Mrs. Stewart Central Magnet School Honors Biology Robert Hooke Used an “early” Light Microscope to observe dead “cells” in bark of a Cork Oak tree He coined the term “cells” because he described what he saw as “many little boxes” that reminded him of the cubicles, or cells, where monks live. Anton Van Leeuwenhoek Made microscopes – able to grind lenses to increase magnification to 10x Hooke’s microscope First to observe living cells Spyrogyra genus – type of algae Termed them Animalcules (protists) All living organisms are composed of one or more cells Matthias Schleiden – plants Theodor Schwann – animals Cells are the basic units of structure and function in an organism Cells come only from the reproduction of existing cells Rudolf Virchow Microscopes are why scientists were able to stop speculating and start observing and exploring the “unseen” world of living and non-living things. Microscopes helped scientists clarify our definition of life Consist of cells Cells display organization Obtain and use energy to perform chemical reactions (metabolism) Change through time (adapt) Respond to their environment/stimulus Reproduce Growth and development Homeostasis Shape Cell shapes reflect the different functions of cells Size A few cells are large enough to be seen by the “naked” eye Surface size. area-to-volume ratio determines cell All materials needed by the cell must enter and exit through the surface (cell membrane/wall) Nutrients come in Wastes are excreted out As a cell becomes larger, the volume increases more than the surface area. There is a point where there is not enough surface area to sustain transport in/out of necessary materials to keep up with volume of cell. Prokaryotes Smaller No nucleus, but a nucleoid DNA is in one circular chromosome No plasma membrane No membrane bound organelles Pro = NO Eukaryotes Larger Nucleus Plasma membrane Membrane bound organelles Organelles carry out life processes within cell DNA in multiple chromosomes within nucleus Eu = DO Cell wall Large central vacuole plastids