Week 1 and 2 Notes
Week 1 and 2 Notes BIO1500
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This 13 page Class Notes was uploaded by Nausheen Zaman on Monday January 18, 2016. The Class Notes belongs to BIO1500 at Wayne State University taught by Dr. William Bradford in Winter 2016. Since its upload, it has received 107 views. For similar materials see Basic Life Diversity in Biology at Wayne State University.
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Date Created: 01/18/16
*NOTE: Please DO NOT return after purchase. Thank you!* Chapter 20: Genes Within Populations ● Genetic Variation and Evolution ○ Genetic Variatio differences in alleles of genes found within individuals in a population ■ Usually raw materials for natural selection ■ Alleles one/more alternative states of a gene ■ Genes basic unit of heredity; sequence of DNA nucleotides that code for a specific protein, tRNA/rRNA OR regulate the transcription of a sequence ■ Population any group of individuals of a single species (usually) occupying an area at the same time ■ Natural selectio differential reproduction of genotypes caused by environmental factors that lead to evolutionary changes in a species ○ Evolution how an entity changes over time (developed by Darwin’s theory) ■ ‘Descent with modification’ = original descriptor of evolution ● Idea! ○ As natural selection acts on organisms, they are better fit to adapt to changing environments ○ Those traits are passed down to offspring and EVOLUTION! ● Many processes lead to evolutionary change ○ Darwin was not the first! ■ He proposed natural selection as a mechanism for evolution ● Mechanism of evolution a method of a species going through evolution ○ JeanBaptiste Lamarck ■ Evolution by inheritance of acquired characteristics ● A parent acquires a characteristic over its lifetime and passes it on to his/her offspring and over time it becomes the norm ■ This theory was made during a time where people weren’t aware of the existence of genes *NOTE: Please DO NOT return after purchase. Thank you!* ■ *The only thing that is passed on is GENETIC change, not a physiological change!* ○ Darwin natural selection/geneticallybased variation leads to evolutionary change ■ Neck length of a giraffe is encoded in genetics ■ Over time, it becomes a survival method and ends up becoming more common within a population ● Populations contain genetic variation ○ Population genetics study of properties of genes in a population ○ A change in population’s genetic composition = GENETICS! ○ Genetic variation raw material for selection ■ In other words, variation must be present for selection to happen ■ Rule of nature ○ Anything driving evolution must be GENETICALLY passed on *NOTE: Please DO NOT return after purchase. Thank you!* ● Polymorphic variation more than one allele present in a population is greater in frequency than any mutation alone ○ Human blood groups ■ >30 blood group genes in addition to the main ABO groups ■ ⅓ of these genes are in alternative form ○ You need many different alleles to be selective in alleles you want ■ You need different types of apples in order to be able to select the ones you really want ○ In order to have different alleles… ■ Different mutations need to form over time in a population to select different alleles ○ Think of lupines! ● HardyWeinburg Principle/Equilibrium A mathematical equation that states that allele and genotype frequency remain constant in a randommating population in the absence of inbreeding, selection or other evolutionary forces ○ In simpler terms, proportion of genotypes don’t change if the following occur: ■ No mutations are actively occurring ■ No genes are transferred to other populations through immigration/emigration ■ Random mating is occurring ■ The population is very large (genetic drift) ■ No natural selection is occurring ○ Allele frequency a measure of occurrence in an allele of a population expressed as proportion of an ENTIRE population ○ *No natural selection occurs with this principle* ● Genetic variation is important for evolution to occur because… ○ Produces a fitter population ○ No genetic variation = no allele variation ○ Gives rise to newer/more desirable traits overtime in a population ● The 5 agents of Evolutionary Change: 1. Mutation ○ Relatively low rate (genes mutate 1/100,000 per chain) ○ Ultimate source of genetic variation ■ Variation not usually driven by mutation (which is important when encoding the gene) ○ Makes evolution possible 2. Gene Flow Movement of alleles between two populations that intermix with each other ○ Animals are PHYSICALLY moving into a new population ○ Gametes ‘drift’ from one area to another 3. Nonrandom mating when the probability of two random individuals mating are not the same for all potential pairings with said individuals (in other words, *NOTE: Please DO NOT return after purchase. Thank you!