BIO1500 Exam 1 Study Guide (Weeks 1-5)
BIO1500 Exam 1 Study Guide (Weeks 1-5) BIO1500
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This 28 page Study Guide was uploaded by Nausheen Zaman on Tuesday February 9, 2016. The Study Guide belongs to BIO1500 at Wayne State University taught by Dr. William Bradford in Winter 2016. Since its upload, it has received 136 views. For similar materials see Basic Life Diversity in Biology at Wayne State University.
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Date Created: 02/09/16
● Germination emergence of radicle (first root) through seed coat ○ Begins when water absorption reactivates seed’s metabolism ■ Osmotic pressure strong enough to break seed coat ■ Oxygen is also necessary (respiration) ○ Dormant seeds may be… ■ Absorbed enough water ■ Respiring ■ Producing proteins/mRNAs ○ … YET it may not germinate unless it receives certain environmental cues ■ Correct wavelength/intensity of light ■ A certain amount of time at an optimal temperature ■ Stratification Mechanically changing normal germination patterns in plants to increase rates of germination/break dormancy ● Important as it helps increase plant yield ○ Require utilization of metabolic reserves (amyloplasts) + protein bodies in embryo/endosperm ○ Fats/oils stored in some seeds → digested → glycerol/fatty acids (yield energy [respiration]/converted [glucose]) ○ Plumule rudimentary terminal bud consisting of epicotyl/immature leaves ○ Cotyledon embryonic leaf that first emerge from a germinating seed ○ Epicotyl stem of seedling between cotyledon + first true leaves ○ Hypocotyl stem of seedling below cotyledons + directly above roots ○ Coleoptil sheath protecting young SHOOTS in grasses/cereals ○ Coleorhiza sheath protecting young ROOTS (radicle) in grasses/cereals ○ Scutellum shieldlike cotyledon in certain monocots ○ Roots = down, Shoots = up (become photosynthetic + postembryonic growth proceeds) ○ **See slides 42 and 43 in Feb 3 lecture slides for modifications** ● Morphogenesis change of an organism’s form based on cellular differentiation and division ○ Globular → cotyledon stage (heart shaped embryonic cells) ■ Two bulges = eudicot, one bulge = monocot ■ Bulges produced by embryonic cells, NOHOOT APICAL MERISTEM (cell group at the tip of the shoot axis that produces lateral organs and regenerates itself) ○ Plant body form = Cellular division plane ■ Controlled by osmotic expansion after cells form, changing cell shapes ○ Also based on cell plant position ■ Microtubules and actin (remember those?) ● Microtubules guide deposits of cellulose as cell wall forms around new cell ○ Expand in the direction of the two leastreinforced cellulose walls ○ Cells in early embryonic development have many cell and organ types (leaves included) ■ Later development cells with multiple potentials narrowed down to meristem regions ■ Many meristems est. (by the time embryogenesis ends, seed is dormant and not much cell division occurs) ○ After germination apical meristems continue adding cells to tips of roots and shoots ○ In angiosperm embryogenesis, development of following occur: ■ Food supply (endosperm) ■ Seed coat (from integument) ■ Fruit surrounding the seed (produced from the ovary) ○ Endosperms vary from plant to plant ■ Coconuts = liquid ‘milk’ ■ Corn = solid (starch) ■ Peas/Beans = Used up during embryogenesis from thick, fleshy cotyledons ○ Seeds need a nutrient reserve in order to develop themselves, since most of their energy is spent in growing and are unable to produce their own food ● Formation of Tissue Systems ○ Primary meristems (cell tissue responsible for forming basic tissue systems) differentiate during embryo’s globular stage ■ No cell movement is involved! ○ Protoderm (basic dermal tissue) → dermal tissue for plant protection ○ Ground meristem (basic ground tissue) → ground tissue for plant’s food/water storage ○ Procambium (inner basic vascular tissue) → vascular tissue for water/nutrient transport Chapter 36: Plant Form ● Plant Body Organization ○ Vascular plants: ■ Root system ● Anchors plants ● Used to absorb water/ions ■ Shoot system ● Supporting stems, photosynthetic leaves, reproductive flowers ● Accessory parts also produced (internodes, axillary buds, etc.) ○ Node In the form of a swollen knob, leaves grow from here ○ Internode