Ecology and Evolution Flashcards
What are the evolutionary traits?
Behavioural
Physiological
Morphological
Fitness
The proportionate contribution an individual makes to future generations
Necessary conditions for Natural Selection
Variation among individuals in some heritable trait
Variation causes individuals to differ in survival and reproduction
Adaptation
Heritable trait that improves an organisms ability to survive and reproduce in prevailing environmental conditions; results from natural selection
Process of acquiring traits that improve fitness
Darwinian Fitness
Relative genetic contribution of an individual to future generations, restricted by genetic architecture
Evolution
Change in gene frequency and hence properties of a population over generations; results from various mechanisms, including but not only natural selection
Population (Genetics Def)
A group of actually or potentially interbreeding individuals sharing a common gene pool
Speciation
Evolution of new species, often through separation of a population into two or more reproductively isolated subpopulations
Types of Speciation
Allopatric
Sympatric
Allopatric Speciation
Geographic isolation followed by reproductive isolation
Sympatric Speciation
Reproductive isolation without geographic isolation
Often behavioural differences (mating/feeding locations)
Thought to be rarer
What is a evolutionary population composed of?
Interbreeding organisms and therefore can be considered a genetic unit
Gene Pool
The sum off all the genes of all individuals in a population
What causes a change in the gene pool?
Selective pressures by the environment on individuals of the population
What causes a change in gene frequency?
Correlation between genotype and phenotype
What does natural selection act on?
Phenotypes NOT genotypes
Phenotype
Observable attributes
Gene
Discrete subunits of DNA that code components of proteins
Allele
Alternative forms of a gene, in diploid organisms, 1 pair of alleles per gene (AA, Aa, aa)
Co-dominance
Heterozygous individuals are a mix of dominant and recessive traits
Assumptions for Hardy-Weinberg Equilibrium
Random Mating No Mutations Large Population Size No Immigration of Emigration All genotypes have equal fitness (no natural selection)
Ways that nonrandom mating occurs
Assortative Mating
Inbreeding Depression
Outbreeding Depression
Assortative Mating
Preferences for certain individuals
Inbreeding Depression
Mating with relatives
Exposure to deleterious recessive genes
Outbreeding Depression
Mating with least similar individuals
Genes are not locally adapted to environment, makes them incompatible
Ways that Mutations occur
Micro-mutation
Macro-mutation
Micro-mutation
Base substitutions
Deletions
Insertions
Macro-mutation
Polyploidy
Chromosomal deletions, duplications, invertions, translocations
Polyploidy
Heritable condition of having more than 2 complete sets of chromosomes (common in plants)
Genetic Drift
Random change in allele frequencies in small popultions due to sampling error
Types of Genetic Drift
Bottleneck Effect
Founder Effect
What happens when Genetic Drift occurs?
Either one or other allels will become fixed
Results in populations lacking in genetic variability
Bottleneck Effect
Drastic reduction in population size
Survivors constitute a random sample
Founder Effect
Few individuals found a new isolated population at some distance from their place of origin
Random sample of original
Rare alleles can become enhanced in the new population
Gene Flow
Immigration and emigration can influence gene pool
Can reduce genetic drift
Can inhibit divergence among subpopulations
Microevolution
The change in allele frequencies that occurs over time within a population
Can lead to macroevolution
Selection
Differential survival and reproduction as a result of phenotypic differences
Selection Pressure
Any force acting on individuals that affects which individuals leave more descendants than others
How do individuals differ in regards to selection?
Show differential reproductive success
Directional Selection
Favors one extreme
Stabilizing selection
Favors the majority (middle)
Disruptive Selection
Favors both extremes
Group Selection
When one group of individuals is eliminated by another group of individuals having superior genetic traits
Changes in gene frequencies result from differential extinction or productivity of groups
Kin Selection
Evolution of a genetic trait expressed by one individual that effects the genotypic fitness of one or more directly related individuals
What introduces two new types of fitness?
Kin Selection
Personal Fitness
Passing on genes to an individuals own offspring
Inclusive Fitness
Additional fitness is acquired by improving the fitness of very close relatives
Sexual Selection
Accounts for male/female dimorphism
Female choice and male combat important
What is the product of selection pressures?
Traits
Some structures may be secondary consequences of other strongly selected adaptations
Some adaptations may no longer be relevant to present
What type of path does selection follow?
Path of least resistance
Coevolution
Interdependent evolution of two or more species having an obvious ecological interaction (antagonistic or cooperative)
Examples of Coevolution
Predator prey systems
Plant-herbivore
Plant-pollinator
Host-parasite
Types of Evolution
Divergent
Convergent
Divergent Evolution
Competition should lead to divergence and specialization, organisms accumulate differences due to different selection pressures
How to test for Divergent Evolution
Comparing traits where they are found together and where their ranges do not overlap (sympatry and allopatry)
Convergent Evolution
Organisms that are not closely related resemble one another
Evolve similar traits, adaptations to similar environments
Similar selection pressures
Adaptive Radiation
The evolution of a variety of forms from a single ancestral stock
Often occurs after colonization of an island or after entry into a new adaptive zone
