Ecology Exam 1 Study Guide

Ecology Study Guide Exam 1: Ecology: the study of the natural environment including relations of organisms to one another and to their surroundings. Physiological ecology: understanding the physiological mechanisms of fitness. Behavioral ecology: understanding the behavioral mechanisms of fitness. Population: group of co-occuring individuals of the same species. Community: collection of populations of all the species that co-occur in a given area at a given point in time. Ecosystem: ecological community plus the non-living environment in which that community exists. Landscape: heterogenous area composed of a cluster of interacting ecosystems that are repeated in a similar manner throughout. Model: a simplification or abstraction of complex real-world phenomena. Intermediate disturbance hypothesis: the number of species that co-occur in an ecological community will be greatest when disturbances occur with intermediate frequency. Biome: large regional or sub-continental ecosystem type, typically defined by the dominant plant life-form in terrestrial systems. Life-form: morphological types (grasses vs. shrubs vs. trees) Physiognomy: form, structure or appearance of a plant community At the equator, the sun is never more than 23.5º latitude from directly overhead – equatorial regions get a lot of incoming electromagnetic radiation and there is little variation among the seasons in incoming electromagnetic radiation.  Intensity of incoming solar radiation varies with latitude.  Large amounts of incoming electromagnetic radiation at the equator drive global convection cells.  Warm air rises; moisture in ascending air condenses, forming clouds. Rain shadow effect accounts for deserts on leeward side of mountain ranges. Climate diagrams:  Units always metric  10ºC marks, 20 mm precipitation intervals (200 mm in rainy areas) Soil profile:  O: uppermost horizon o Really rich in organic matter o As you go down, increasingly decomposed organic matter  A: mixture of small inorganic particles o Filtered organic matter o Humus: partially broken-down organic matter; great for soil  B: contains a lot of substances leached from A horizon; deposited o Colorful  C: lowest; large pieces of parent material o Large pieces of rock intermixed with soil o May contain plant roots Xeric: dry Mesic: moist Herbaceous: no wood/VC Woody: contains VC Deciduous: lack leaves at some point in year Evergreen: leaves always present Needle-leaved: leaves are width of leaf lamina Broad-leaved: broad lamina or blade Coniferous: cone-bearing Forest: tree-dominated vegetation with closed canopy Woodland: tree-dominated vegetation with more open canopy Tropical Rain Forest  Climate: warm-hot with very little seasonal variation in temperature, abundant rainfall throughout the year  Location: Amazon Basin and E coast central America, Congo Basin, SE Asian islands  Dominant plants: Broad-leaved, evergreen trees, woody vines (lianas), epiphytes  Disturbances: Small- and large-scale windthrows Tropical seasonal or dry forest  Climate: warm-hot temperatures, more rainfall than savannas, pronounced dry season  Locations: 15-20º N and S; India and SE Asia, W coast central America  Dominant plants: dry season deciduous trees  Species diversity: second highest species diversity of any terrestrial biome behind tropical wet forest  Tend to flower at end of dry season  Cut at higher rate than rainforests Tropical savannas  Climate: warm-hot, moderate annual rainfall (100 – 150 cm), pronounced dry season  Location: E and central Africa, S. America south of Amazon Basin, Australia  Dominant plants: grasses with scattered trees (park-like physiognomy = savanna)  Disturbance: dry-season surface fires Deserts  Climate: <25 cm precipitation, highly seasonal precipitation (long dry season), extreme temporal variation in rainfall  Location: 25 - 35º N and S, leeward side of mountain ranges  Dominant plants: stem succulents, drought-deciduous shrubs, herbaceous annuals/ephemerals, cryptogamic (lichens, algae, mosses) crust  Net primary productivity: very low, even lower than tundra Chapparal and Sclerophyllous Woodland  Location: Mediterranean region, S. California, Central Chile, SW Australia, Cape of Good Hope  Climate: Mediterranean climate – cool moist winters, hot rainless summers  Dominant plants: evergreen shrubs, short trees with tough, small leaves  Disturbance: frequent, intense surface or crown fires Temperate Grasslands  Climate: 25-75 cm rainfall, moderate temperatures  Locations: central N. America, central Asia, Argentina  Dominant plants: herbaceous vegetation, primarily grasses, scattered forbs  Disturbance: frequent low intensity surface fires As precipitation decreases, height of grasses decreases (sod-forming  bunch grasses). Temperate Deciduous Forest  Climate: abundant rainfall (75-150 cm), moderate temperatures but strong seasonal fluctuations  Location: eastern N. America, W. Europe, E. Asia (China, Japan, Korea)  Dominant plants: broad-leaved, winter-deciduous trees  Disturbance: windthrows (individual trees or entire stands), infrequent low intensity surface fires Northern Coniferous Forest (Taiga)  Location: circumboreal (Canada, N. Europe, Siberia), south of tundra   Dominant plants: needle-leaved, conifers, mostly evergreen Disturbance: 1) Intense crown or surface fires, return interval approx. 