Variation & Evolution Flashcards
(41 cards)
Method for T-test
- Calculate mean of each sample
- Calculate deviation from the mean (x-x̅)
- Calculate deviation squared (x-x̅)^2 for each sample
- Total deviation squared for each sample
- Calculate standard deviation for each sample (square root of total (x x̅)^2 over n)
- Calculate T value (x̅1 - x̅2 over {s1^2 over n1} + {s2^2 over n2})
Why is t test used?
To compare the … of … sets of … data
Mean
2
Continuous
How do you change an experiment so that T-test would be the most applicable test?
… number of …
Larger
Samples
Null hypothesis
There is no … difference between the … observed & expected results
Statistically significant
Mean
Accept null hypothesis
If value of t is … than the … value (at 0.05)
Deviation is due to … alone
Less
Critical
Chance
Reject null hypothesis
If value of t is … than the … value (at 0.05)
Deviation is … due to … alone - external factors
Greater
Critical
Not
Chance
Calculating degrees of freedom of sets of data
2 sets of data - (n1-1) + (n2-1)
Explain the meaning of probability = 0.05
There is a 5% chance that any … difference between the means is due to … alone
Observed
Chance
Variation
= … between organisms of the … species
Differences
Same
Discontinuous variation
Shows limited no. Of …, with no …
Controlled by one gene (m…)
E… has no effect on gene … (phenotype)
E.g. different blood groups
Phenotypes
Intermediates
Monogenic
Environment
Expression
Continuous variation
Shows … from one extreme to the other
Controlled by many genes (p…)
Phenotype determined by …. Of all genes (p…) & the …
Graph shows normal distribution curve
height, IQ etc.
Graduation
Polygenic
Interactions
Polygenes
Environment
Heritable variation
= … in phenotypes due to … - variation can be …
Difference
Genetics
Inherited
Non-heritable variation
= … in phenotypes due to … - cannot be …
Differences
Environment
Inherited
Natural selection
= organisms better … to their environment survive & …, while those less well adapted fail to do so
New … of alleles produce unique … when expressed as … undergo selection determining their … for the environment
Better adapted are more likely to pass on … characteristics to succeeding generations
Adapted
Reproduce
Combination
Genotypes
Phenotypes
Suitability
Successful
Selective agencies
= … factors that alter frequency of … in a population
E.g. f… supply, b… sites, c…
Selective agencies … for advantageous …
Environment
Alleles
Food, breeding & climate
Select
Alleles
Selection pressure
= effect of selective … acting on the … through N… S…
Agencies
Population
Natural selection
Selected for
… gives a selective …, so … responsible or phenotype is selected for - more likely to be … on to next …
Phenotype
Advantage
Alleles
Passed
Generation
Selected against
Phenotype gives a selective …, so … responsible are selected against - … likely to be passed on to next …
Disadvantage
Alleles
Less
Generation
Gene pool
= total of all the … for all the … in a population
For gene pool to remain stable:
- … population
- no selection …
- … is random
- no …
- all genotypes are equally …
- no gene …
Alleles
Genes
Large
Pressure
Mating
Mutation
Fertile
Flow
Genetic drift
= change in … frequency by …
Important evolutionary mechanism in s…/i… pops
Allele
Chance
Small/isolated
E.g. of genetic drift: Founder effect
Few individuals become … e.g. colonise on island - these are founder members and hold a small sample of the original gene …
By chance, frequency of alleles has changed
Founder pop remains … but undergoes genetic …, becoming different from the … pop
Isolated
Pool
Small
Drift
Parental
Evolution through NS
Theory: existing speices have arisen through … of … species b NS
Observations:
- … is present in a pop
- individuals within pop have potential to produce large amount of … but no. Of adults stays … between ….
Deductions:
- there is a struggle for survival (…) - only fittest … survive
- surviving individual reach reproductive age & …, passing on advantageous … to their … enabling success (selective advantage) thus changing … frequency
If environment changes, features need dot survive Change so NS is …
Modification
Ancestral
Variation
Offspring
Same
Generations
Competition
Phenotypes
Reproduce
Alleles
Offspring
Allele
Continuous
Species
Groups of organisms that can … to form … offspring
Interbreed
Fertile
Speciation
New … forming
Will not take place under H-W principle
Occurs due to:
- genetic … in … populations
- the … effect of disproportionate … frequencies in … population
- … selection
Species
Hardy-Weinberg
Drift
Isolated
Founder
Allele
Small
Natural
