BILD 3 Midterm
Terms
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- descent with modification
- all organisms evolved from a common ancestor
- Linnaeus
- Classification: hierarchical categories two part names
- Cuvier
- Paleontology: catastrophism, earth's biota has changed
- Hutton/Lyell
- Geology: Gradualism (big changes occur through gradual processes) Uniformitarianism (same geologic processes operated in the past as today)
- Lamarck
- Evolution: mechanism = inheritance of acquired characteristics; use disuse
- Malthus
- Economics: population growth is faster than increase in food production -- lead to famine
- adaptive radiation
- rapid speciation of a single lineage to fill ecological niches (common for isolated ecosystems.. e.g. islands)
- Wallace
- observed variation within and between species & described process of evolution by natural selection
- **evolution is different from natural selection!**
- yee.
- evolution
- genetic change over time
- microevolution
- change in genetic composition (allele frequency) of a population over time
- macroevolution
- genetic change over time at the species level or higher
- fossil
- any trace of an organism that lived in the past ex: irish elk proved extinction
- Law of Succession
- fossils in one region are similar to extant oranisms in that same region
- transitional forms ("missing link")
- organisms have characteristics of both extinct and extant forms ex: tiktaalik (transition b/w aquatic & land dwelling). NOT NECESSARILY AN ANCESTOR OF MODERN FORM - can be on extinct side
- vestigial organs
- functionless or rudimentary organs in one species that are useful in another species. ex: blind cave tetra w/ eye ex2: flightless birds w/ wings ex3: goosebumps and wisdom teeth in humans
- Structural Homology
- similarity due to inheritance of traits from a common ancestor ex: mammalian forelimbs
- Developmental Homology
- similarities during development despite differences in adults ex: vertebrate embryos have tail remnants
- Molecular Homology
- similarities at the molecular level ex: genetic code - same codons specify same amino acids
- phenotype
- characteristic of an organism due to both genes and the environment
- genotype
- genetic composition of the organism
- natural selection
- differential survival and reproduction of phenotypes
- fitness
- contribution an individual makes to the gene pool of the generation, relative to the contribution of other individuals
- artificial selection
- natural selection imposed by humans for a specific goal (e.g. breeding of crops or animals) ex: cauliflower from wild cabbage plant
- mutation
- change in genetic material of an organism.
- sexual recombination
- "reshuffles the deck" - creates new genetic combinations 1. crossing over 2. independent assortment (whether a gamete gets maternal or paternal copy of chromosome is random) 3. fertilization - combines genes from different individuals
- sources of variation
- mutation & sexual recombination
- **mutation doesn't cause evolution but it is necessary**
- **
- How does evolution happen?
- 1. individuals vary 2. variation is heritable 3. individuals with certain traits survive longer and reproduce more (natural selection)
- heritability
- proportion of variation in a trait that is genetic heritability = genetic/phenotypic (b/w 0-1)
- directional selection
- the extreme phenotype is most fit. WILL change population mean will DECREASE variation ex: fishing for pink salmon
- stablizing selection
- intermediate phenotypes are most fit. will NOT change the population mean will DECREASE variation ex: humna birth weight ex2: female fly lays eggs on goldenrod & forms galls - large galls predated by birds, small galls by wasps
- disruptive selection
- two extreme phenotypes are more fit than intermediate phenotypes will NOT change population mean will INCREASE variation ex: seedcrackers are polymorphic for bill size - specialize on large or small seeds
- frequency dependent selection
- fitness of phenotype depends on the phenotype frequencies in the population
- negative frequency dependent selection
- fitness decreases with frequency. ex: cichlid fish - mouth twisted to left or right ex2: side blotched lizards/rock paper scissors ex3: evolution of sex ratio
- positive frequency dependent selection
- fitness increases with frequency. ex: yellow jackets' warning colors
- population
- group of individuals from the same species that live in the same area and have the potential to mate
- probability
- formal study of the laws of chance (b/w 0-1)
- Hardy Weinberg Equilibrium principle
- Null model. 1. if allele frequencies are p & q, genotype frequencies are p2, 2pq, & q2 2. allele frequency will not change from generation to generation unless something changes them
- HW equilibrium assumptions
- 1. no selection 2. mating is random 3. population is large enough that there are no chance events (genetic drift) 4. No gene flow from outside populations 5. No mutation
- gene
- functional unit of heredity
- allele
- alternative forms of a gene
- locus
- location on a chromosome
- homozygote
- same 2 alleles at a locus
- heterozygote
- different alleles at a locus
- gametes
- egg and sperm
- zygote
- fertilized egg
- genetic drift
- changes in the genetic composition of a population caused by chance events
- genetic bottleneck
- a reduction in population size to a low enough level for a long enough time that allele frequencies change randomly
- founder effect
- small number of individuals start a new population
- gene flow
- movement of alleles between populations ex: blue tits - island: nest in sync w/ tree leafing on poor host mainland: nest in sync on good host but out of sync on poor host b/c of gene flow
- gene flow is a ________ force
- homogenizing
- phylogeny
- evolutionary history of a group of species (Phylogenetic tree - picture of that history)
- systematists
- those who study the evoltionary relationships among organisms
- **organisms that look alike aren't necessarily more closely related**
- ex: birds and crocodiles are more closely related (share a more recent common ancestor) than crocodiles and lizards
- node
- branching point of a phylogenetic tree; represents a common ancestor
- sister taxa
- 2 taxa tha derive from immediate common ancestor (each other's closest relative)
- monophyletic (clade)
- contains common ancestors and all descendents
- paraphyletic
- contains common ancestor and some but not all descendants
- polyphyletic
- taxa with different recent ancestor
- ingroup
- group of taxa that are of interest, assumed to be monophyletic
- outgroup
- one or more taxa assumed to be phylogenetically outside the ingroup
- homoplasy
- character shared between two or more species that was NOT present in common ancestor. due to convergent evolution
- convergent evolution
- independent evolution of the same character in 2 or more species -selection (enviroment) -random (ex: DNA sequences)
- Homologies can be ______ or ________
- ancestral (orginated in ancestor) OR derived (unique to clade)
- synapomorphies
- shared derived homologies
- outgroup comparisons
- can distinguish between ancestral and derived character states
- parsimony
- principle for developing phylogenies. tree with fewest evolutionary changes is correct
- maximum likelihood
- finds the most likely tree given a certain model of DNA change; assumes equal rates of DNA change
- Phylogenies are useful because...
