Transcript Ecology
AP Bio Summer Assignment, Part 4 Ecology Content Ecology: the scientific study of the interactions between organisms and the environment – The ecological study of species involves biotic and abiotic influences. – Biotic = living or once living (organisms) – Abiotic = nonliving (temp, water, salinity, sunlight, soil, minerals) Ecological Heirarchy – Organism – Population: group of individuals of same species living in a particular geographic area – Community: all the organisms of all the species that inhabit a particular area – Ecosystem: all the abiotic factors + community of species in a certain area – Biosphere: global ecosystem Patterns of Dispersal: Clumped. For many animals, such as these wolves, living in groups increases the effectiveness of hunting, spreads the work of protecting and caring for young, and helps exclude other individuals from their territory. 1. Clumped – most common; near required resource Uniform. Birds nesting on small islands, such as these king penguins on South Georgia Island in the South Atlantic Ocean, often exhibit uniform spacing, maintained by aggressive interactions between neighbors. 2. Uniform – usually antagonistic interactions 3. Random – not common in nature Random. Dandelions grow from windblown seeds that land at random and later germinate. Demography: the study of vital statistics that affect population size – Additions occur through birth & immigration and subtractions occur through death & emigration. – A graphical way of representing the data is a survivorship curve. – This is a plot of the number of individuals in a cohort still alive at each age. Survivorship Curves: • Type I curve: low death rate early in life (humans) • Type II curve: constant death rate over lifespan (squirrels) • Type III curve: high death rate early in life (oysters) – Zero population growth: B + I = D + E – Exponential population growth: ideal conditions, population grows rapidly 2,000 Population size (N) dN = 1.0N dt 1,500 dN = 0.5N dt 1,000 500 0 0 5 10 Number of generations 15 – Unlimited resources are rare – Logistic model: incorporates carrying capacity (K) – K = maximum stable population which can be sustained by environment – dN/dt = rmax((K-N)/K) – S-shaped curve – K-selection: pop. close to carrying capacity – r-selection: maximize reproductive success K-selection r-selection Live around K Exponential growth High prenatal care Little or no care Low birth numbers High birth numbers Good survival of young Poor survival of young Density-dependent Density independent ie. Humans ie. cockroaches Factors that Limit Population Growth – Density-Dependent Limiting Factors: population size matters – i.e. Predation, disease, competition, territoriality, waste accumulation – Density-Independent factors: population size is not a factor – i.e. Natural disasters: fire, flood, weather Interspecific Interactions – Can be positive (+), negative (-) or neutral (0) – Includes competition, predation, and symbiosis – Interspecific (different species) competition for resources can occur when resources are in short supply. – Species interaction is -/- – Competitive exclusion principle: Two species which cannot coexist in a community if their niches are identical. – The one with the slight reproductive advantage will eliminate the other. – Intraspecific (same species) competition for resources can occur when resources are in short supply. Ecological niche: the sum total of an organism’s use of abiotic/biotic resources in the environment – Fundamental niche = niche potentially occupied by the species – Realized niche = portion of fundamental niche the species actually occupies Chthamalus Balanus High tide High tide Chthamalus realized niche Chthamalus fundamental niche Balanus realized niche Ocean Low tide Ocean Low tide Predation (+/-) Defensive adaptations include: – Cryptic coloration – camouflaged by coloring – Aposematic or warning coloration – bright color of poisonous animals – Batesian mimicry – harmless species mimic color of harmful species – Mullerian mimicry – 2 bad-tasting species resemble each other; both to be avoided – Herbivory – plants avoid this by chemical toxins, spines, & thorns Ecological Succession – Primary Succession – Plants & animals invade where soil has not yet formed – Ex. colonization of volcanic island or glacier Ecological Succession – Secondary Succession – Occurs when existing community is cleared by a disturbance that leaves soil intact – Ex. abandoned farm, forest fire Soon after fire. As this photo taken soon after the fire shows, the burn left a patchy landscape. Note the unburned trees in the distance. One year after fire. This photo of the same general area taken the following year indicates