* completely random organisms are mating in a population without any outside factors affecting their choice) ○ Two types of nonrandom mating: ■ Assortative mating Phenotypically SIMILAR individuals mate (i.e. both organisms have green eyes and carry the homozygous allele for green eyes) ● Increases chances of a HOMOZYGOUS population ● Inbreeding is most common form of assortative mating ■ Disassortative mating Phenotypically DIFFERENT individuals are mating (i.e. one organism has green eyes and the other has hazel eyes, and both carry homo/heterozygous alleles for the trait) ● Increases chances of a HETEROZYGOUS population ○ Totally random mutations occur due to environmental circumstances ■ Necessary for raw material that is used for natural selection 4. Genetic drif How allele frequencies change very rapidly due to environmental changes in small populations ○ In small populations, often can change by chance alone ○ Magnitude of genetic drift is negatively related to population size ○ Founder effect when few organisms from the original population move away and ‘find’ a new population elsewhere. The traits that were prominent in the ‘founding’ population will not always be reminiscent of the original, larger population ■ Loss of certain alleles can occur in an isolated populations ■ Some alleles can be lost/drastically changed from the ‘new’ population ○ Bottleneck effect when a population is drastically reduced by disease, hunting, natural disasters, etc. The alleles that are rarer in a population are more likely to be lost, resulting in a loss of genetic variability as the survivors are a completely random genetic sample of the original population ■ Elephant seals! ■ Less variations = less factors and flexibility to choose from when species is evolving (i.e. alleles that carry resistance to a disease) 5. Selection Variability in the amount of progeny (offspring) individuals leave behind, and this rate is affected by phenotype and behavior ○ Artificial select when individuals are chosen to mate together to give rise to a preferred trait in a population (i.e. breeding farm animals for better products) ○ Natural selectio random mating regardless of preferred alleles (more genetic variation occurs that way) ● 3 Condition for natural selection to occur and result in evolutionary changes 1. Variation in a population must exist *NOTE: Please DO NOT return after purchase. Thank you!* 2. Individual variation = differences in number of surviving offspring in the next generation 3. Variation must be GENETICALLY inherited, not a gradual change in an individual during its lifetime (i.e. Lamarck’s theory) ● Natural selection is ONLY one of several processes that can result in evolution ● Evolution = historical record/outcome of variation through time ○ Populations become better adapted to their environment through evolution driven by natural selection ● Selection to avoid predators ○ Pocket mice, fur color and environment ■ Pocket mice with black fur are more likely to survive on lava rock than on sand, and sand colored pocket mice can survive better on sand than on lava rock ● IMPORTANT: There can be different phenotypes present in a species, but if there is no preference as far as survival goes, neither phenotype is under selective pressure ○ Twins raised in different places can have the same genotype, but not the same phenotype ■ These physical changes are NOT passed down to offspring ● Selection to match climatic (weather) changes ○ Enzymes proteins that are capable of speeding up chemical reactions by lowering activation energy ■ Allele frequencies vary with latitude (different enzymes work in different temperatures, and some species that can survive in one area may not be able to survive in an area higher/lower in altitude) ■ Fish are a good example of this ○ Simpler examples: body build, fur/no fur, behavior, etc. ● Selection for pesticide resistance ○ Mostly in insects and plants ○ Houseflies have pesticideresistant alleles (go figure) ■ pen decreases UPTAKE of insecticide by having more closed channels ■ kdr/dld decrease TARGET SITES for insecticide by having fewer channels ● Phenotypes + better fitness = higher frequency ○ Fitness Individuals with a certain phenotype leave more offspring behind than individuals with an alternate phenotype ○ More fit phenotype = more offspring ○ Has many components ■ Survival ■ Sexual selection more success in attracting mates ■ # of offspring/mating ■ Favored traits for one component might not be favored for another ■ Selection favors phenotypes with a greater fitness ● *Refer to ‘waterstrider slides’* *NOTE: Please DO NOT return after purchase. Thank you!