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79 Cards in this Set
- Front
- Back
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Charles Darwin's two theories
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1) Evidence that many species of organisms existing now are descendants of ancestral species
2) Natural selection - a mechanism for evolutionary progress |
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Aristotle
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Species are fixed and unchanging. God created everything perfect.
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Linnaeus
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Adaptations are evidence that creator designed each species for a specific purpose (not evolutionary)
Founder of Taxonomy |
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Cuvier
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Catastrophism (in strata of sedimentary rock) not gradual evolutionary change
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Hutton and Lyell
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Changes in earth's surface can result from slow continuous actions even today (basically gradualism) --- Influences Darwin
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Lamarck
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Species evolve through use and disuse, and inheritance of acquired traits (for example dyed hair)
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Darwin's voyage on the Beagle
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All organisms are related through descent from an ancestor in the remote past. History of life is like a tree with lots of branches.
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Ernst Mayr
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dissects Darwin's theory
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Ernst Mayr's Theories: Observations
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1) Population would increase exponentially if all individuals reproduced successfully
2) Populations tend to stay stable in size 3) Resources are limited 4) Members of a population vary extensively in their characteristics 5) Much of this variation is heritable |
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Ernst Mayr's Inferences
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1) If there are more individuals than the environment can support, it leads to a struggle for existance among individuals in the population (SURVIVAL OF THE FITTEST)
2) Survival depends in part on inherited traits - better chance surviving 3) Unequal ability of individuals to survive and reproduce will lead to gradual change in population b/c of natural selection. |
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Microevolution
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change in genetic makeup of population from generation to generation
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Population genetics
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how populatioin change genetically
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Modern Synthesis
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Integrates Mendelian genetics with Darwinian theory of evolution by natural selection
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Population
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localized group of individuals is capable of interbreeding and producing fertile offspring
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Gene Pool
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Total aggregate of genes in a population at one time, consists of all gene loci in all individuals in the population
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Fixed Gene
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if only one gene exists for a particular gene locus
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Hardy Weinberg Theorum
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a population NOT EVOLVING where allele frequencies stay constant, random mating occurs
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Artificial Selection
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humans modify species over many generations by selecting/breeding individuals with desired traits
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Natural Selection
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differential success in reproduction because of heritable traits and environment way to adapt to environment (survival of the fittest)
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Homology
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similarity resulting from common ancestry. Could be similar anatomical resemblance, comparative embryology, and vestigial organs that are remnants from ancestors
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Similar mammals & Similar Environments
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without an actual common ancesto, but have homologies
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Hardy-Weinberg Equation
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p^2 +2pq + q^2
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5 Conditions for Hardy-Weinberg Equilibrium
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Large Population size, no gene flow, no mutations, random mating, no natural selection
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We use Hardy-Weinberg to...
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estimate percentage of human population carrying allele for inherited diseases
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Mutations
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changes in nucleotide sequence of DNA, causes new genes and alleles to arise (point mutations, chromosomal mutations, gene duplications). More rapid in microorganisms
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Point Mutations
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changes in one base of a gene that can have a significant impact on phenotype
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Chromosomal mutations
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mutations that delete, disrupt, duplicate, or rearrange many loci at once are almost certain to be harmful. Only on rare occasions is this beneficial.
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Genetic drift
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unpredictable fluctuation in allelic frequencies from one generation to the next. (smaller the pop. greater chance for gen. drift)
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Bottleneck Effect
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sudden change in the environment drastically reduces the size of a population. Few survivors can only pass on THEIR gene pool (no longer reflects full pop. gene pool)
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Founder effect
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few individuals become isolated from a larger population and establish a new population whose gene pool is not the same.
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Gene flow
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genetic additions or subtractions to or from a population resulting from movement of fertile individuals or gametes (genes moving in or out)
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Genetic variation
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exists naturally in populations.
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Polymorphic
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when a character exists in two or more discrete forms in the population
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Geographic Variation
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differences in gene pools among populations or parts of populations
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Cline
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graded change in a trait along a geographic axis
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Factors contributing to preservation of genetic variation
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diploidy, balanced polymorphism
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Heterozygote advantage
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heterozygous at certain locus, gives them an advantage for survival (ex. sickle-cell disease)
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fitness
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contribution an organism makes to the gene pool of the next generation relative to the contributions of other members
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Three modes of selection
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Directional, disruptive, stabilizing
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4 Reasons why natural selection can't produce perfection
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1) Evolution is limited by historical constraints (work with what you got)
2) Adaptations are mostly compromises 3) Chance and natural selection interact 4) Selection can only edit existing variations |
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Speciation
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process by which new species arise
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Microevolution
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change in the genetic makeup of a population from generation to generation; adaptations confined to a single gene pool.
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Macroevolution
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evolutionary change above species level (novelties) that define higher levels of taxonomy.