100 yrs, 2) outbreaks of insect herbivores Tundra  Location: northern latitudes between coniferous forest and ice cap  Dominant plants: grasses, sedges, dwarf woody plants, lichens  Net primary productivity: very low Permafrost: permanently frozen layer of soil that is no more than 1 meter below the soil surface. Evolution: changes in the genetic composition of a population from one generation to the next. Population genetics: study of changes in the frequencies of genotypes and alleles from one generation to the next. Natural selection: differential reproductive success among phenotypes within a population as a result of certain phenotypes being better suited to the environment than other phenotypes. Phenotypic plasticity: flexibility in the expression of a genotype; the same genotype may express different phenotypes under different environmental conditions. Ecotype: a genetically differentiated sub-species that is well-adapted to a particular set of environmental conditions. Common Garden Experiment  Are parental phenotypic differences retained when grown under identical environmental conditions? Reciprical Transplant Experiment:  Does offspring phenotype resemble parental phenotype or the phenotype of individuals native to the new area? Gene: a discrete unit of hereditary information; a region of the genome that codes for a specific protein. Allele: different forms of the same gene; different nucleotide sequences at the same location in the genome. Calculating genotype frequencies  Consider a single gene in a diploid organism. “A” represents that dominant allele for that gene and “a” represents the recessive allele for that gene.  The population contains 50 individuals whose genotype is AA, 30 individuals whose genotype is Aa and 20 individuals whose genotype is aa  The genotype frequencies are o f(AA) = 50 AA individuals / 100 individuals in the population = 0.5 o f(Aa) = 30 Aa individuals / 100 individuals in the population = 0.3 o f(aa) = 20 aa individuals / 100 individuals in the population = 0.2 Calculating allele frequencies  Using the same population of 100 diploid individuals, the are 200 total alleles for the gene in the population because each of the 100 individuals has 2 alleles (one on each chromosome)  How many of the 200 total alleles are “A” alleles? -- The 50 AA individuals contribute 100 A alleles (2 per individual) and the 30 Aa individuals contribute 30 A alleles (one per individual) = 130 A alleles o f(A) = 130 A alleles / 200 total alleles = 0.65  How many of the 200 total alleles are “a” alleles? – The 20 aa individuals contribute 40 a alleles (2 per individual) and the 30 Aa individuals contribute 30 a alleles (one per individual) = 70 a alleles o f(a) = 70 a alleles / 200 total alleles = 0.35 Hardy-Weinberg Equilibrium Model: a model that predicts the genotype frequencies in the offspring generation, given allele frequencies in parental generation, if the population is not evolving; a null model that helps us understand the processes that cause evolution in populations.  p = f(dominant allele), q = f(recessive allele)  If the population is not evolving then genotypes frequencies in the next generation are f(Aa) = 2XpXq f(aa) = qXq o f(AA) = pXp  Using our earlier example where p = 0.65 and q = 0.35, then if the population is at HardyWeinberg Equilibrium then in the next generation the genotype frequencies should be o f(AA) = 0.65 X 0.65 = 0.4225 o f(Aa) = 2 X (0.65 X 0.35) = 0.455 o f(aa) = 0.35 X 0.35 = 0.1225 Under what conditions would a population be at Hardy-Weinberg Equilibrium and, hence, not evolving? 1. Mating must be random 2. No mutation must occur 3. No gene flow into or out of the population (no emigration and no immigration) 4. No natural selection must occur 5. Population size must be large Quantitative traits: traits that vary continuously, meaning take on a wide range of values (e.g. height, mass). Polygenic traits: traits whose phenotype is the result of the combined effect of many genes. Such traits often are quantitative. Stabilizing selection: NS that favors individuals with the mean value for the trait. Directional selection: NS that favors individuals at one extreme of the trait distribution. Disruptive selection: NS that favors individuals at both extremes of the trait distribution. Types of non-random mating:  Assortative mating: mating with individuals of similar genotype more than would be expected if mating were random  Disassortative mating: mating with individuals of different genotypes more than would be expect if mating were random Large population size is essential for a population to be at Hardy-Weinberg Equilibrium because it minimizes the influence of chance events on allele frequencies.  