Unit 12
Chapter Overview
Students explore the biomes of the world and living and nonliving features that characterize individual biomes. Students analyze how organisms respond to external factors, interpret relationships between organisms, analyze the flow of matter and energy through trophic levels and cycles, recognize the effect of changing resources on survival, and describe the impact of environmental change, including human impact, on ecosystem stability.
Main Ideas
Ecosystems have been shaped by geography, climate, and evolution to support a characteristic group of organisms that interact with one another.
Matter and energy in ecosystems pass through food webs. At each trophic level in a food web, energy is used and lost to the environment.
At each tropic level in a food web, matter is used and cycled but not lost. Various processes within cycles, such as the carbon and nitrogen cycles, recycle matter through the system.
Environmental change can impact ecosystem stability. Events and processes occurring during succession may eventually lead to a new, stable ecosystem.
Misconceptions
Students may think energy accumulates in an ecosystem, so that a top predator has all of the energy from the organisms below it, rather than 90% of it being lost to the environment at each level.
Students may think a species high on the food web is a predator to everything below it.
Students may think the arrows in a food web point to what an organism eats, rather than representing the flow of energy. (This causes students to place all arrows in a food web in the wrong direction.)
Students may think producers receive their energy through the absorption of nutrients, rather than through the process of photosynthesis.
Vocabulary
Atom – smallest unit of matter
Biomolecule – made of atoms (carbohydrates, lipids, proteins, nucleic acids)
Cell – smallest unit of a living thing, one organism or part of an organism
Tissue – a group of cells working together
Organ – different tissues working together
Organ System – a group of different organs working together
Organism – a living thing, can be unicellular or multicellular
Population – organisms of the same species, living in the same place, at the same time
Community – an interacting group of different species in a common location
Ecosystem – all living organisms (biotic factors) in an area with the physical environment (abiotic factors) functioning together as a unit
Biome – a major zone with similar life forms and environmental conditions, 11 total in the world
Biosphere – all living things and their environments
Autotroph – producer that makes its own food by capturing the sun’s solar energy and makes glucose through the process of photosynthesis
Heterotroph – consumer that must eat something in order to obtain chemical energy (food energy)
Herbivore – organism that only consumes (eats) producers for chemical energy
Carnivore – organism that only consumes (eats) herbivores or other carnivores for chemical energy
Omnivore – organism that is both an herbivore and carnivore, meaning they eat meat and plants
Decomposer – organism that gets energy from
breaking down dead consumers and producers and returns nutrients to the soil
Detritivore – organism that feeds on the remains of dead plants and animals and other dead material (detritus)
Food Chain – shows one path of how energy moves through an ecosystem
Food Web – shows many paths of how energy moves through an ecosystem, made up of many different food chains
Trophic Level – shows an organisms place in a food chain or web
Energy Pyramid – graphical model that shows the amount of useful chemical energy that is passed on to each organism of a food chain
10% Rule – only 10% of the energy received from an organism is passed on to the organism which eats it
Biomagnification – an increase in concentration of a substance throughout the food chain, especially chemicals
Limiting Factors – any factors (things) that affect an organism’s ability to survive in its environment, affect population growth
Carrying Capacity – largest number of individuals of a particular species that can survive over long periods of time in a given environment
Competition – organisms of the same or different species attempt to use the same ecological resource (food, water, space) in the same place at the same time
Predation – interaction in which one organism (predator) captures and feeds on another organism (prey)
Mutualism (+, +) – symbiotic relationship in which both organisms benefit
Commensalism (+, 0) – symbiotic relationship in which one organism benefits, the other is unaffected
Parasitism (+, -) – symbiotic relationship in which one organism (parasite) benefits, the other (host) is harmed
Ecological Succession - the natural, gradual changes in the types of species that live in an area; it can be primary or secondary
Primary Succession – no soil at the beginning, soil must be made, mosses and lichens are the pioneer species, slower
Secondary Succession – soil is still there, weeds and grasses are the pioneer species, faster
Pioneer Species – the first species to populate the new area
Equilibrium (in an ecosystem) – the numbers and types of organisms no longer change rapidly, they come in balance with the resources
Climax Community – community which has reached equilibrium
Dispersal – organisms move to a new place by wind, water, or living things
Notes
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