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Transcript
Ecology of Organisms and Populations Ch. 18 Ecology Study of interactions between organisms and their environment Ecology can be divided into four increasingly comprehensive levels: Organismal ecology Population ecology Community ecology Ecosystem ecology Ecology Organismal ecology Is concerned with evolutionary adaptations that enable individual organisms to meet the challenges posed by their abiotic environments. http://www.seabird.org/assets/killer%20whales%20internet%202.jpg Ecology Population ecology Is concerned with populations, groups of individuals of the same species living in the same area. Concentrates mainly on factors that affect population density and growth. http://newsimg.bbc.co.uk/media/images/44609000/jpg/_44609350_puffins512.jpg Ecology Community ecology Is concerned with communities, assemblages of populations of different species. Focuses on how interactions between species affect community structure and organization. http://www.mass.gov/envir/forest/images/multiLayerForest.jpg Ecology Ecosystem ecology Is concerned with ecosystems, which include all the abiotic factors in addition to the community of species in a certain area. Focuses on energy flow and the cycling of chemicals among the various abiotic and biotic factors. http://www.african-books.com/images/Animals/montage.jpg Components of the Environment The abiotic component Consists of nonliving chemical and physical factors. The biotic component Includes the living factors. Abiotic Factors of the Biosphere On a global scale, ecologists have recognized striking regional patterns in the distribution of terrestrial and aquatic life. Global distribution patterns Reflect regional differences in climate and other abiotic factors. Sunlight Solar energy powers nearly all ecosystems. Availability of sunlight affects aquatic and terrestrial environments. http://artfiles.art.com/images/-/Aflo/Sun-Shining-in-BlueSky-Over-Tree-in-Winter-Snow-Biei-Hokkaido-JapanPhotographic-Print-C13062664.jpeg Water Aquatic organisms may face problems with water balance. For terrestrial organisms, the main water problem is drying out. Temperature Environmental temperature http://www.wildherps.com/images/herps/standard/desert_iguana.jpg http://www.sciam.com/media/inline/A186A7F7-D8EADDDF-0F715313A7DA2A91_1.jpg Is an important abiotic factor because of its effect on metabolism. Wind Some organisms depend on nutrients blown to them by wind. Organisms such as plants depend on wind to disperse pollen and seeds. Can also affect the pattern of a plant’s growth. http://www.asdk12.org/staff/vanarsdale_mark/pages/Ecology_Images/wind_tree.jpg Rocks and Soil Soil variation contributes to the patchiness we see in terrestrial landscapes. In streams and rivers, the composition of the soil can affect water chemistry. Periodic Disturbances Catastrophic disturbances Can devastate biological communities. After a disturbance, An area is recolonized by organisms, or repopulated by survivors. The structure of the community undergoes a succession of changes during the rebound. Ecosystems What biotic and abiotic factors do you see in this picture of the rain forest? Ecosystems What biotic and abiotic factors do you see in this picture of a tundra? Populations • A population is… Members of the same species… Who live in the same place At the same time. Populations • The environment where a population lives: habitat. Populations Population ecologists study many things about populations in their habitats: Population size Population density Population growth Population Density Population density Is the number of individuals of a species per unit of area or volume. In most cases, it is impractical or impossible to count all individuals in a population. In some cases, population densities are estimated by indirect indicators, such as number of bird nests or rodent burrows. Populations Populations are densest where there are resources available. Populations Patterns of Dispersion The dispersion pattern of a population is the way individuals are spaced within the population’s geographic range. Clumped Pattern of Dispersion Individuals aggregate in patches. Uniform Pattern of Dispersion Results from interactions among the individuals of a population. Random Pattern of Dispersion Individuals are spaced in a patternless, unpredictable way. Population Growth Models Two models, the exponential growth model and the logistic growth model, will help us understand population growth. The growth rate Is the change in population size per time interval. The Exponential Growth Model: The Ideal of an Unlimited Environment The exponential growth model Describes the rate of expansion of a population under ideal, unregulated conditions. The Exponential Growth Model: The Ideal of an Unlimited Environment • A key feature of the exponential growth model is that the rate at which a population grows depends on the number of individuals already in the population. The Logistic Growth Model: The Reality of a Limited Environment In nature, a population may grow exponentially for a while, but eventually one or more environmental factors will limit its growth. Population-limiting factors restrict population growth. