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Ecosystems, Energy Flow, Evolution, Cycles 5-10% of your APES Exam Ecology • Species that can naturally mate together and form fertile and viable off spring are called Species. • Organisms of the same species (intraspecific) that interact with each other and live in the same area form a population • Populations that interact with different species (interspecific) but live in the same area are called communities • When these communities interact with their environment it’s called and ecosystem. • Different ecosystems make up a biosphere • Species -> Population-> Community-> Ecosystem -> Biosphere Population Dispersion Ecosystem Characteristics • 1. Physical Appearance- Relative size; stratification and distribution of populations and species • 2. Species Diversity: number of different species • 3. Species Abundance: Number of individuals in each species • 4. Niche Structure: Number of ecological niches; how they resemble or differ from each other; species interaction Ecological Niches • An organisms “job” in the ecosystem • Described by its adaptive traits, habitat and place in the food web • Generalists (cockroaches, mice, humans) have broad Niches • Specialists (pandas) have narrow Niches Competitive Exclusion Principle • When 2 species are able to live and thrive in the same environment until you put them together. Competition • Intraspecific (between same species) or Interspecific (between different species) • Driving force of evolution • Interference Competition: preventing another organism from getting to its resource • Exploitation Competition: using a resource so it depletes and others can’t use it Amensalism • Interaction with 2 species where one suffers and the other doesn’t benefit at all. • Example: The bread mold Penicillium secrets penicillin which is a chemical that kills bacteria. • Example: Black walnut tree secretes a chemical that kills neighboring plants. Commensalism • Interaction with 2 species where one benefits and the other is not affected • Example: Remora on Shark (just needs a ride) • Example: Orchids living on Trees (just needs a home) • Example: Hermit crabs using left over shells of marine life (using something another has created) Mutualism • Interaction where both species benefits • Example: Bees Pollinating Flowers, Flowers feeding Bees Parasitism • One benefits and the other is harmed. • Example: Tick and Dog Keystone Species • This organisms presence contributes to a diversity of live and whose extinction would lead to extinction of other organisms. Also prevents over population. • Example: Sea Otters in a Kelp Forest • Example: Grizzly Bears moving nutrients from rivers to forests by way of salmon • Example: Sea Stars praying on Urchins and Mussels this keeps their populations down. Biomes Biome Antarctic Surrounding South Pole. Rainfall <2 cm per year Benthos Bottom of the ocean. No sunlight, no plant life. Dead organisms recycle matter, chemosynthesis Coastal Zones Estuaries, wetlands, coral reefs. High diversity and counts of plants and animal species due to runoff from land Coral Reefs VERY Diverse, VERY sensitive- disappearing at an alarming rate Deserts Form 15-25 degrees north and south of the equator. Rainfall <20 cm per year. Soils often have abundant nutrients but lack organisms. Freshwater Lakes Includes swamps, bogs, and wetlands. Important breeding areas for insects and amphibians, Critical for water supply. Easily polluted. Oligotrophic lakes are clear and low in nutrients. Eutrophic Lakes are rich in nutrients and life. Grasslands Rainfall is seasonal. Too wet for deserts, too dry for forests. 25% of all land. Overused for agriculture. Few plants because of fires and water availability Biomes Biome Hydrothermal Vents Occur in the deep ocean where hot-water vents rich in sulfur compounds are found and provide energy for chemosynthetic bacteria Intertidal Lots of biodiversity. Area between high and low tide. Water movement brings nutrients and removes wastes. Sensitive to pollution Ocean 75% of earths surface. Low diversity and productivity except near shoreline. Low nitrogen and phosphorus = limited plant growth and small organisms Savanna Warm year-round. Scattered trees. Intermediate between grasslands and forest. Extended dry season followed by rainy season. Contains herding animals. Taiga/Coniferous Found between 45-60 degrees north latitude. 17% of land surface. 