Bio 200 Exam 1 Study Guide
Bio 200 Exam 1 Study Guide BIO 200LLB
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This 13 page Study Guide was uploaded by Nicole on Thursday October 1, 2015. The Study Guide belongs to BIO 200LLB at University at Buffalo taught by Lindqvist, C in Fall 2015. Since its upload, it has received 596 views. For similar materials see Evolutionary Biology in Biological Sciences at University at Buffalo.
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Date Created: 10/01/15
Bio Review: Exam 1 Early Earth: Hadean “Hell” Eon: -‐Lasted ~800 million years -‐No Oceans -‐No free Oxygen -‐Planet was fully molten -‐No protective atmosphere -‐Towards the end of Hadean, Earth cooled in about 150 million years (fast in geologic time) -‐Earth was bombarded by asteroids, which caused cracks on the surface. Steam & gas was released and allowed for the formation of an atmosphere -‐Clouds formed & rain gave rise to oceans -‐No ozone layer, little UV protection -‐Ends between 4.2 and 3.8 billion years ago with first signs of life Source: http://geologycafe.com/images/timescale_highlights.jpg Key Time Points: Time Event 4.6 BYA Earth Forms 4.0 BYA Earth begins to cool ~3.8 BYA First Life forms 2.5 BYA Oxygen accumulates (photosynthesis) 1.7 BYA 1 Eukaryotes st 1 BYA 1 Multicellular Organisms 450 MYA 1 Land Plants 420 MYA 1 Land Animals 250 MYA Permian Extinction 230 MYA 1 Dinosaurs 200 MYA 1 Mammals 65 MYA K-‐T Extinction 2 MYA First Humans Panspermia-‐theory that life first evolved elsewhere in the universe but was seeded to Earth What Earth looked like 3.8 BYA -‐Molten rock -‐All life must have been aquatic -‐No free Oxygen -‐Created reducing atmosphere -‐Electron adding-‐ molecules form very readily -‐High Energy Environment -‐Little to no UV blocking 4 Steps to Life on Early Earth: 1.) Abiotic Synthesis of Organic Molecules -‐Miller-‐Urey Experiment attempted to recreate Earth’s early atmosphere in 1953 -‐In early 1990’s we discovered that earth’s early atmosphere was predominantly composed of CO and N , 2either o2 which were found in original experiment -‐Samplings of the more modern experimental “oceans” that form contain the building blocks of life (amino acids, nucleotides, sugars, lipids, ATP), and were formed in only one week 2.) Formation of Polymers -‐Polymers (protein, DNA) form when monomers (amino acids, nucleotides) get together and form a chain -‐Role of Clay -‐Positively charged, rich in iron and zinc, which attracted negatively-‐ charged monomers -‐Would indicate that first life formed near clay-‐rich shores 3.) Formation of Protobions -‐Aggregates of abiotically produced organic molecules surrounded by a membrane -‐Lipids -‐Hydrophobic tails and hydrophilic heads form together to create liposome (lipid bilayer) -‐Forms cavity that can hold chemicals-‐begins to look like a cell 4.) Origin of Heredity Material -‐First hereditary material was likely RNA -‐RNA can be formed abiotically more easily than DNA can -‐Can replicate itself (even more likely in presence of Zinc) -‐Contains hereditary information -‐Has catalytic properties-‐can act as an enzyme (unlike DNA) -‐Recent research suggests that RNA can be composed completely of sugars and hydrogenous bases, both components that would have been found on early Earth -‐Viroids-‐may have led to first life -‐Tiny particles of raw RNA, smaller than a virus -‐Enough genetic information to infect a plant and trick the plant’s genetic machinery into replicating a viroid -‐Because they cannot replicate on their own, viroids still cannot be considered life History of Evolutionary Theory People to Remember: -‐Anaximander -‐Greek Philosopher-‐Transmutation, common descent -‐Carolus Linnaeus -‐Binomial Classification -‐James Hutton -‐Gradualism-‐Geologic differences happened over long periods of time -‐Adam Smith -‐Competition -‐Jean-‐Baptiste Lamarck -‐Acquired Traits (giraffes) -‐Thomas Malthus -‐Population growth limited by resources -‐George Cuvier -‐“Catastrophism”, fossils (extinction occurs) -‐Charles Lyell -‐Uniformitarianism-‐“Present is the key to the past” -‐Charles Darwin -‐Species change