Week 7-Evolution Flashcards
(33 cards)
Evolution: where did this idea come
from?
■ 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.
Evolution: Who’s Charles Darwin?
■ 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.
What’s evolution and natural selection?
■ 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
What are selection pressures?
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.
What is evolution about?
■ 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.
What is fast evolution+example?
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.
What’s an example of slow evolution?
Coelacanth same for 150 million years
What are the 4 big evolutionary principles?
1.Principle of natural design for gene replication
2.Superabundance
3.Natural Variation
4.Selection pressures
What’s the principle of natural design for gene replication?
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
What’s superabundance?
Animals and plants produce more offspring than necessary.
What’s natural variation?
Each offspring is somehow different
What are types of selection pressures?
-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
What are adaptations?
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
What’s an evolutionary trade off?
In evolution, organisms cannot invest in everything, so they either invest in one trait or another
What’s a trade off?
-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.
What’s sexual selection pressures?
Genes only make it to the next generation if they convince the individual who holds them to reproduce. (intersexual and intrasexual competition)
What’s intersexual competition?
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.
What’s intrasexual competition?
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.
What do males and females look for in their mates?
Men look for indicators of fertility AND Females look for good genes and resources.
What are social or group selection pressure?
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.
What’s Environment of evolutionary
adaptiveness (EEA) and what were the selection pressures at that time?
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
How is the EEA significantly different from modern society?
The ancestors of modern humans lived in smaller groups, had more cohesive cultures, and had more stable and rich contexts for identity and meaning.
What can we think about human evolution?
-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
How are not all existing behaviours or structures adaptive?
-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.