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Biological Species Concept
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Defines a species as a population or group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring, but are unable to produce viable fertile offspring with members of other populations
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Reproductive isolation
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existence of biological barriers that impede members of two species from producing viable, fertile hybrids
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Prezygotic barrier - definition
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Barriers that prevent mating or hinder fertilization
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Postzygotic barrier - definition
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Barriers that prevent a fertilized egg from developing into a fertile adult
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Prezygotic barrier examples (5)
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1) Habitat Isolation - two species in same area but not same habitat
2) Behavioral Isolation - Signals unique to a species not responded to by members of other species 3) Temporal Isolation - may breed at different times 4) Mechanical Isolation - anatomically incompatible 5) Gametic Isolation - gametes may meet, but unable to fuse to form a zygote |
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Postzygotic barrier examples
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1) Reduced hybrid viability - zygote is formed, but genetic incompatibility may cause development to stop
2) Reduced hybrid fertility - Viable offspring cannot reproduce 3) Hybrid breakdown - Can produce viable, fertile "hybrids", but when two hybrids mate, offspring is weak/sterile |
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Allopatric speciation
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Population forms a new species because it is geographically isolated from the parent population.
**Small Newly isolated populations undergo it more frequently, because more likely to have gene pools significantly altered |
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Sympatric speciation
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Small part of population becomes new population without being geographically separated from parent population
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Geological events or processes that can fragment a population
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emergence of a mountain range, formation of a land bridge, evaporation in a large lake that produces lots of small lakes
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Autopolyploid plants
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formed through nondisjunction in meiosis that can lead to sympatric speciation. These plants cannot breed with diploid members and produce fertile offspring
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Polyploid speciation
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occurs in animals, not common. When sympatric speciation can result from part of population switching to a new habitat, food source, or other resource.
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Adaptive radiation
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many new species arise from a single common ancestor - usually happens when a few organisms move to new,distant areas or when environmental changes cause numerous extinctions (niches for survivors) (bottleneck and founder)
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Punctuated equilibrium
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periods of apparant stasis punctuated by sudden change observed in the fossil record.
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Exaptations
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Structures that evolve in one context, but become co-opted for another function (bird feathers co-opted for flying after functioning in thermoregulation)
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"Evo-devo"
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field of study where evolutionary biology and developmental biology converge - how slight genetic divergences can be magnified into major morphological differences between species
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Allometric growth
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different growth rates of various parts of an organism's body during development - can change adult form significantly; potential for evolutionary change
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Homeotic genes
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determine location and organization of body parts. For ex. Hos genes; can change adult form, so potential for evolutionary change
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Phylogeny
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evolutionary history of a species or a group of related species
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systematics
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an analytical approach to understanding the diversity and relationships of organisms.
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traditional systematics
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used morphological and biochemical resemblance among organisms as a basis for inferring evolutionary relationships.
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molecular systematics
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newer tool that uses comparisons of DNA, RNA, and other molecules to infer evolutionary relationships. Often a comparison of different genes and proteins.
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fossil record
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sequence in which fossils appear in the layers of sedimentary rock. fossils (remnants or impressions of dead organisms) are usually found in sedimentary rock.
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paleontologists
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those who study the fossil record
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why is the fossil record incomplete?
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because it favors organisms that existed for a long time, were relatively abundant and widespread, and had shells or hard bony skeletons
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convergent evolution
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two organisms developed similarities as they adapted to similar environmental challenges; not because they evolved from a common ancestor. LIKENESSES ARE ANALAGOUS
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analogous
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the likenesses that result from convergent evolution. opposite of homologous likenesses. for ex. four-chambered heart of birds and mammals is analogous
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DNA sequences and their role in phylogeny
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The more alike the DNA sequences of two organisms are, the more closely related they are evolutionarily. Rate of evolution of DNA sequences varies from one part of genome to another, and comparing different sequences helpsp investigate relationships between groups that diverged a long time ago.
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Taxonomy
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ordered division of organisms into categories based on a set of characteristics used to assess similarities and differences.
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Binomial nomenclature
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used to describe species; consists of genus and species. not the common name.
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Classification of organisms
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Domain - Kingdom - Phylum - Class - Order - Family - Genus - Species
(aka King Philip Came Over For Good Spaghetti) |
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phylogenetic trees
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branching diagrams that depict hypotheses about evolutionary relationships.
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cladogram
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patterns of shared characteristics among taxa
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phylogenetic tree
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cladogram forms the basis of a phylogenetic tree if shared characteristics can be explained by common ancestry
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clade
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a group of species that include an ancestral species and all its descendants. within a phylogenetic tree.
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maximum parsimony
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dictates that a theory with the simplest explanation that is consistant with the facts should be investigated first, for a phylogenetic tree
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molecular clocks
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methods used to measure the absolute time of evolutionary change based on observation that some genes and other regions of the genome appear to evolve at constant rates
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