bio exam review
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- 2 major points in "the origin of species"
- 1. evidence that many organisms are descendants of ancestral species
- 2 major points in "the origins of species"
- 2. mechanism for evolutionary process = natural selection, evolutionary adaptation is result of evolutionary adaptation
- why are fossils important to darwinian evolution?
- they are remains/traces of organisms from past, deeper/older the strata, the more dissimilar fossils are from current life, show extinctions
- where are fossils found?
- sedimentary rock strata, each stratum has fossils that rep. species from that period of earth's history
- paleontology? developed by?
- Georges Cuvier study of fossils
- Catastrophism
- each boundary between strata represents a catastrophe, only major catastrophes can change the basic formation of the earth
- Gradualism
- change takes place through the cumulative effect of slow but continuous processes
- Uniformitarianism
- charles lyell mechanisms of change are constant over time, change result of slow continuous processes
- 2 major aspects of Lamarcks theory of evolution
- species evolved through 1. use/disuse of body parts 2. inheritance of acquired characteristics
- "descent with modification"
- evolution, all organisms are related through descent from an ancestor that lived in the remote past
- 4 observations of natural selection and adaption
- 1. members of a pop very greatly in their traits 2. traits are inherited from parents to offspring 3. all species are capable of producing more offspring than the environment can support 4. owing to lack of food/resources, many of these offspring dont survive
- 2 inferences of natural selection and adaption
- 1. individuals whose inherited traits give them a higher prob of surviving and adapting leave more offspring 2. unequal ability of individuals to survive and reproduce will lead to an accumulation of favorable traits over generations
- examples of Darwinian natural selection
- 1. predation and coloration in guppies 2. evolution of drug resistant HIV
- smallest unit of evolution
- a population
- population
- a localized group of individuals capable of interbreeding and producing fertile offspring
- gene pool
- total combination of genes in a population at any one time
- hardy-weinberg theorem
- describes a population in which there there random mating and where allele frequencies dont change-describes a population that is not evolving
- hardy-weinberg equation
- p^2+2pq+q^2=1 p^2=dominant 2pq=heterozygous q^2=recessive p=freq of dominant allele q=freq of recessive allele
- 3 major factors that can alter allele frequencies
- 1. natural selection 2. genetic drift 3. gene flow
- natural selection and alleles
- differential reproductive success
- genetic drift
- allele frequency fluctuate unpredictably from 1 generation to the next
- bottleneck effect
- sudden reduction in a population size due to a change in the environment
- founder effect
- occurs when a few individuals become isolated from a larger population
- gene flow
- movement of alleles among populations
- discrete characteristics
- can be classified on an either-or basis
- quantitative characteristics
- vary along a continuum within a population
- morphs
- individuals that differ in DISCRETE characters
- phenotypic polymorphism
- a population in which 2 or more distinct morphs for a character are readily noticeable
- genotypic polymorphism
- the heritable components of characters that occur in a population
- 3 modes of natural selection
- 1. directional=favors individuals at 1 end of phenotypic range 2. disruptive=favors individuals at both extremes of phenotypic range 3. stabilizing=favors intermediate and acts out against the extreme
- 3 mechanisms preserving genetic variation
- 1. diploidy 2. balancing selection (heterozygote advantage and frequency-dependent selection) 3. neutral variation
- diploidy
- maintains genetic variation in "hidden" recessive alleles which are propagated in heterozygous individuals. rarer the allele, greater the protection
- balancing selection
- natural selection maintains stable frequencies of 2+ phenotypic forms in a pop... balanced polymorphism heterozygote advantage frequency-dependent selection
- neutral variation
- genetic variation appears to confer no selective advantage/disadvantage
- sexual selection
- natural selection for mating success
- heterozygote advantage
- when heterozygotes have a higher fitness then both homozygotes ex=sickle cell anemia
- frequency-dependent selection
- fitness of phenotype declines if it becomes too common in the pop, selection can favor whichever phenotype is less common
- sexual dimorphism
- marked differences between the sexes in secondary sexual characteristics-size
- intra-sexual selection