* ● Evolutionary forces and their interactions ○ The five mechanisms for evolution can either act for/against each other ○ Theoretically if each generation had the same mutations of a gene, then the mutation will happen (very rare) ○ Selection is for a reason of fitness (nonrandom), drift is very random ■ Selection usually overwhelms drift except in smaller populations ■ Drift, however can decrease an allele favored by selection ○ Gene flow can be one of two things: ■ Constructive Beneficial mutations are spread out to other populations ■ Constraining Adaptation impeded by inferior allee from other populations ● bent grass at copper mines is a good example of constraining gene flow Chapter 30: Seedless Plants ● Origins of Land Plants ○ A common ancestor for all green algae and land plants was traced as far back as 1 BYA ○ A single species of freshwater green algae = entire terrestrial (landinhabiting) plant lineage ○ Kingdom Viridiplantae common kingdom for all plant species ○ Green algae → two major clades (sections) ■ Chlorophytes never saw land ■ Charophytes related to all land plantes ○ Land plant characteristics: ■ Multicellular haploid/diploid stages ■ Diploid embryo protection (usually) ■ Smaller haploid stage (usually) *NOTE: Please DO NOT return after purchase. Thank you!* ● Adaptations to terrestrial life ○ Protection frdessication(drying out) ■ Way cuticle(protective layer over leaves and stemstomata (microscopic openings for gaseous exchange within a plant) ○ Tracheids (dead cells that taper at the ends and overlap one another in xylem) used to move water ■ Tracheophytes plants that have tracheids that conduct water and food throughout the plant ● Xylem tissue that transports water and solutes throughout plant body ● Phloem tissue that transports mainly water in and out of the plant body ○ Mutations cause by UV radiation ■ Shifts to dominant diploid generation (two copies of the same genetic code can be used for backup if one gene is mutated) ■ Haplodiplontic life cyc Diploid sporophytes → MEIOSIS → haploid spores → MITOSIS → multicellular, haploid gametophyte ● Mitosis/Meiosis Review ○ Ploidy # of complete chromosome sets in a cell (haploid = 1 set/cell (n), diploid = 2 sets/cell (2n), triploid = 3 sets/cell (3n), etc.) ○ Mitosis Cells separated into two identical daughter cells with identical genetic makeup ■ ‘Photocopied cells’ *NOTE: Please DO NOT return after purchase. Thank you!* ○ Meiosis Cells separated into four haploid cells with different genetic makeup ■ Important for genetic diversity ○ Syngamy fusion of 2 cells/nuclei during reproduction ○ Diplontic cyc reproductive cycle for diploid organisms ■ *Refer ‘Animal Life Cycslide* ○ Sporophyte Latin for ‘spore plant’, sporeproducing plants ○ Gametophyte Latin for ‘gamete plant’, gameteproducing area of a plant ■ *Refer tGeneral Plant Life Cyclide ● Haplodiplontic Life Cycle ○ A diploid generation can better survive UV radiation because organisms have two copies of the same genes and there is a backup in case something is mutated (better adaptation to mutations) ○ Most plants exist in a haploid (gametophyte) state ○ Phyte = plants ○ Greater amount of variability in alleles for diploid organisms ■ *Refer tslide 1in the Jan. 15 lecture slides* ○ Most green multicellular plants are haplodiplontic, including multicellular algae ○ Many brown, red and green algae are haplodiplontic ○ Eggs/sperms depend on sporophyte ○ ALL land plants = haplodiplontic ■ Generation sizes may vary ■ Mosses large gametophytes, small/dependent sporophyte ■ Angiosperms small/dependent gametophytes, large sporophytes ● Bryophytes ○ Closest living relative to first land plants ○ Nontracheophytes (lack tracheids) have other conducting cells ○ Have rhizoid (underground network of fibers that anchor the plant to the ground) ■ Mycorrhizal association(symbiotic relation between fungi and roots of a plant) important in increasing water uptake in early plants/bryophytes ○ Myco fungi ○ Rhiz roots ○ Simple, highly adapted to terrestrial environments ○ 24,700 species inlades(ancestor and all its descendants): Liverworts, Mosses, Hornworts ○ Dominant haploid gametophyte conspicuous/photosynthetic ○ Small (surface area and masswise) and dependent (attached to gametophyte for nutrition) sporophyte ○ Water required for sexual reproduction ○ Mosses (Bryophyta) ■ Gametophytes small, leaflike structures around stemlike axis ● Have no true leaves/vascular tissue ● Have stomata on sporophyte capsule *NOTE: Please DO NOT return after purchase. Thank you!* ● Most basal no additional characteristics) group ■ Anchored to substrate by rhizoids ■ Multicellular gametangia at the very tips of gametophytes ● Archegonia female gametangia ● Antheridia male gametangia ○ Sperm is flagellated, must swim in water ■ As sporophyte develops, base is embedded into the gametophyte tissues (nutritional source) ○ Liverworts (Hepaticophyta) ■ 20% → flattened gametophytes, liverlike lobes ● Female gametangia formed in umbrellashaped structures (they look more like palm trees though) ■ 80% → mosslike in appearance ■ Undergo asexual reproduction ● Gemmae sexual cells in certain plants that are released from gemmae cups ■ Called liverworts because their leaves are livershaped (I don’t really see it…) ■ Some liverworts have photosynthetic cells that are fixed open (NOT stomata) ■ Have rhizoids *NOTE: Please DO NOT return after purchase. Thank you!