1.1 Flashcards
1
Q
Hypothesis (3)
A
- Observations and the questions they raise allow scientists to come up with a tentative explanation/ prediction of facts called a HYPOTHESIS.
- Hypotheses must be explained by the behaviour of what we observe.
- We conduct experiments to fail to falsify them. If it survives attempts at falsification, we consider it a fact.
2
Q
Experiments (1)
A
- Test the accuracy of the hypothesis
3
Q
Control Experiment (1)
A
- When a population being studied is kept in the same conditions and setting, until a deliberate variable is introduced to a portion of the population
4
Q
Variable (1)
A
- Condition of treatment that is different among the population
5
Q
Test Group (2)
A
- The population which the variable is given to.
- It is hypothesized that they will exhibit some effect different from the control group.
6
Q
Control Group (2)
A
- The population that remains the same and is not expected to exhibit any changes.
- Ensure that there is a baseline to compare the test group.
7
Q
Theory (1)
A
- Large body of experiments/ observations that prove the hypothesis.
8
Q
Replication (2.5)
A
- Experiment can be repeated many time with similar results.
- Participants should have the same conditions. Ex. Do not separate the dosed mice and non-dosed mice in cages because now you need to take into account the conditions of each cage.
9
Q
Randomization/ Blinding (2.5)
A
- Units are assigned to treatments randomly.
- This eliminates bias as the experimenter nor the participant know the results.
–> Ultimately eliminates confirmation bias as experimenters are not cherry-picking information that confirm their beliefs.
10
Q
Observational Studies (3)
A
- Look at certain situations to come to a conclusion.
- Scientists are cautious about making conclusions from observational studies as because they cannot be replicated, they are bias (what the experimenter chooses to observe), and we cannot control.
- We cannot always do experiments as they are costly, not time efficient, unethical and unpractical.
11
Q
Dinosaur Case (2)
A
- Dinosaurs went extinct via meteor is the hypothesis, but we cannot replicate what happened to prove validity.
- Case of confirmation bias.
12
Q
Evolution (4)
A
- Change in the genetic makeup of a population over time and the relationship between species.
- The theory of evolution replaced the theory of special creation which was thought that God created unique species.
- One major way evolution occurs is through natural selection.
- Driven by changes in allele frequencies (what traits are dominant and what traits are recessive)
13
Q
Natural Selection (2) PENDING
A
- The variation best adapted for the survival, growth, and reproduction in a given population that will be passed down to the next generation.
- Charles Darwin
14
Q
Environmental Variation (1.5)
A
- Variation due to the environment.
Ex. Apples growing in an area full of insects will develop evolutionary traits so that apples growing in future seasons will be able to ward off bugs. This gives the apples a better chance of survival.
15
Q
Genetic Variation (2.5)
A
- Genetic material that is transmitted from parent to offspring.
- Differences in an individual’s DNA can lead to differences among the individual’s RNA and proteins, which can lead to a variety of phenotypes (physical characteristics) that can be observed.
Ex. Hair colour, colour of apples
16
Q
Mutations 1 (2)
A
- Arises when there is an error during DNA replication, or when DNA becomes damaged, often by UV rays from the sun.
- These mutations cannot be fixed and therefore will be passed down from generation to generation.
17
Q
Fossils (2)
A
- Physical traces of organisms in the past, giving us phylogenic information of the shapes or organisms from their bone structure.
- Fossil dating tells us how old fossils are and ultimately provides insight into the history of life.
18
Q
Extinction (1.5)
Q: How convincing is it as support for the theory that species got here by gradual evolution?
A
- Many fossils have been left by organisms that are no longer around for millions of years.
Q: How convincing is it as support for the theory that species got here by gradual evolution?
A: Because extinction shows that organisms were unable to survive and reproduce to continue the growth of their population. Adapting to meet those needs happens gradually as we see organisms that look similar to the ones that have gone extinct but with stronger resistance to their environments and circumstances for survival.
–> Leads to transitional forms, where one species disappears from the fossil records, a similar species often appears.
19
Q
Vestigial Traits (1.5)
A
- Structures that have no function, but is similar to functioning structures in related species.
Ex. Tailbone in humans and tail of monkey
20
Q
Tuberculosis Case (2)
A
- Fast pace/ exponential growth of bacteria in the lungs that have become resistant to drug administered.
