AP Environmental Science Unit Two
ECOSYSTEMS Unit Two
The Ecosystem: Sustaining Life on Earth The Biosphere is a closed system consisting of air, water and soil that recycled over time Sustaining life on Earth requires more than individuals Life is sustained by interactions of many organisms functioning together in ecosystems Physical and chemical environments
Basic Characteristics of Ecosystems Ecosystems have several fundamental characteristics 1.Structure Made up of two major parts; living (ecological community)and non living (physical chemical enviro)
2. Processes Basic Characteristics of Ecosystems Cycling of chemical elements and Flow of energy 3. Change Undergo development through Succession Gaia Hypothesis-is an idea that life has been and still is the dominant force shaping our physical environments
Ecosystems: Populations Unit Two
Population Ecology Population ecology- the study of the influence of the environment on fluctuations in population size and composition Population- group of individuals of the same species, that occupy the same area, use the same resources, and have a high chance of interacting and breeding with each other. See Handout depicting the framework of population ecology
Ecosystems: Communities Unit Two
Community Ecology Community ecology- the study of factors involved in determining a community s structure - the composition and relative abundance of its species Community- a collection of different species living close enough to allow for potential interaction
Basic Characteristics of Ecosystems At its simplest a community will have At least one species that is a producer At least one species that is a decomposer Plus a fluid medium
Ecological Communities Ecological community defined in two ways A set of interacting species found in the same place and functioning together to maintain life. Operational def= all the species found in an area, whether or not they interact.
Ecosystems: Interactions Unit Two
Interaction between Species (symbiotic relationships) Competition (-,-) The outcome is negative for both groups Mutualism (+,+) Benefits both participants Predation, Parasitism, Herbivory (+,-) The outcome benefits one and is detrimental to the other.
Examples of Mutualism Bacteria (nitrogen fixation) and Legumes (root nodules offer protection and food) Mycorrhizae: Fungi (increase root surface area for water absorption) and plants (provide food) Bacteria (digest cellulose) and ruminant mammals (provide safety and food) Plants and their pollinators Algae and Coral Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Competition Interspecific competition Occurs when species compete for a particular resource that is in short supply Strong competition can lead to competitive exclusion The local elimination of one of the two competing species Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The Competitive Exclusion Principle The competitive exclusion principle States that two species competing for the same limiting resources cannot coexist in the same place Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Ecosystems: Niches Unit Two
Ecological Niches The ecological niche Is the total of an organism s use of the biotic and abiotic resources in its environment Habitat = organism s address Niche = organism s profession Tolerance limits: any environmental condition that limits a species survival Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The niche concept allows restatement of the competitive exclusion principle Two species cannot coexist in a community if their niches are identical Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
However, ecologically similar species can coexist in a community If there are one or more significant difference in their niches EXPERIMENT Ecologist Joseph Connell studied two barnacle species Balanus balanoides and Chthamalus stellatus that have a stratified distribution on rocks along the coast of Scotland. RESULTS When Connell removed Balanus from the lower strata, the Chthamalus population spread into that area. Chthamalus Balanus Balanus realized niche High tide Chthamalus realized niche High tide Chthamalus fundamental niche Ocean Low tide Ocean Low tide Figure 53.2 In nature, Balanus fails to survive high on the rocks because it is unable to resist desiccation (drying out) during low tides. Its realized niche is therefore similar to its fundamental niche. In contrast, Chthamalus is usually concentrated on the upper strata of rocks. To determine the fundamental of niche of Chthamalus, Connell removed Balanus from the lower strata. CONCLUSION The spread of Chthamalus when Balanus was removed indicates that competitive exclusion makes the realized niche of Chthamalus much smaller than its fundamental niche. Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Dominant Species Dominant species Are those species in a community that are most abundant or have the highest biomass Exert powerful control over the occurrence and distribution of other species Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
One hypothesis suggests that dominant species Are most competitive in exploiting limited resources Another hypothesis for dominant species success Is that they are most successful at avoiding predators Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Ecosystems: Keystone Species Unit Two
