Evolution Flashcards
Darwin’s 4 points of natural selection
- There is variation among individuals of populations
- Some of that variation is inherited
- Populations tend to produce more offspring than the environment can support
- Those individuals whose traits best adapt them to the environment will survive better and leave more offspring
Evidence for evolution (4)
- The fossil record- changing life forms deposited in rock
- Biogeography- animals in some locations are more alike
- Comparative anatomy- convergent evolution
- Molecular biology- similar DNA/RNA sequences
Proximate explanation
Answers the question what or how, can be used to explain how the body works.
Ultimate explanation
Answers the question why. Why do we get sick?
How is fitness measured?
By reproductive success. For something to be impacted by evolution it must impact survival related to evolutionary success.
P
Frequency of the dominant allele in the population
q
Frequency of the recessive allele in the population
p^2
Percentage of homozygous dominant individuals
q^2
Percentage of homozygous recessive individuals
2pq
Percentage of heterozygous individuals.
Gene
Location on your DNA that codes for a protein.
Allele
Version of a gene.
Dominant allele
Will be expressed over a recessive allele. A recessive allele will only be expressed if homozygous.
Evolution
- Descent with modification
- Individuals do not evolve, populations do
- Occurs as the number of certain alleles increases or decreases over time.
Gene pools
- Populations make up gene pools
2. All the alleles found in a population
Allele frequency
- Proportion of an allele in a population
- Evolution involves the change of allele frequencies
- The sum of the frequencies must always equal 1.
Hardy Weinburg Principle
- Developed to help explain why dominant genes can be rarely expressed
- Both allele and genotype frequencies will remain unchanged unless outside forces change those frequencies
- Without any interference genotypes will not change
Restrictions to the Hardy Weinburg Principle
- Mating must be completely random
- There can be no mutation
- No immigration
- Population must be infinitely large
- No selection can act on the population
- Alleles must segregate according to Mendel’s first ;aw
Sources of genetic variation
- Genetic recombination
- Independent assortment
- Mutation- the only source of new genetic variation
Stabilizing Selection
- Extremes have the lowest fitness
2. Most genotypes fall in the middle, like a bell curve
Directional selection
- Removes one end of the phenotypic range
2. Only peacocks with colorful tails will mate successfully
Disruptive selection
Selection against the intermediate types, and selection for the extremes.
Genetic drift
- Change in allele frequency due to random chance
2. Is most readily seen in small populations, can occur if a portion of the population is lost
Population bottleneck
- When a population experiences a catastrophe
- Extreme loss of population
- Can cause a founder effect
Founder effect
Establishment of a new allele frequency if a few individuals become isolated from a larger population.
Adaptations
Heritable characteristics that enhance an organism’s ability to survive and reproduce in specific environments, can be caused by natural selection
Homologous structures
Characters in related species have underlying similarity but different functions. Anatomical homologies in embryos are not visible in adult organisms.
Convergent evolution
- Similar functions of different structures due to environment.
- Can never create a single species
Point mutations
Changes in one nucleotide base in a gene
Chromosomal mutations
Delete, replicate, or rearrange genes.
Population
A group of individuals of the same species living in the same location.
Fixed allele
Allele that all members of a population are homozygous for.
Gene flow
When the population gains or loses alleles by genetic additions or subtractions (movement of gametes or individuals).
Diploidy
Diploid individuals can hide recessive alleles.
Allopatric speciation
A population forms a new species when it’s geographically isolated from the parent population. Organisms may find themselves in a new place (pollen blown by wind) or geographically separated (creation of the grand canyon.
Sympatric speciation
A small part of the population creates a new species without a change in environment. Mechanisms- hybridization, polyploidy.
Adaptive radiation
- Many new species arise from a single common ancestor and fill different ecological niches.
- Form of divergent evolution
Gradualism
Species descend from a common ancestor and diverge more and more in morphology as they acquire unique adaptations.
Punctuated equilibrium
Periods of apparent stasis punctuated by sudden changes observed in the fossil record.
Species
A reproductively isolated group of potentially interbreeding populations that produce fertile offspring.
Binomial nomenclature
Way of naming organisms, starts with genus then species.
Taxonomy
Naming and classifying of organisms
Cladogram
Classifies organisms according to when they branched from common ancestors.
Evolutionary tree
Based on the number of shared similarities in groups.
Polyploidy
Multiple sets of chromosomes.
Hybridization
Different organisms mate and produce hybrid offspring (mules).
Prezygotic barriers
- Keep sperm and egg from meeting and zygote doesn’t form.
- Ecological barriers- 2 species occupy different parts of the same territory.
- Behavioral barriers- animals don’t interact due to different social tendencies
- Mechanical barriers- genitalia aren’t compatible
- Gametic barriers- incompatibility between sperm and egg.
Postzygotic barriers
- Hybrid inviability- genetic differences in chromosomes lead to problems for development.
- Hybrid breakdown- F1 generation produces a weak F2 generation that cannot reproduce
- Hybrid sterility- hybrid offspring is unable to produce viable offspring.
Coevolution
Reciprocal influence of 2 species on their evolutionary direction. Predator-prey relationships.
Clade
A group of species that includes an ancestral species and all its descendants.
Heterotroph Hypothesis
Life began under the conditions of early earth
Conditions of origin of life
- No oxygen (hydrogen, ammonia, methane)
2. More lightning, volcanic activity, UV radiation
Heterotrophs
First cells, can’t make their own food. First cells were also anaerobic organisms.
What causes rapid change in gene pools?
Competition
Does the genome of an individual change?
No. Only the frequency of alleles in a gene pool change.
