Evolution test 1
Why Evolution is Important (3 points)
1. Diversity of life
2. Artificial selection
3. Response to ongoing environmental change
Explain artificial selection and what the selection pressure is
It's when humans choose desirable traits in organisms to reproduce over generations (driving their evolution)
humans are the selection pressure
Macro-evolutionary changes
Larger scale, long term changes that result in new species (ex. transition from water to land)
Microevolution with an example
Change in allele frequencies from one generation to the next
ex. evolution in response to climate change (brown owls becoming more common compared to gray ones due to less snow)
Genetic variation
Members of populations vary in traits they display
Genetic inheritence
Offspring tend to resemble parents
Differential reproductive success
traits that some biological lifeforms possess that differ and alter their likelihood of survival
Result of variation, inheritance, and differential reproductive success
Evolution by natural selection
Mutations
Primary source of genetic variation, each individual has ~60-180 mutations per diploid genome
What kinds of cells are heritable
Germ-line cells ARE heritable
Somatic cells AREN'T heritable
Synonymous mutation
Doesn't alter amino acid (silent)
Nonsynonymous mutation
Leads to a different encoded amino acid (can be beneficial)
Nonsense mutation
Creates new stop codon (deleterious)
Insertion mutation
Adds nucleotides to a sequence
Deletion mutation
Removes nucleotides from a sequence
In-frame mutation
addition or removal of three nucleotides from a protein-coding sequence (doesn't disrupt reading frame)
Frameshift mutation
only one amino acid is retained, more problematic
Fitness of mutation types
Beneficial mutation = greater than 1
Neutral mutation = 1
Deleterious mutation = in between 0 and 1
Lethal mutation = 0
What are the least and most common mutations
Neutral is the most common (synonymous)
Beneficial ones are the least common
Selective agent
Imposes selection pressure
Artificial vs Natural Selection
In natural selection, nature selects the most successful traits
In artificial selection, humans select the traits
Natural selection
Individuals are selected for, populations/species don't evolve
Evolution can happen when there is:
Variation, inheritance, differential reproductive success, phenotypes
Norm of reaction curves
curve for a specific genotype, reflects different phenotypes that arise from a single genotype (depending on environmental conditions)
Phenotypic plasticity
One genotype can develop into different phenotypes depedning on the environment
Fitness
The ability of individuals to survive and reproduce in the environment in which they find themselves
Relative fitness
Fitness of phenotype / fitness of most successful phenotype
Selection coefficient
how much fitnesd reduction of less fit phenotype
ex. If fitness of a phenotype is 0.4, the selection coefficient = 1 - 0.4 = 0.6
Genetic drift
random fluctuations in allele frequencies
Where is more genetic drift prevalent
smaller populations (one allele is driven to fixation in smaller populations)
What can genetic drift lead to
allele fixation (freq = 100%)
Antagonistic Pleiotropy
Trade off between fitness in diff conditions
Adaptation
Heritable, behavioural, morphological, physiological, or genetic trait evolved through natural selection
Example of adaptation
fur coats are an adaptation to living in cold climates
Exaptation (with example)
Trait thought to have evolved to serve one function is cop-opted to serve another
ex. Dinosaurs had feathers that helped thermoregulation, birds then exapted this trait to let them fly
Hypervariable immune genes in vertebrates are an example of what
Complex adaptation
Adaptation misconceptions
1. All traits are adaptations
traits can be beneficial (adaptive), neutral, or maladaptive (bad)
2. Adaptations are perfect solutions to changes
adaptations are context dependent, and can arise from random genetic mutations
3. Adaptations will always result in higher complexity
some adaptations can evolve to increase or decrease complexity
4. Adaptation is the inevitable of evolution
there are multiple non adaptive evolutionary processes
Genetic drift
random fluctuations in the frequency of an existing gene variant in a population
Gene flow
transfer of genetic material from one population to another
can sexual selection be adaptive or maladaptive?
True
Neutral theory
Genetic drift explains the fate of genetic variation
Adaptation: evolution primarily proceeds by natural selection and selection plays a dominant role in molecular evolution
Life history strategy
schedule and manner of investment in survivorship and reproduction over an individuals lifetime
Life history trade-off
Increase in one life history trait and another one being decreased as a result
Eugenics
Beliefs and practices that aim to improve the "genetic quality" of a human population (unfounded in science)
examples of Eugenics
anti immigration sentiments, belief that one race is superior
Adaptationist thinking in different contexts
The idea of different races of humans is a product of social, economic, and political processed, not genetic/biological reality