Biology is the science of life, but defining life requires more than asking whether something can move or reproduce. This lesson explores the characteristics biologists use together to identify living organisms.
Living organisms share eight characteristics: order, sensitivity or response to stimuli, reproduction, adaptation, growth and development, regulation or homeostasis, energy processing, and evolution. No single characteristic alone is a complete test for life; considered together, they provide a useful framework.
All flashcards
What are the eight characteristics biologists use together to describe life?
Order, response to stimuli, reproduction, adaptation, growth and development, homeostasis, energy processing, and evolution.
What is homeostasis?
The maintenance of a relatively stable internal environment despite changes in external conditions.
What is chemotaxis?
Movement in response to a chemical stimulus; movement toward it is positive, and movement away is negative.
How does reproduction pass hereditary information between generations?
Reproduction transmits hereditary information to offspring, influencing inherited characteristics and helping direct growth and development.
Why are viruses not generally classified as living organisms?
They are not made of cells and rely on a living cell's machinery to reproduce.
Quiz questions
What does an internal node on a phylogenetic tree represent?Answer: A common ancestor and a point where lineages diverged.
What molecular evidence did Carl Woese use to help distinguish major lineages of life?Answer: Comparisons of conserved genetic sequences, including ribosomal RNA.
Which domain includes organisms with eukaryotic cells?Answer: Eukarya.
Which biological level includes a community together with nonliving environmental components?Answer: An ecosystem.
Which feature distinguishes eukaryotic cells from prokaryotic cells?Answer: Eukaryotic cells have a membrane-bound nucleus.
Based on Biology 2e by Mary Ann Clark, Matthew Douglas, Jung Choi (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.