Keystone Species Keystone species Are not necessarily abundant in a community Exert strong control on a community by their ecological roles, or niches Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Field studies of sea stars Exhibit their role as a keystone species in intertidal communities Number of species present 20 15 10 5 0 With Pisaster (control) Without Pisaster (experimental) 1963 64 65 66 67 68 69 70 71 72 73 Figure 53.16a,b (a) The sea star Pisaster ochraceous feeds preferentially on mussels but will consume other invertebrates. (b) When Pisaster was removed from an intertidal zone, mussels eventually took over the rock face and eliminated most other invertebrates and algae. In a control area from which Pisaster was not removed, there was little change in species diversity. Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Observation of sea otter populations and their predation Shows the effect the otters have on ocean communities Grams per 0.25 Otter number (% m 2 max. count) 100 80 60 40 20 0 (a) Sea otter abundance 400 300 200 100 0 (b) Sea urchin biomass Number per 0.25 m 2 10 8 6 4 2 0 1972 1985 1989 1993 1997 Year Figure 53.17 Food chain before killer whale involvement in chain (c) Total kelp density Food chain after killer whales started preying on otters Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Ecosystems: Species Diversity Unit Two
What is Biological Diversity Bio diversity refers to the variety of life forms in an area. Expressed as # of species in an area Or # of genetic types in an area
Biological Evolution How did biological diversity come about? Before modern science many felt it was to amazing to have come about by chance. Must have been created by God everything in the world is marvelously ordered by divine providence and wisdom for the safety and protection of us all -Cicero
Biological Evolution Charles Darwin Ninth century Explanation of diversity known as biological evolution Refers to the change in inherited characteristics of a population from generation to generation.
Biological Evolution New species arise as a result of competition for resources the difference among individuals in their adaptations to environmental conditions Four processes lead to evolution Mutation, natural selection, migration and genetic drift
Mutation Genes are inherited from one generation to the next Genes made up of DNA DNA made up bases A,C,G,T How these letters are combined determines the massage passed to a cell
Mutation When cells divide DNA is reproduced Each cell gets a copy If an error occurs in the reproduction of DNA it gets passed to new cells DNA change = Mutation
Mutation
Natural Selection Some individuals may be better suited to the environment than others. Those better able to survive and reproduce leave more offspring. Their descendants form a larger proportion of the next generation.
Natural Selection Four primary characteristics Genetic variability Environmental variability Differential reproduction that varied with the environment Influence of the environment on survival and reproduction
Natural Selection The accumulation of changes may lead to reproductive isolation Resulting in a new species Species = a group of individuals that can reproduce with each other.
Migration and Geographic Isolation Two populations become geographically isolated for a long time Enough change accumulates so that they no longer reproduce Two new species have formed Migration important evo process (e.g. Hawaii honey creeper and Darwin s finches)
Adaptive Radiation Galapagos Islands Darwin observed numerous finches related to a single finch elsewhere Each with a different niche Process called adaptive radiation
Founder Effect and Genetic Drift Founder effect Small # of individuals are isolated from larger pop. Less genetic variation than original pop Which characteristics present affected by chance Genetic drift is changes in freq of a gene simply by chance Ind may NOT be better adapted
Conservation Genetics In a large population, genetic diversity tends to be preserved. A loss/gain of a few individuals has little effect on the total gene pool. However, in small populations small events can have large effects on the gene pool. Genetic Drift Change in gene frequency due to a random event Founder Effect Few individuals start a new population. 46
Conservation Genetics Demographic bottleneck - just a few members of a species survive a catastrophic event such as a natural disaster Founder effects and demographic bottlenecks reduce genetic diversity. There also may be inbreeding due to small population size. Inbreeding may lead to the expression of recessive genes that have a deleterious effect population. on the 47
Genetic Drift 48
Basic Concepts of Biological Diversity Genetic diversity: total # of genetic characteristics of a specific species, sub species or group of species. Habitat diversity: the different kinds of habitat in a given unit area. Species diversity: Species richness- total # of sp Species evenness- the relative abundance of sp Species dominance- the most abundant sp
10 species; 100 ind, 87 elephants, 9 sp w/ 2 ind each
10 species; 100 ind, 10 ind each species
Species Diversity Merely counting the number of species is not enough to describe biological diversity.