2 types: /Boreal Forest open woodland and dense forests. More precipitation than the tundra. Soils are acidic b/c of decomposing tree needles. Temperate Found in milder temp than Taiga. Rapid decomposition. Exploited by humans. Deciduous forest Tall deciduous trees. Low density of large mammals. Temperate Rain Forest 100+ inches of rain each year. Lack of light to lower layers = less diversity Biomes Biome Chaparral/ Scrubland Hot dry summers, mild cool winters. Dense shrub growth. Erosion common after fires Temperate Woodlands Drier climate than deciduous forests. Fires common. Dominate by small trees. Tropical Rain Forests Very Diverse. Lots of Rain. High contrast in temps. Found within Hadley cells. Soil nutrients are low. Quick decomposition Tundra 60 degrees and above north latitude. Influenced by polar cells. Permafrost abundant. Low vegetation= low soil nutrients Photosynthesis/Cellular Respiration • Plants remove CO2 from atmosphere and convert it to carbohydrates (glucose) and other organic compounds. • Plants capture light energy in the chlorophyll. • Glucose is derived from its oxidation during cellular respiration • Oxygen gas is then released into the atmosphere • Cellular respiration is the opposite of photosynthesis. • In respiration, glucose is oxidized to produce CO2, Water and chemical energy (ATP) Photosynthesis Cellular Respiration Food Webs Food Webs Ecological Pyramids • Sunlight is the ultimate source of energy for most biological processes • Less than 3% of the sun that reaches earth is used for photosynthesis • In a food chain, only 10-20% of the energy is passed up to the next level. • The other 80-90% is lost Ecological Pyramids Ecological Pyramids Biodiversity • Genetic diversity: range of all genetic traits, both expresses and recessive, that makes up the gene pool for a species. • Species diversity: the number of different species that live in a certain area. • Ecosystem diversity: range of habitats that can be found in a defined area, bother biotic and abiotic components. Biodiversity Diversity Increasers Diversity Decreasers • Diverse Habitats • Disturbance in the habitat (fire, storms etc) • Environmental conditions with low variations • Trophic levels with high diversity • Middle states of succession • Evolution • Environmental stress • Extreme environments • Extreme limitations in the supply of a fundamental resource • Extreme amounts of disturbances • Introduction of new species from a different area • Geographic Isolation Evolution • Supported by structural evidence and the fossil record • Macroevolution: Long term, large scale changes to a population • Microevolution: small genetic changes to a population Speciation • When a segment of the population becomes so isolated that gene flow stops and those members of the population can no longer mate successfully with the rest of their species. • Adaptive Radiation: rapid speciation to fill ecological niches and is driven by natural selection or mutation Isolation • Geographic Isolation: a geographic barrier prevents species from mating and eventually leads to speciation. • Pre-mating isolation: things that isolate species BEFORE they get a chance to mate Example: Mating times, nocturnal species, anatomy • Post-Mating Isolation: things that prevent gametes from being fertilized or fertile offspring from being born. Example: baby kills mother, sperm doesn’t fertilize egg. Convergent Evolution • Process where organisms not closely related to each other independently acquire similar (analogous) characteristics while evolving in separate and varying ecosystems • Examples: Insects, birds and bats all have wings Evolutionary Relay • Occurs when independent species acquire similar characteristics through their evolution in similar ecosystems although not at the same time. • Example: development of dorsal fin in sharks and in extinct marine reptiles. Parallel Evolution • 2 independent species evolve together at the same time and in the same ecosystem and acquire similar characteristics. • Example: similar patterns in leaves have occurred on different plants over and over again Gradualism • Evolution is a very slow and stepwise process over millions of years. Punctuated Equilibrium • Some species arose suddenly in a short period of time (thousands of years). After long periods of stability. • These bursts are thought to have happened because of a quick change in the environment • Example: flowering plants appeared without any pre-flowering