Evolution of Health and Disease - Exam 1

science

science

system of obtaining knowledge in the form of testable theories and hypotheses with aim of explaining/predicting natural phenomena

goal of science

describe our world and understand the causes of our observations

what questions

description/identity (____ is this thing)

why questions

cause/explanation (____ this happens)

how questions

function/quantity (___ this thing works)

fact

observation that's been repeatedly confirmed

hypothesis

tentative statement about natural world, leading to deductions that can be tested

theory

well-established explanation of natural world that is based on tested hypotheses (why question)

law

statements based on repeated experiments/observations, that describe/predict a range of natural phenomenon (how or why question)

Scientific method

1. observation/question

2. research topic area

3. form hypothesis

4. test with experiment

5. analyze data

6. report conclusion

7. repeat

deductive reasoning

consider set of hypotheses and draw logical conclusion from them (general --> specific) A is B, and B is C, so A is C

problems with deduction

• unable to verify the premises

• falsehoods can be concluded

inductive reasoning

aim for broad generalizations based off specific observations; using available data to draw best conclusion possible (specific --> general)

problems with inductive reasoning

• even if premises are true, conclusion might not be

• particular doesn't extend to general

• biases on data collection

abductive reasoning

based on limited/incomplete info; looks for most likely explanation for data, given previous knowledge

problems with abductive reasoning

no guarantee that the explanation is T or F

logical empiricism: hypothetico-deductive method

1. hypothesis formed by inductive reasoning (observe and hypothesize)

2. test hypothesis by validating/falsifying the deductions made from hypothesis

3. if hypothesis is true, so are deductions. so test deductions with experiments/observations

4. deductions false = hypothesis wrong

5. deduction true = hypothesis might be true, test again with new deductions

testable and falsifiable

for statements to be scientific, they must be ___

bias

any factor that might influence data collection or interpretation, conferring disproportional weight to one of many possible interpretations

where does bias come from?

context personal beliefs preconceptions biased information sources

how peer assessment can check our biases

our biases are more evident to colleague than to ourselves

confirmation bias

tendency to seek out and use info that confirms our views and expectations

• can lead to false or suboptimal conclusions

error

difference between observed/measured values and true info in nature (the +/- at end of number)

accuracy

trueness of an answer, how close to true value you are

precision

refers to spread of values, how close to each other your measures are

PRECISION

most important characteristic of a scientific answer -- repeatability and falsifiability

systematic error

• affects accuracy

• caused by instrumental/ methodological or personal mistakes

• corrected by perfecting methods / techniques

random error

• affects precision

• happens by chance/ uncontrollable fluctuations

• can't be eliminated but can be quantified with statistics

standard deviation

statistical treatment that lets you access the normal distribution of data (capital Sx on calc)

normal distribution

silly little bell curve 68.3% of data in 1SD 95.4% of data in 2SD 99.7% of data in 3SD

file drawer effect / publication bias

• scientists often don't publish studies that don't have statistically significant results

• scientists waste money doing experiments that are already proven false

recall bias

• responses to surveys or self-reporting about experiences biased by individuals' lives

• data skewed bc certain ppl remember things better

citation bias

• bias towards familiar sources

• citations of only favorite journals = confirmation bias

sampling bias

• when not all members of population have an equal chance of being selected for a sample (ie non-response, undercoverage, voluntary response, recall)

selection bias

when researchers influence data collection by collecting data to fit hypothesis (not randomly)

observation

what you experience with senses (data, facts)

inferences

conclusions you can make with past knowledge (hypothesis, educated guess)

darwin-wallace theory of evolution by natural selection

1. resources are scare = individuals compete

2. some individuals have better traits = better at securing resources

3. those individuals have more reproductive successful = pass down good traits

4. over time, entire population will be descendants with good traits

Experimental Design

aims to create a proper scientific experiment steps:

1. question

2. planning experiment - variable

3. collect data

4. analyze results

Mendel's experiments

• common garden pea as model organism (bc great variety, numbers, convenience, easy to cross)

