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An Introduction To Ecology Chapter 18 18.1 Ecology – study of interactions between organisms and environment. Consists of abiotic (nonliving; i.e. temperature, light, etc) and biotic (living) factors. Levels of Organization The levels of organization are designed to allow scientists to understand and study relationships more easily Levels of Organization all one all smallest large group interacting organisms living individual region of unit and populations of similar with living different nonliving of organs the living typical thing same cellsin an organized kind plants kinds working ecosystem things living and of to in work animals interacting one together tissues together area that within includes workinga certain together several area ecosystems cell Species – a group of organisms that can breed and produce fertile offspring Populations – groups of individuals that are the same species and living in the same area Communities – a group of organisms of different species living together in the same area Ecosystems – all the populations living together with the nonliving environment Biomes – groups of similar ecosystems that have similar climates and similar communities Biosphere – combines all the parts of the earth in which life exists Ecology 18.2 Components of an Ecosystem Abiotic – the nonliving components of an ecosystem Light – affects photosynthesis Temperature – affects metabolism Water supply Oxygen supply Minerals Soil/Rocks pH Examples of Abiotic Factors Biotic – the living components of an ecosystem Plants Animals Protists Fungus Bacteria Examples of Biotic Factors Organisms in a changing environment Each organism can survive within a limited range of environmental conditions Tolerance curve- a graph of performance versus values of an environmental variable such as temperature Acclimation- the process of an organism adjusting tolerance to abiotic factors Organsims can survive unfavorable environmental conditions through: Dormancy- entering a state of reduced activity Migration-moving to a favorable habitat Structure Habitat – the physical area in which an organism lives (includes climate, topography, soil and water chemistry, plant and animal life, etc.) Niche – the way of life of a species (includes its habitat, feeding habits, reproductive behavior, etc.) species can be generalists (broad niche) or specialists (narrow niche) 18.3 Energy Transfer All energy comes from the sun Plants harness the sun’s energy in which process? Plants need light for photosynthesis, what else do they need? We call plants producers because they produce energy from the sun Measuring productivity Gross primary productivity-rate at which producers in an ecosystem capture energy of sunlight by producing organic compounds Biomass-organic material produced in an ecosystem Net primary productivity-rate at which biomass accumulates Primary Producers (Autotrophs) Energy from the sun is captured by plants, algae, or bacteria through photosynthesis. Energy from chemicals is captured by some bacteria through chemosynthesis. Capture energy from the sun or from chemicals and store it in the bonds of sugars, making it available to the rest of the community Did You Know? Deep-sea vents, far from sunlight, support entire communities of fish, clams, and other sea animals, which depend on energy converted through chemosynthesis. Consumers (Heterotrophs) Rely on other organisms for energy and nutrients Use oxygen to break bonds in sugar and release its energy through cellular respiration (primary producers do this, too) Types of Consumers: Herbivores: plant-eaters Carnivores: meat-eaters Omnivores: combination-eaters Detritivores and decomposers: recycle nutrients within the ecosystem by breaking down nonliving organic matter California Condor Did You Know? Scavengers, such as vultures and condors, are just large detritivores. When one organisms eats another, molecules are metabolized and energy is transferred An organism’s trophic level indicates the organism’s position in a sequence of energy transfers Trophic Levels Lesson 5.3 Ecological Communities Energy in Communities An organism’s rank in a feeding hierarchy is its trophic level. Primary producers always occupy the first trophic level of any community. In general, only about 10% of the energy available at any trophic level is passed to the next; most of the rest is lost to the environment as heat. Pyramid of Energy What is a food chain? Food chain: Linear series of feeding relationships A Basic Food Chain Plants absorb light from the sun, which is turned into energy to grow. We call these producers. The vegetarian animals eat the plants, they are called primary consumers. Secondary consumers prey on primary consumers. Food Web- interrelated food chains in an ecosystem MATTER CYCLING IN ECOSYSTEMS Nutrient Cycles: Global Recycling Global Cycles recycle nutrients through the earth’s air, land, water, and living organisms. Nutrients are the elements and compounds that organisms need to live, grow, and reproduce. Biogeochemical cycles move these substances through air, water, soil, rock and living organisms. Covered in Photo/Resp. Chapter! Water Cycle Key Terms: Ground water-water found in soil or in underground formations of porous rock Transpiration-process by which water evaporates from leaves of plants in terrestrial ecosystems Evaporation-adds water to the atmopshere Precipitation-the process by which water leaves the atmosphere Water Cycle Carbon Cycle Fourth most abundant element in universe Building block of all living things Main Pathway– in and out of living matter Key Terms Carbon Cycle- Circulation of carbon through ecosystems Carbon- A non-metallic element found in coal, petroleum and natural gas. Major component of life. Soil Respiration- Carbohydrates are oxidized and returned to the air by soil microorganisms that decompose dead animals Key Terms Continued Atmosphere- layer of gasses Fossil Fuels- Carbon-rich fuel