between two nodes, leaves grow from here ○ Axillary bud Lateral shoot apex where axil of a leaf develops into a branch/flower cluster ○ Axil Upper angle between a leaf stalk/branch from which a stem is growing ○ Stipul small leaflike appendage to leaf borne in pairs of a leaf stalk ○ Petiol leafstalk ○ Distinguishing plant cell features: ■ Vacuole size ■ Living/not at maturity ■ Thickness of cellulose wall secretions ● Some cells only ONE primary cellulose wall synthesized by protoplast ● Other cells more reinforce with multiple cellulose layers (often contribute to support plant body ● Tissue Systems and Functions ○ Consist of one/more cell types ○ Extend through root/shoot systems ● Meristems clumps of small cells with dense cytoplasm and large nuclei ○ Like stem cell in animals ○ Apical meristems extends root/shoot systems ■ At tips of stems and roots ■ Produce primary plant body (primary plant tissues for basic plant functions) ■ Delicate cells! ● Root cap (roots)/Leaf primordia (shoots) protects apical meristems ■ **See slide 12 from Feb 8 slides for specified functions** ○ Lateral meristems increases root/shoot girth (circumference) THINK OF TREES~ ■ Secondary growth ■ Occurs both in gymno/angipsperms ■ Woody plants have two types of meristems: ● Cork cambium outer bark ● Vascular cambium secondary vascular tissue (secondary xylem) between xylem and phloem in vascular bundles ○ Secondary phloem close to outer surfaces ○ Girdling (removing bark) kills the tree by cutting off the phloem and therefore the circulation in the tree ■ Forms from ground tissue (not in monocots!) ○ Primary growth cell divisions at tips of roots/shoots ○ Secondary growth cell divisions in lateral meristems to thicken roots ■ Monocots do NOT have secondary growth (differs from typical patterns if they DO have secondary growth) ● Dermal Tissue outer protective cover ○ **See slide 19 for general info** ○ Guard cells sausageshaped cells in leaf epidermis ■ Flank the stoma ○ Trichomes hairlike outgrowths from epidermis ■ Keeps leaves cool/reduces evaporation by covering stomatal openings ■ Some secret substances to keep herbivores away ○ Root hair tubular extensions from individual epidermal cells ■ Increase roots surface area and absorption efficiency ■ DO NOT CONFUSE WITH LATERAL ROOTS ● Ground Tissue function in storage, photosynthesis, secretion ○ Parenchyma storage, photosynthesis and secretion ■ most common plant cell type with living protoplasts ■ less specialized than other plants ○ Collenchyma provides support, protection ■ Support for PLANTS and ORGANS ■ Longer, cell walls thickness vary ■ Flexible with living protoplasts ○ Sclerenchyma provides support and protection ■ Tough thick walls (contain lignin) ■ Lack living protoplasts at maturity ■ Strengthen TISSUES ● Vascular conduction of fluid and dissolved substances *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 *Note: Please DO NOT return after purchase. Thank you!* Chapter 31: Seed Plants ● Evolution of Seed Plants ○ First appeared 300 MYA *million years ago* ■ Evolved from progymnosperms (sporebearing plants) ■ Large # ogene duplicationsa level of molecular evolution where new genetic material is created from existing whole genome duplicatio (when an entire genome is revamped to consist of entirely new genes from the original species) ○ ~319 MYA → seed plants evolved ○ ~192 MYA → Angiosperms (flowering plants) appeared ○ Success attributed to seed evolution, the seed: ■ Protects/provides nourishment for enclosed embryo ■ Allows germination to pause for periods of harsh weather before germinating ■ Later develop into fruit for enhanced dispersal ● Gene duplications = new gene functions ○ Duplicate gene = a backup gene that can mutate without being lethal to the organism ○ Different types of divergence: ■ Subfunctionalizati where a gene is split into two separate genes with different traits ■ Neofunctionalizati where a gene is completely revamped using traits expressed in the old gene ■ Degeneration/Gene loss where a gene is completely gone/replaced ● Seed = embryo protection and nourishment ○ Embryo protected byintegument (extra sporophyte tissue layer that hardens into seed coat) ● Water not needed for sexual reproduction ○ Male gametophytes ■ Pollen grains (sperm) ■ Dispersed by the wind (pollinator) ■ No need for water ollen tub(a tube from the pollen grain that deposits the sperm into the egg once it is on a stigma of a flower) ○ Female gametophytes ■ Develop within ovule(part of the ovary containing an unfertilized egg) ■ Enclosed within diploid sporophyte tissues (angiosperms) ● Ovary ovule + surrounding protective tissues → later develop into fruit Why is water not essential for fertilization in seed The male gametophyte evolved to make pollen grains and other mechanisms to aid their reproduction when water isn’t around. *REFER TO PLANT TABLE!!!!