Ib ess exam notes

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  • 1. IB ESS/GURU IB ESS EXAM NOTES TOPIC 1: Systems and Models Systems: an assemblage of parts and their relationship forming a functioning entirety or whole o Open systems: exchanges matter and energy o Closed systems: exchanges only energy o Isolated systems: neither matter nor energy and is theoretical Laws of thermodynamics o 1st: energy is neither created nor destroyed, only changes forms o 2nd: the entropy of a closed system increases; when energy is transformed into work, some energy is always lost as waste heat Equilibrium oSteady-state: in open systems, continuous inputs and outputs of energy and matter, system as a whole remains in a constant state, no long term changes. o Static: no change over time; when the state of equilibrium is distributed, the system adapts a new equilibrium; cant occur in living systems o Stable: the system returns to the same equilibrium after disturbances o Unstable: system returns to a new equilibrium after disturbances Feedback o Positive: results in a further decrease of output and the system is destabilized and pushed into a new state of equilibrium o Negative: tends to neutralize or counteract any deviation from an equilibrium and tends to stabilize systems Transfers and transformations o Transfers: - The movement of material through living organisms - Movement of material in non-living process - The movement of energy o Transformations - Matter to matter - Energy to energy - Matter to energy - Energy to matter The Gaia model
  • 2. IB ESS/GURU o Views earth as a living organism o The earth has a disease TOPIC 2: Ecosystems Definitions: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. Biotic factors: living components Abiotic factors: non-living physical and chemical components Species: a particular type of organism Population: a group of individuals of the same species living in the same area at the same time Habitat: the environment where a species normally lives Ecological niche: how an organism makes a living Community: a group of populations living and interacting with each other in a common habitat Ecosystem: a community of independent organisms (biotic factors) and the physical environment (abiotic factors) which they inhabit Biome: a collection of ecosystems sharing common climatic conditions Respiration: a process of breaking down food in order to release energy Photosynthesis: a process of producers making their own food (glucose) and producing oxygen from water and carbon dioxide Biomass: the living mass of an organism or organisms but sometimes refers to dry mass Gross Productivity: the total gain in energy or biomass per unit area per unit time a. o GPP: by producers b. o GSP: by consumers Net Productivity: the total gain in energy or biomass per unit area per unit time after allowing for losses to respiration a. o NPP: by producers b. o NSP: by consumers Biomes: 1. 2. 3. 4. 5. climate latitude (distance from equator) altitude (height above sea level) wind and water currents P/E ratio (precipitation over evaporation ratio)
  • 3. IB ESS/GURU latent heat: heat that is either taken in or produced when water changes from state to state Different Biomes: Tropical Rainforest hot and wet areas with broadleaved ever green forest. Within 50 north or south of the equator. High rainfall and high temperature, high insolation as near equator. There are amazingly high levels of biodiversity, many species and many individuals of specie. There are very large evergreen trees, small shrubs, orchids.It is estimated that tropical rainforest produces 40% of NPP of terrestrial ecosystems. But the problems it has, are that 50% of human population live near the equator, so they damage the biome, they are exploited for human economical needs. Desert dry areas which are usually hot in the day and cold in the night, there are tropical, temperate and cold deserts. It covers 20-30% of earths surface, about 300 of north or south of the equator. Water is limited in the deserts. There are few species and very low biodiversity, there are only the ones who adapted to the conditions. Soil can be rich, because the nutrients are not washed away from the water. NPP is low because the amount of plants and animals are limited, because of the water. Desertification is the human activity. Temperate Grassland fairly flat areas, that are covered with grass, they are located 400 600 from the equator, either north or south. The net productivity is not very high, because its only grass that grows on the land, nothing else. And with that the animals that are growing are small size as well. Humans use grass lands for the crops. Temperate Forest - mild climate and deciduous forest. Located 400 600 north or south of the equator, it has 4 seasons, there also are fewer species than tropical rainforest, it has the second highest NPP after the tropical rainforest. Much of the temperate forests, have been cleared because of human activities. Arctic Tundra Tree less plain with permafrost, cold and very low precipitation, dark nights. It is 10% of lands surface, it is located on the arctic cap. Water is limiting but the fire can stop the climax community forming. There are no trees but there Is a thick mat, covered by mosses and grasses. It has very low biodiversity, and soil is poor. With that the NPP is very low, humans use it for mining.
  • 4. IB ESS/GURU Ecosystem Structure: Food chains and trophic levels 1. 2. 3. 4. 5. 6. 7. food chain: shows a flow of energy from one organism to the next food web: shows a complex network of interrelated food chains trophic level: a position that an organism or a group of organisms in a community occupies in a food chain producers or autotrophs: which manufacture their own food from inorganic substances consumers or heterotrophs: which feed on autotrophs or other heterotrophs to obtain energy decomposers: consumers that obtain energy from dead organisms detritivores: consumers that derive their food from detritus or decomposing organic material Ecological pyramids 1. Pyramid of numbers: shows the number of organisms at each trophic level in a food chain o advantages: o o easy method of giving an overview o good for comparing changes in population numbers over different times disadvantages: o all organisms included regardless of their size o numbers can be too great to represent accurately 2. Pyramid of biomass: contains the biomass at each trophic level o advantages: overcomes the problems of pyramids of numbers o disadvantages: 3. only uses samples from populations, so its impossible to measure biomass exactly organisms must be killed to measure dry mass pyramid of productivity: contains the flow of energy through each trophic level; shows the energy being generated and available as food to the next trophic level during a fixed period of time o advantages: o shows the actual energy transferred and allows for rate of production disadvantages: very difficult and complex to collect energy data as the rate of biomass production over time is required 4. bioaccumulation and biomagnification o o bioaccumulation: increase in concentration in one organism over time biomagnification: increase in concentration with the increase in trophic levels
  • 5. IB ESS/GURU 5. o trophic efficiency: only 10% of the energy is transferred to the next, so the trophic efficiency=10% Population Interactions A population is a group of organisms of the same species living in the same area at the same time and capable of interbreeding. Population density is the average number of individuals in a stated area. Competition Competition between members of the same species is Intraspecific competition. Individuals of the different species, competeting for the same resource is called Interspecific competition. The other outcome is that one species may totally outcompete the other, this is the principle of Competitive exclusion. Predation happens when one animal, the predator, eats another animal, the prey. Herbivory is defined as an animal eating green plant. Parasitism - is a relationship between two species in which one species lives in or on another gaining its food from it. Mutualism - s a relationship between two or more species in which both or all benefit and none suffer. Succession Succession is the change in species composition in an ecosystem over time It may occur on bare ground where soul formation starts the process or where no soil has already formed, or where the vegetation has been removed. Early in succession, GPP and respiration are low and so NPP is high as biomass accumulates. Secondary succession occurs on souls that are already developed and ready to accept seeds carried in by the wind. Also there are often dormant seeds left in the soil from previous community. This shortens the number of seral stages the community goes through.
  • 6. IB ESS/GURU Changes occurring during a succession (refer to Fig. 14.4 on page 268) the size of organisms increases energy flow becomes more complex soil depth, humus, water-holding capacity, mineral content and cycling increase Biodiversity increases and then falls as the climax community is reached NPP and GPP rise and then fall Production: respiration ratio falls Species diversity in successions Early stages of succession: few species Species diversity increases with the succession Increase continues until a balance is reached between possibilities for new species to establish, existing species to expand their range and loc