through time, common descent -‐Alfred Russel Wallace -‐Wallace’s Line, natural selection Darwin: Modern Five Parts of Darwin’s Theory: -‐Individuals vary -‐Populations tend to overbreed relative to available resources, leading to a struggle fro survival -‐Better variations have better survival -‐Survivors will reproduce & non-‐survivors won’t (not always necessary criteria) -‐Traits leading to better survival & reproduction must be heritable Do Individuals vary? Yes! Do populations tend to overbreed? Yes-‐ Oak trees put out many more seeds that can possibly survive. Somewhere between 0.01-‐0.1% of seedlings are expected to survive -‐One oak tree will release over one thousand acorns in its lifetime Do better variations for a particular environment have higher survival rates? Rosemary and Peter Grant-‐ worked on Daphne Major Island in Galapagos -‐Two of Darwin’s finches live on this island-‐large and medium ground finch -‐Variation in head & beak size in medium ground finches -‐Survival of these birds is based on seed availability -‐1977-‐Severe La Nina -‐Extreme drought, extreme population decline (from 1,400 finches to 200 finches in just one year) -‐Soft seeds quickly eaten, leaving only hard seeds remaining -‐Birds with longer and deeper beaks out-‐survived those with smaller beaks -‐1984-‐ El Nino, very wet year -‐Abundance of small seeds (can fall out of large beaks) -‐Smaller beaked birds survived better than those with large beaks -‐Solidifies theory that better variations have better survival rates Do survivors have more offspring and pass on their selected traits to the next generation? -‐Grants plotted beak size of parents by the beak size of offspring & found very strong correlation – strongly suggests that traits are heritable -‐Evolution actually changed the average beak size across generations, causing more birds to have large beaks -‐Concludes that traits leading to better survival and reproduction must be heritable Why isn’t everyone satisfied? Implications Involved in accepting this theory: -‐Earth must be old enough for evolution to have occurred -‐Fossils should show evidence of change through time -‐Older rock strata should have fewer fossils of modern species than younger rock strata -‐Fossils of intermediate forms must be found Is Earth Old enough? -‐Hutton & Lyell both believed so -‐Depth of canyons & thickness of rock strata both indicate very long & gradual natural process -‐We can now date the oldest found rocks to be 4.6 billion years old -‐Found oldest life to be about 3.8 billion years old -‐Earth is old enough Do fossils show that species are mutable? -‐Cuvier showed that extinction occurred and that recent species were no longer extant -‐Darwin’s fossils -‐Megatherium-‐Giant sloths 1.1m tall & weighed up to 6,000 lbs -‐Toxodon-‐ capybara like species 1.5m tall & weighted up to 1.5 tons -‐Glyptodon-‐Giant armadillos, 1.5m tall, weighed as much as average sedan -‐Fossils were closely related to animals alive at the time, but were not the same species Do younger rocks strata have more modern fossils than older rock strata? -‐Lyell’s data on mollusks proved this to be true Are there fossils of intermediate forms? -‐3 years before his death, Archaeopteryx fossils were found -‐Has traits of both birds and reptiles-‐intermediate form -‐Provides solid evidence of transitional forms -‐Whales, Horses & Tiktaalik (intermediate between fish & amphibian) all good examples of intermediate forms Gregor Mendel (1822-‐1884) Mendel’s Five-‐Element Model: -‐Parents transmit information about traits to their offspring -‐Each individual receives two copies of each factor to encode each trait -‐Not all factors are the same and different combinations lead to different traits -‐Two factors do not blend -‐Presence of a factor does not guarantee it will be expressed-‐ it can be latent Genotype -‐Alleles found in individuals -‐Homozygote dominant has different genotype that heterozygote dominant -‐AA differs from Aa even if both flowers are purple Phenotypes -‐AA=Aa -‐Physical characteristics of organisms -‐Phenotype ration 3:1 st Mendel’s 1 Law of Heredity-‐Principle