The Layout Of Life (from BIG to small) Biosphere (planet earth: water, land and sky) Biomes (Tundra, Taiga, Dessert, Ocean, Lake) Ecosystem (all of the plants and animals in a community that live together in a particular biome) Climate and the Biosphere • • Our “Biosphere” = EARTH Climate refers to the prevailing weather conditions in an area as dictated by temperature, rainfall, and these factors: 1) 2) 3) 4) Variations in solar radiation due to a spherical earth; The tilt of the earth’s axis as it rotates about the sun; Distribution of land masses and oceans; and Topography (landscape) features. Distribution of solar energy Seasons Biomes of the World • A biome is a large biogeographical unit of the biosphere that has a particular mix of plants and animals that are adapted to living under certain environmental conditions. • Terrestrial: Tundra, Taiga, Coniferous and Deciduous Forests, Temperate Rain Forests, Grasslands, Shrublands (Chaparrel), Desert, • Aquatic: Freshwater (lakes), Saltwater (Ocean), Estuaries (salt and fresh combined) • A community consists of all the various populations in an area. • An ecosystem is the community plus its nonliving habitat, including abiotic (nonliving: the soil, rocks, etc.) and biotic (living: plants and animals) components. • Ecology is the study of these ecosystems! • Ecology is the study of these ecosystems! • Ecology is not just about plants, animals and their environmets…… ………………..it’s also about the humans! (as our lives tend to affect all other lives disproportionately!) Ecological levels in a coral reef Community Composition and Diversity • The composition of a community is a listing of populations present. • The diversity of a community adds in the relative abundance of individuals. • Ecologists have ideas about why populations assemble together in the same place at the same time. • The interactive model of community structure views the community as a stable assemblage that remains the same over time. • The individualistic model views a community as a collection of species where each responds to its own requirements and tolerance factors. Two terrestrial communities Patterns of distribution within a population • Abiotic factors such as water, temperature, and availability of organic nutrients often determine a population’s distribution and density. • Biotic factors, such as the availability of food, or presence of disease, affect the distribution of populations. Patterns of Population Growth • Each population has a particular pattern of growth. • The per capita rate of increase is calculated by subtracting the number of deaths from the number of births and dividing by the number of individuals in the population. • It is assumed that immigration and emigration are equal. (that is: MOVE IN = MOVE OUT) Population Growth and Density (one is dependent on the other) • Environmental resistance occurs when most environments restrict growth, and exponential growth cannot continue indefinitely. • When the population reaches carrying capacity, the population stops growing because environmental resistance opposes biotic potential How are population numbers kept in check? 1. Competition: • Competition occurs when two species try to use a resource that is in limited supply. • According to the competitive exclusion principle, no two species can occupy the same ecological niche at the same time when resources are limiting. • Resource partitioning occurs when resources are partitioned between two or more species. 2. Predation • Predation occurs when one living organism, the predator, feeds on another, the prey. • Predators include lions, whales that filter feed, parasites that draw blood from hosts, and herbivores that eat grass, trees, and shrubs. Predator-Prey Population Dynamics • Predator-prey interactions between two species are influenced by environmental factors. • Cycling of population densities may occur, as in the case of the Canadian lynx and hare; predators kill off prey and then the predator population declines when food is in short supply. NOTICE: THEY BALANCE EACHOTHER…SO NEITHER IS COMPLETELY DEMOLISHED! • Predator-prey systems are not usually simple two-species systems. Predator-prey interaction: lynx and snowshoe hare 3. Prey Defenses • Prey defenses against predation take many forms: camouflage, use of fright, and warning coloration are three prey defense mechanisms. • Coevolution occurs when two species adapt to selective pressures of each other. Antipredator (Prey) defenses 4. Symbiosis • Symbiosis refers to close interactions between members of two populations. • Three types of symbiosis occur: parasitism, commensalism, and mutualism. • Symbiotic associations do not necessarily fall neatly into these three categoties. Parasitism • In the symbiotic relationship called parasitism, the parasite benefits and the host is harmed. • Parasites derive nourishment from their host and the effect can be mild or fatal to the host. • Many parasites use a secondary host to disperse or complete their stages of development, as is the case in the life cycle of a deer tick. Commensalism • In commensalism, one species benefits and the other is neither benefited nor harmed. • Often a host provides a home or transportation