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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
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)
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).
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)
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.
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).
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.
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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