A. Light 1. Photoperiodism-relationship of a variety of activites to the length of day. 2. For light to activate functions, organisms need clock/calendar 3. Breeding in plants a. Short day plants--adapted in temperate zones for Spring and Fall, when day lengths are short and light can pentrate to substrate because of lack of leaves b. Long day plants--plants that bloom mid-summer when days are long. Quesition: Is it the day length or the lack of sunlight at night that triggers the plant. Research goes both ways. c. Day neutral plants-day length has no effect on plant flower 4. Length of life in plants a. Plants adapted to survive only one season, annuals b. Plants that last two years, grow one, bloom the other, biennials c. Plants that live more than two years, some years for growth, many years for reproduction. 5. Response to light conditions a. Shade-tolerant--can survive in low intensity situations b. Shader-intolerant--can only survive when exposed to full sunlight. 6. New areas of interest include gap analysis and light specks. a. Gap analysis is what happens when open space comes into being when a tree falls and leaves an area exposed to high intensity light. Light specks are the flickers of light that pass through the canopy. 7. Light in animals, particularly birds--may trigger reproductive behavior in temperate birds in the Spring. Light levels in the White Crown Sparrow (Zonotrica leucopis) are audited by the pineal body. When threshold levels are reached, organism becomes reproductive. B. Light and Photosynthesis in Plants 1. Use of accessory pigments in aquatic plants 2. Adaptations of leaf shape in aquatic and terrestrial plants a. Dividing up of leaf surface area in aquatic plants to better utilize photons other than those passing vertically through the water column. Same leaf shape also prevents shading by upper leaves. b. Geometric arrangement of leaves on terrestrial plants to maximize photosynthetic surface area 3. Different pathways of carbon in photosynthesis a. Typical pathway-Calvin or C3 cycle 1. Outcome of photon hitting chlorophyll is the production of ribulose diphosphate, a three carbon chain. b. Alternate pathway--C4 cycle 1. Outcome of photon hitting chlorophyll is the production of malic or aspartic acids. This represents the PEP process phospho-enol- pyruvate. 2. Difference in leaf anatomy 3. Common amongst sedges, grasses, etc., where light intensities are high. c. Another alternate pathway--Crassulacean 1. Outcome of photon hitting cholorphyll is the production of malic or aspartic acids. The CO2 is taken in at night to avoid daytime transpiratory losses. 2. Found in many desert plants. C. Soils and creatures 1. Presence or absence of certain trace minerals may have important effect on what species are present. Trace minerals function in minute amounts and may be integral components in catalysts, etc. 2. Most common example is the specilization of plants growing on serpentine soils (soils high in Magnesium and low in other materials). Many of the plants found growing in these soils are endemic and can only survive in such areas because of their specialization for such soils. May not compete well when placed in non-serpentine soils nearby. 3. Edaphic species (ecotypes) D. pH and other features 1. Acid rain and changes in pH of soils and lakes. May cause demise of organisms that have narrow ranges of tolerance. Other concomittant effects may be how they affect the behavior of metalic ions, eg., Aluminum. Amount of CaCO3 in soils and lakes may affect their ability to buffer pH changes 2. Salinity a. Example of wind-blown ions, eg., coastal dunes b. Salinization of soils eg., San Joaquin valley of Calif. E. Fire 1. Effects on seed production and germination a. Sierra redwood-seeds are very small, require highly mineralized soil. Regular fires have little effect of the large trees, but reduces leaf litter/ duff to minerals which when present in the soil enhance the germination process of the seed 2. Maintenance of the prarie a. Question as to whether maintained by climatic conditions or by regular passage of fire through the ecosystem b. Yellowstone Fire