* *Note: Please DO NOT return after purchase. Thank you!* ● Gymnosperms (‘naked seeds’) ○ Lack flowers + fruits ○ Have ovule → seed that is exposed ocal(modified shoot/leaf) ○ Conifers (Coniferophyta) ■ Most familiar gymnosperm phylum (pines, spruces, firs, etc.) ● Coastal redwood tallest living vascular plant ● Bristlecone pine oldest living tree ■ Found in colder temperatures and drier regions ■ Source of important products ● Timber, paper, restaxol(compound that inhibits cancerous growths) ■ Pines ● >100 species (all in Northern hemisphere) ● Produces tough needlelike leaves in clusters ○ Thick cuticles + recessed stomata = decreased water loss ○ Also secrete resin through canals to deter insect + fungal attacks ● Thick bark = survives fires and subzero temperatures ■ Pine Reproduction ● Male gametophytes = pollen grains (fmicrospores(smaller male spores) in male cones via meiosis) ○ Male cones… ■ Develop in clusters of 3070 ■ Typically at lower branch tips ■ 14 cm long ■ Small, papery scales arranged in spirals/whorls ○ Pair o microsporangia(sporangia containing microspores) form as sacs within each scale ○ Microspore mother cellsdiploid cells that form microspores) in microsporangia go through meiosis ■ Mother cell → four microspores → fourcelled pollen grain with air sacs for buoyancy ● Female pine cones form on upper branches of the same tree ○ Larger with woody scales ○ Two ovules on each scale containing a megasporangium calleducellus (central part of ovule with the embryo sac) ■ Nucellus surrounded by integument icropyle (a small opening on the ovule that allows pollen tube to penetrate and deposit sperm cells to the egg) on each end ○ Megaspore mother cell (diploid cells that form megaspores) within each megasporangium (sporangia only containing megaspores) reproduces via meiosis *Note: Please DO NOT return after purchase. Thank you!* ■ Becomes a row of four megaspores → three break down → remaining one = female gametophyte ○ Mature female gametophyte consists of thousands of cells, with 26 archegonia formed at the micropylar end ■ Each archegonium = single egg ● Female cones usually take 2 or more season to mature ○ First spring female cone scales spread apart for pollen to drift in between open scales ■ Some grains get stuck in sticky fluid from micropyle → drawn down through micropyle to top of nucellus → scales close ● Female gametophyte not mature for a year ○ Meanwhile… ■ Pollen tube emerges from pollen grain ■ Tube digests from nucellus → archegonia ○ During pollen tube growth… ■ One of the four cells of the pollen grain, the generative cell(the cell that gives rise to sperm cells) undergoes mitosis → two identical cells → one cell → two sperm cells ○ 15 months later… ■ Pollen tube finally reaches archegonia and deposits sperm ■ One sperm + egg = zygote → embryo with seed ● Other sperm + pollen cells degenerate ■ After dispersal and germination of seed, next gen. sporophyte grows into a tree ○ Cycads (Cycadophyta) ■ Slow growing gymnosperms from tropical/subtropical places ■ Resemble palm trees ■ Life cycle similar to pine ● Female cone = 45kg! ■ Have largest sperm cells of all organisms ○ Gnetophytes (Gnetophyta) ■ Only gymnosperm with vessels in xylem ■ Three (unusual) genera ● Gnetum ● Welwitschia ● Ephedra ○ Meth and ephedrine produced from these plants! ○ Ginkgophytes (Ginkgophyta) ■ Only one living species remains (Gingko biloba) ■ Flagellated sperm) *Note: Please DO NOT return after purchase. Thank you!