1
Q
natural selection
A
- unless there is a massive disruption of some kind, an ecosystem with remain relatively stable
- balance between predators and prey, foliage and plants availability, chemistry in the water
- darwin felt this was important because it means not everyone is surviving
- differences in the traits they have that allow some to survive and some not too
2
Q
natural selection + genes
A
- changes in average genotype over time
- the genes that go into the next generation and represent the population
- individuals that carry those games are more likely to succeed, and have reproductive success
- also means changes to the phenotype → some traits will become more common
3
Q
variability
A
within a species
4
Q
heredity
A
- variability is heredible
- e.g. predisposition to addiction, personality, intelligence
5
Q
differential reproductive succes
A
- some individuals get more of their genes into the next generation than others
- can be done by: have sex, do things that benefit family members and those that look most similar to you, increase the likelihood people related to you reproduce you will also have more reproductive success (you don’t need to be the one to do it)
6
Q
directional selection
A
- the population shifts in a particular direction as a result of selective pressures
- doesn’t always go bigger, sometimes smaller is better
- e.g. being a smaller form of prey, the smaller you are the easier it is to hide
- photos in notes
7
Q
direction selection example - brain size and power
A
- more cortex = smarter the species
- selection for intelligence
- brains are energy intensive so it takes a lot of calories to support the brain, its functions and cooling it down
- needs to be a distinct survival advantage to having a large brain for it to evolve
- evidence in ancestral history that human skulls have gotten larger over time
- e.g. complexity in societies, tools, artwork, etc that coincide with the increase in brain size
8
Q
disruptive selection
A
- start of with a population with normal distribution, some with higher values, some with smaller, but now the extremes are preferable rather than the middle
- creates categories within a species
- e.g. domesticated dogs or human skin colour
- where one version of the body works best for one type and another version of the body works best for another
9
Q
disruptive selection - pelvic example
A
- selective pressure
- offspring have large heads = need for larger pelvis
- not just about getting babies out, but for bipedal locomotion (2 feet) the structure on your pelvis affects your ability to move efficiently
- pelvis is heavier, larger and tipped differently in female bodies
10
Q
stabilizing selection
A
- once the selection has occurred and the trait is functional for the species, we begin to see stabilizing selection
- stabilizing selection maintains a trait
- both ends of the traits are selected against making the average the most functional in that environment
11
Q
gene mutations
A
- mutations are mainly neutral and have 0 impact
- some can be maladaptive (generally selected against)
- some will be beneficial and selected more commonly as we go along
- selection changes the likelihood of these genes/traits
12
Q
trait neutrality involves:
A
- don’t have a positive or a negative impact on the population
- pre-adaptions
- genetic drift
- spandrels
13
Q
trait neutrality - don’t have a positive or a negative impact on the population
A
- can become common for other reasons but are meaningless for survival or reproduction
- loosely related to racial or regional differences
- at a population level are meaningless effects
- e.g. widows peak, tongue folding, attached or detached earlobes
14
Q
trait neutrality - pre-adaptations
A
- environment changes can shift trait neutrality
- traits may become advantageous for survival or reproduction
- recognize in hindsight not in advance
15
Q
trait neutrality - genetic drift
A
- because we have variability, a lot is random variability of neutral traits making it possible that individuals with those traits will become reproductively successful for different reasons
16
Q
genetic drift example
A
e.g. red hair and freckles associated with scotland and ireland → because people who were more successful in those environments had those traits → correlated with advantages but not an advantage in itself
17
Q
trait neutrality - spandrels
A
- can be a byproduct of another process
- was not what was set out to create but it had to be there for said thing to happen
- they can become pre-adpations
18
Q
spandrels example
A
e.g. snails have a hole in the middle of the snail because it is curved → not an adaption and is meaningless → however species who have evolved from snails have had that hole become part of their reproductive track
19
Q
punctuated equilibrium
A
- ecosystems marked or interrupted on a regular basis
- ecosystems in balance/stable → punctuated by random events/natural disasters/catastrophes/changes in climate → selective pressures for or against particular traits → rapid evolutionary change
- e.g. cambrian explosion
20
Q
cambrian explosion
A
- a relatively rapid period of diversification of complex animal life that began around 538.8 million years ago, at the start of the Cambrian Period
- single cell to multicell organisms → massive influx of oxygen (massive change) → necessary for building large/more complex bodies because skeletones needs oxygen → species with genetic mutations that contribute to larger size can now become bigger → explosion of species that exist on this planet → new equilibrium that maintains stable till another large change
21
Q
natural selection → evolution
A
- natural selection is the MECHANISM
- evolution is the RESULT
- evolution has no agenda, no goal, and no endpoint
22
Q
fossil records as supporting evidence
A
- fossil records are critical and important but have flaws in that there are gaps and things we cannot see in a fossil record
- goal in using fossil records is to see continuity from one species to another
23
Q
Tiktaalik
A
- early pteropods (4 legged animals)
- what happened between water species and land species? What was the transitional species?