of Segregation -‐Two parental alleles segregate during gamete formation to be rejoined at random during fertilization Monohybrid Cross: -‐Parental Generation Ry * rY -‐3:1 ratio Dihybrid Crosses-‐Mendel’s 2 nd Law of Heredity-‐Law of Independent Assortment Parental Generation: RRYY * rryy -‐F1-‐ RrYy -‐ Dihybrid Crosses lead to 9:3:3:1 phenotype ratio -‐In Dihybrid cross, alleles of each gene assort independently http://cnx.org/resources/ceb880bf9a58402dc053bb94ff94ec158ffc2a3a/Fig ure_12_03_02.png Mendel was Unaware: Genes are Sometimes Linked -‐Certain alleles are almost always expressed together -‐Linked genes are on the same chromosomes and do not assort independently Polygenic Inheritance -‐Traits can be controlled by multiple factors -‐Epistasis-‐Lab coat color determined by 2 genes that interact -‐Without knowing gene type, it is impossible to know dog color -‐Sickle cell anemia -‐Multiple effect of one gene-‐decreased ability to transport oxygen but decreases susceptibility to malaria Dominance is Not Always Complete -‐Incomplete dominance: Parental phenotypes blend in the heterozygote -‐Blending ends with the heterozygote -‐Co-‐dominance-‐heterozygotes show both parental phenotypes unblended -‐Dominance is not always complete co-‐dominance Environmental Differences’ Effect on Factor Expression -‐Siamese cats-‐ melanin in Siamese cats is due to temperature-‐ near core, temperature is too high to allow expression of melanin-‐producing enzyme Chromosomes: Terminology: Karyotype-‐Map of set of chromosomes Chromatids-‐When chromosomes condense & become visible but before they replicate Sister Chromatids-‐The two identical chromatid copies formed during replication Centromere-‐Part of the chromosome that links sister chromatids Chromosome-‐Pair of sister chromatids form the chromosome Homologous Pair-‐Same chromosome type from mom and dad Mitosis -‐Interphase -‐DNA is diffused and hard to see -‐Phase where DNA is replicated -‐Only phase of cell cycle where DNA is accessible to proteins involved in replication -‐Prophase -‐Mitosis begins -‐Chromatin becomes more compact & becomes visible -‐Now consist of identical sister chromatids -‐Mitotic spindle forms-‐structure that will pull the cell apart -‐Prometaphase -‐Nuclear envelope breaks down -‐Kinetochore microtubules, which are connected to the poles, attach to the chromosomes -‐Metaphase -‐Chromosomes line up at mid-‐line of cell-‐Equatorial position -‐Chromosomes are condensed and highly quarreled -‐Anaphase -‐Sister chromatids are pulled apart to opposite ends of the cell Telophase -‐Last phase of mitosis -‐Chromosomes are fully separated -‐Cell cleaves in half to form two daughter cells -‐Daughter cells have same number of chromosomes as parent cell-‐identical copies Meiosis: -‐Following interphase, chromosomes begin to condense and a meiotic spindle forms -‐Homologous pairs join in center of cell -‐Each chromosome will end up at each end of the cell -‐Cell divides to form 2 daughter cells -‐Daughter cells are genetically distinct & have only half as many chromosomes as parent cell (when gametes join, there will be the right number of chromosomes) Ploidy=number of copies of chromosomes A cell with one copy is a Haploid (1N)-‐Gametes Cell with 2 copies is a Diploid (2N) More than two copies is a polyploidy (xN) Mitosis: 2Nà4Nà2N Meiosis: 2Nà4Nà2Nà1N Crossing Over -‐Occurs in the beginning of meiosis when homologous pairs join -‐Enzymes break & rejoin chromatids on homologous chromosomes-‐DNA from non-‐ sister chromatids can be exchanged -‐Now chromosomes from dad may have DNA from mom’s chromosome on it -‐Chromosomes may have many or very few crossovers Recombination -‐Now genetic material from parents is mixed-‐leads to much higher variation among offspring Gene Linkage -‐When genes are unlinked, the F1 generation can produce gamete combinations -‐When traits are linked A will not appear with b and B will not appear with a -‐Distance between genes on chromosomes has a lot to do with whether or not they will be linked -‐Genes close together on chromosome are tightly linked, while genes further apart are