* ■ Dioecious(male/female on different trees) ● Angiosperms (flowering plants) ○ Highly specialized and recently evolved ○ Highly diversified (>300K species) with various structures and pollinators ○ Ovules enclosed in diploid tissue during pollination ○ Carpel (modified leaf that covers a seed) → fruit ○ Floral structure ○ Flower whorls ■ Thought to have been evolved from leaves ■ Outemost whorl calyx/sepal(35) ● Leaflike, green ■ Second whorl corolla/petal (35) ● Separate, fused together or missing (windpollinated flowers only) ● Function to attract pollinators ■ Third whorlandroecium/stamens ● Pollen produced here ● Each stamen = pollen bearing panther and a stalfilamen) ○ Filament may be missing in some plants ■ Innermost whorlgynoecium/pistil ● Consists of one/more carpels housing female gametophyte ■ Carpel = Three major regions ● Ovary swollen base containing ovules (later develops into fruit) ● Stigma tip where pollen gets stuck (sticky/feathery) ● Styl neck/stalk leading down to ovary ○ Flowers = gametophyte generation ■ Modified stems bear modified leaves *Note: Please DO NOT return after purchase. Thank you!* ■ Primordium (The rudimentary stage of a plant) → pedicel (a bud developed at the end of a stalk that later turns into a flower) → expands to form receptacle (where other parts are attached) ■ Parts arranged into circhorls) ○ Egg production ■ Megaspore mother cell goes through meiosis → Produces 4 megaspores → 3 disappear → Nucleus of remaining megaspore divides once mitotically → two daughter nuclei divide TWICE → 8 haploid nuclei → integuments become seed coat ■ Polar nuclei One nucleus from fournucleigroup travel towards center ■ Cell walls form around remaining nuclei ■ Group closest to micropyle = one cell (egg) + tw ynergids cells that help the pollen to reach the egg cell) ■ Other group =ntipodals(no real function and break down) ■ Female gametophyte = resulting sac with eight nuclei in seven cells (embryo sac) ● Completely dependent on sporophyte for nutrition, multicellular, haploid ○ Pollen production ■ Occurs in anthers ● Anthers have patches of tissues (comes in fours) that become chambers with nutritive cells inside ● Tissue in each patch = many diploid microspore mother cells that undergo meiosis simultaneously producing four microspores ● Microspore nucleus divides ONCE → four nuclei separate → two layered wall develops around each microspore → walls between adjacent pairs of microspores break down as anther matures ○ Binucleate cells with two nuceli) microspores = pollen grains ○ Pollination & male gametophyte ■ Pollinatio a mechanical transfer of pollen from the anther to the stigma of a flowering plant ■ Takes place between flowers of differing plants ■ Brought about by insects, water, gravity, wind and animals ■ ¼ of all angiosperms pollen grain deposited directly to stigma of its own flower selfpollinati n) ■ May/May not be followed by fertilization ● Depends on genetic compatibility of pollen grain and stigma ■ If stigma receptive → tube cell develops into pollen tube → guided towards embryo sac → grows through style and into micropyle → generative cell develops into two sperm cells from their nucleus (nonflagellated) ○ Double Fertilization *Note: Please DO NOT return after purchase. Thank you!* ■ Pollen tube enter embryo sac → destroys synergid → discharges contents → one sperm + one egg = diploid zygote (new sporophyte) → other sperm + two polar nucelriploid endospermnucleus (a endosperm formed from diploid parents is usually triploid (2m: 1p)) If the endosperm failed to develop in a seed, how would the seed’s fitness be affected? Explain? The fitness of the seed will not exist because the endosperm is an essential for the seed to survive. The endosperm provides nutrients for the seed and it can’t survive without it. ● Seeds ○ Gymno/angiosperms embryonic development arrested after fertilization ○ Integuments → relativeimpermeable (nothing can really pass through) seed coat → Dormant (inactive) embryo enclosed along with stored food → germination occurs with presence of water and oxygen to embryo ○ Important adaptation because… ■ Dormancy under unfavorable conditions ■ Protect the young plant at most vulnerable stage ■ Provides food for embryo ■ Facilitation of embryo’s dispersal ○ Serotiny adaptations that ensure embryos develop only under certain conditions ○ Pyriscence Seeds that don’t disperse until activated by fire (i.e. jack pine) ○ Some seeds germinate after inhibitory chemicals are leached (drain away naturally) from seed coat (ensures sufficient water availability) ○ Some seeds germinate through animal’s