The Number of Species on Earth 1.5 million have been named Total # could be 3 million or more New species discovered all the time E.g. Serra Geral do Tocantins Ecological Station 14 new species
The Number of Species on Earth Scientists group living things on the basis of evolutionary relationships. Three domains Eukarya Bacteria Archaea Eukarya have a nucleus and organelles, Bacteria and Archaea do not.
The Number of Species on Earth Eukaryote cell Bacterial (prokaryote) cell
The Number of Species on Earth Most of the species on Earth are insects or plants. Many species of fungi and protists. Relatively few mammals.
Environmental Factors that Influence Diversity
Ecosystems: Edge Effects Unit Two
Edges and Boundaries Edge Effects - important aspect of community structure is the boundary between one habitat and others Ecotones - boundaries between adjacent communities Sharp boundaries - closed communities Indistinct boundaries - open communities 60
Ecotones 61
Example of ecological gradients and changes in plant and animal communities with changes in elevation.
Example of ecological gradients and changes in plant and animal communities with changes in elevation.
The Distribution of Species on Earth In terrestrial environments temperature and water are the most important factors determining the distribution of life In aquatic environments light and nutrients are the most important factors determining the distribution of life Other less important factors include: ph, wind, soil composition, climate, altitude etc in reality there are many factors that effect the distribution of life
BIOGEOCHEMICAL CYCLES Unit Two
Biogeochemical Cycles A biogeochemical cycle is the complete path a chemical takes through the four major components of Earth s system. Atmosphere Hydrosphere Lithosphere Biosphere
Chemical Reactions Chemicals in the four major components have different average storage time Long in lithosphere (rocks) Short in the atmosphere Intermediate in the hydrosphere and biosphere
Biogeochem Cycles and Life Of the 103 known elements only 24 required for life. Macronutrients- required in large amounts Big six = C, H, N, O, P, S Micronutrients- required either in small/ moderate amounts For life to persist elements must be available at right time, right amount, and right concentrations relative to one another.
Biogeochem Cycles and Life For life to persist elements must be available at right time, right amount, and right concentrations relative to one another. When this does not happen chemical can become a limiting factor
Conservation of Matter Unit Two
Conservation of Matter The law of conservation of mass, also known as principle of mass/matter conservation is that the mass of a closed system (in the sense of a completely isolated system) will remain constant over time. A similar statement is that mass cannot be created/ destroyed, although it may be rearranged in space, and changed into different types of particles. In other words: all of earth s stuff is constant, it is simply recycled and moved around through time
Water Cycle Unit Two
Material Cycles Hydrologic Cycle - path of water through the environment Solar energy (the engine ) continually evaporates water stored in the oceans and land, and distributes water vapor around the globe. - Condenses over land surfaces, supporting all terrestrial systems Responsible for cellular metabolism, nutrient flow in ecosystems, and global distribution of heat and energy Def: Transpiration is the loss of water through plant pores. Similar to our sweating. 74
Hydrologic Cycle 75
BIOLOGICAL IMPORTANCE Water is essential for all life, water also influences production & decomposition FORMS AVAILABLE TO LIFE Mainly liquid water RESERVOIRS Rough estimations: 97% in oceans, 2% in glaciers and ice caps, 1% in rivers and lakes KEY PROCESSES Evaporation, Condensation and Precipitation
Carbon Cycle Unit Two
Carbon Cycle Begins with intake of CO 2 during photosynthesis. Carbon atoms are incorporated into sugar which is eventually released by cellular respiration either in the plant or in organisms that consumed it. Sometimes the carbon is not recycled for a long time. Coal and oil are the remains of organisms that lived millions of years ago. The carbon in these is released when we burn them. Some carbon is also locked in calcium carbonate (shells, limestone). Carbon atoms form the backbone of all life. Carbon atoms form the foundation of life s macromolecules: carbohydrates, proteins, fats and nucleic acids 78