What kinds of chance events might affect allele frequencies? - deaths that are unrelated to an individual’s fitness – “being in the wrong place at the wrong time” - randomness in which alleles are present in the sperm or egg cells that are successful in fertilization Genetic drift: random or chance fluctuations in allele frequencies from one generation to the next Macroclimate: long-term weather patterns at the regional spatial scale (>10 km); climate data reported by weather stations and presented in climate diagrams. Microclimate: variation in climate variables at small spatial scales (kms, meters, cm) and over short periods of time. Factors driving microclimatic variation  At the scale of kilometers o Altitude o Proximity to large bodies of water  At the sub-kilometer scale o Aspect – direction that a slope faces o Over-topping vegetation o Color of the soil (or rock) surface Effects of altitude on microclimate o Temperature decreases with increasing elevation because 1. Adiabatic cooling: as air expands and becomes less dense, it cools 2. Thinner atmosphere at higher elevation results in less absorption of re-radiating IR Effects of large bodies of water on temperature o Proximity to large bodies of water moderates temperatures because 1. Water has a high specific heat – it can absorb a large amount of energy without changing temperature 2. Water has a high latent heat of vaporization – converting water from liquid to gaseous form absorbs a lot of heat from its surroundings 3. Water has a high latent heat of fusion – converting water from liquid to solid form gives off a lot of heat Throughout the year the position of the sun varies from directly over the Tropic of Cancer (northern summer solstice) to directly over the Tropic of Capricorn (northern winter solstice) -in the northern temperate and polar zones, sunlight always comes from the south. Aspect, through its effect on microclimate, can strongly affect plant species composition Principle of allocation: because organisms have limited resources available to them allocating resources to one function (e.g. growth) reduces the amount of resources available to perform other functions (e.g. reproduction) Organisms can regulate their body temperature through metabolic heat production and through manipulating physical processes of heat exchange with the environment (conduction, convection, radiation and evaporative heat loss) Desert plant adaptations o Sparse, open growth form o Reduce heat gain by conduction by elevating leaves above soil surface o Increase heat loss by convection by open growth form and small leaves o Reduce heat gain by radiation by white hairs on epidermis which reflect incoming electromagnetic radiation, and manipulate orientation of leaves (parallel to sunlight). Alpine plant adaptations o Cushion plant growth form (hemispherical, low, ground-hugging) o Increase contact with ground to increase conduction o Dense, hemispherical form reduces air circulation through the plant to reduce heat loss by convection. Endotherms can dissipate excess heat by increasing blood flow to vessels in the skin where heat can be radiated to the surrounding cooler environment o Note how these vessels are not covered with hair, which would insulate and prevent heat transfer Thermal neutral zone: the range of environmental temperatures over which an endothermic animal does not change its rate of metabolic heat production o Tropical species have narrower zone How can endothermic animals conserve heat in ‘heat-sucking’ aquatic environments? 1. Internal respiratory surfaces (lungs), rather than gills – reduce surface area in contact with water 2. Efficient mechanisms of insulating the body – extensive layers of fat or air-trapping fur 3. Counter-current heat exchange mechanisms to conserve heat within the body core and prevent it from being lost in extremities with high surface area Countercurrent heat exchange in an endotherm’s appendage o Warm incoming blood flow, cool returning blood flow Inactivity as a means of dealing with extreme temperature conditions  Increasing physiological adjustments o Resting in microclimate with moderate temperatures  Torpor  Hibernation/Estivation Torpor: state of low metabolic rate and lowered body temperature If an animal remains in a state of torpor for an extended period of time, like a season, then  Hibernation: state of torpor that occurs during the winter and is of long duration  Estivation: state of torpor that occurs during hot times of year and is of long duration True hibernation is characterized by 1. Thermal dormancy – ability to dramatically drop internal body temperature yet still carry out essential core body functions 2. Behavioral