how rapidly the community began to recover. A variety of herbaceous plants, different from those in the former forest, cover the ground. Matter Cycles in Ecosystem – Biogeochemical cycles: nutrient cycles that contain both biotic and abiotic components – organic inorganic parts of an ecosystem – 4 Nutrient Cycles: water, carbon, nitrogen, phosphorus Carbon Cycle CO2 in atmosphere Photosynthesis – Key Idea: Cellular respiration Burning of fossil fuels and wood Higher-level Primary consumers consumers Carbon compounds in water Detritus Decomposition CO2 removed by photosynthesis; added by burning fossil fuels & cellular respiration Nitrogen Cycle N2 in atmosphere – Nitrification in Soil: – ammonium nitrite nitrate – Absorbed by Plants Assimilation Denitrifying – bacteria NO3 Nitrogen-fixing bacteria in root Decomposers nodules of legumes Ammonification Nitrification NH3 Nitrogen-fixing soil bacteria NO2– NH4+ Nitrifying bacteria – Nitrogen Fixation (Key Idea): – N2 enters plants through a mutualistic relationship with bacteria in the roots Nitrifying bacteria – Denitrification: – Release N to atmosphere Water cycle Transpiration Water vapor Evaporation abiotic reservoir: surface water atmospheric water enter food chain: precipitation plant uptake recycle: Solar energy transpiration return to abiotic: evaporation & runoff Precipitation Oceans Runoff Lakes Percolation in soil Groundwater Aquifer Phosphorus cycle Plants Land animals Soluble soil phosphate Loss in drainage fungi) Rocks and minerals Decomposers Phosphates (bacteria & fungi) in solution Animal tissue and feces abiotic reservoir: rocks, minerals, soil enter food chain: erosion releases soluble phosphate uptake by plants recycle: decomposing bacteria Animal tissue & fungi Urine and feces return to abiotic: loss toDecomposers ocean (bacteria and sediment Aquatic animals Plants and algae Precipitates Loss to deep sediment Acid Precipitation – Rain, snow, or fog with a pH less than 5.6 – Caused by burning of wood & fossil fuels – Sulfur oxides and nitrogen oxides released – React with water in the atmosphere to produce sulfuric and nitric acids – pH less than 5; rain is naturally acidic (~5.6) due to water vapor reacting with carbon dioxide to form carbonic acid. – These acids fall back to earth as acid precipitation, and can damage ecosystems greatly. – The acids can kill plants and aquatic organisms by changing the pH of the soil and water and/or damaging leaves and skin. It does NOT poison them!! Concentration of PCBs Biological Magnification Herring gull eggs 124 ppm Smelt 1.04 ppm – Fat soluble toxins become more concentrated in Lake trout successive trophic levels of a 4.83 ppm food web – Toxins cannot be broken down & magnify in concentration as you move through a food chain – Examples: Zooplankton 0.123 ppm Phytoplankton 0.025 ppm mercury & PCBs in fish Greenhouse Effect – The trapping of heat in the atmosphere of the Earth due to certain greenhouse gases. – CO2, water vapor, and methane cause the Earth to retain some of the infrared radiation from the sun that would ordinarily escape to the atmosphere. – The Earth needs this heat, but too much could be disastrous. Rising Atmospheric CO2 Since the Industrial Revolution, the concentration of CO2 in the atmosphere has increased greatly as a result of burning fossil fuels. In 2015, the level of CO2 in the atmosphere hit a record high of over 400 ppm. Global Warming – Several studies predict a doubling of CO2 in the atmosphere will cause a 2º C increase in the average temperature of Earth. – Rising temperatures cause polar ice cap melting, which causes sea levels to rise and will flood coastal areas. – It is important that humans attempt to stabilize their use of fossil fuels. Human Activities Deplete Atmospheric Ozone – Life on earth is protected from the damaging affects of ultraviolet radiation (UV) by a layer of O3, or ozone. – Chlorine-containing compounds (CFCs) erode the ozone layer. Progress: The Ozone Layer – Montreal Protocol – September 1987; in effect January 1989 – International treaty designed to protect the ozone layer by phasing out the production of and reducing the use of damaging chemicals. – It is working! The holes in the ozone layer are decreasing in size. Return to 1980 levels between 2050-2070. – Serves as an example that global environmental issues can be addressed successfully, but the impact of the efforts takes time. Four major threats to biodiversity 1. Habitat destruction – Human alteration of habitat is the single greatest cause of habitat destruction. 2. Introduced Species: invasive/nonnative/exotic species 3. Overexploitation: harvest wild plants/animals 4. Food Chain Disruption: extinction of keystone species