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings The Logistic Growth Model: The Reality of a Limited Environment The logistic growth model Describes growth of an idealized population that is slowed by limiting factors. A comparison of the logistic growth model and the exponential growth model Carrying Capacity Is the number of individuals in a population that the environment can just maintain with no net increase or decrease. http://www.abc.net.au/reslib/200710/r189329_709751.jpg Regulation of Population Growth Density-Dependent Factors Are population-limiting factors whose effects intensify as the population increases in size. Increase a population’s death rate and decrease the birth rate. Regulation of Population Growth Density-independent factors Are population-limiting factors whose intensity is unrelated to population density. Include events such as seasonal freezing. In many natural populations, density-independent factors limit population size before densitydependent factors become important. Growth Rate Four influences: Birth rate Death rate Immigration Emigration Birth + Immigration – Death – Emigration Population Cycles Some populations Have regular boomand-bust cycles. Boom-and-bust cycles of the snowshoe hare and one of its predators, the lynx Communities and Ecosystems Ch. 19 Key Properties of Communities Diversity—variety of different kinds of organisms that make it up Prevalent form of vegetation— determines kinds of organisms that will survive in the area Stability—ability to resist change and return to its original species composition after being disturbed Trophic level—feeding relationships among the various species Diversity Which community is more diverse? The diversity of a community Is the variety of different kinds of organisms that make up the community. Species richness, the total number of different species in the community Relative abundance of the different species Interactions Between Populations of Different Species Interspecific interactions—occur b/w populations of different species Coevolution—a change in one species acts as a selective force on another species Interspecific Competition Competition occurs when 2 or more populations overlap in their niches Limiting resources Food Space Mates Generally, one will out-compete the other Competition in Nature Two possible Outcomes 1. Weaker competitor becomes extinct 2. One or both species may evolve enough to use a different set of resources (resource partitioning) Competition cannot operate for long periods of time Competitive Exclusion Principle Two species cannot coexist in a community if their niches are identical Joseph H. Connell Study Interactions Between Populations of Different Species Predation—consumption of one organism by another Parasitism—specialized predator (parasite) lives on/in its host, not killed immediately Endoparasitism—live inside host (tapeworms/viruses) Ectoparasitism—live on surface of host (mosquitoes/aphids) Herbivory—herbivores consume plants http://www.dldigital.com/images/z_oldimages/2002-10-d28aphid2-fr18.jpg Predator Adaptations Most predators have acute senses. Many predators Have adaptations such as claws, teeth, fangs, stingers, or poison to help catch and subdue prey. Are fast and agile. http://upload.wikimedia.org/wikipedia/commons/thumb/7/7c/H awk_eating_prey.jpg/300px-Hawk_eating_prey.jpg http://images.encarta.msn.com/xrefmedia/sharemed/targets/images/pho/00123/ 00123ed3.jpg Plant Defenses Against Hebivores www.treklens.com/.../Sweden/phot o198584.htm Physical defenses thorns, hooks/spines on leaves http://en.wikipedia.org/wiki/Image:Toxic odendron_radicans.jpg Chemical defenses Make plant distasteful or poisonous Morphine from opium poppy Nicotine from tobacco Poison Ivy http://images.wildmadagascar.org/pictu res/isalo/walking_stick0071.jpg Animal Defenses Against Predators Behavioral defenses Alarm cries Distraction displays Cryptic coloration/shape (camouflage) Blend in with environment Asposematic coloration Red/black; yellow/black Stick Insect www.laspilitas.com/.../Monarch_butte rfly.htm Mechanical/chemical defenses Quills, spines, and other similar structures Toxins—distasteful or poisonous Monarch butterfly on Milkweed Animal Defenses Against Predators Mimicry—prey resembles species that cannot be eaten Batesian mimicry: Imitate color patterns or appearance of more dangerous/unpalatable organisms Müllerian mimicry: 2 unpalatable species that inhabit the same community mimic each other Animal Defenses Against Predators Mimicry can be used to lure prey Snapping turtle wriggles tongue like a worm to attract and capture small fish http://www.lancashiremcs.org.uk/g allery/pics/lophius.jpg Angler Fish attract prey close enough to their mouths to be easily grabbed Symbiotic