suppression – many muscles become completely inactive because brain over-rides normal sensory stimuli and some endogenous physiological rhythms 3. Metabolic inhibition – ability to depress energy-related and anabolic chemical reactions within the body Measures of water availability in air  Relative humidity = actual mass of water vapor per unit volume of air / mass of water vapor per unit volume of air that is saturated with water  Water vapor pressure = amount of pressure exerted by water vapor in air o Vapor pressure deficit = difference between actual water pressure and water vapor pressure if air were saturated As temperature increases, the amount of water vapor required to saturate air also increases. Measures of water availability in aquatic systems  Salinity: amount of solute dissolved per unit volume of water (water availability declines with greater salinity)  Osmotic pressure: pressure exerted by water as it flows from areas of higher to lower water availability across a permeable membrane Water availability in soil  Water potential (ψ): the capacity of water to do work  Water potential is a function of 1. Solute concentration 2. Matric forces* 3. Physical pressure Mechanisms of water exchange with environment by terrestrial animals  Water acquisition - drinking - acquisition of water from food - absorption from the environment  Water loss - evaporation - secretions and excretion Mechanisms of water exchange with the environment by terrestrial plants  Acquisition - absorption from soil - absorption from air  Loss - transpiration (from stomata, but also across the epidermis) - secretions - supplying reproductive tissues that disperse away from the plant Water conservation adaptations in terrestrial animals 1. Water-proof body covering (high densities of saturated hydrocarbons in insect cuticle) 2. Highly concentrated urine and feces (juxtamedullary nephrons of mammals and birds) 3. Activity restricted to times of day or microclimates were water loss is less severe Water conservation adaptations in terrestrial plants 1. Waterproof body covering – waxy cuticle on top of the epidermis 2. Restricting the amount of leaf area exposed to surrounding dessicating environment (small thick leaves, abscise leaves) 3. Prevent moist air from dispersing away from stomata (recessed stomata, leaf hairs) 4. Modified photosynthetic mechanisms (C4, CAM photosynthesis) Osmoregulation can be very energetically expensive because of the need to move solutes against concentration gradients Many marine invertebrates and cartilaginous fish minimize energetic cost of osmoregulation by being approximately isosmotic to the aquatic environment. Saltwater fish - Drink a lot - Desalinate the water they drink (kidney, chloride cells in gills) - Urinate little Freshwater fish - Drink little - Urinate a lot - Import salts through gills (chloride cells) Stable isotope analysis: a technique to identify the sources of resources used by organisms that relies upon different pools of resources in the environment containing different ratios of stable forms of chemical elements (isotopes) Solar constant: the amount of solar radiation that reaches the earth’s outer atmosphere = 2 gcal/cm2/yr Filters acting on solar radiation before hitting the earth’s surface  Atmospheric gases and dust – reduces solar radiation by >33%; strongly filters UV and irregularly filters IR, lesser effect on visible light (PAR)  Clouds – strongly filters IR, filters UV, lesser effect on visible light (PAR)  Over-topping Vegetation – strongly filters visible light (PAR), lesser effect on IR Photosynthesis in Green Plants 6CO2 + 12H2O  C6H12O6 + 6O2 + 6H20 C3 Photosynthesis  Rubisco binds CO2 to Ribulose bisphosphate, which fragments into 2 molecules of phosphoglyceric acid  Most widespread photosynthetic pathway  Prone to photorespiration at high temperatures  Least common among plant species that live in hot, dry climates Photorespiration: Rubisco binds oxygen rather than CO2; results in plant releasing 1 molecule of CO2; decreases the efficiency of photosynthesis C4 Photosynthesis  High CO2 concentration in bundle sheath cells: 4C acids shuttle CO2 captured in mesophyll cells into bundle sheath cells  Less prone to photorespiration  Common photosynthetic pathway in Poaceae; more common in species in hot dry climates  High light compensation point makes C4 plants not very competitive C4 photosynthesis: capture CO2 in mesophyll cells using PEP and shuttle 4-carbon acid into bundle sheath cells C4 plants are more abundant in hotter, drier ecosystems CAM photosynthesis  Photosynthetic pathway that allows plant to open stomata, store CO2 at night then close stomata and photosynthesize during the day  Most water efficient type of photosynthesis  Occurs primarily in desert succulent plants (Cactaceae, Crassulaceae, Aizoaceae) Photosynthetic pathway & water used to fix 1 g CO2 400-500g  C3  C4 250-300g  CAM 50-100g