Biology
description
Transcript of Biology
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BiologyCell Theory
Chapter 7
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Cell- smallest unit that can carry on all the processes of life
2 types of organisms:1. Unicellular organism- living thing that
consists of only ONE cellEx: paramecium, bacteria
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2. Multicellular organism- living thing that consists of MORE THAN one cell
Ex: humans, plants, animals
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Knowledge of cells began with the invention of the lens in the 1600s and has increased today with the electron microscopes
Robert Hooke- 1st person to view cells under the microscope
observed thin slices of cork (plant)
saw little empty boxes - called cells
Hooke was the 1st to look!
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Hooke’s microscope and the cells he saw
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Anton von Leewenhoek- 1st person to view living cells in 1675
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In 1838, Mathias Schleiden stated that ALL PLANTS were made up of cells
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In 1839, Theodor Schwann stated that ALL ANIMALS were made of cells
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In 1855, Rudolph Virchow concluded that CELLS COME ONLY FROM EXISITNG CELLS
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Cell theoryAll these observations were combined to form the cell theory:
1. All living things are composed of one or more cells.
2. Cells are an organism’s basic unit of structure and function.
3. Cells come only from existing cells.
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Cellsnot all cells are the same, but they do have some similarities: all have a cell membraneall will have some DNA (genetic material)
all will perform the processes of life
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there are some cells that have little structures that will perform certain functions for the cell
these structures are ORGANELLES
they’re like our organs in our bodies
there are 2 categories of cells:
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1. Prokaryotic cellssimplest type of cellsno membrane bound organelles
no nucleushave cell membrane
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The only organisms to have prokaryotic cells are
bacteria
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2. Eukaryotic cellshave membrane bound organelleshave nucleususually larger, more complex
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ALL other organisms are made up of eukaryotic cells
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How do they compare?
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Microscopescompound light microscope- uses 2 or more lenses to magnify objects
can magnify up to 1500 x
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Electron microscopesuse a beam of
electrons to magnify objects
developed in 1930-1940s
magnifies 50 000x and more!
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Scanning Electron Microscope
3-D picture is produced
sweeps beams of e- over specimen
magnifies up to 60 000x
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Transmission Electron Microscope
aims beams of e- through specimen
can magnify up to 100 000x
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Scanning Tunneling Microscope
probe detects atoms at surface of specimen
can magnify objects up to 100 000 000x!