Ecosystem Ecology Ch. 3

General Info Life is sustained by the interactions of many organisms functioning together, through their physical and chemical environments Levels of Organization Species - any organism that is able to interbreed and produce fertile offspring Populations - groups of the same species living in the same area at the same time Communities - groups of populations that live together in a defined area Ch 6, pg. 150

Biosphere - combined areas of planet where life exists Ecosystem - the relationship of the community with its nonliving environment Biomes - ecosystems in different locations with similar climate and communities (e.g. desert, temperate forest, arctic, etc) Biosphere - combined areas of planet where life exists Ch 6, pg. 150

Ecosystem Structure and Boundaries Biotic and abiotic components provide ecosystem boundaries and distinguish one from another Abiotic - water, temperature, light, soil and atmospheric conditions, pH, salinity, etc. Biotic – living organisms, food, predation, competition Watersheds and topographic features are often used to delineate the boundaries of an ecosystem Know boundaries to determine components, and flow of energy and matter Pg. 58-59 Some ecosystems have well defined boundaries and others do not. All of the land in a given landscape that drains into a particular river, lake, stream or wetland. Topography determines the watershed

Variety of scales, wide range of sizes Pg. 59

Ecosystem Processes Two basic types: Chemical cycling – movement and recycling of elements between the environment and organisms Flow of energy Chemical cycling will be covered in the next chapter

Energy Flow Review Energy is the ability to do work or transfer heat Potential vs. kinetic 1st and 2nd law of thermodynamics Nearly all the energy that powers ecosystems comes from the Sun Main energy source for most life on earth Photosynthesis and respiration IB – know difference between energy transfer and transformation. 1st law of thermodynamics (“law of conservation of energy”) = energy is neither created nor destroyed, 2nd law = changed from one form to another. when energy is transformed, the quantity remains the same, but ability to do work diminishes

Producers (autotrophs) use energy from the environment to produce their own food Photosynthetic - plants, algae, and some bacteria use energy in sunlight to make complex organic molecules Pg. 60-61

Chemosynthetic - several types of bacteria use energy in inorganic chemical bonds to live (e.g. ocean floor thermal vents, Yellowstone hot springs, etc.) Bacteria inside mussels and tubeworms

Consumers (heterotroph) - any organism that consumes another organism to obtain energy through cellular respiration Pg. 60-61

Primary consumer - herbivore Secondary consumer - carnivore Tertiary consumer - eats 2° consumers Omnivore Scavengers – carnivores that consume dead animals Detritivores – break down dead tissues and waste products (detritus) into smaller particles; e.g. crabs, snails, beetles, earthworms, etc. Decomposer – any organism that breaks down dead organic material and recycles nutrients in to ecosystems; e.g. bacteria and fungi Pg. 61-62

Trophic levels – successive levels of organisms consuming one another As organisms eat and in turn are eaten, energy is transferred Flow of energy begins with the sun or inorganic compounds and travels in one direction Illustrated by a food chain or food web Trophe means nourishment in Greek

Food chain – linear sequence of consumption from producers through tertiary consumers

Food web - complex model of feeding relationships: how energy and matter move between trophic levels

Ecological Pyramids - diagram that shows the relative amount of energy or matter contained within each trophic level in a food chain/web

Pyramid of Numbers Based on the number of individuals at each trophic level

Energy Pyramid Proportion of consumed energy that can be passed to the next trophic level is ecological efficiency Only about 10% of energy available at one trophic level is transferred to the next Why? How does this relate to 2nd law? CTI – “Should Humans Eat Lower on the Food chain? More than 90% of energy transferred is lost as heat; less than 10% is fixed as new tissue. As energy flows thru a web, it is degraded and less and less usable. IB kids needs to be very familiar with section 5.6

Biomass Pyramid Total amount of organic matter in an ecosystem. Represents the total amount of potential food available for each trophic level

Ecosystem Productivity Amount of energy available in an ecosystem determines how much life it can support Biological production is the capture of usable energy from the environment to produce organic matter (increase biomass) Gross primary production – total amount of energy captured by producers over a given period of time Net primary production – energy captured minus the energy used to respire NPP = GPP – R (where R = respiratory loss) WORKING IT OUT 5.1 & 5.2 Primary production is done by autotrophs Secondary production is done by heterotrophs

F. Ecosystem disturbances Event caused by physical, chemical or biological agents that results in changes in population size or community composition Natural vs. anthropogenic Short term or long term Why are ecologists interested in studying disturbances? Natural – hurricane, ice storms, tsunamis, floods, tornados, volcanic eruptions, forest fires, Anthro – clear cutting forest, agriculture, human settlements, air pollution, mtn top mining, Disturbances affect the flow of energy and matter thru an ecosystem. Whether the ecosystem can resist the impact and if/how long it takes to recover to original condition

What did the researchers do? Outcome? Watershed Studies All of the land in a given landscape that drains into a particular stream, river, lake or wetland Study biogeochemical cycles to determine impact of disturbance Hubbard Brook ecosystem of New Hampshire What did the researchers do? Outcome? Scientists can measure all ecosystem processes to determine extent of damage and predict how long it will take to recover For 50 years, researchers clear cut six watersheds to determine importance of trees in retaining soil nutrients. Control? 30-106 acres. Impenetrable bedrock below. Measure hydrological and biogeochem cycles. Nitrates leak into the stream water. Large amounts of nutrients accumulate in the vegetation and soil. Terrestrial ecosystems increase the retention of nutrients on land.

Resistance vs. Resilience Not every disturbance is a disaster Example? Resistance - measure of how much a disturbance can affect its flows of energy and matter Net productivity remains constant Rate at which an ecosystem can recover to its original condition = resilience Low vs. high? Depends on biogeochemical and hydrologic cycles Severe anthropogenic disturbance requires restoration ecology Low intensity fire kills some species, but benefits fire-adapted species Drought recovers quickly vs. climate change

What does this graph indicate? Intermediate Disturbance Hypothesis Ecosystems experiencing intermediate levels of disturbance are more diverse than those with high or low disturbance levels What does this graph indicate? Relationship between ecosystem disturbance and species diversity. Rare disturbances = intense competition among species Frequent disturbance = few highly competitive species, high population growth rates. Highest species diversity occurs in intermediate dist ecosystems

Ecosystem Services Instrumental Values Intrinsic Values Referred to by economists as ecosystem services Benefits that humans obtain from natural ecosystems Have monetary value that must be considered DO THE MATH pg. 78 Types: Provisional Regulating Support Systems Resilience Cultural Intrinsic Values Why should we care about other species? Value protecting biodiversity? Instrumental-tool to accomplish goal (lumber, pharmaceuticals) Provisions- Goods that humans can use directly.(Pacific yew tree has anticancer properties) Regulating services- The service provided by natural systems that helps regulate environmental conditions. (Rainforest removes CO2 from atmosphere, wetlands recharge water) Support systems- The support services that natural ecosystems provide such as pollination, natural filters and pest control. Resilience- Resilience of an ecosystem ensures that it will continue to provide benefits to humans. This greatly depends on species diversity. Cultural services- Ecosystems provide cultural or aesthetic benefits to many people.