Carbon Cycle The parts of the cycle that remove carbon dioxide from the atmosphere (vegetation) are called carbon sinks. The parts of the cycle that release carbon dioxide are called carbon sources. Burning of fuels generates huge quantities of carbon dioxide that cannot be taken up fast enough by the carbon sinks. This excess carbon dioxide contributes to global warming. 79
Carbon Cycle 80
BIOLOGICAL IMPORTANCE Carbon is the backbone of all organic compounds essential for life. FORMS AVAILABLE TO LIFE CO2 used by autotrophs, many other organic forms used by the rest of life. RESERVOIRS Fossil fuels, sediments of aquatic ecosystems, dissolved carbon in oceans, plant/animal biomass, atmosphere, sedimentary rocks (the largest) KEY PROCESSES Mainly photosynthesis and cellular respiration, burning of fossil fuels, volcanoes
Nitrogen Cycle Unit Two
Nitrogen Cycle Nitrogen is needed to make proteins and nucleic acids such as DNA (Chap. 2). Nitrogen-fixing bacteria have an enzyme caled nitrogenase that splits the triple covalent bond between the atoms of nitrogen in nitrogen gas. Higher organisms are therefore dependent on these bacteria to make nitrogen available for their use. Plants take up inorganic nitrogen from the environment and build protein molecules which are later eaten by consumers. - Members of the bean family (legumes) have nitrogen-fixing bacteria living in their root tissue. ex. peas, alfalfa, many beans 83
Nitrogen nodules on bean plant 84
Nitrogen Cycle Nitrogen re-enters the environment: - Death of organisms - Excrement and urinary wastes - Humans have profoundly altered the nitrogen cycle via use of synthetic fertilizers, nitrogen-fixing crops, and fossil fuels. - Nitrogen and phosphorous are most likely to be the limiting factors of plant growth. - Ironic since nearly 80% of the atmosphere is Nitrogen gas! 85
Nitrogen Cycle Atmosphere N 2 N 2 Atmosphere Soil N 2 Nitrogen-fixing bacteria Nitrate and nitrogenous organic compounds exported in xylem to shoot system H + (From soil) Denitrifying bacteria Soil NH 3 (ammonia) NH 4 + NH 4 + (ammonium) Nitrifying bacteria NO 3 (nitrate) Organic material (humus) Ammonifying bacteria Root 86
Nitrogen Cycle 87
BIOLOGICAL IMPORTANCE Nitrogen is an important part of proteins and nucleic acids. FORMS AVAILABLE TO LIFE Bacteria can use ammonium (NH4 + ), nitrates (NO3 - ), nitrites (NO2 - ) and some organic forms. Plants use all of the above except nitrites (NO2 - ). Animals can only use organic forms. RESERVOIRS Atmosphere(the largest), soils, sediments of aquatic ecosystems, dissolved in water and biomass of living organisms KEY PROCESSES Mainly nitrogen fixation, lightning, industrial fertilizers
Phosphorous Cycle Unit Two
Phosphorous Cycle Phosphorous is needed to make DNA, ATP (the energy currency of the cell) and other important biomolecules (Chap. 2). Phosphorous compounds are leached from rocks and minerals and usually transported in aqueous form. Taken in and incorporated by producers - Passed on to consumers Returned to environment by decomposition Cycle takes a long time as deep ocean sediments are significant sinks 90
Phosphorus Cycle 91
BIOLOGICAL IMPORTANCE Phosphorus is an important part of phospholipids (needed to make cell membranes), nucleic acids and ATP. In addition phosphorus is a mineral constituent of bones and teeth. FORMS AVAILABLE TO LIFE Phosphates (PO4 3- ) absorbed by plants RESERVOIRS Sedimentary rocks, soil, dissolved in the ocean and in biomass of organisms. KEY PROCESSES Weathering of rocks, leaching form soil, eaten by consumers, excretion by organisms
Sulfur Cycle Unit Two
Sulfur Cycle Most sulfur is tied up in underground rocks and minerals. Inorganic sulfur is released into air by weathering and volcanic eruptions. Cycle is complicated by large number of oxidation states the element can assume. Human activities release large amounts of sulfur, primarily by burning fossil fuels. - Important determinant in rainfall acidity 94
Sulfur Cycle 95
BIOLOGICAL IMPORTANCE FORMS AVAILABLE TO LIFE RESERVOIRS KEY PROCESSES