AP Biology Unit 7 Review - Natural Selection

==Natural Selection==

}}Key features}}

• ^^Natural selection:^^ The process by which individuals with more favorable traits are more likely to survive, reproduce, and pass on their alleles to future generations
• There is @@variation@@ in heritable traits within a population
• Species produce more offspring than the environment can support
• Individuals w/ more favorable traits are more likely to survive + reproduce

@@This will lead to the accumulation of favorable traits over generations@@

}}Evidence of natural selection}}

• ^^Homology^^: Structural similarities resulting from common ancestry. Not always as reliable because of analogous structures + convergent evolution (species independently develop similar structures due to similar environmental pressures)
• ^^Fossil record:^^ Shows extinct species + change over time, but not all organisms can be fossilized so the fossil record is biased
• ^^Embryology^^ can show similarities in structures very early in development
• ^^Molecular data^^: (DNA, amino acids) directly shows differences between the genetics of organisms

==Phylogeny==

}}Phylogenetic trees}}

• @@Represent possible evolutionary relationships@@

• ^^Sister taxa^^: Share an immediate common ancestor

• ^^Basal taxon/outgroup:^^ Diverges early in the group’s history, near the whole group´s common ancestor

• ^^Monopholyetic group:^^ Branch and every subsequent taxon

• ^^Paraphyletic group:^^ A monophyletic group that leaves out a taxon

• ^^Polyphyletic group:^^ Group of different taxa with a different common ancestor

  

  

==Hardy-Weinberg + Population Genetics==

}}HW Equilibrium}}

• ^^Population^^: A group of individuals of the same species in the same area that produce viable and fertile offspring

• @@HW allele frequency:@@ Dominant allele frequency + recessive allele frequency = 1 (p + q = 1)

• @@HW genotype frequenc@@y: Homozygous dominant frequency (p²) + Heterozygous frequency (2pq) + Homozygous recessive frequency (q²) = 1, (p² + 2pq + q² = 1)

• 

• @@REQUIREMENTS:@@ No mutations, random mating, no natural selection, very large population, no gene flow

• @@Mechanisms of evolution@@ are mutation, gene flow, non-random mating, genetic drift, and natural selection

  }}Population genetics}}

• ^^Genetic drift:^^ Change in allele frequency due to random chance

• ^^Founder effect:^^ Few individuals are isolated from the larger population, creating a new and less genetically varied gene pool (part of genetic drift)

• ^^Bottleneck effect:^^ Drastic population reduction due to a sudden environmental change, gene pool after the event will be different (part of genetic drift)

  

• ^^Gene flow:^^ movement of alleles among populations between gametes

• ^^Fitness^^: An individual´s reproductive success/how many offspring it´s able to produce

• ^^Directional selection^^: Conditions favor 1 end of the phenotypic range

• ^^Disruptive selection:^^ Conditions favor individuals at both ends of the phenotypic range

• ^^Stabilizing selection:^^ Conditions favor individuals in the middle of the phenotypic range

• ^^Sexual selection^^: Natural selection for mating success

[[Reproductive Isolation: Existence of biological factors impeding members of 2 species from interbreeding and producing fertile offspring[[

}}Species???!}}

• ^^Biological species concept:^^ A species is a group of populations whose members can interbreed and produce fertile offspring
• @@Other species concepts@@ are morphological (species based on morphology), ecological (classified by ecological niche), and phylogenetic.

}}Prezygotic Barriers- Block Fertilization}}

• ^^Habitat Isolation:^^ 2 species occupy different habitats and rarely/don’t encounter each other
• ^^Temporal Isolation:^^ Species breed at different times of day, seasons, or years
• ^^Behavioral Isolation:^^ Courtship rituals and other unique mating behaviors make species incompatible
• ^^Mechanical Isolation:^^ Morphological differences prevent successful mating
• ^^Gametic Isolation:^^ The sperm of one species can’t fertilize the egg of the other species

}}Postzygotic Barriers- Prevent hybrid zygote from developing into fertile/viable adult}}

• ^^Reduced hybrid viability:^^ The genes of the 2 species interact in a way that impairs the hybrid offspring’s development or survival

• ^^Reduced hybrid fertility:^^ Hybrid is sterile (unable to reproduce)

• ^^Hybrid breakdown:^^ The hybrid is able to reproduce, but the hybrid’s offspring are feeble or sterile

  

}}Allopatric Speciation- One species splits into 2+ due to a geographical divide that prevents gene flow}}

• As @@geo divide@@ interrupts gene flow, @@intrinsic barriers@@ (barriers that make 2 species sexually incompatible) such as genetic differences or sexual selection arise

  

}}Sympatric Speciation- Speciation in a population that is not geographically separated}}

• ^^Polyploidy:^^ Offspring receive an extra set(s) of chromosomes due to errors during cell division. Creates a reproductive barrier.

• ^^Habitat differentiation:^^ Species develop by using different resources in their geographical area and slowly separating from the initial species

• ^^Sexual selection^^

• ^^Adaptive Radiation^^: One species diversifies into multiple species to fill empty ecological niches

  

==Chapters 23-24==

}}23}}

• @@Radiometric dating@@ uses half lives
• @@Mass extinctions@@ pave the way for adaptive radiation because it frees up ecological niches

}}24}}

• @@Gram + bacteria@@ has thick simpler walls high in peptidogylcan

• @@Gram - bacteria@@ has a thin peptidoglycan wall between possibly toxic outer membrane and inner membrane

  

• ^^Transduction:^^ movement of genes between prokaryotes via phages (viruses that infect bacteria)

• ^^Conjugation^^: Genetic material transferred directly between prokaryotes

• ^^Transformation^^: A bacteria takes up a piece of DNA in its environment