Evolution Flashcards
(24 cards)
what is ultimate source of all genetic variation?
Mutations
- without them evolution cannot occur
What is Darwinian (or evolutionary) fitness?
A measure of an individuals relative reproductive success.
or
An individual’s relative contribution of genotype (or phenotype) to future
generations.
extra note : individuals that pass more genes to the next generation have a higher evolutionary fitness than those that pass on fewer genes.
What is an effect of a harmful mutation / what is it ?
Harmful mutations reduce an organism’s fitness
( ie. reducing the survival
and/or fertility of an individual )
What is an effect of a very advantageous / beneficial mutation/ what is it?
increase an organism’s fitness, by increasing likelihood of survival and/or reproductive success and/or fertility of an individual.
a) What is Gene Flow?
b) What is a result of little to no gene
flow?
a) The movement of alleles between
populations caused by
dispersal and subsequent mating.
b) Restricted or no gene flow between populations can lead to the genetic
divergence of the two populations, if it persists, it can lead to speciation .
Why are mutations also considered a weak evolutionary mechanism?
- Most mutations are silent/neutral with
respect to fitness - Only affect one individual
- It takes other evolutionary
mechanisms to increase or
decrease the new allele frequency in
the population.
What is Natural Selection?
non-random differences in the survival and reproduction of individuals with certain genotypes (& associated phenotypes) in a population over
time.
what are the requirements for Natural Selection to occur?
- VARIATION:
in trait/phenotype amongst individuals in the population. - DIFFERENCES IN FITNESS: (survival/reproduction) associated with the difference in phenotypes.
- PHENOTYPE MUST BE HERITABLE (genetic component).
a) What is an adaptation?
b) How to know if a trait is an adaptation?
a)
- when populations become more well adapted to the environment as a result of mutations and natural selection
- HERITABLE (adaptive) trait that increases the ability of an individual to survive and reproduce compared to individuals without that trait.
b)
it is heritable, functional, or affects fitness
What are the three modes of Natural Selection?
- Directional-
favours individuals with a phenotype at one end of the distribution of a trait - Stabilizing-
Selects against extreme phenotypes at both ends of the frequency distribution. ( favours intermediate phenotypes) - Disruptive-
Both extremes are favoured at the expense of intermediate phenotypes
Sexual Selection (& what are the two types) ?
A type of non-random mating
(i) Intrasexual :
Competition for mates; male-male interactions (mostly)
(ii) Intersexual :
Mate choice: female mate choice(mostly)
What is Genetic Drift ?
Genetic drift (or drifting of allele frequencies) refers to changes in allele frequencies in a population over time due to random differences in survival and/or reproduction.
- ( occurs in all populations that are not infinite in size)
what are the 2 opportunities in genetic drift?
1) Bottleneck Event :
Population size is greatly reduced (often over a short time period) for at least one generation (usually due to a catastrophe such as a wildfire, flood, etc.)
2) Founder Event:
New population is founded by a few individuals, founding members isolated from the original population (so no gene flow), Allele frequencies in the newly founded population likely very different from original population
What is the Hardy-Weinberg Equation
(Equilibrium)?
+ equation & assumptions
Equation is used to calculate EXPECTED genotype frequencies in a population
p^2 + 2pq + q^2 = 1
(AA) (Aa) (aa)
assumptions:
* Random fusion of gametes (random
mating)
* The population is infinitely large
* No natural selection
* No gene flow
* No mutations
What is a phylogenetic tree?
diagram that depicts the hypothesized evolutionary relationships amongst species or other taxa
What is a monophyletic group (or clade)?
part of the phylogeny that includes:
the ancestor (unique or common) + all of its descendants of that ancestor.
What is a paraphyletic group?
A group that contains the common ancestor, but not all descendants .
what is a polyphyletic group?
A group that that does NOT include the most recent common ancestor to that group .
What are Synapomorphies ?
homologous traits that were inherited from most recent common
ancestor to the group
What is the Principle of Parsimony?
used to determine which tree represents the“besthypothesis”
(parsimony is the assumption that the simplest explanation is most likely to be true)
What is the difference between a homologous and an analogous (homoplasies) trait?
Homologous:
traits shared by 2 or more taxa because the trait was inherited from a common ancestor.
Analogous traits/ homoplasies:
arise due to convergent evolution, independent solution to an environmental demand –not from a common ancestor.
What are the 4 species concepts?
- Biological:
can individuals mate and produce via offspring or not? - Morphospecies:
uses differences in morphology to distinguish species. - can be used for both living & extinct species - Ecological:
Organisms are classified as the same species if they have the same
ecological niche (i.e. same habitat, food, predators, etc.) and as different species if they do not. - Phylogenetic :
smallest set of organisms that share an ancestor and can be distinguished from other sets of organisms by synapomorphies
What is speciation?
steps?
An evolutionary process of by which new species form.
steps:
1) genetically isolated
2) diverge genetically
3) Reproductive isolation
Allopatric:
- Geographic separation of populations
- No gene flow between populations
Sympatric:
- No physical barrier to separate
individuals in the population.
- Some other mechanism results in
reproductive isolation between
populations
what is allopatric vs sympatric speciation?
Allopatric:
- Geographic separation of populations
- No gene flow between populations
a) Dispersal- movement of individuals
away from their source population
b) Vicariance- physical splitting of
one population into two or more
smaller populations due to the
formation of a geographic barrier,
Sympatric:
- No physical barrier to separate
individuals in the population.
- Some other mechanism results in
reproductive isolation between
populations