Relationships Non-Beneficial Parasitism—host harmed Beneficial Mutualism—both partners benefit Lichens-association b/w fungus and algae Nitrogen-fixing bacteria and legumes Community Structure Predators can moderate competition among its prey species Keystone species can alter the whole community Community Structure Lake Davis, CA Introduction of a http://www.dfg.ca.gov/lakedavis/ Northern Pike http://aquanauts_dc.homestead.com/files/northern_pike1.jpg species (exotic species) into a community can have drastic affects on the existing community members Disturbances in a Community Storms, fire, floods, droughts, overgrazing, or detrimental human activities: Remove organisms Alter resource availability Create opportunities for new species that have not previously occupied the habitat Humans are the biggest disturbance Logging, agriculture, overgrazing Ecological Succession Primary succession Begins in a virtually lifeless area where soil has not formed Lichens and mosses colonize first Soil gradually forms and small plants and shrubs take root Secondary succession Occurs where an existing community has been cleared by some disturbance that leaves soil in tact Earliest plants to recolonize are often those that grow from wind-blown or animal-borne seeds Ecological Succession Tolerance to abiotic conditions determines early species Competition among early species shape the succession of an area Mt. St. Helen 1980 Eruption MSH80_st_helens_spirit_lake_before_may_18_1980.jpg http://www.jqjacobs.net/photos/volcano/st_helens.html http://denali.gsfc.nasa.gov/research/volc2/MSHreflection.gif Mt. St. Helen Secondary Succession http://www.kgw.com/newslocal/stories/L_IMAGE.101688cd0b5.93.88.fa.7c.2791 3b573.jpg Red alder disperses easily and is capable of rapid growth on the nutrientpoor, volcanic deposits. A red-legged frog –one of the creatures living in one of the dozens of ponds created after the eruption. 70 species of birds, including hummingbirds, western meadowlarks and Savannah sparrows www.kgw.com/news-local/stories/kgw_051505_env... www.kgw.com/news-local/stories/kgw_051505_env... An Overview of Ecosystem Dynamics An ecosystem Is a biological community and the abiotic factors with which the community interacts. – Energy flow • Is the passage of energy through the components of the ecosystem. – Chemical cycling • Is the use and reuse of chemical elements within the ecosystem. Energy Flows through an ecosystem when consumers feed on producers. Cannot be recycled within an ecosystem, but must flow through continuously. Ecosystem Dynamics Energy Depend on the transfer of substances in the feeding relationships, or trophic structure, of an ecosystem. Trophic relationships Determine an ecosystem’s routes of energy flow and chemical cycling. Trophic flow and chemical cycling levels Divide the species of an ecosystem based on their main sources of nutrition. Trophic Relationships Ecosystems divided into trophic levels (feeding levels) Producers—autotrophs (mostly photosynthetic) Primary consumers—herbivores Secondary consumers—carnivores that eat herbivores Tertiary consumers—carnivores that eat other carnivores Detrivores—consumers that eat dead or decaying matter Food Chain/Food Web Energy Flow in Ecosystems Each level in a food web contains a different quantity of stored chemical energy When consumers eat producers or 2 consumers eat 1 consumers, some energy is lost in each transfer from one level to the next Energy pyramid A diagram that represents the cumulative loss of energy from a food chain. Chemical Cycling in Ecosystems Ecosystems Depend on a recycling of chemical elements. Biogeochemical cycles Are chemical cycles in an ecosystem that involve both biotic and abiotic components. Biogeochemical Cycles Three key points : Each circuit has an abiotic reservoir. A portion of chemical cycling can rely completely on geological processes. Some chemicals require processing before they are available as inorganic nutrients. Examples of Biogeochemical Cycles Carbon Nitrogen Phosphorus Water Carbon Cycle Human Impacts: Greenhouse Effect Increase of atmospheric CO2 Combustion of fossil fuels Burning of wood from deforestation Increase in global temperature Nitrogen Cycle Human Impact: Cultivation—turns up soil and ↑ decomposition of organic matter; Releases more nitrogen Harvesting ↓ nitrogen from ecosystem Adding industrially synthesized fertilizers to soil has resulted in doubling globe’s supply Excess nitrogen leeches into soil and into rivers, streams, and lakes and ground water— – ↑ levels are toxic to aquatic organisms and humans – Algal blooms in lakes ↑ eutrophication Phosphorus Cycle Human Impact: Sewage treatment facilities and fertilizers ↑ amounts of phosphates to aquatic systems, causing eutrophication of lakes. Water Cycle Human Impact: Destruction of tropical rain forest Will change the amount of water vapor in the air. May alter local and global weather patterns. To irrigate crops, humans pump large amounts of ground water to the surface.