for another species. • For example, barnacles attach to backs of whales, remoras attach to sharks, clown fishes live within the tentacles of sea anemones, and cattle egrets eat insects off large grazing mammals. Egret symbiosis Mutualism • In mutualism, both members benefit. • Cleaning symbiosis involves crustaceans, fish, and birds that act as cleaners of a variety of vertebrate clients. • In some cases, the cleaners may exploit the situation and feed on host tissues, but cleaning appears to improve the fitness of the client. Cleaning symbiosis Human Population Growth • The human population is expanding exponentially. • The doubling time is the length of time it takes for a population to double, currently estimated at 53 years. • Only when birthrate equals death rate will there be zero population growth. More-Developed Versus Less-Developed Countries • Most of the expected increase in human population will occur in certain less-developed countries (LDCs) of Africa, Asia, and Latin America. • Doubling time in more-developed countries (MDCs) is about 100 years because a decrease in death rate due to medical advances was followed by a decrease in birth rates. World population growth • Despite introduction of medical care, LDCs still have twice the MDC growth rate. • Support for family planning, social progress, and delayed childbearing could help prevent an expected increase in population size. • So what?!?! So……..the natural balance of all the ecosystems cannot support continued exponential growth of the human population !!!!RESOURCES ARE LIMITED and we are depleting them without restoring them!!! Age Distributions • Many MDCs have a stable age structure, but most LDCs have a youthful profile—a large proportion of the population is younger than age of 15. • This means their populations will expand greatly in the near future. (so we’d better get ready!) • Zero population growth or replacement reproduction does not occur when each couple has only two children because there is momentum from younger women entering reproductive years. Chapter 34: Ecosystems and Human Interferences Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Nature of Ecosystems: FRAGILE! • An ecosystem contains biotic (living) components and abiotic (nonliving) components. • The biotic components of ecosystems are the populations of organisms. • The abiotic components include inorganic nutrients, water, temperature, and prevailing wind. Biotic Components of an Ecosystem • Autotrophs are producers that produce food for themselves and for consumers. • Most are photosynthetic organisms but some chemosynthetic bacteria are autotrophs. • Heterotrophs are consumers that take in preformed food. Biotic components • Consumers may be: • Herbivores – animals that eat plants, • Carnivores – animals that eat other animals, • Omnivores, such as humans, that eat plants and animals, or • Decomposers, bacteria and fungi, that break down dead organic waste. • Detritus is partially decomposed organic matter in the soil and water; beetles, earthworms, and termites are detritus feeders. Consumers Energy Flow and Chemical Cycling • Every ecosystem is characterized by two phenomena: 1) Energy flows in one direction from the sun to producers through several levels of consumers, and 2) Chemicals cycle when inorganic nutrients pass from producers through consumers and returned to the atmosphere or soil. Nature of an ecosystem • Only a small portion of energy and nutrients made by autotrophs is passed on to heterotrophs, and only a small amount is passed to each succeeding consumer; much energy is used at each level for cellular respiration and much is lost as heat. • Ecosystems are dependent on a continual supply of solar energy. • The laws of thermodynamics support the concept that energy flows through an ecosystem. Energy balances Energy Flow • The feeding relationships in an ecosystem are interconnected in a food web. Forest food webs Food chain Ecological Pyramids • The shortness of food chains can be attributed to the loss of energy between trophic levels. • Generally, only about 10% of the energy in one trophic level is available to the next trophic level. • This relationship explains why so few carnivores can be supported in a food web. Ecological pyramid Global Biogeochemical Cycles • All organisms require a variety of organic and inorganic nutrients. • Since pathways by which chemicals cycle through ecosystems involve both biotic and abiotic components, they are known as biogeochemical cycles. • Biogeochemical cycles often contain reservoirs, such as fossil fuels, sediments, and rocks that contain elements available on a limited basis to living things. • Nutrients flow between terrestrial and aquatic ecosystems. Model for chemical cycling The Water Cycle • In the water, or hydrologic cycle, the sun’s rays cause fresh water to evaporate from the oceans, leaving the salts behind. • Vaporized fresh water rises into the atmosphere, cools, and falls as rain over oceans and land. • Precipitation, as rain and snow, over land results in bodies of fresh water plus groundwater, including aquifers. • Water is held in lakes, ponds, streams, and groundwater. • Evaporation from terrestrial ecosystems includes