digestive systems (weakens seed coat, aiding in dispersal) ● Fruits ○ Protect seeds ○ Defined as mature ovaries ○ During seed formation flower ovary → fruit ■ Fruits can also develop without seed development (commercial bananas) ○ Fruits are adapted for dispersal ■ Pericarp ovary wall ● Exocarp, mesocarp, endocarp (think of the 3 tissue layers of an embryo, except with ‘carp’ at the end because it comes from a ‘carpel’) ■ Fate determines fruit type ■ Contain 3 genotypes in 1 package ● Fruits/seed coat = prior sporophyte gen. ● Developing seed = remnants of gametophyte gen. ● Embryo = next sporophyte gen. ○ Types: ■ True berries ● Fleshy pericarp, thin skin ● Multiple seeds in one/more ovaries *Note: Please DO NOT return after purchase. Thank you!* ● Tomatoes ■ Legumes ● Split two carpel edges ● Seeds attached to edges ● Pericarp dry at maturity ■ Drupes ● Seed enclosed in a hard pit ● Peaches, plums, cherries ● Each pericarp layer is different in structure and function ● Endocarp = pit ■ Samaras ● Not split ● Wing from outer tissues ● Maples, elms ■ Aggregate Fruits ● Many ovaries on a single flower ● Blackberries, strawberries ● Ovaries NOT fused and covered by continuous pericarp ■ Multiple Fruits ● Flowers form fruits around a single stem ● Fruits fuse together ● Pineapple ○ Fruit dispersal = ability for angiosperms to colonize large areas ■ Ingestion/transport of birds/other vertebrates ■ Attaching to outside and catching a ride ■ Blowing in the wind ■ Floating in water Chapter 41: Plant Reproduction ● Reproductive development ○ Angiosperms = evolutionary innovation with flowers/fruits ○ Plants go through developmental changes leading to reproductive maturity by adding meristems (Region of plant tissue full of newly dividing cells ○ Germinating seed → vegetative plant vorphogenesis (biological process that allows organisms to develop their shape via cellular growth/differentiation) ○ *Refer to Slide 16 on Jan29 lecture slides* ○ Once plants are competent for reproduction a combo of factors (light, temperature, water, promotive/inhibitory signals) determine when a flower will be produced ● Phase Change transition to flowering (triggered by internal signals) ○ Can be subtle or obvious ○ Oak trees lower branches (juvenile phase) hold on to their leaves in the fall ○ Juvenile ivy = adventitious (formed accidentally or in an unusual placement) roots *Note: Please DO NOT return after purchase. Thank you!* ● Flower Production ○ Four geneticallyregulated pathways have been identified, plants (usually) depend on one, but all four can be present in a plant ○ Lightdependent pathway (Photoperiodic pathway Based on amount of light/dark in a 24hr cycle ■ Shortday plant = flower when daylight is shorter (cocklebur) ■ Longday plants = flower when daylight is longer (clovers) ■ Day neutral plant= don’t depend on light at all ■ Obligate long/shortday plan= SHARP DISTINCTION between the two ■ Facultative long/shortday pla= VERY LITTLE DISTINCTION between them (flowering occurs quicker/slower based on how much light there is) ■ Light used as a cue for: ● Optimal abiotic conditions ● Available pollinators ● Decreased resource competition ■ Can be manipulated! (Poinsettias) ○ Tempdependent pathway ■ Vernalization when a plant requires a period of cold weather before flowering (i.e. daffodils, tulips) ○ Gibberellindependent pathway ■ Gibberellin a hormone that promotes elongation and flowering ○ Autonomous pathway ■ No environmental cues needed for flowering (some species of tobacco plants) ● Flower types ○ Complete a flower with all four floral parts (sepal, petal, stamen, carpel) ○ Incomplete a flower lacking one or more of the floral parts ○ Perfect ○ Imperfect ● Trends in Floral Evolution *See slide 34 of Jan29 lecture slides for table* ○ 2 major trends ■ Separate floral parts grouped/fused ■ Floral parts lost/reduced ● Modifications usually relate to pollination mechanisms ○ Floral symmetry ■ Primitive = radial (buttercups) ■ Advanced = bilaterally symmetrical (orchids, snapdragons, etc.) ○ Ovary position ■ Varies across species ■ Superior = hypogynous ■ Inferior = epigynous *Note: Please DO NOT return after purchase. Thank you!* ● Pollination when pollen is placed on a stigma ○ Self pollinatiCross pollinatio (when pollen fro
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