• cross pollinates 2 true breeds (P1) for same trait, obtaining F1 gen

• self the F1 to obtain F2

• reciprocal crossing (repeat the crossing with different pollen donor)

model organism

non-human organism used to better understand biological processes

selfing

self pollinate

variables

factors in experiment that can influence results. must be quantifiable or measurable

independent variable

changed in experiment

dependent variable

responds to IV

controlled variable

held constant

conditions

different number of treatments you'll do

control

a treatment you know the results of beforehand

true breed strains

strains that display the same characteristics for generations

3:1 (dominant to recessive)

monohybrid or one-factor crossing

9:3:3:1 (both dominant to one dominant to other dominant to both recessive)

dihybrid or two-factor crossing

Mendel's Laws of Inheritance

1. law of segregation - each gamete carries only one factor for a trait

2. law of independent assortment - factors for different traits are independently passed through the gamete

3. law of dominance - some traits stronger (dominant) and some traits weaker (recessive)

gene

"factors of inheritance," part of DNA that codes for a specific characteristic

alleles

variations of genes (T or t)

phenotype

physical expression of a gene (purple flower or white flower)

genotype

the genetic code for a trait

homozygous dominant

TT

homozygous recessive

tt

Heterozygous

Tt or tT

evolution

any process of formation of growth and development (basically just change)

biological evolution

change in population properties over generations

survival of the fittest

• resources are scarce = individuals compete

• some individuals have better traits = secure resources better

sexual selection

• individuals with better traits have more reproductive success

• pass traits to offspring

• with time, descendant will be entire population

species evolve

genetic information must change from one generation to the next, so ______, not organisms

population

all members of a species in the same area (smallest level of evo)

genetic variation

individuals in pop dont have exact same genes

population genetics

investigate the change of genetic composition of a population over time

gene pool

sum of all genetic material from all individuals in pop

Evolution at molecular scale

change in gene pool composition or frequency over time

frequency

relative proportions of genetic variation in gene pool

genotype frequency

homozygous dom = pp = p^2 heterozygous = 2pq homozygous recessive = qq = q^2

phenotype frequency

dominant frequency = p^2 + 2pq recessive frequency = q^2

allele frequency

p = frequency of dominant allele q = frequency of recessive allele p = 1 - q q = 1 - p

Hardy-Weinberg equilibrium

• under certain ideal conditions, allele frequencies will remain constant from generation to generation in sexually reproducing populations p^2 + 2pq + q^2 = 1

• if no active processes of evo, use this to predict population genetics

P(A) + P(B) - P(A and B)

"either/or"

P(A) * P(B)

"and"

process

mechanisms a set of events that will lead to a given recognizable result

patterns

set of recognizable results caused by identifiable pattern

5 processes of evolution

1. mutation

2. gene drift

3. genetic flow

4. non-random mating

5. natural selection

autosome

non-sex inherited gene

allosome

sex-inherited gene

natural selection

• Darwin-Wallace theory AGAIN

• conditions needed: variation in a trait, variation in reproductive success, correlation between trait and reproductive success, trait is heritable

non-random mating

the goal of species is to leave their genes in the next generation, so individuals must pick the best partner possible to increase likelihood of offspring success

Dissassortative mating

individuals mate more often with individuals of different phenotype

assortative mating

individuals mate more often with individuals of a similar phenotype

inbreeding

extreme case of assortative mating when individuals mate with close genetic relatives

inbreeding depression

inbreeding increase frequency of homozygous recessive traits that may be bad. population survivability decreases as harmful recessive phenotypes increase

mutations

any alteration in genetic structure of organism

• spontaneous and random (can happen at any time and is unpredictable)

• natural selection determines if good or bad

gene flow/migration

• movement of existing genes from one pop to another

• alters genotype and allelic frequency of pop

factors affecting gene flow

• mobility (can organism or gametes move)

• territoriality (does species stay is same area)

• nature of environment (physical barriers)

effects of gene flow on pop

• adds variety to gene pool

• increase/ decrease survivability of pop by increasing spread of good/bad alleles

gene drift

• alleles change in frequency due to chance events (random and unbiased)

• more impactful in small populations

• random walk process bc no discernable pattern

bottleneck effect

small number of individuals survive at random

founder effect

few individuals become isolated and settle in area without previous population

• the only alleles in new pop are those brought by founders

tension between drift and flow

drift causes pops to diverge by removing alleles flow prevents divergence by introducing new alleles

adaptive evolution

increase in frequency on beneficial alleles and decrease in deleterious alleles due to selection

cline

gradual geographic variation across an ecological gradient

diversifying selection

selection that favors 2+ distinct phenotypes

evolutionary fitness

individual's ability to survive and reproduce

frequency-dependent selection

selection that favors phenotypes that are either common (positive frequency-dependent selection) or rare (negative frequency-dependent selection)