from ancient animals and plants Photosynthesis- Energy (sun)+ Water+ Carbon dioxide Carbohydrates+ Oxygen Cellular Respiration- Glucose+ Oxygen CO2+ H20+ Energy (ATP) Decomposition- breakdown of matter by bacteria and fungi Biological Importance of Carbon All living organisms contain carbon CO2 is found in all living organisms Plants use carbon dioxide and water to form simple sugars (photosynthesis) Carbon is needed for life Carbon dioxide is a greenhouse gas Carbon is necessary for life, but carbon dioxide can be harmful Carbon Cycle Nitrogen cycle Organisms need nitrogen to make proteins and nucleic acids Nitrogen gas makes up 78% of the atmosphere Most plants can only use nitrogen in the form of nitrate Nitrogen fixation- process of converting nitrogen gas into nitrate Nitrogen fixing bacteria transform nitrogen into a usable form Recycling nitrogen Decomposers break down decaying organisms and release the nitrogen they contain as NH3 Ammonification- changing NH3 (ammonia) into NH4 +(ammonium) Nitrification-soil bacteria take up ammonium and oxidize it into (nitrites) NO2-and (nitrates) NO3Denitrification-process where anaerobic bacteria break down nitrates and release nitrogen gas into the atmosphere Nitrogen Cycle Importance of the Phosphorus cycle Phosphorus is an essential nutrient for plants and animals It is a part of DNA-molecules and RNAmolecules, molecules that store energy (ATP and ADP) Phosphorus is also a building block of certain parts of the human and animal body, such as the bones and teeth. Difference in the Phosphorus cycle The phosphorus cycle differs from the nitrogen and carbon cycles because phosphorus is unable to achieve the gaseous state in the atmosphere. Phosphorus is mainly found in water, soil and sediments. In the atmosphere, phosphorus is found as fine dust particles. By: Jermaine Loutin (Jose Marti Six Form Envi.) The Phosphorus Cycle Ch 19 Populations 19.1 Understanding populations Population ecology: studies changes in population size and the factors that regulate populations over time A. Populations are affected by size, density and dispersion 1. Population size- number of individuals 2. Population density: the number of individuals of a species per unit area or volume Ex: number of earthworms per cubic meter of soil Normally determined by sampling Estimates are more accurate for larger populations 3. Population dispersion a. Clumped dispersion pattern: individuals are grouped in patches Most common in nature Due to unequal distribution of resources in the environment b. Uniform dispersion pattern: even spreading Usually results from interaction between individuals Ex: territories c. Random dispersion pattern: unpredictable spacing Ex: plants grown from windblown seeds B. Population dynamics: interactions between biotic and abiotic factors that cause variation in population size 1. Population growth Population increases occur through birth (natality)and immigration Immigration-movement of individuals into a population Population decreases occur through death (mortality) and emigration Populations are also affected by life expectancy or how long and individual is expected to live Emigration-movement of individuals out of a population May be influenced by factors such as food availability and water quality 2. Age structure-distribution of individuals among different ages in a population 3. Patterns of mortality Survivorship: the chance of an individual in a given population surviving to various ages Survivorship curves: plot survivorship as the proportion of individuals from an initial population that are alive at each age Allows for species comparison a. Type I survivorship: animals that produce few offspring and nurture them to maturity Ex: humans and other large mammals b. Type III curve: opposite of a Type I Many offspring are produced but few make it to maturity Ex: many invertebrates c. Type II curve: survivorship is constant over the lifespan Individuals are equally vulnerable at every stage of the life cycle Ex: lizards and rodents 19.2 Measuring Populations A. Population size Determined by the following equation: Growth rate =(individuals added)- (individuals subtracted) or (birthrate + immigration rate) – (death rate + emigration rate) Growing populations have a positive growth rate; shrinking populations have a negative growth rate. Usually expressed in terms of individuals per 1000 Population changes are expressed as percentages: Growth rateX100= % growth B. Exponential growth model: the rate of population growth under ideal conditions As the population size grows, more individuals are added during each interval Graphing this data gives a Jshape curve Exponential growth can NOT continue indefinitely Eventually, one or more environmental factors will limit growth Ex: space and food supply C. Logistic growth model: idealized population growth that is slowed by limiting factors as the population size increases Results in formation of an S-shape curve K is the carrying capacity - maximum population size that a particular environment can sustain K varies depending on the species and the resources available Influenced by predators, parasites, food sources, and abiotic factors Emphasizes that resources are finite At low populations, resources are abundant and the population is able to grow nearly exponentially Population stabilizes at the carrying capacity when the birth rate equals the death rate D. Population Regulations Density-independent factors- factors that reduce the population by the same proportion. Influence does not change with population density. These are usually abiotic factors They include natural phenomena, such as weather events Drought, flooding, extreme, heat or cold, tornadoes, hurricanes, fires, etc. Density-dependent factors- Influence changes with population density. Any factor in the environment that depends on the number of members in a population per unit area Usually biotic factors, these include: Predation, Disease, Parasites, Competition