loosely linked as they can be easily separated during recombination DNA -‐Double helix-‐two strands of genetic material (Discovered thanks to Rosalind Franklin’s X-‐ray of DNA) -‐Backbone made up of repeating sugar and phosphate units -‐H-‐bonds hold nucleotides together-‐specifically pair certain nucleotides together Four nucleotides: -‐Adenine (A)-‐pairs with Thymine -‐Thymine (T) -‐Cytosine (C)-‐Pairs with Guanine -‐Guanine (G) Semiconservative DNA Replication-‐ Produces molecules with both old and new DNA, but each molecule contains one complete old and one complete new strand -‐Due to complimentary pairing, information of strands is rarely lost -‐Helix unzips original strand, breaks bonds between nucleotides and enzymes work together to bring new nucleotides to parental chain & form daughter strands -‐DNA Polymerase matches existing nucleotides on parental chain with complimentary bases & form bonds between the new pairs Transcription -‐Process of copying DNA to RNA -‐Replication and transcription occur in the nucleus Translation-‐RNA to proteins -‐Occurs outside the nucleus RNA -‐Always single stranded -‐Adenine pairs with Uracil rather than Thymine Protein -‐Made up of amino acids -‐All proteins are different combinations of only 20 amino acids -‐Codons-‐3-‐letter units that encode amino acids -‐Some codons stop translation Allele Frequency -‐Allele frequency is simply the number of times that an allele occurs in a population How do Allele Frequencies change? 1.) Gene flow a. Migration of alleles from one population to another 2.) Non-‐random mating a. Assortative mating-‐organisms of similar phenotypes tend to mate together more often than expected by random chance b. Increases homozygous organism ratio 3.) Genetic Drift a. Random changes in allele frequencies-‐has bigger effect in small populations b. Founder Effect-‐When a portion of a population becomes separated and interbreeds to form new allele frequencies c. Bottleneck Effect-‐When a natural disaster wipes out the majority of a population. The remaining survivors will reproduce to create new, less diverse allele frequencies (Finches on Daphna Major island) 4.) Mutation a. Ultimate source of genetic variation, though not a driving force in changes to allele frequencies b. Findings of Francis Crick & Sydney Brenner: i. -‐Codons are not spaced and read in threes ii. -‐Reading frame is critical c. Point Mutations: i. Frame-‐Shift Mutations-‐disastrous effects, causes entire chain of amino acids to be translated incorrectly ii. Silent Mutations-‐also called synonymous substitution-‐no change in amino acid sequence iii. Missense Mutations-‐also called non-‐synonymous substitution-‐ occurs when one amino acid is replaced by another iv. Nonsense Mutations-‐ Substitution of a base by a stop codon-‐ early termination of translation almost always results in the loss of function for the protein d. Chromosomal Mutations: i. Deletion-‐when large chunk of chromosome is deleted, causes a significant loss of genes ii. Duplication-‐when a large region of the chromosome is copied iii. Inversion-‐ when a section of the chromosome is reversed & placed back into the chromosome. So long as this does not happen in the middle of a gene, it usually has no effect iv. Translocation-‐when a piece of chromosome attaches to it’s non-‐homologous pair during crossing over Meiosis Nondisjunction -‐Occurs when chromosomes fail to separate during metaphase 1 Aneuploidy -‐Have gained or lost a chromosome -‐Very common in sex chromosomes (5% of conceptions) -‐Klinefelter’s syndrome: XXY -‐Turner’s Syndrome: XO -‐Monosomy-‐ when a gamete has lost a chromosome-‐fatal -‐Trisomy-‐gamete with an extra chromosome (occasionally individuals can survive this)-‐Down Syndrome –extra chromosome Polyploidy -‐Entire genome is copied -‐Can be caused by meiotic error where homologous chromosomes do not separate or can be result of hybridization between 2 different species -‐Rarely happens in animals & is often fatal if it does occur -‐Extremely common in plants -‐Bananas have 3 sets of chromosomes rather than 2 5.) Natural Selection Factors required for