Science 10: Unit 3 - Biology

Chapter 7

Abiogenesis Vs. Biogenesis:

Abiogenesis: The belief that all life from Earth initially developed from non-living things(rocks, etc.)

Biogenesis: The belief that life can only come from other living things

The Cell Theory Development:

- Robert Hooke(1635): Looked at bark under a microscope, saw a bunch of tiny boxes. Because they looked like prison cells, he called them "cells".

- Leeuwenhoek(1632): Studied blood cells, the first person to describe single-celled organisms

- Schleiden and Schwann(1810): Discovered that all organisms have cells and that animal and plant cells are different

- Virchow: Discovered that cells come from other cells

The Cell Theory:

- All living things are made of cells

- Cells are the basic unit of life

- Cells are made of preexisting cells

The Development of Microscopes:

Compound Light Microscopes: Uses two or more lenses put together to magnify the image. Uses a focused light to illuminate the image. Use prepared slides to look through. We use these in science class because they are effective and cheap. Allows cells to be viewed

Electron Microscopes: Uses a beam of electrons to illuminate cells, have magnification up to 1.2 million times. Allows cell's internal structures to be viewed

- Transmission Electron Microscope: A beam of electrons is beamed through a specimen to create a 2D image. Can magnify 10,000 x to 100,000 x.

- Scanning Electron Microscope: Sweeps a beam of electrons over a specimen to create a 3D image. Can magnify up to 300,000 x, but works better when 10,000x. Can see the details on cell structures.

Confocal Laser Scanning Microscope: A laser beam scans an image axis by axis, allowing a series of 2D images from different points of view to be created.

Scanning Tunneling Microscope: A metal probe that attracts electrons allows a 3D view of atomic structures, such as DNA.

Stem Cells:

Stem cells are basic, "blank" cells that can be reproduce to create any other kind of specialized cells. It is different from a specialized cell, because a specialized cell can only create identical cells. Stem cells are dormant in children and adults until they are needed for something. For example, a major skin injury will require stem cells to turn into skin cells to help the injury recover. Scientists use stem cells to cure a number of diseases.

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Use this to study for the final and unit exam.