transpiration from plants. • Eventually all water returns to the oceans. • Groundwater “mining” in the arid West and southern Florida is removing water faster than underground sources can be recharged. The water cycle The Carbon Cycle • In the carbon cycle, a gaseous cycle, organisms exchange carbon dioxide with the atmosphere. • Shells in ocean sediments, organic compounds in living and dead organisms, and fossil fuels are all reservoirs for carbon. • Fossil fuels were formed during the Carboniferous period, 286 to 360 million years ago. The carbon cycle Carbon Dioxide and Global Warming • The transfer rate , the amount of a nutrient that moves from one compartment of the environment to another, can be altered by human activities, allowing more carbon dioxide to be added to the atmosphere. • Atmospheric carbon dioxide has risen from 280 ppm to 350 ppm due to burning of fossil fuels and forests. • Besides CO2, nitrous oxide and methane are also greenhouse gases. • Similar to the panes of a greenhouse, these gases allow the sun’s rays to pass through but hinder the escape of infrared (heat) wavelengths. • Buildup of more of these “greenhouse gases” could lead to more global warming. • The effects of global warming could include a rise in sea level, affecting coastal cities, and a change in global climate patterns with disastrous effects. Earth’s radiation balances The Nitrogen Cycle • Nitrogen makes up 78% of the atmosphere but plants are unable to make use of this nitrogen gas and need a supply of ammonium or nitrate. • The nitrogen cycle, a gaseous cycle, is dependent upon a number of bacteria. • During nitrogen fixation, nitrogen-fixing bacteria living in nodules on the roots of legumes convert atmospheric nitrogen to nitrogen-containing organic compounds available to a host plant. • Cyanobacteria in aquatic ecosystems and free-living bacteria in the soil also fix nitrogen gas. • Bacteria in soil carry out nitrification when they convert ammonium to nitrate in a twostep process: first, nitrite-producing bacteria convert ammonium to nitrite and then nitrate-producing bacteria convert nitrite to nitrate. • During denitrification, denitrifying bacteria in soil convert nitrate back to nitrogen gas but this does not quite balance nitrogen fixation. The nitrogen cycle Nitrogen and Air Pollution • Human activities convert atmospheric nitrogen to fertilizer which when broken down by soil bacteria adds nitrogen oxides to the atmosphere at three times the normal rate. • Humans also burn fossil fuels which put nitrogen oxides (NOx) and sulfur dioxide (SO2) in the atmosphere. • Nitrogen oxides and sulfur dioxide react with water vapor to form acids that contribute to acid deposition. • Acid deposition is killing lakes and forests and also corrodes marble, metal, and stonework. • Nitrogen oxides and hydrocarbons (HC) react to form photochemical smog, which contains ozone and PAN (peroxyacetylnitrate), oxidants harmful to animal and plant life. Acid deposition • A thermal inversion, where these pollutants are trapped under warm, stagnant air concentrates pollutants to dangerous levels. • Nitrous oxide is not only a greenhouse gas, but contributes to the breakdown of the ozone shield that protects surface life from harmful levels of solar radiation. Thermal inversion The Phosphorus Cycle • The phosphorus cycle is a sedimentary cycle. • Only limited quantities are made available to plants by the weathering of sedimentary rocks; phosphorus is a limiting inorganic nutrient. • The biotic community recycles phosphorus back to the producers, temporarily incorporating it into ATP, nucleotides, teeth, bone and shells, and then returning it to the ecosystem via decomposition. The phosphorus cycle Phosphorus and Water Pollution • Phosphates are mined for fertilizer production; when phosphates and nitrates enter lakes and ponds, eutrophication occurs. • Many kinds of wastes enter rivers which flow to the oceans; oceans are now degraded from added pollutants. • If pollutants are not decomposed, they may increase in concentration as they pass up the food chain, a process called biological magnification. Chapter Summary • An ecosystem includes autotrophs that make their own food and heterotrophs that take in preformed food. • Solar energy enters biotic communities via photosynthesis, and as organic molecule pass from one organism to another, heat is returned to the atmosphere. • Chemicals cycle within and between ecosystems in global biogeochemical cycles. • Biogeochemical cycles are gaseous (carbon cycle, nitrogen cycle) or sedimentary (phosphorus cycle). • The addition of carbon dioxide (and other gases) to the atmosphere is associated with global warming. • The production of fertilizers from nitrogen gas is associated with acid deposition, photochemical smog, and temperature inversions. • Fertilizer also contains mined phosphate; fertilizer runoff is associated with water pollution. • Certain pollutants undergo biological magnification as they pass through the food chain. Thank you all so so much for your sweet card and wonderful gifts! Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Here’s to YOU, My amazing students!!!! Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.