Chpt.1 Cell Theory

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Cell Theory

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All organisms are made of cells and all cells come from preexisting cells

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Implications of Cell Theory

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-If all cells come from preexisting cells, then all individuals in a population of single-celled organisms must be related by similar ancestry
-In multicellular organisms, all cells trace back to fertilized egg

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Pasteur's Experiment

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Spontaneous generation hypothesis: Cells arise spontaneously from nonliving material
Prediction: cells in both flasks
All-cells-from-cells Hypothesis: Cells are produced only when preexisting cells grow and divide
Prediction: no cells in swan neck flask

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The theory of evolution by natural selection

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species are related to one another and can change through time

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natural selection

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occurs if two conditions are met:
1)Individuals within a population vary in characteristics that are heritable
2)In a particular environment, certain versions of these heritable traits help individuals survive better/reproduce more than do other versions
-characteristics of a population change as a result of natural selection acting on individuals

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population

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group of individuals of same species living in the same area at the same time

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heritable

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traits that can be passed on to offspring

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fitness

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the ability of an individual to survive and reproduce; measured in units of offspring produced

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adaption

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a trait that increases the fitness of an individual in a particular environment

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central ideas of cell theory and theory of evolutions by natural selections

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1)The cell is the fundamental structural unit in all organisms
2)All species are related by common ancestry and change over time in response to natural selection

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speciation

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when natural selection causes a population to diverge and form a new species

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taxonomy

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The effor to name and classify all organisms
Taxanomic Levels: Kingdom> Phylum> Class> Order> Family> Genus> Species

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binomial nomenclature

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Genus species(ital.)
i.e. Homo sapiens(ital.)

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Where is fundamental division of organisms?

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Linnaeus - Plants and Animals
Eukaryotes(nucl.) and Prokaryotes
60's-Five Kingdoms: Moner (prok), Protista (unicell. euk.), Plantae, Fungi, Animalia

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phylogeny

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new goal for taxonomy: the true historical relationships between organisms

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Fundamental division at molecular level

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Bacteria and Archaea (single-cell proks) and Eukaryotes
-these create a new taxonomic level: Domain

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genetic drift

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-undirected; random change in allele frequency that's due to chance in a population
-random w/respect to fitness
-more pronounced in smaller populations
-can lead to random loss/fixation of a gene over time (declines genetic variance)
-can occur in any sampling event, no just in gametes (founder effect, bottleneck)

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sampling error

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the accidental selection of a non represetative sample from some larger population, due to chance

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founder effect

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change in allele frequency due to random sampling during a founder event (group of individuals form a new population)

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genetic bottleneck

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a sudden reduction in the number of alleles in a population

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gene flow

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-movement of alleles from one population to another
-equalizes allele frequencies btwn populations, keeps them from speciating

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mutation

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-ultimate source of genetic variance
-random
neutral>deleterious>beneficial
i.e. E coli competition with stair step results

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inbreeding

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-mating btwn close relatives
-always violates Hardy-Weinberg principle
-increases frequency of homozygosity
-indirectly causes evolution because it exposes and weeds out deleterious recessives

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inbreeding depression

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loss of fitness that happens when homozygosity increases and heterozygosity decreases
-many recessive alleles represent loss of function alleles; heterozygosity can compensate for this
-many genes, especially for fighting disease are under selection for heterozygous advantage