| A | B |
|---|
| A group of similar organisms that can interbreed and produce fertile offspring | Species |
| Organisms of the same species that live in the same place and at the same time | Population |
| Different populations of different species that live in the same place at the same time | Community |
| A community of living organisms plus their nonliving environment | Ecosystem |
| The living organisms in an ecosystem | Biotic Factors |
| The nonliving parts of an ecosystem; examples: rocks, soil, air, water | Abiotic Factors |
| An organism's role in its environment | Niche |
| The place where an organism lives | Habitat |
| The conflict between organisms when they try to use the same resources at the same time | Competition |
| The relationship between two species that live closely together | Symbiotic Relationship |
| A symbiotic relationship in which both species benefit | Mutualism |
| A symbiotic relationship in which only one species benefits but the other is neither helped nor harmed | Commensalism |
| A symbiotic relationship in which one species benefits and the other is harmed | Parasitism |
| Each step in a food chain that represents how many times energy has been transferred from one organism to the next | Trophic Level |
| A representation in the shape of a pyramid that shows how energy is passed from one trophic level to the next | Energy Pyramid |
| The largest number of organisms that can be supported to live in an ecosystem | Carrying Capacity |
| Things that limit how many organisms can live in a population | Limiting Factors |
| Limiting factors that depend on the number of organisms in a population | Density Dependent Factors |
| Limiting factors that do not depend on the number of organisms in a population | Density Independent Factors |
| Unrestricted population growth that follows a J-shaped patter | Exponential Growth |
| A state of stability in an ecosystem when the populations do not change very much | Dynamic Equilibrium |
| The type of changes that occurs in an ecosystem that has no soil; occurs after a major disturbance | Primary Succession |
| The type of changes that occurs in an ecosystem after a disturbance that does not remove the soil | Secondary Succession |
| The buildup of chemicals in consumers as the chemicals are passed up the food chain | Biological Magnification |
| Preserving and restoring natural habitats | Conservation |
| A plant process that uses energy from the sun to convert carbon dioxide into carbohydrates | Photosynthesis |
| Converting inorganic carbon, as in carbon dioxide, to organic carbon, as in sugar | Carbon fixation |
| Different types of sugars made by plants | Carbohydrates |
| Process used by all living organisms that uses energy from carbohydrates and releases carbon dioxide back into the atmosphere | Cellular respiration |
| The burning of fossil fuels that releases carbon dioxide into the atmosphere | Combustion |
| The part of the earth where living organisms are found | Biosphere |
| The cycles that move water, carbon, oxygen, and nitrogen through living and nonliving parts of the ecosystem | Biogeochemical cycles |
| Water that travels from the atmosphere to the ground | Precipitation |
| The evaporation of water from the leaves of plants | Transpiration |
| A type of bacteria found living in the soil or on root nodules; convert nitrogen gas into ammonia | Nitrogen-fixing bacteria |
| A process that converts nitrogen gas into ammonia | Nitrogen fixation |
| A process that converts ammonia into nitrates and nitrites | Nitrification |
| Organisms, such as bacteria and fungi, that break down dead organisms and put nitrogen back into the soil | Decomposers |
| A process that coverts nitrates in the soil back into atmospheric nitrogen gas | Denitrification |
