Study GuidePlant Biology–Cells1. Cell Theory1.1What Is Cell Theory?Cell theory is a basic idea in biology that explains what cells are and why they are important. Themodern cell theorysays:•All living organisms are made ofone or more cells.•New cells come from pre-existing cells. This means life has continued without a break fromthe first cells that appeared on Earth more than3.5 billion years ago.•Hereditary information (DNA)is passed from a parent cell to its daughter cells.•All thebasic chemical reactions of lifehappen inside cells.In simple words:cells are the building blocks of life, and everything living depends on them.1.2Methods of Studying CellsMicroscopesThe study of cells is calledcytology. Our knowledge of cells has grown because microscopes haveimproved over time.Light Microscopes•Invented in the1500s.•Can magnify objects100× to 1000×.•Their maximum resolving power is about0.2μm (micrometer).•Resolution depends on thewavelength of visible light, which limits how clear the image canbe.Resolutionmeans the ability to see two close objects as separate.Preview Mode
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