plants in the fossil record Ecological Services • The following are some services ecosystems give us. – – – – – – – – – – – – Moderate weather extremes Disperse seeds Mitigate drought and floods Protect people from the sun’s rays Cycle and move nutrients Protect waterways from erosion Detoxify wastes Purify air and water Pollinate crops Regulate disease carrying organisms Control pests Maintain biodiversity When an essay question asks: What ecological services does ______ provide… Succession • Gradual and orderly change in an ecosystem with the goal to be a “Climax Community” • Sometimes this means starting over after a disturbance (fire, earthquake, flood) • Rates of succession are determined by – Facilitation: one species modifies and environment to the extent it meets the needs of another species – Inhibition: when one species modifies the environment to an extent that it is not suitable for another species – Tolerance: when species are not affected by the presence of other species. Early Succession • Early successional species are generalists (Pioneer species) • They have short reproductive times and low biomass and fast reproductive rates (R-Select). Late Succession • Late successional species include larger perennial plants and animals with greater biomass. They have longer generational times and higher parental care (K-select). Types of Succession Type Description Allogenic Changes in the environment that make conditions beneficial to new plant communities Primary The colonization and establishment of pioneer species on bare ground (lichen and moss) Progressive Communities become more complex over time by having a higher species diversity and greater biomass Retrogressive The environment deteriorates and results in less biodiversity and biomass Secondary Begins in an area where the natural community has been disturbed but topsoil remains (after a forest fire or flood) Succession Carbon Cycle • Carbon is the basic building block of life and a fundamental element found in carbohydrates, fats, proteins and nucleic acids. Carbon Cycle • Carbon “SINKS” – Plant Matter: a portion of atmospheric carbon is removed by photosynthesis and is incorporated into plant structures – Terrestrial Biosphere: freshwater systems and nonliving organic material are included. Forests store 86% of the planet’s above ground carbon and 73% of the planet’s soil carbon. Carbon can be stored here for several hundreds of years in trees and several thousands of years in soils Carbon Cycle • Carbon SINKS cont.: – Oceans: Dissolved inorganic carbon in the form of CO2. Living and nonliving marine biota included (shells, skeletons). Removing carbon dioxide from the water raises the pH making the ocean more basic. – Sedimentary Deposits: Limestone and carbon trapped in fossil fuels and coal. Limestone is the largest reservoir of carbon in the carbon cycle Carbon Cycle • Carbon is released into the atmosphere through: – Cellular respiration of plants and animals (CO2). Anaerobic respiration releases carbon in the form of methane (CH4). – Decay of organic matter by decomposers, if oxygen is present it’s released as CO2. If no oxygen it’s released as CH4. – Burning of fossil fuels, wood, coal etc. – Volcanic eruptions – Weatherization of rocks- this breaks down to CO2 or carbonic acid H2CO3 – Release of carbon dioxide by warmer water Carbon Cycle Nitrogen Cycle • Nitrogen makes up 78% of the atmosphere • Essential in the formation of amino acids, proteins and nucleic acids. Nitrogen Cycle- Nitrogen Fixation • Converts N2 into ammonia (NH3) or Nitrate (NO3-) • 10% of nitrogen fixing is through high-energy fixation (lightening) where Nitrogen and oxygen combine to form nitrates which are carried to the surface in rainfall as Nitric Acid (HNO3) • Biological Fixation (90%)- Molecular nitrogen (N2) is split into 2 free nitrogens, then attach to an hydrogen to from ammonia (NH3). Nitrogen Cycle- Nitrogen Fixation • Fixation process is accomplished by several microorganisms (Rhizobium is associated with the root nodules of legumes) • Free-living aerobic bacteria Azobacter and Clostridium in the soil also fix nitrogen. • The end product here is ammonia Nitrogen Cycle- Nitrification • This is when ammonia (NH3) is oxidized to nitrite (NO2-) or nitrate (NO3-)- these forms are most useable by plants. • Nitrosomanas oxidize ammonia to nitrite and water • Nitrobacter oxidize nitrite to nitrate • Microorganisms are essential in this