- predicted a fish (ability to swim and live its entire life under water) but also had to have the ability to walk (use limbs to swim and walk)
- was a fish but had a skeletal structure to prop itself up on its front fins
24
Q
homology as supporting evidence
A
- describes a similarity between entities (organisms, genes, anatomical structures) due to shared ancestry, even if they serve different functions or appear differently
- where we originally got most of those biological classifications/visual evidence we still depend on
- the more similar two species look, the more likely they are to be related
25
homology
looking for similarities in physical form across a variety of species
26
homology examples
- humans, cats, whales and bats have the same bones in their forelimbs
- bones may vary in shape or size but the number of bones and where the bones connect is very similar or identical
- whale flippers still have fingers inside it, similarly to the wings of a bat
- bones are conserved across dramatic evolutionary changes (important to understand)
27
vestigial traits as supporting evidence examples
- the flightless cormorant have wings
- their wings are useless for flying but they still produces flight feathers even though its wings are not strong enough to carry its body
- minimal muscle mass being devoted to the wings → selected against in favour of larger muscles in legs (primary way of travel)
28
vestigial traits
- leftover/artifact
- don't serve the purpose they originally did
29
darwins finches observation as supporting evidence
- the finches
were a cluster of species found in and around the Galapagos islands
- observations were fundamental for him to understand his hypothesis on natural selection
- there were very few genetic differences between the birds, with the exception of what effected the beak size and digestive operations
- access to food and kind of food between the islands is what created change in this species
- e.g. the birds with access to larger nuts or small shellfish ended up with larger, nut cracker like beaks
30
phylogenetics as supporting evidence
- the study of the evolutionary relationships among biological organisms or their genes
- calculation of similarity/difference between the genomes of different species to identify mutations associated with certain traits and calculating the age of those mutations
- develop timeline of speciation based on ‘age’ of genetic and fossil differences
31
comparative method as supporting evidence
- look at evidence of similarities across species as well as where species differ and how you can understand difference based on selective pressures in the environments
- looking at the relationship between a selective pressure and a trait
32
divergent evolution
- where do two species that are closely related differ because of their different selective pressures
- e.g. two water birds → penguins and loons
- penguins have a layer of fat that is larger than any other species → a loon diving in a lake will not require the same level of insulation of a penguin
33
convergent evolution
- looking at species that are not closely related and can be dramatically different but examining what features they have in common
- two very different species are trying to solve the same problem, using similar adaptations, but through very different genetic routes
- e.g. arctic animals; arctic hair, arctic goose, arctic fox → have all adapted to camouflage in an environment that is mostly white
34
breeding as supporting evidence
- breeds are subtypes of a species that can’t always breed together naturally
- breed for specific reasons, looks and traits
35
artificial selection
- selectively breed organisms for specific, desirable traits
- controlled
36
russian farm fox experiment (1940s)
- research program where silver foxes were selectively bred silver foxes for tameness alone to understand the process of animal domestication
- categorized into 3 classes based on temperament with class 3 having attempted to flee or bite, class 2 was not friendly but allowed themselves to be touched and class 1 was accepting toward experimenters and approached with curiosity
- only bred class 1 and 3 foxes
- creation of class 1e also called the "domesticated elite" with foxes researchers labelled as dog-like because they sought out human attention, licked experimenters and wagged tails
psych 373: evolution & human behaviour
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