Unit 9: Evolution Flashcards
Natural selection
Individuals whose traits enable them to better obtain food, escape predators or tolerate physical conditions will survive and reproduce more successfully than those without those traits
Why is environment the driving force behind natural selection, and therefore evolution?
Organisms must adapt their characteristics to the environment they are in so that they can survive
Biogeography
Geographic distribution of species
3 keys points about natural selection
- Natural selection occurs through interactions between individual organisms and their environment
- Natural selection can only amplify or diminish heritable traits
- Natural selection is the result of environmental factors that vary from place to place
How does biogeography provide evidence for evolution?
Organisms evolve from ancestral species. Organisms migrate and adapt to their new environment, eventually creating a new species
Homologous structures
Features that often have different functions but are structurally similar because of common ancestry
Vestigial organs
Structures of marginal or no importance to the organisms
How does molecular biology provide evidence for Darwin’s claim that all life forms are related?
Similarities in genes or DNA sequences/proteins reflect evolutionary relationship
Population
A group of individuals of the same species living in the same place at the same time
Gene pool
Total collection of genes in a population at any one time
How do new alleles arise in a gene pool?
Mutations
What is the importance of sexual reproduction?
It causes variation in a population
Hardy-Weinberg equilibrium
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Required conditions to be in equilibrium
- Very large population
- No gene flow between population
- No mutations
- Random mating
- No natural selection
Hardy-Weinberg equation
P^2 + 2pq + q^2=1
Genetic drift. How can it occur?
Change in gene pool population due to chance
It can occur though the bottleneck effect or founder effect
Bottleneck effect
Drastic reduction in population size
Founder effect
Differences in gene pool of the larger population left
Stabilizing selection
Favors intermediate phenotypes. It typically occurs in relatively environments (ex. Human broth weight)
Directional selection
Shifts the overall makeup of the population by acting against individuals at one of the phenotypic extremes. Most common during periods of environmental change
Disruptive selection
Typically occurs when environmental conditions are varied in a way that favors individuals at both extremes of a phenotypic range. Can lead to two or more contrasting phenotypes in a population
Sexual dimorphism
Distinction in appearance where a male and female of an animal species have different characteristics (lions mane, peacock feathers, antlers)
Sexual selection
Form of natural selection in which individuals with certain characteristics are more likely than other individuals to obtain mates
How does penicillin usually work?
Prevents the formation of bacterial cell wall
What makes some bacteria resistant to penicillin?
Contains a gene that codes for a protein to break down penicillin
Heterozygotes advantage
Heterozygotes have a greater reproductive success than homozygotes, resulting in 2 or more alleles for a character are maintained in a population
4 reasons why natural selection does not create perfect organisms
- Selection can act only on existing variations
- Evolution is limited by historical constraints
- Adaptations are often compromises
- Chance, natural selection and the environment interact
Neutral mutation
A mutation with no effect
How does stabilizing selection impact variation?
There is less variation
How does directional selection impact variation?
There is no more/less variation
How does disruptive selection impact variation?
There is more variation
Artificial selection
Humans selecting traits
4 components of Charles Darwin’s theory of evolution
- Variation
- Inheritance
- High rate of population growth
- Differential survival and reproduction
Inheritance of acquired characteristics
Traits acquired during an organism’s lifetime will be passed on to offspring (not true)
Use vs. disuse
Using a trait will strengthen it, not using it will make it go away over time
Micro evolution
Change in allele frequency
Macro evolution
Change in phenotype
Analogous structures
Organisms in similar environments acquire certain traits
Intersexual selection
2 organisms of the same sex compete and the opposite sex chooses the mate
Intrasexual selection
2 organisms of the same species compete and the winner gets the mate
Why does it take longer for recessive alleles to reach fixation rather than dominant alleles?
More of the species has the dominant allele, due to homozygous dominants and heterozygotes
