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Transcript
BIG Idea I The process of evolution drives the diversity and unity of life EVOLUTION is a change in the genetic makeup of a population over time 1.A.1 Natural Selection is a major mechanism of evolution a. Darwin’s theory - populations produce more offspring than can survive - inheritable variations occur individuals in a population - resources are limited so there is competition - individuals with more favorable variations or phenotypes are more likely to survive and produce more offspring - traits are passed to next generation (through their genes) Remember: it’s the environment that “selects” for or against the individuals Remember: natural selection acts on the PHENOTYPE (recall tho – phenotype is determined by genotype) Remember: natural selection is the only force that makes a population better “fit” to its environment Remember: Environments change – so what genes are selected “for” in one environment may be selected “against” if environments change (e.g. global warming (fur coats not a needed adaptation in warm temps) h. mathematical approaches are used to calculate changes in allele frequency, providing evidence for the occurrence of evolution in a population. Remember : H-W says that populations are NOT evolving, if you find that the allele frequencies change (e.g. p= .2 in year one and then .7 in year 10) then you have evidence that the population IS evolving! Be able to analyze graphical analysis of allele frequencies: Be able to apply the H-W equation b. Evolutionary fitness is measured by reproductive success Remember: Evolutionary fitness is the amount of genes that are passed on to next generation – more offspring more genes! Remember: Evolution is defined as “differential reproductive success” c. Genetic variation and mutation play roles in natural selection. A diverse gene pool is important for the survival of a species in a changing environment. - Heterozygosity is “good” for populations – allows population to respond to a changing environment. If too many alleles are “fixed” populations may go extinct. Remember: as environments change populations may have to respond to different selective pressures – so having diversity makes the population flexible. d. Environments can be more or less stable or fluctuating, and this affects evolutionary rate and direction; different genetic variations can be selected in each generation. - stable environments – rates are slower, unstable – faster e. An adaptation is a genetic variation that is favored by selection and is manifested as a trait that provides an advantage to an organism in a particular environment. 1.A.2 Natural Selection acts on phenotypic variations in populations a. environments change and act as selective mechanism on populations ·flowering time in relation to global climate change Plants are flowering earlier as temps get warmer Remember: organisms don’t “adapt” (this is always murky water!) – organisms are born with variations and variations are “selected” by the environment. Remember: Lemark said giraffe’s adapt by stretching their necks (this is the theory of acquired characteristics and is a BIG no no in evolutionary terms! Don’t use this – be careful of your language!) f. In addition to natural selection, chance and random events can influence the evolutionary process, especially for small populations ·peppered moth (directional selection) Remember: Population lab – Genetic drift (chance events) can move populations towards one allele or the other – this is not natural selection and can’t be predicted or controlled -Two types of Genetic drift (Bottlenecks and Founder Effect) Both are situations where new populations may not resemble original population s Both occur when there is a drastic reduction in the gene pool Bottleneck – Prairie Chicken loss of range= loss of genetic diversity Founder – Amish - Ellis-van Creveld syndrome – polydactyly g. 5 Conditions for a population or an allele to be in Hard-Weinberg equilibrium: 1. Large population size 2. no Gene Flow (immigration or emigration) 3. no mutations 4. random mating 5. no natural selection Remember: H-W equations: p2 + 2pq + q2 = 1 and p + q = 1 Always start with finding the % of the recessives (that’s q2 )! Take the square root of q2 and you’ll have q Subtract q from 1 and you have p. Plug them into the equation p2 = homozygous dominants (AA) 2pq = heterozygotes (Aa) b. Phenotypic variations are not directed by the environment but occur through RANDOM changes in the DNA and through new gene combinations. Remember: natural selection is only an “editing” mechanism, it cannot CREATE new genes – only mutation can do that Remember: organisms cannot change their genes- they have what they were born with. e.g. Organisms cannot “evolve” a new body color. Remember: new gene combinations arise through MEIOSIS – 1. crossing over 2. Independent assortment 3. Random fertilization Artificial selection: (wild mustard) Selective pressures can cause populations to change c. some phenotypic variations significantly increase or decrease fitness of the organism and the population Loss of genetic diversity within a crop species: - diversity allows for some members to survive - monocrops (all one crop) is disasterous if disease strikes ·sickle cell anemia ( fitness (except in areas where malaria is present) ·peppered moth ·DDT resistance in insects Overuse of antibiotics: Remember: insects are not developing resistance – a small number are born with a variation to be resistant. When DDT is sprayed, it kills all the non-resistant insects leaving only resistant ones. They mate and soon the entire population is resistant to the pesticide. Also – insects don’t have an immune system (remember TOLL like receptors?) Remember: The DDT is selecting which organism will live Remember: this also is true of antibiotic – resistance in bacteria 1.A.3: Evolutionary change is also driven by random processes a. Genetic drift is a nonselective process occurring in small pop’s This is a BIG BiG problem that CB wants you to remember! d. Humans impact variation in other species ·artificial selection ·Loss of genetic diversity within a crop species ·overuse of antibiotics (see above) b. reduction of genetic variation within a given population can increase the differences between populations of the same species 1.A.4: Biological evolution is supported by scientific evidence from many disciplines, including mathematics a. scientific evidence of biological evolution uses information from geographical (biogeography), geological (fossils), physical (comparative anatomy), chemical (DNA, RNA, protein analysis) and mathematical applications. Carbon-14 dating Relationship within phylogenetic trees 2. Morphological homologies represent features shared by common ancestry. Vestigial structures are remnants of functional structures, which can be compared to fossils