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Give information about the plant endocrine system, incl. mechanisms of action, types of cellular responses, and major hormone categories.
- Hormones (chemical messengers) function to coordinate growth & development and mediate response to external cues (affect division, elongation, gene expression, and differentiation of cells)
- Hormones are produced in a variety of locations, and are active even in small amounts (not used in their mechanisms, so they can continue to affect another cell)
- Hormones work by signal transduction pathways: ligand (substance that binds to a receptor), target tissue (tissue equipped with receptors specific to a particular ligand)
- Hormone sequence of action: reception, signal transduction, cellular response
- Examples of cellular responses: Altering gene expression (protein synthesis regulation), activating or deactivating enzymes (protein kinase enzymes), changing the properties of membranes (permeability to ions)
- Cellular response may differ based on hormone concentration, developmental state of tissue, interplay of two or more hormones, tissue type
- Major hormone categories: Auxins, Cytokinins, Gibberellins, Ethylene, Abscisic Acid
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Auxin – Produced where? Function? Other information?
- Manufactured in apical bud meristem, young leaves, and seed embryo
- Major stimulator of shoot elongation, root growth (Callus tissue), Apical dominance, fruit development, and inhibition of fruit/leaf abscission
- Has been used to create seedless fruits
- Stimulates vascular cambium (secondary growth)
- Used to prevent pre-harvest drop of fruit (makes cells in the abscission zone less sensitive to ethylene)
- Functions in vascular tissue differentiation
- Synthetic auxins: (2,4-D) – herbicidal compound (mechanism unknown). Agent orange (South Vietnam)
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Gibberellins – Produced where? Function? Other information?
- Produced in root and bud apical meristem, young leaves and embryos
- Functions in shoot elongation through division and cell elongation (causes growth in dwarf mutants)
- Stimulates fruit growth without fertilization (commercial use allows for seedless grapes)
- Signals seeds to break dormancy and to germinate (ex. water soaked into the seed -> release of GA).
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Ethylene – Produced where? Function? Other information?
- Synthesized in most tissues in response to stress (especially in ripening fruits and/or leaf senescence)
- Promotes fruit ripening and abscission of fruit/leaves
- In fruit ripening, seems to play a role in promoting chlorophyll degradation, formation of other pigments, digestion of pectin (middle lamella), synthesis of sugars from a variety of other nutrients
- Leaf, flower, and fruit abscission (Ethylene triggers enzymes that break down cell walls in petiole)
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Define systematics. What is the goal? What criteria is used?
- The science of evolutionary history (naming / classifying an organism through evolution)
- The goal of systematic is to find all branches of the phylogenic tree of life
- Comparative anatomy, physiology, embryology, and comparative molecular techniques (eg DNA, RNA, protein) are used together in systematic and taxonomy.
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What is phylogeny? Describe the various groups that can be formed when classifying taxa.
- Phylogeny: (evolutionary history) characteristics of organisms are products of their evolutionary past. Studies in phylogeny result in diagrams (“family tree”).
- Monophyletic groups: created by looking for shared unique features among organisms.
- A monophyletic taxon contains ALL members who descended from a common ancestor (none are excluded)
- Natural taxa: taxa where all members have shared ancestry, and correctly reflect the ancestral past of that group.
- Artifical taxa: taxa that do not correctly reflect the ancestral past of that group. Can come in two forms; paraphyletic and polyphyletic
- Polyphyletic: taxa where members descended from more than one ancestral line, and may only resemble each other because of similar evolutionary pressure.
- Paraphyletic: A group that does not include one or more descendants of a common ancestor (one or more are excluded).
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Describe cladistics in detail.
- The goal is to understand the evolutionary relationships present among organisms.
- Focuses more specifically on shared characteristics that are unique (eg. Presence/absence of flowers)
- Cladograms are created in an attempt to show groups that share a common ancestor.
- CLADOGRAMS DO NOT IMPLY THAT A SPECIFIC GROUP EVOLVED INTO ANOTHER.
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Describe reproduction and gene exchange in prokaryotes.
- Binary fission: a type of asexual reproduction that produces clone populations, represented by the formula Nf = (Ni)2n where n is the generation # and N is the number of bacteria
- There is a large amount of mutants produced during binary fission which gives an evolutionary advantage through adaptability.
- Recombination (gene exchange) mechanisms allow genes to be passed between different bacteria
- Conjugation: the transfer of DNA across a pilus
- Transformation: DNA is absorbed from the environment
- Transduction: viruses move DNA between bacteria
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