- competition among individuals of 1 sex (males) for mates of the opposite sex
- inter-sexual selection
- mate choice, when individuals of 1 sex (females) are choosy in selecting mate-male showiness
- speciation
- process by which 1 species splits into 2+ more species
- microevolution
- adaptions that evolve within a pop, confined to 1 gene pool
- macroevolution
- change above species level, broad pattern of evolution over a long time span
- biological species concept
- a species is a group of pops whose members have the potential to interbreed in nature and produce viable, fertile offspring
- reproductive isolation
- biological factors that prevent members of 2 species from producing viable, fertile offspring
- prezygotic barriers
- impede mating between species or hinder fertilization of ova -habitat isolation -temporal isolation -behavioral isolation -mechanical isolation -gametic isolation
- postzygotic barriers
- prevent hybrid zygote from developing into a viable, fertile adult -reduced hybrid viability -reduced hybrid fertility -hybrid breakdown
- allopatric speciation
- when a pop is divided geographically, separate pops may evolve independently through mutation, gene flow, and genetic drift
- sympatric speciation
- takes place in geographically overlapping pops through chromosomal changes (polyploid) and nonrandom mating (sexual selection and habitat differentiation)
- autopolyploid
- individual with more than 2 chromosome sets derived from a single species, gametes are diploid and offspring is tetraploid
- allopolyploid
- species with multiple sets of chromosomes derived from different species
- example of sympatric speciation
- cichlid fish, color differentiation
- 4.6 bya?
- earth is formed
- 3.9-3.8 bya?
- atmosphere is formed?
- 3.5 bya?
- prokaryotes appear
- 2.1-2.7 bya?
- eukaryotes appear, oxygen revolution
- 2.1 bya?
- oldest eukaryote fossils
- 1.2-1.5 bya?
- early multicellular eukaryotes=small algae
- 600 mya?
- large, complex multicellular organisms appear, oxygen levels rise
- 4 stages in origin of life
- 1. abiotic synthesis of small organic molecules (nucleotides and amino acids) 2. macromolecules (proteins and nucleic acids) 3. protobionts 4. self-replicating molecules allowing for continuity of life
- serial endosymbiosis
- mitochrondia and plastids were formally small prokaryotes living within larger host cells
- cambrian explosion
- explosion of diversity, first 20 million years of cambrian period, animals with hard plates and exoskeletons
- continental drift
- process by which earths continents move slowly over underlying hot mantle
- 2 mass extinctions
- 1. permian, ~250 mya, separates paleozoic and mesozoic, caused by volcanoes 2. cretaceous, ~65 mya, separates mesozoic and cenozoic, caused by meteorite, dinos died
- phylogeny
- evolutionary history of a species or group of related species
- taxonomy and creator
- created by carolus linnaeus, ordered division of organisms into categories based on a set of phenotypic characteristics used to assess similarities/differences, includes binomial nomenclature and hierarchal classification
- how can phylogeny and classification be linked?
- systematists depict evolutionary relationships in branching phylogenetic trees, look at morphologies, genes, and biochemistry
- monophyletic clade
- ancestor species and all of its descendants
- paraphyletic grouping
- ancestor species and some but not all descendants
- polyphyletic grouping
- consists of various species that lack a common ancestor
- shared ancestral features
- homologous structure that predates the branching of a particular clade from other members of that clade
- shared derived feature
- an evolutionary novelty unique to a particular clade
- outgroup
- a species/group of species that is closely related to the ingroup
- ingroup
- the various species under study
- outgroup comparison
- differentiate between shared derived and shared ancestral characteristics, based on assumption that homologies present in both outgroup and ingroup must be primitive characters that predate the divergence of both groups from a common ancestor
- relationship between homoplasies and convergent evolution?
- convergent evolution occurs when environmental pressures and natural selection produce similar/analogous adaptions in organisms from different evolutionary lineages
- orthologous genes
- found in a single copy in the genome and are homologous between species, can only diverge after speciation, nucleotide substitutions are proportional to the time since they last shared a common ancestor
- paralogous genes
- result from gene duplication so are found in more than 1 copy of genome, can diverge within the clade that carries them and often evolve new functions, nucleotide substitutions are proportional to the time since the genes duplicated