Natural Selection to Operate: -‐Must be variation in the population -‐Variation must lead to differences among individuals in lifetime reproductive success -‐Variation must be transmitted to the next generation Common Selective Forces 1.) Predation 2.) Climatic factors 3.) Parasitism 4.) Mate Attraction 5.) Resource acquisition Stabilizing Selection -‐When just one variation of a trait works best for the species -‐Decreases range of traits found in a population so that all species are closer to a mean value Directional Selection -‐When the environment changes, mean for a trait moves higher or lower Disruptive Selection -‐Where extremes exist for each trait range, but there is a very low percent of population near the mean Balancing Selection -‐Heterozygote advantage -‐Sickle-‐cell anemia-‐heterozygote has advantage of malaria immunity that homozygotes do not -‐Negative Frequency dependent selection -‐Fitness of a species becomes higher as the frequency of its genotype increases -‐Rare individuals have a higher fitness than common individuals -‐Maintains polymorphisms among prey species-‐rare species is less likely to be recognized by predators Sexual Selection -‐Traits are selected purely because they attract better mates Reproductive Strategies: -‐Mate choice -‐Mating frequency -‐Mate guarding -‐Long-‐term mating behavior (monogamy vs. polygyny) -‐Parental care -‐Offspring spacing Females are Selective: -‐Females invest far more in reproduction -‐Energy-‐Human eggs are 195,000x larger than sperm and contain far more nutrients -‐Time-‐Gestation and child rearing leave females to deal with their choices for years While Females Choose, Males Compete -‐Competition through aggression or display-‐over access to females -‐Sexual dimorphism-‐males have special characteristics like horns and antlers for fighting, and elaborate display characteristics (peacock feathers) In Absent Fathers, Females look for: -‐Oldest, largest & healthiest males -‐All of these traits show good genes, clearly the male has been able to survive & support himself for a long time Handicap Principle -‐Males show off characteristics that are actually a handicap to their survival -‐If a male bird has to carry around a huge set of healthy tail feathers (a handicap to him), he must be especially fit Runaway Selection -‐Elaborate & exaggerated male ornamental features that no longer serve a practical purpose for survival -‐Natural selection will eventually stop runaway selection, as impractical traits will lead to lower fitness Speciation -‐When all small evolutionary changes add up to a big evolutionary moment Allopatric: Occurring in separate, non-‐overlapping geographical areas Sympatric-‐Occupying the same overlapping geographic areas Prezygotic Isolating Mechanisms: 1.) Geographic: species from different locations do not mate, as they do not interact 2.) Behavioral: during the selection of a possible mate, individuals from different species may discard each other, as they don’t have the same mating rituals. 3.) Temporal: individuals from different species may mate at different times of the year 4.) Mechanical: different species may have different sex organs, which are not compatible 5.) Gametic: Chemicals In this case gametes won’t recognize each other and fertilization won’t take place. Postzygotic Isolation 1.) Hybrid viability: sometimes the hybrid dies prematurely. 2.) Hybrid fertility: even if an offspring is produced from the mating of different species usually they are infertile as they generally have a random mixed number of chromosomes (so it’s not the same even between hybrids). 3.) Hybrid breakdown: if the hybrid results to be fertile, the hybrid population might breakdown over time (offspring may be less fertile) “Missing Link” Isolation -‐Intermediate populations that link 2 populations together go extinct, the gene flow between 2 populations is cut off Monophyletic vs. polyphyletic vs. paraphyletic Phylogenies Source: http://www.mun.ca/biology/scarr/139417.jpg Parsimony-‐phylogeny that requires the fewest independent evolutionary events
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