?

Answer 33

One female forms mating bonds with more than one male. It does not tend to happen in mammals. It happens in species where the male investment is bigger than the female’s.