* ○ Hornworts (Anthocerophyta) ■ Unlike liverworts, they are photosynthetic and have stomata (sporophyte only) ● Think of mosses! ● Sporophytes nutritionally dependent on the gametophyte tissues ○ True for ALL bryophytes! ■ Cells usually have a single large chloroplast ● Tracheophytes (Vascular Plants) ○ Include 7 extant phyla grouped into 3 clades ■ Lycophytes (club mosses) ■ Pterophytes (fern) ■ Seed plants (gymnosperms, angiosperms) ○ Characteristics ■ Smaller gametophyte stage compared to a larger sporophyte stage during evolution of this group ■ Reduction of multicellular gametangia ■ Have leaves, stems, stomata ● Sperm can swim through water ■ Xylem Tissue that conducts water and minerals from roots → shoots ■ Phloem Tissue that conducts mainly sucrose and hormones throughout the plant ● This makes the plant grow taller ● Developed during sporophyte stage ■ Cuticles and stomata are in vascular plants ■ Stems ● Early fossil evidence suggests stems but NO LEAVES ● Lack of extensive root systems limited early tracheophytes ■ Roots *NOTE: Please DO NOT return after purchase. Thank you!* ● Provide transport/support ● Lycophytes diverged before ‘true roots’ evolved ■ Leaves ● This increased surface area for photosynthesis (the process where glucose and CO2 are converted into oxygen and water via sunlight and other chemical reactions) ● Evolved two times! ○ Euphylls (true leaves) ferns/seed plants, have a single vascular vein when it evolved from a stem with vascular tissue ○ Lycophylls lycophytes, derived from branching stems of vascular tissue later filled with photosynthetic tissue ■ Why would vascular tissue be prevalent in the sporophyte, but not the gametophyte generation? T he sporophyte generation in tracheids is larger and dominant than the gametophyte generation, so it needs a better support system to sustain itself ● Club mosses (Lycophytes) ○ Abundant in tropical areas ○ Sister group of all vascular plants (ancient ancestor to the first vascular plants that evolved) ○ Characteristics: ■ Lack seeds ■ Resemble true mosses on a superficial level ■ Dominant sporophyte (leafy stems, no more than 30 cm long), dependent gametophyte ● Pterophytes ○ Phylogenetic relationships between between ferns and their relatives are still being sorted out ○ Ptero = ‘wings’ (think of pterodactyls they have wings!) ○ Characteristics ■ All form anther/archegonia ■ All require water for flagellated sperm ○ Whisk ferns ■ Found in tropical areas ■ Sporophytes evenly forking green stems without roots/true leaves ■ Gametophytes some form elements of vascular tissues (this is the only gametophyte known to do this!) ■ Believed that they lost leaves/roots when they diverged from the fern lineage ○ Horsetails ■ Usually found in damp places, most less than a meter tall ■ All 15 species homosporous (spores that ARE NOT differentiated by sex) *NOTE: Please DO NOT return after purchase. Thank you!* ■ Sporophyte ribbed, jointed photosynthetic stems rising from underground rhizomes with roots at nodes ■ Silica deposits in cells gave them a hard grainy feel ● Called ‘scouring rush’ as they were originally used by pioneers in the West to scour pans ○ Ferns ■ Most abundant group of seedless vascular plants ● ~11,000 species, 75% grow in tropical places ■ Conspicuous sporophyte, even smaller gametophyte ● Both are photosynthetic ■ Life cycle ● Different from a moss ● Sporophyte structurally more complex with vascular tissue, welldifferentiated roots, stems and leaves ○ More developed, independent and dominant than the gametophyte ○ Gametophyte lacks vascular tissue or another other characteristic of the sporophyte ● In the diploid gametophyte stage, antheridia swim towards archegonia after receiving a chemical signal from the archegonia ● Sporophytes have rhizomes ● Fronds (leaves) develop from rhizome tip as ‘fiddleheads’ (tight coils) ○ Fun fact! Fiddleheads are considered a delicacy in several cuisines, but some species contain secondary compounds linked to stomach cancer ● Sori Distinct sporangia clusters found on frond underside ● Diploid spore mother cells in sporangia → haploid spores (via meiosis) ● Spores → gametophytes (via germination) ● ORGANISM OF THE DAY: Wild Mustard Plant (Brassica oleracea) ○ This plant is where all our leafy green vegetables are derived from! ■ Kale = leaves ■ Broccoli = flower buds and stem ■ Cauliflower = flower buds ■ Brussel sprouts = lateral leaf buds ■ Cabbage = terminal leaf bud ○ CAL (cauliflower) and AP1 (Apetala1) gene mutation made regular flowers → masses of arrested flower buds ■ Both needed for transition to making flowers, arose through the duplication of single ancestral gene in brassica group ■ When absent meristems continue to make branches, but flower production is delayed *NOTE: Please DO NOT return after purchase. Thank you!* ■ **Refer to slide 5 for the evolution of Cauliflower and Broccoli** ○ Wild mustard still found along rocky coasts of Spain/Mediterranean region ○ These vegetables were produced from artificial selection ■ Large broccoli/cauliflower head = lots of vegetable material
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