- 1. Shows how an ecologically important trait has evolved 2. solves crime
- molecular clock
- way of estimating absolute age of evolutionary change - species divergence
- speciation
- divergence of lineage to create new species
- speciescape
- size is proportional to the number of described species in the higher taxon it represents
- biological species concept
- species is a group whose members have the potential to interbreed in nature and produce viable, fertile offspring
- what unites a species?
- gene flow
- reproductive isolation
- barriers that prevent different species from producing viable offspring
- prezygotic barriers
- individuals never mate ex: 2 species of green lacewings that are morphologically indistinguishable but sing different songs
- postzygotic barriers
- mating occurs but offspring not viable or fertile ex: donkey + horse = mule (sterile)
- morphospecies concept
- species defined by morphological traits -used by paleontologists to define fossils
- phylogenetic species concept
- set of organisms with unique genetic history
- problems with biological species concept
- 1. mating/lack of mating can be hard to see 2. ability to mate vs likelihood of mating 3. cannot be applied to fossils 4. cannot be applied to asexual organisms
- problem with morphospecies concept
- cryptic species (morphologically identical but genetically distinct)
- allopatric speciation
- reproductive isolation occurs because populations are geographically separated
- 2 types of allopatric speciation
- 1. vicariance: divergence of one population to two 2. dispersal: divergence of a small population away from a large ancestral population
- sympatric speciation
- speciation in geographically overlapping populations
- 2 types of sympatric speciation
- 1. Habitat differentiation (ex: apple maggot fly has strong association with host plant) 2. polyploid (organism with >2 copies of chromosomes)
- reproductive isolation as a byproduct
- ex: beetles look like caterpillar frass
- reproductive isolation as an adaptation (reinforcement)
- to prevent unfit hybrids
- ecology
- the study of the interactions between organisms and their environment
- population density
- the number of individuals per unit area
- how to measure population density
- 1. count 2. count then extrapolate 3. proxy (nest, damage, droppings) 4. mark-recapture
- clumped dispersion
- individuals aggregate in patches ex:wolves
- uniform dispersion
- individuals are evenly distributed ex: penguins
- random dispersion
- position of each individual is independent of other organisms
- demography
- study of population growth
- life tables
- age specific summary of the survival pattern of a population
- survivorship curves
- way to express survival information graphically
- type I survivorship curve
- survivorship is high for young/middle aged; low for old ex: humans
- type II survivorship curve
- equal rate of survivorship ex: squirrels
- type III survivorship curve
- survivorship is low for young/middle aged ex: oysters
- life histories
- pattern of age specific survival and reproduction of an organism
- semelparity
- "big bang" reproduction produce many offspring once and die offspring not well provisioned
- iteroparity
- repeated reproduction produce fewer well provisioned offspring & do so repeatedly over time
- factors that favor semelparity
- -unpredictable environments -low probability that any one offspring will survive -low probability that adults will live to reproduce again
- factors that favor iteroparity
- -dependable environment -high probability of offspring survival
- **all organisms face _______ in how to allocate finite resources***
- tradeoffs
- populations can change in size through
- birth death emigration immigration
- population growth equations
- dN/dt = (b-d)N = rN Nt=Noert
- logistic growth equation
- dN/dt= rmaxN(K-N)/K
- carrying capacity (K)
- the maximum population size the environment can support
- density independent factors
- affect population independent of its density ex: disturbance, landslide, fire, etc
- density dependent factors
- birth and or death rates change with density
- types of density dependent population regulation
- 1. intraspecific competition for resources - as density increases, individual reproduction decreases 2. density dependent predation - ex: trout preferentially prey on most abundant insect in stream 3. territoriality - ex: cheetahs 4. density dependent disease spread - ex: TB spreads in densely populated aread 5. Wastes - ex: wine: alcohol byproduct of yeast fermentation. 6. Intrinsic factors - ex: mice decrease reproductive rates in crowded pop... aggressive interactions
- metapopulations
- groups of populations linked by immigration and emigration (can be a buffer against extinction of populations)
- age structure
- the relativ number of individuals at each age -affects a country's future growth
- mark-recapture assumptions
- 1. marked & unmarked individuals have the same probability of being captured 2. marked organisms mix completely back into the population 3. no individuals are born, die, immigrate, or emigrate during the re-sampling interval