Week 8 Notes
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This 4 page Class Notes was uploaded by Nausheen Zaman on Saturday March 5, 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 52 views. For similar materials see Basic Life Diversity in Biology at Wayne State University.
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Date Created: 03/05/16
Chapter 40: Sensory Systems in Plants ● Circadian clocks/rhythms ○ First observed in sensitive plants (leaves that reacted to touch) ■ Was observed that this happened a lot at night, even if there was no light, they still close during the nighttime ○ Continuing absence of external inputs (will continue responding in a 24hr cycle) ○ Will gradually become affected when put into darkness for a while (trains itself back into a cycle) ○ Temperature increases → protein activity increases ■ Clock notices and compensates for activity differences in plants ○ This is also true in animals ● Phototropism ○ Plants gravitating towards a light source ○ This happens when auxins concentrate towards the darker side of the plant ■ Makes the plant look like it is leaning towards the light source ○ This is more of a shoot mechanism elongates on the upper side ● Gravitropism ○ Plants that grow towards a center of gravity ○ When a plant is knocked over, it can reorient itself to grow towards the ground towards the center of gravity ○ Shoots have negative gravitropism, roots do not ○ Gravity is by the plant cell’s perception (remember columella cells?) → changed from a electrical to a chemical signal in a plant → tells the cells to grow up/down ● Shoots ○ Endodermal layer cells called the endodermis have amyloplasts ■ These cells have starches and move in response to gravity ■ Tells the cells in circumference to respond in whatever direction is necessary ○ Presents negative gravitropism (grows AGAINST gravity) ○ Roots exhibit positive gravitropism (grows TOWARDS gravity) ○ Mutations occur when there is a loss of functional endodermis that lack amyloplasts ● Thigmomorphogenesis ○ Plant responses to mechanical stimuli (touthigmotropism ○ Plants grow independent from the direction of initialhigmonastic responses ○ Good example of this are Venus flytraps (snap shut in response to touch) ○ Thigmonasty is reversible over time (venus flytraps reopen after 30 mins) ○ Tendrils (modified stems) curls around plants due to a response in its outer cells that allow the outer cells of the plant to elongate and the inner cells don’t ■ Coiling happens within ten minutes ● Turgidity ○ If cells become turgid, causes movements within a plant ○ Pulvinus leavesMimosa pudica) ■ When there is touch, electric signals causes the water concentration to change in the leaf and the leaf closes up ■ The water is transferred back later and the leave relaxes again ○ This also happens with sunflowers ■ Young sunflowers turn towards the sun to maximize the amount of sunlight and in turn have more effective photosynthesis ● Seed Dormancy ○ Results in a response to unfavorable conditions ○ Seed needs to be somehow damaged to be broken out of its dormancy (fire, water, manually, etc.) ○ Abscission (loss of leaves) ■ Happens a lot in cooler climates ■ Allows a plant to lose parts of itself that are of a disadvantage to the plant during the winter ■ When leaves are young → changes in temp and water, forms abscission layers → protective layer (protects stem), ○ Orchids and their petals ■ They die off after the plant is pollinated ● Response to Chilling ○ The lipid bilayer needs to be fluid in order for the seed to be chilled effectively ○ As temp decreases → the metabolic processes in the seed decreases ○ When a lipid bilayer has a monounsaturated/saturated mix in the bilayer… ■ Easily more fluid than ○ When the cell is exposed to ice ■ The cell and solute concentration is out of whack → ice attracts the solutes outside away from the cell → the cell shrinks as a result of less solutes inside the cell and more solutes outside the cells ■ Some cells have a mechanism (antifreeze proteins) that fights to decrease the amount of solute loss both inside and outside the cell ● Thermal Response ○ Due to response of heatshock proteins ■ As temp increases → denaturation of proteins increases ■ heatshock proteins helps the denatured proteins fold in the correct way again ○ Acquired thermotolerance plants gradually adapt to certain temperatures, allowing the temperatures to increase in the plant and continue the cycle Chapter 32: Fungi ● Basic fungi points ○ Very diverse (uni/multicellular) ○ Can be both sexual and asexual ○ 90% of soil biomass is fungus (most of it you can’t see!) ● Defining fungi ○ Mycologists people who study fungi ■ Believe there are as many as 1.5 million species ○ Plants that decompose materials ○ Heterotrophs extract, absorb and digest nutrients from it’s surroundings ○ Animals have more in common with fungi than with plants ● Blastidiomycota, Chytridiomycota, and Neocallimastigomycota → used to be thought of as one large group but has been divided recently to different groups ● General Fungi Biology ○ Hyphae long, slender filaments that are characteristic of multicellular fungi, monokaryotic (one haploid nucleus) ■ Some are continuous with two nuclei (dikaryotic 2 haploid nuclei) ○ Septa cells that are in between hyphae cells that transport materials throughout the fungi ○ Mycelium mass of connected hyphae, constantly growing outwards from hyphae tips ○ Fungal cell walls have chitin hard shelllike material made of polysaccharides ■ exoskeletons for arthropods insects and crustaceans ○ Heterokaryotic nuclei are two different haploid individual (sexual reproduction) ○ Homokaryotic nuclei are genetically identical to one another (asexual reproduction) ● Fungi have ‘closed mitosis’ ○ Split in between two different nuclei ○ Split with spindle pole bodies ● Reproduction ○ Typically fungi with asexual reproduction do so when the environment is suitable ○ Fungal sexual reproduction occurs when environment is harsh and they need to vary their genetic makeup in order to have higher chance of survival ○ Fruiting bodies mushrooms, shelves, etc ○ Do not have male and female, have + and cells ○ Spores are most common means of reproduction ■ Can form from sexual/asexual reproduction processes ■ Most dispersed by wind, some can even travel by water vapor ● Fungi are HETEROTROPHS ○ Do not photosynthesize ○ Large surface area/volume ratio ○ Can break down cellulose and lignin (basically wood) ○ Some are carnivorous (fungal parasites) ■ Some fungi trap nematodes ● Zombie Fungus! (video) ○ Attacks ants ○ Controls ants to go to environments that are optimal for the fungus → latches onto a leaf of a plant → fungus eventually grows out of the dead ant ● Chytridiomycota ○ Usually parasitic ○ Consist of a pod with zoospores inside that attack the host ○ Chytrid and Frogs (video) ■ Also called BD ■ Disrupts the amphibian’s skin functions and eventually kills the frog ■ Chytrids live in water ■ Research is being done in order to stop BD from affecting frogs ● Blastocladiomycetes ○ Haplodiplontic life cycle ○ Have more sexual reproduction ● Zygomycota ○ Bread mold ● KNOW WHEN THE MONO/DIKARYOTIC STAGES BEGIN AND END! ● Glomeromycota ○ Have a mutualistic relationship between plants ○ Cannot survive without host plants ● Basidiomycota ○ Mushrooms, shelf fungi, puffballs, etc. ○ Majority of life cycle is dikaryotic (n + n) ■ Shown by presence of basidiocarps ● Ascomycota ○ Similar to basidiocarps ○ Yeast ■ Unicellular ■ Utilize fermentation (breaks down glucose into ethanol and carbon dioxide)
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