Chapter 13-15 Flashcards
Population
group of the the same species living in the same region at a given time
Variation
in a population, a condition in which members of that population differ in one or more traits
Kinds of variation (6)
structural, behavioural, biochemical, developmental, physiological, geographic
Biochemical
differences that occur in chemical processes that occur in organisms, including blood groups, pigments/colours of skin/fur, and the production of enzymes.
Cline
gradual change in a trait in members of a population across its geographic range.
Monomorphic
refers to a population in which all members are identical with regard to a particular phenotypic trait
Polymorphic
refers to a population whose members show several variants of a particular trait.
Discontinuous variation
type of variation in which members of a population can be grouped into a few non-overlapping classes with regard to expression of a trait e.g. digits on hand
Continuous variation
type of variation in which members of a population vary across a range. e.g. height
Causes of variation (4)
environmental factors, genetic agents, interaction between genetic agents and the environment, internal factors
Internal factors examples
hormone levels, infections, chemicals ingested
Genetic factors that cause variation
mono/polygenic traits, mutation, chromosome number e.t.c.
Polygenic inheritance
each gene has two alleles: a plus (+) allele that adds a small amount to the trait and a minus (−) + + − − genotype shows the same phenotype as a + − + − genotype.
Number of possible variations formula
2n + 1 (n=polygenes)
Gene pool
sum total of genetic information present in a population
When there is only one allele present in gene pool
said to be fixed
Allele frequencies
incidence or frequencies of particular alleles in a population
Allele frequency equation
frequency dom allele + frequency recessive allele = 1
Hardy-Weinberg principle
concept that allele frequencies in a population remain constant from one generation to the next if a set of conditions are met and no agent of change acts on the population.
Set of conditions for Hardy-Weinberg principle
population must be large, random mating, all matings equally fertile producing viable offspring, population is closed (no migration)
Hardy-Weinberg equilibrium
reached when the allele frequencies in a large, closed population remain constant, and will stay the same until agent of change acts on population
Random mating
all possible matings are equally likely to occur.
A phenotype that makes a greater contribution to a gene pool…
has higher fitness value and has a selective advantage
Fitness value
measure of genetic contribution to the next generation
Selective advantage
relative higher genetic fitness of a phenotype
Complete selection
cannot pass on trait because it dies before reproducing
Partial selection
fewer organism of particular phenotype produced
Genetic drift
changes, unpredictable in direction, in allele frequencies from one generation to the next owing to the action of chance events
The smaller the population…
the more impact of genetic drift (can cause eventual loss of allele)
Bottleneck effect
chance effects on allele frequencies in a population as a result of a major reduction in population size. Survivors that reproduce are unrepresentative.
Founder effect
chance effects on allele frequencies in a population that is formed from a small unrepresentative sample of a larger population. Sample migrated.
Theory of evolution by natural selection basis
high birth rates = high death rates, each type of organism shows variation, offspring are similar to their parents because they inherit from them.
Natural selection evolution theory
- individuals show variation from each other
- offspring resemble parents
- more offspring are born than can survive/reproduce
- there is a struggle for existence
Darwin-Wallace theory of evolution through natural selection conclusion
it is a mechanism of evolution, testable through observation and experiment
Natural selection acts on phenotypes through
selection pressures e.g. environmental factors
Adaptive value
degree to which phenotype contributes to reproductive success of individuals that have it
Transmutation
species can change and give rise to new species
Evolution
process of change, typically over geological time, that produces new species from ancestral species
Evidence of evolution
fossil record, biogeography, comparative anatomy, molecular evidence