MEPX
Chapter 9 of 10All chapters
  1. 1What living things share
  2. 2Cells
  3. 3DNA
  4. 4Inheritance
  5. 5Mutation and variation
  6. 6Genes and environment
  7. 7From cells to organisms
  8. 8Reproduction
  9. 9Populations and ecosystems
  10. 10Modern genetics

Chapter 9 of 10

Populations and ecosystems

Biology above the organism.

Interactions

Organisms compete, eat each other, cooperate and depend on each other. Energy enters through photosynthesis and is lost as heat at every step up a food chain.

  • Roughly a tenth of the energy passes to the next level, which limits chain length.
  • Removing one species can change an ecosystem out of proportion to its size.

Population growth

Growth is exponential when resources allow and levels off as they run out, giving the S-shaped logistic curve seen in bacteria, deer and human populations alike.