and provide evidence for evolution. Remember: Homologous structures come from common ancestry and are representative of DIVERGENT evolution b. molecular, morphological and genetic information of existing and extinct organisms add to our understanding of evolution. (know each of these) ·1. Fossils can be dated by a variety of methods that provide evidence for evolution. These include the age of the rocks where a fossil is found (RELATIVE DATING), the rate of decay of isotopes including carbon-14, the relationships within phylogenetic trees, and the mathematical calculations that take into account information from chemical properties and/or geographical data. Relative dating: (correlation to infer the relative age of rocks & fossils) Remember: Analogous structures do not come from common ancestry – but rather evolutionary pressures. They are representative of CONVERGENT evolution Vestigial structures: 2. Major features of the genetic code are shared by all modern living systems 3. Metabolic pathways are conserved across all currently recognized domains b. Structural evidence supports the relatedness of all eukaryotes ·cytoskeleton ·membrane-bound organelles (mitochondria and/or chloroplasts) ·linear chromosomes ·endomembrane systems, including the nuclear envelope 3. Biochemical and genetic similarities, in particular DNA nucleotide and protein sequences, provide evidence for evolution and ancestry. 4. Mathematical models and simulations can be used to illustrate and support evolutionary concepts · graphical analyses of allele frequencies in a population · analysis of sequence data sets · analysis of phylogenetic trees · construction of phylogenetic trees based on sequence data 1.B.2: Phylogenetic trees and cladograms are graphical representations (models) of evolutionary history that can be tested. a. Phylogenetic trees and cladograms can represent traits that are either derived or lost due to evolution 1B: Organisms are linked by lines of descent from common ancestry 1.B.1: Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. a. structural and functional evidence supports the relatedness of all domains 1. DNA and RNA are carriers of genetic information through transcription, translation and replication ·number of heart chambers in animals · opposable thumbs · absence of legs in some sea mammals b. Phylogenetic trees and cladograms illustrate speciation that has occurred, in that relatedness of any two groups on the tree is shown by how recently two groups had a common ancestor c. Phylogenetic trees and cladograms can be constructed from morphological similarities of living or fossil species, and from DNA and protein sequence similarities, by employing computer programs that have sophisticated ways of measuring relatedness among organisms (BLAST lab!) d. Phylogenetic trees are dynamic (constantly being revised), based on the biological data used, new mathematical and computational ideas and current and emerging knowledge. 1 C: Life continues to evolve within a changing environment 1.C.1 speciation and extinction have occurred throughout the Earth’s history. a. speciation rates can vary, especially when adaptive radiation occurs when new habitats become available. b. New species arise from reproductive isolation over time, which can involve scales of hundreds of thousands or even millions of years, or speciation can occur rapidly through mechanisms such as polyploidy in plants. - SYMPATRIC SPECIATION ·autopolyploidy, allopolyploidy b. species extinction rates are rapid at times of ecological stress · 5 Major extinctions on Earth 1.C.3 Populations of organisms continue to evolve a. scientific evidence supports the idea that evolution has occurred in all species b. scientific evidence supports the idea that evolution continues to occur ·chemical resistance (mutations for resistance to antibiotics, pesticides, herbicides or chemotherapy drugs occur in the absence of the chemical) · Human impact on ecosystems and species extinction rates (refer to your Darwin200 Evo packet reading) 1.C.2: speciation may occur when two populations become reproductively isolated from one another a. speciation results in diversity of life forms. Species can be physically separated by a geographic barrier (allopatric speciation) such as an ocean or a mountain range, or various pre-zygotic and post-zygotic mechanisms can maintain reproductive isolation and prevent gene flow. Remember: the key to maintaining a species is Reproductive Isolation Remember: species definition: members of a population that are capable of interbreeding and producing viable (fertile) offspring. ·emergent diseases · observed directional phenotypic change in a population (Grant’s observations of Darwin’s finches in the Galapagos (this was in your Darwin200 reading!)) ·a Eukaryotic example that describes evolution of a structure or process such as heart chambers, limbs, the brain and the immune system 1D: The origin of living systems is explained by natural processes 1.D.1: There are several hypotheses about the natural origin of life on Earth, each with supporting scientific evidence. a. scientific evidence supports the various models - know EACH of the following; ·1. Primitive Earth provided inorganic precursors from which organic molecules could have been synthesized due to the presence of available free energy and the absence of a significant quantity of oxygen. ·2. In turn these molecules served as monomers or building blocks for the formation of more complex molecules, including amino acids and nucleotides. ·3. The joining of these monomers produced polymers with the ability to replicate, store and transfer information. ·4. These complex reaction sets could have occurred in solutions (organic soup model) or as reactions on solid reactive surfaces. ·5. The RNA World hypothesis proposes that RNA (not DNA) could have been the earliest genetic material. Urey- Miller experiment: b. Molecular and genetic evidence from extant (living) and extinct organisms indicates that all organisms on Earth share a common ancestral origin of life. - understand EACH of the following: 1. scientific evidence includes molecular building blocks that are common to all life forms. 2. Scientific evidence includes a common genetic code. RNA World Hypothesis: 1.D.2: Scientific evidence from many different disciplines supports models of the origin of life. a. Geological evidence provides support for models of the origin of life on Earth - understand EACH of the following: 1. The earth formed approximately 4.6 billion years ago (bya) and the environment was too hostile for life until 3.9 bya, while the earliest fossil evidence for life dates to 3.5 bya. Taken together, this evidence provides a plausible range of dates when the origin of life could have occurred. 2. Chemical experiments have shown that it is possible to form complex organic molecules in the absence of life. (Urey-Miller!)