Biolopy - Chapter 13: Evolution Flashcards
Evolution
- Gradual development and change of heritable traits (allele frequencies) in populations over successive generations
- Increases biodiversity
5 Evidence of Evolution
1) Paleontology (dinosaurs)
2) Biogeography evidence
3) Embryology (early stage, we are all goo)
4) Comparative Anatomy (homologous/analogous/vestigial)
5) Biochemical methods (common conserved DNA)
Homologous structures
- May or may not have perform the same function but have common ancestor
- e.g. forearm of bird and human
Analogous structures
- Same function, not have a common ancestor
- e.g. bird and bat wings
Vestigial structures
-serve no purpose but are homologous to functional structures in other organisms
Natural Selection
-gradual, non-random process where allele frequencies change as a result of environmental interaction
Survival of the fittest
- occurs as individuals with greatest fitness have greatest success to pass on more DNA to future generations compared to less fit parent
- leads to the evolution of the population, not individual
4 Requirements for Natural Selection
1) Competition for survival
2) Variation in traits
3) Heritable traits
4) Variation in traits must be significant for reproduction/survival
Stabilizing Selection
- Bell curve
- mainstream (average) is favored
Directional Selection
-one extreme favored
Disruptive Selection
-rare traits are favored, mainstream is not
Sexual Selection
- non-randoming mating between males and females
- females favor high quality offspring
- males prefer high quanitity of partners to increase # of offspring
Artificial Selection
this is how we got pugs :((
Hardy-Weinberg Purpose
- calculates genetic frequency during genetic equilibrium, where no change in gene frequencies occur)
- the population is under Hardy-Weinberg Equilibrium when both factors are true
Hardy-Weinberg Equilibrium Formula
p + q = 1
p^2 + 2pq + q^2 = 1
p: freq of homozygous dominant
2pq: freq of heterozygous
q^2: freq of homozyougs recessive
Requirements for Hardy-Weinberg Equilibrium
1) Large population
2) Random mating
3) no mutation
4) no natural selection
5) no migration (gene flow)
Mneumonic HW Equilibrium
Large, Random M&M
Microevolution
Gene frequencies change within a population over generations
5 Factors Causing Microevolution
1) Genetic drift
2) Non-random mating
3) Mutations
4) Natural Selection
5) Gene Flow
Genetic Drift
- allele frequencies change by chance
1) Bottleneck Effect: smaller gene pool, some alleles may be lost
2) Founder Effect: individuals migrate away from the population
4 Sources of Genetic Variation
1) Mutation
2) Sexual Reproduction
3) Balanced Polymorphism
4) Polyploidy
Mutation
Must not be fatal in order to contribute to genetic variation
Sexual Reproduction
- crossing over
- independent assortment and random joining of gametes
Balanced Polymorphism
- maintains a variety of phenotypes within a population
- Heterozygotes advantage
- Minority advantage
- hybrid advantage
- neutral variations
Polyploidy
- Plants have multiple copies of alleles
- can mask effects of harmful recessive allele
Macroevolution
- Long term and occurs at a level at or higher than species
- Species are reproductively isolated, resulting in a lack of gene flow between differing species
Prezygotic Isolation
- Prevents fertilization from occurring between species
- includes:
- Habitat isolation: occupying different habitats
- Temporal isolation: reproducing at different times/seasons
- Behavioral isolation: different courtships
- Mechanical isolation: cannot smash genitalia together
- Gamete isolation: gametes do not recognize/fertilize each other
Postzygotic Isolation
- backup in case hybrid zygote forms
- hybrid mortality: different chromosome #, hybrid not viablee
- hybrid sterility: hybrid zygote sterile
- hybrid F2 breakdown: offspring of hybrids have decreased fitness
Speciation
-how species form starting with reproductive isolation which leads to interruption of gene flow
Allopatric Speciation
- due to geographical barrier
- adaptive radiation occurs when many species arise from one ancestor as they adapt differently to their environments
Sympatric Speciation
- occurs without a geographical border
- Balanced polymorphism: different phenotypes are isolated within the same area
- Polyploidy: in plants results from nondisjunction during meiosis
- Hybridization: some hybrids more fit than normal
Theories of Macroevolution
1) Phyletic gradualism: evolution happened gradually via accumulation of small inteermediary changes (not likely to be true)
2) Punctuated equilibrium: short spurts of evolutionary changes during periods of stasis (supported by fossil evidence)
Divergent Evolution
Diverge from common ancestor
Convergent Evolution (Homoplasy)
Unrelated species adapt to similar environments and develop analogous structures
Parallel Evolution
Diverge from common ancestor but undergo similar changes
Coevolution
Two species impart selective pressure on each other
-Camouflage, aposematic coloration, mimicry
Types of Mimicry
1) Batesian mimicry: non-harmful animal resembles harmful one
2) Mullerian mimicry: two poisonous animals resemble each other to warn their predators
Parsimony
- The simpler the explanation, the better
- Trees minimizing evolutionary reversals, convergent evolution and parallel evolution are preferred
Origins of Life Timeline (Big Bang, Earth, Prokaryotes, Eukaryotes)
Big Bang: 14 billion years ago
Earth: 4.5 billion years ago
Prokaryotes: 3.5 billion years ago
Eukaryotes: 2 billion yeears ago
Earth’s Current Atmosphere
Nitrogen = 78%
Oygen = 21%
Argon gas = 0.9%
Trace amounts of CO2, methane, ozone
Primordial Earth
- consisted of inorganic compounds and no oxygen (reducing environment)
- primordial sea formed when earth cooled down
- the development of autotrophs led to the production of oxygen
Organic “Soup” Theory
- Oparin and Haldane
- Believed that oxygen is too reactive for organic chemicals to be produced in primordial atmosphere
- therefore, oxygen must have been lacking in primordial atmosphere
- strong reactions (lightning, UV, volcanic heat) drove reactions that formed organic compounds
Miller-Urey Experiment
- Mimicked reducing environment proposed by Organic Soup Theory
- inorganic compounds + no oxygen + electrodes + heat
- Amino acids, organic acids were formed but no nucleic acids
