Ecology Exam 2 BIOTIC FACTORS Allelopathy Allelopathy Example if coral B tries to grow into coral A s territory A releases a chemical chemical deterrence of one species by another that causes tissue necrosis of B Example microbial deterrence of penicillin Common with plants marine invertebrates corals sponges Sessile organisms o Intense competition for space light and food Soil sickness inability of some species to survive or grow in the presence of others o Example Pickering 1977 grass apple seedlings Grass emits something that prevents the seedlings from growing o Example deleterious effects of black walnut on tomato and alfalfa o Example Barely inhibiting the growth of weed species Disease Parasites Example Hawaiian Islands o Large scale extinction events and distributional changes in native birds o Before human impact native birds had a broad distribution elevation 1 Habitat destruction for faming in low lands Decrease in native bird abundance Increase in non native bird abundance 2 Arrival of non native birds enhanced malarial parasite abundance which are found at mid elevations Native birds are more susceptible to malaria distribution is limited to where mosquitoes are not abundant Physical Factors Climatology Temperature moisture precipitation interaction is very important climate affects organisms o 2 primary factors that geographical ecologists use to map ecozones biomes o Temperature o Temperature gradients on Earth determined by Incoming solar radiation Total isolation at poles is 40 of that delivered to the equator warmer at equator than north pole Distribution of land and water Oceans moderate temperatures have high specific heats lots of energy to change temperature high thermal capacity can store lots of energy temperature variation greatest in the interiors of continents Warmer 1st inland in the spring colder 1st inland in the winter Precipitation o Habitats can also differ considerably in the amount of precipitation they receive High precipitation at equator low at the poles Mountain also receive a lot of rain and have a shadow on their leeward side Temperature and Moisture as Limiting Factors o o What ultimately matters is evaporation and transpiration Evaporation Transpiration process water loss to the atmosphere physical process how much water an organism loses biological Both are highly dependent on temperature both increase with increased temperature Polar regions low precipitation not arid because of low evaporation Deserts low precipitation very arid because of high evaporation o Can influence survival reproduction development of young mortality due to thermal stress and interactions competition predation parasitism with other species o Animals temperature appears to be most important to distributional limits Minimum temperatures are very important energetic demands of living in cold weather Precipitation isn t as important as temperature for animals o Plants precipitation is key Wide variety in drought resistance Drought pressure is very important to distribution and abundance Winter drought temperature effects on the ability of plants to take up water Drought Resistance a plant s control over the following Increased water storage ex cactus Closing stomata or thick wavy cuticles to reduce transpiration Reduced water loss Deeper root system Dictates water and nutrient uptake Smaller leaves reduces overall surface area reduces area for which transpiration can occur Shed leaves eliminates surface area reduces transpiration area Interacting Effects of Temperature and Moisture o It s rare for 1 factor to be solely important o Typically it is the interaction between temperature and moisture that sets distributional limits o Example Loblolly pine Both winter temperature and precipitation are important Cold temperatures limit the ability of pines to take up water during the winter Hence winter drought is more accentuated in northerly areas Zonation on Rocky Shores o Chthamalus stellatus CS barnacle found high on the rock resistant o Semibalanus balanoides SB barnacle found low on the rock not as to desiccation stress tolerant of desiccation stress o o o Joe Connell 1961 conducted an experiment removed SB under the water and CS did well along the rock face lower distribution of CS is limited by biological processes competition o BB can t deal with desiccation stress high are preyed on by Nucella low compete with algae for space low best in the mid tidal range Adapting to Environmental Variation e l b a t c i d e r p n u e r o M t n e m n o r i v n e t n e t s i s n o c n i t n e m n o r i v n e Canalization Genetic polymorphism trait variation is under strict genetic control phenotypes are genetically fixed and constant across all environments in certain environments individuals differ genetically for traits that improve survivorship in different environments traits differ genetically and certain genotypes are found o Spatial segregation of the different genotypes o Example Clausen et al 1948 yarrow plant height is strongly dictated by winter temperature and precipitation Phenotypic plasticity within generation changes in a trait induced by environmental cues change results in improved fitness in the given environment o Examples crabs and snails in marine environments crayfish fish and snails tadpoles and dragonfly larvae in ponds and lakes plants in response to herbivorous insects Strategy favored by natural selection will depend on temporal and spatial scale of environmental variation Phenotypic Plasticity The capacity to express such developmental change is likely under genetic control and can thus evolve by means of natural selection 1 There have to be reliable cues that signal what the environment is like 2 Most common in highly variable or unpredictable environment 3 Must be costs associated with the alternative phenotype Two types of plasticity o Developmental Conversions discrete rather than continuous phenotypic variation irreversible on off responses Example Curt Lively 1986 on Chthamalus anisopome in Gulf of occur very early in ontogeny produce California Acanthina angelica predatory snail which mounts barnacles to eat them wherever the hole is Bent Correlation between snail abundance and frequency of bents tested by having juvenile barnacles and either allowing the snail to crawl on them or having no snail present snail present bent less vulnerable to snail predation but less internal volume no absent conic more vulnerable to snail predation but more