- The resistant bacteria multiply and replace the sensitive bacteria, which causes the disease again.
21
Q
Geographic Relationship (Relationship Between Species) (2)
A
- Species from the same geographical area are often related.
- Traits that are seen between species in that particular area are often derived from their common ancestors.
22
Q
Homology (1.5)
Q: Homologies assume evolution; how can they be used as evidence for evolution?
A
- Similarities that are due to a common ancestry.
Ex. Similar limb bone structure in turtles and humans.
A: Evolve to suit the purpose of the individual organism.
23
Q
Genetic Homolgy (1)
A
- Homology at the level of genetic coding.
- Genetic code itself is shared by all living organisms.
24
Q
Developmental Homology (1.5)
A
- Homology in the traits of the embryos
Ex. Embryos of all vertebrates show striking similarities.
25
Structural Homology (1.5)
- Homology at the level of developed organisms. Similar features in organisms that share a common ancestor, but the features serve completely different functions.
Ex. Bat wing, penguin wing
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Adaptation
- Organisms evolve to become better suited for their environment (physical aka competing for food, land, and not being eaten themselves, and biological environment aka the best way to reproduce to pass on favorable genes to the next generation)
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Variation (1)
- The individuals that make a population vary in the traits they possess, like size, shape, physiological details
28
Heritability (1.5)
- Some of these differences can be inherited by offspring.
Ex. Tall people will most likely produce tall offspring
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Differential Reproductive Success (1.5)
- In each generation, some organisms leave more offspring than others.
Ex. Green beetles tend to get eaten by birds and survive to reproduce less often than brown beetles do. Therefore, brown beetles get to reproduce more which is more favourable for their survival.
30
Selection (1.2)
- Reproductive success is not random but is influenced by differences in traits, including heritable.
Ex. Certain traits are more favourable for reproduction, therefore more individuals will want to mate with that specific trait and produce offspring with that trait in the next generation.
31
How will natural selection occur? (2)
- Due to heritable variation in traits
- Selection (i.e differential reproductive success) based on traits
32
Fitness (2)
- Means simply an ability to do well under natural selection (reproduce and survive).
- Average reproductive success, given a suite of heritable traits (how well they do with the traits they are given --> survive, grow, reproduce)
33
Inheritance of Acquired Characteristics (Lamarck) (2.5)
- The idea that individuals change in response to their environment, and pass those changes to offspring.
Ex. Giraffes reaching for food.
- More recently, we found that these traits do not usually get passed down to offspring.
34
Goal-Directed Evolution
- Organisms evolve towards a specific goal.
- Evolving forward.
- However, there are lot of evidence against this, because:
--> Vestigial traits still exist (there is no goal in having them around)
--> Bidirectional evolution (birds gain, lose flying ability)
35
Adaptation (1.4)
- Genetic change that increases the fitness of organisms.
--> Not a direct response to the environment
--> Very slow
--> Passed on to offspring and forms the basis of evolutionary change
Ex. Polar bears have thick fur, and thick layers of fat under their skin.
36
Acclimation (1.2)
- The ability of organisms to respond directly to their environment
--> When organisms acclimate this does not affect the traits of their offspring.
Ex. if you exercise every day, you will become stronger, but this will not be passed down to your children
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Why Acclimate? (1.5)
- Because it is beneficial for survival.
Ex. In many cases, the response is induced by sudden environmental change, such as heat or cold stress. Short term.
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Are responses to changed conditions always good? (2.5)
- No. Systems respond in ways that have usually been good through evolutionary time.
- We do it because we're programmed to do so. Because it's beneficial.
Ex. Some forms of altitude sickness are probably due to the acclimation system going off track.
39
Tradeoff (1.10)
- Much of adaptation is the result of compromise between conflicted goals.
Ex. Brightly coloured individuals are more attractive to mates, and to predators.
Ex. Larger individuals compete more effectively but are less efficient at reproducing.
40
Historical Constraints
- Evolution is in small steps.
Ex. Vestigial traits are often things that evolution cannot get rid of.
Ex. Blindspot in the vertebrate eye
41
Some Genetics (4)
- Our basic traits are determined by GENES
- A location where a gene can occur is called a LOCUS.
