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3.3
vocab
| Term | Definition |
|---|---|
| periods | eras are subdivided into periods |
| epochs | periods are subdivided into epochs |
| mass extinction | the extinction of many species on Earth within a short period of time |
| land bridge | connects two continents that were previously separated |
| eons | the longest unit of geological time |
| eras | eons are subdivided into eras |
| geographic isolation | the separation of a population of organisms from the rest of its species |
| cell theory | all living things are made of one or more cells, the cell is the smallest unit of life, and all new cells come from preexisting cells |
| macromolecules | form by joining many small molecules together |
| nucleic acids | macromolecules that form when long chains of molecules called nucleotides join tofether |
| proteins | long chains of amino acid molecules |
| lipid | large macromolecule that dose not dissolve in water |
| carbohydrates | one sugar molecule, two sugar molecules, or a long chain of sugar molecules |
| cell membrane | flexible covering that protects the inside of the cell from the environment outside the cell |
| cell wall | stiff structure outside the cell membrane |
| cytoplasm | fluid inside the cell that contains salts and other molecules |
| cytoskeleton | a network of threadlike proteins that are joined together |
| organells | specialized functions |
| nucleus | part of a eukrayotic cell that directs cell activities and contains genetic information stored in DNA |
| chloroplasts | are membrane-bound organelles that use light energy and make food--a sugar called gluecose--form water and carbon dioxide in a process known as photosynthesis |