process Nitrogen Cycle- Assimilation • Nitrates are the form of nitrogen most commonly assimilated by plants through root hairs. • Rains and extensive irrigation can leach soluble nitrates and nitrites into groundwater (too much of this is the water can interfere with blood-oxygen levels in infants) • Soluble nitrates run off the land and into aquatic areas causing cultural eutrophication • Animals assimilate nitrogen-based compounds by consuming plants or other organisms that consume plants Nitrogen Cycle- Ammonification • When a plant or animal dies, or an animal excretes, the initial form of nitrogen is found in amino acids and nucleic acids. • Bacteria and sometimes fungi, convert this organic nitrogen back into ammonia (NH3) Nitrogen Cycle- Denitrification • When nitrates are reduced to gaseous nitrogen. • This process is used by facultative anaerobes. • These organisms flourish in an aerobic environment but also break down NO3- in anaerobic environments to use the oxygen and release the nitrogen • Examples include fungi and bacteria Pseudomonas Nitrogen Cycle Nitrogen Cycle • Humans activity has more than doubled the annual transfer of nitrogen to the biologically available forms through: – Extensive cultivation of legumes – Extensive use of chemical fertilizer – Pollution emitted by vehicles and industrial plants (NOx) – Biomass burning – Cattle and feedlots – Industrial processes Bad forms of Nitrogen • Fossil fuel combustion (NOx) • NOx is a precursor of tropospheric ozone production and contributes to smog and acid rain • Ammonia (NH3) in the atmosphere has tripled since the Industrial Revolution. Ammonia acts as an aerosol and decreases air quality • Nitrous Oxide(N2O) a significant greenhouse gas and breaks down atmospheric (good) ozone Phosphorus Cycle • Essential for the formation of nucleotides, ATP fats in the cell membrane, bones, teeth and shells. • Not found in the atmosphere • Generally found as phosphates (PO4-) or hydrogen phosphate ion (HPO4) • Often a limiting factor in soils because of its low concentration and solubility. Phosphorus Cycle • Phosphorus is slowly released from terrestrial rocks by weathering and acid rain • It then dissolves into the soil and is taken up by plants Phosphorus Cycle • Human impacts on the cycle: – Mined large quantities of rocks containing phosphorus for inorganic fertilizers and detergents – Clear-cutting tropical habitats for agriculture – Allow runoff from feedlots, from fertilizers and from the discharge of sewage plants leading to cultural eutrophication – Humans apply phosphorous to fields for fertilizer. Phosphorus Cycle Sulfur Cycle • Found mostly in underground rocks and deep oceanic deposits. • Natural release of sulfur into the atmosphere if from weathering of rocks and gasses released from seafloor vents and volcanic eruptions • It is released mainly as hydrogen sulfide (H2S) and sulfur dioxide (SO2) Sulfur Cycle • Once in the atmosphere is it converted to sulfur trioxide (SO3) and sulfuric acid H2SO4. • The acid mixes with rain and falls back to the surface as acid rain. • Sulfate (SO4-2) salt particles enter the atmosphere from sea spray, dust storms and forest fires. • These sulfate ions are eventually absorbed by plants to make proteins. Sulfur Cycle • Humans effect this cycle by: – Refining and burning fossil fuels – Converting (smelting) sulfur-containing metallic mineral ores into free metals such as copper, lead and zinc Water Cycle • Powered by the Sun’s energy and Gravity • Oceans hold 97% of all the water on the planet are the source of 78% of global precipitation. • Oceans are the source of 86% of all global evaporation and this keeps the surface of the earth from overheating • The water cycle is in a state of dynamic equilibrium- evaporation= precipitation • Warm air holds more water that cold air. Water Cycle Human Activity Effect on Water Cycle Withdrawing water from lakes, aquifers and rivers Groundwater depletion and saltwater intrusion Clearing land for agriculture and urbanization Increases runoff, Decreased infiltration, increased flood risk, accelerated soil erosion Agriculture Runoff contains nitrates, phosphates, ammonia etc. Destruction of wetlands Disturbing natural processes that purify water Pollution of water Increased occurrences of infectious agents such as cholera, dysentery, etc. Sewage runoff, feedlot runoff Cultural eutrophication Building power plants Increased thermal pollution Water Cycle