- A particular version of a gene is called an ALLELE
- Complex organisms have two alleles on each locus (different or same)
42
Loci (3)
- Complex organisms have two alleles at each locus (same or different allele)
- An organism with different alleles are called heterozygous (Aa).
- Organisms with two copies of the same allele at a particular locus is referred to as homozygous (AA/ aa).
43
Genotypes and phenotypes (2)
- Genotype is the collection of an individual alleles (their genetic makeup)
- Phenotype is the collection of an individual's physiological and physical traits (what is observed)
44
Peppered Moth Case (1) + Dominance (1)
- During the Industrial Revolution, when there was a lot of smog, moths evolved into a black shade to camouflage.
X is white, x is black
XX = black
xx = white
Xx = black
X is the dominant allele while x is the recessive allele.
- Aka simple dominance
45
Complex Dominance (3)
- Describe things that are not close to simple dominance
- Co-dominance (when both alleles are visible in the phenotype)
- Incomplete dominance (A mix of the alleles to create a new phenotype)
46
Blood type (1)
- Blood type gene has three alleles (IA, IB, & i); These form four blood types.
47
Analyzing Genotype Frequencies (2.1)
- Calculate expected frequencies under our assumptions
--> Usually calculated by assuming that alleles assort randomly and independently (like flipping a coin)
- Measure observed frequencies in the population
48
Hardy-Weinberg Equilibrium (4.1)
- A null model: it tells us what to expect if complicating effects are absent
- Allows us to calculate allele and genotype frequencies under certain assumptions.
- Allows to calculate an expectation for genotype frequencies and compare it to the observed.
- The following are the assumptions that must to met to be in HWE
1. No genetic drift
2. No gene flow
3. No mutation
4. Random mating (no sexual selection)
5. No natural selection (differential survival and reproductive success)
--> This means there is no change in allele frequency from generation to generation
49
Human HLA genes (2.2)
- Gene used by immune system to recognise disease- causing virus
- Data shows that more people are heterozygous for HLA genes than predicted by HWE. Why?
--> Heterozyous people are more likely to survive, thus having more offspring.
--> People are more attracted to those with HLA types.
50
Directional Selection (Trait level NS) (2)
- Favours one extreme over the other or the intermediate
- Moves graph to one direction.
51
Stabilizing Selection (Trait level NS) (1)
- Favours the intermediate phenotype, acts against variant. Basically likes to keep the population the same.
52
Disruptive Selection (Trait level NS) (2.5) + Hawthorn flies
- Favours both extreme phenotypes, as oppose to the intermediate.
EX. Big beak and small beak are favourable for big and small seed, but suppose the forst does not have any medium size seeds.
- Leads to speciation; formation of a new species
HAWTHORN FLIES: Before the introduction of apples, all maggot flies' life cycles were coordinated with hawthorns. The introduction of apple trees, which produce fruit earlier than hawthorns, produced two genetically distinct populations of flies, each coordinated with the fruiting time of its host tree species.
53
Frequency Dependence (Trait level NS) (2)
- Closely related to disruptive selection
- Some traits do relatively better if that are rare?
EX. What would happen if almost all of the birds had large bills...more small seeds available, small bills become an advantage, an example of frequency dependance and disruptive selection where both extremes are favoured
54
Advantageous (allele level NS) (2)
- An allele that has greater fitness in a particular context.
- Increase positive natural selection
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Deleterious (allele level NS) (3)
- An allele that has less fitness than others in a particular context
- It will tend to decrease due to negative natural selection
- Most mutations
56
Balancing Selection (allele level NS) (2)
- Maintains allele diversity when there is no longer a best allele
- Note that disruptive selection at the trait level will always cause some balancing selection
57
Heterozygous advantage (allele level NS) (1.5)
- When heterozygotes have higher fitness.
EX. Sickle cell - people with heterozygote genotype trait will get less sick with malaria whereas people who are homozygous will have too much instability and severe anemia
58
Genetic Drift (3)
- A change in allele frequencies due to random chance
- Lead to random changes in the allele frequencies.
- It is important to note that drift is much stronger in small populations than in large ones (law of average)
- Reduces genetic variation
59
Founder Effects (Genetic Drift) (1)
- An individual from a group forms its own population, changing the allele frequency from the original to be isolated.
60
Bottleneck Effect (Genetic Drift) (2)
- Drastic reduction in population. As the population re-establishes, there is a change in allele frequency from the original population.
