7.2

• What is the definition of a population?

  A species that occupy the same habitat
• What is the definition of a habitat?

  The place in which an organism lives
• What is the definition of a community?

  Populations of different species interacting
• What is the definition of an ecosystem?

  The interactions between biotic and abiotic factors
• What do food chains show?

  Feeding relationships and energy flow between organisms
• What is the definition of biomass?

  The total mass of living material
• What are trophic levels?

  The stages in a food chain
• What do arrows in a food chain represent?

  The direction of biomass transfer
• Describe a simple food chain.

  • producer → primary consumer → secondary consumer → tertiary consumer
• What is a producer?

  An organism that makes its own food
• What types of organisms are primary producers?

  Photosynthetic organisms like green plants and algae
• What is a primary consumer?

  An organism that feeds on producers
• What is a secondary consumer?

  An organism that feeds on primary consumers
• What is a tertiary consumer?

  An organism that feeds on secondary consumers
• What is a predator?

  A consumer that kills and eats other animals
• What is prey?

  An animal that is killed and eaten by another animal
• Describe the pattern of predators and prey in a stable community.

  The numbers of predators and prey rise and fall in cycles
• Why are producers the first trophic level?

  They provide all biomass for the food chain
• What is the role of producers in the food chain?

  • Provide biomass through photosynthesis
  • Serve as the base for all trophic levels
  • Transfer energy to primary consumers
• What piece of apparatus is used to measure the abundance and distribution of organisms in an area?

  Quadrat
• What piece of apparatus is used to study the distribution of organisms across a gradient?

  Belt transect
• What does the term "mean" refer to in the context of organism abundance?

  The average number of organisms
• How is the arithmetic mean calculated?

  Sum of each number of each organism divided by total
• What does the term "mode" refer to in the context of organism abundance?

  The most populous organism
• What does the term "median" refer to in the context of organism abundance?

  The middle value when arranged from lowest to highest
• Describe how materials cycle through the living and non-living components of an ecosystem.

  • Organisms take in elements from surroundings
  • Elements converted to complex molecules (biomass)
  • Elements transferred along food chains
  • Returned to environment during excretion and decomposition
• Name three molecules that are cycled through ecosystems.

  Oxygen, carbon dioxide, and water
• Describe the carbon cycle.

  • Plants fix carbon dioxide during photosynthesis
  • Organic molecules passed to organisms that eat plants
  • Carbon dioxide released by respiration
  • Burning fossil fuels releases carbon dioxide
• What do organisms take in from their surroundings?

  Elements from soil and air
• What happens to elements taken in by organisms?

  They are converted to complex molecules
• How are elements transferred in ecosystems?

  Along food chains
• What occurs to elements during excretion and decomposition?

  They are returned to the environment
• Name three molecules cycled through ecosystems.

  Oxygen, carbon dioxide, and water
• What is the first step in the carbon cycle?

  Plants fix carbon dioxide during photosynthesis
• How is carbon passed along the food chain?

  Through organisms that eat the plants
• How is carbon dioxide released back into the atmosphere?

  By respiration from animals and plants
• What human activity releases carbon dioxide into the atmosphere?

  Burning fossil fuels
• Why is the carbon cycle important for living organisms?

  It provides energy for vital functions
• What is the first step in the water cycle?

  Water evaporates from lakes and oceans
• What happens to evaporated water in the water cycle?

  It condenses into clouds