- Can even occur when a benefitial/ advantageous mutation takes over population.
61
Fixation and loss (2)
- Allele may drift to 0 (lost --> negative) or 1 (fixed --> POSITIVE)
- Neutral differences will either be fixed or lost at random
62
Gene Flow (2)
- Movement of alleles from one population to another
- This happens when individuals move from one population to another and breed.
63
Mutation (4.5)
- Heritable errors in copying DNA
- Dont cause evolution
- Only source of new alleles
- Mutations occur:
1. Single DNA base might change
2. Chucks of DNA is added or subtracted
3. Whole gene/ chromosome is duplicated
4. Copying errors (new genetic sequence)
5. Lateral gene transfer : The transfer of genetic material between species.
64
Sex (1)
- Not a new source of alleles, but a source of new combination
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Inbreeding (1)
- Mating between close relatives
66
Inbreeding depression (1)
- Those who inbreed have lower fitness
67
Sexual Selection (1.5)
- Occurs when there is heritable variation in traits related to success in obtaining mate
Ex. buck with large antlers can fight better to obtain mate
68
Sexual Dimorphism (1.5)
- Refers to trait differences between males and females
Ex. Brighter colours --> variation in reproductive success
69
How are species defined? (2)
- As evolutionary units
- Individuals within a speies evolve together while individuals of difference species evolve independelty
70
Biological species (4)
1. Dont breed in nature
2. Breed but fail to produce offspring
3. Produce invaible offspring (does not develop in adulthood)
4. Produce steril offspring (cannot themselves reproduce)
71
Prezygotic (1)
- Prevents succesful mating (different habitats, gametic incompatibility)
72
Postzygotic (1)
- Prevents offspring from producing offspring of their own (zygote mortality, sterile)
73
Ecological species concept (1.3)
- An ecological species is a set of related organisms occupying the same biological niche (make a single population that ensure the same conditions)
--> Exploit the same resources
--> Tolerate similar environments
--> Face similar natural enemies
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Monophyletic group (1)
- Defined by a single common ancestor and consists of all descendants of the ancestor.
75
Generating Species (3.1)
- New species are generated from old species
- One species can gradually evolve into another
- Species can also diverge and split into two species
---> This is the origin of diversity
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Allopatry (1)
- Organisms living apart due to geographical barrier from each other.
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Dispersal (1)
- Isolated populations of the same species can develop if some individuals disperse to a new area and colonize.
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Peripatric Speciation (1)
- Populations on a small island are likely to be founded later, by small groups and to have a smaller population.
79
Vicariance (2)
- Isolated population of the same species can develop when a population is split by a geographical or ecological barrier.
- When pop can split with no moving around.
80
Sympatry (2.1)
- Refers to organisms living in the same geographical area.
- The evolution of populations within the same geographic area into separate species
--> disruptive selection
81
Genetic incompatibility (1)
- If two populations are in the same place, but can't produce fertile offspring, they are reproductively isolated.
82
Hybridization (1)
- Some species seem to have arisen as hybrids between two species
83
Polyploidy (4)
- Reproductive mistakes can occur that produce individuals with extra copies of each chromosome.
- Polyploidy produces instant reproductive isolation (they cannot mate with just anyone).
- They face obstacles to compete with ancestral species.
- Can be beneficial to by keeping one gene and mutating the other.
84
Reuniting (1)
- What happens when isolated populations come back together?
85
Fusion (3)
- When two isolated populations come into contact, they may fuse -- go back together.
- Adaptive differences may be small
- Adaptive difference may be overwhelmed by gene flow
86
Reinforcement (3)
- Hybrid offsprings have low fitness because of incompatible and disruptive selection.
- In these cases, we expect natural selection for traits that reinforce the distinction between the two species.
- Different mating times, different mating calls
87
Hybrid Zones (1)
- When hybrid offspring are functional, and well-adapted to the overlap zone, there may be a zone where hybrids occur. Not clear if we should consider the species to be different
88
Exclusion (1)
- One species may eliminate the other, either by competition or by better success in mating.
89
Mating success (2)
- Better mating success of one species than the other.
- Most genes are dominated by one species, but mitochondrial genes are mixed between two species.
90
Modern Human
- Modern humans spread through the world and out-compete earlier human populations.
