Slide 1 of 31 Copyright Pearson Prentice Hall Biology

Slide 2 of 31 Copyright Pearson Prentice Hall 7-1 Life Is Cellular

Slide 3 of 31 Copyright Pearson Prentice Hall The Discovery of the Cell Because there were no instruments to make cells visible, the existence of cells was unknown for most of human history. This changed with the invention of the microscope.

7-1 Life Is Cellular Slide 4 of 31 Copyright Pearson Prentice Hall The Discovery of the Cell Early Microscopes Leeuwenhoek invented the simple microscope that had only 1 lens and magnified 400x

7-1 Life Is Cellular Slide 5 of 31 Robert Hooke is given credit for the compound microscope, which has at least 2 lenses. In 1665, he used one of these microscopes to look at a thin slice of cork, a plant material. Cork looked like thousands of tiny, empty chambers. Hooke called these chambers “cells.” Cells are the basic units of life. Copyright Pearson Prentice Hall

7-1 Life Is Cellular Slide 6 of 31 Copyright Pearson Prentice Hall The Discovery of the Cell Hooke’s Drawing of Cork Cells

7-1 Life Is Cellular Slide 7 of 31 Copyright Pearson Prentice Hall The Discovery of the Cell At the same time, Anton van Leeuwenhoek used a single-lens microscope to observe pond water and other things. The microscope revealed a world of tiny living organisms that he called “animalcules”.

7-1 Life Is Cellular Slide 8 of 31 Copyright Pearson Prentice Hall The Discovery of the Cell What is the cell theory?

7-1 Life Is Cellular Slide 9 of 31 Copyright Pearson Prentice Hall The Discovery of the Cell The Cell Theory In 1838, Schleiden concluded that all plants were made of cells. In 1839, Schwann stated that all animals were made of cells. In 1855, Rudolph Virchow concluded that new cells were created only from division of existing cells. These discoveries led to the cell theory.

7-1 Life Is Cellular Slide 10 of 31 Copyright Pearson Prentice Hall The Discovery of the Cell The cell theory states: All living things are composed of cells. Cells are the basic units of structure and function in living things. New cells are produced from existing cells.

7-1 Life Is Cellular Slide 11 of 31 Copyright Pearson Prentice Hall Exploring the Cell New technologies allow researchers to study the structure and movement of living cells in great detail.

7-1 Life Is Cellular Slide 12 of 31 Copyright Pearson Prentice Hall Exploring the Cell Electron Microscopes Electron microscopes reveal details 1000 times smaller than those visible in light microscopes. Electron microscopy can be used to visualize only nonliving, preserved cells and tissues.

7-1 Life Is Cellular Slide 13 of 31 Copyright Pearson Prentice Hall Exploring the Cell Transmission electron microscopes (TEMs) Used to study cell structures and large protein molecules Specimens must be cut into ultra-thin slices

7-1 Life Is Cellular Slide 14 of 31 Copyright Pearson Prentice Hall Exploring the Cell Scanning electron microscopes (SEMs) Produce three-dimensional images of cells Specimens do not have to be cut into thin slices

7-1 Life Is Cellular Slide 15 of 31 Copyright Pearson Prentice Hall Exploring the Cell Scanning Electron Micrograph of Neurons

7-1 Life Is Cellular Slide 16 of 31 Copyright Pearson Prentice Hall Exploring the Cell Scanning Probe Microscopes Scanning probe microscopes allow us to observe single atoms. Images are produced by tracing surfaces of samples with a fine probe.

7-1 Life Is Cellular Slide 17 of 31 Copyright Pearson Prentice Hall Exploring the Cell Scanning Probe Micrograph of DNA

7-1 Life Is Cellular Slide 18 of 31 There are two types of magnification used with microscopy: Magnification of the microscope – refers to how much the microscope magnifies the object being viewed. Magnification of the illustration – refers to the size of a drawing compared to the actual size of the object. Copyright Pearson Prentice Hall

7-1 Life Is Cellular Slide 19 of 31 The microscope’s magnification can be calculated by multiplying the magnification of the ocular lens by the magnification of the objective lens. Ex: ocular lens = 10x objective lens = 40x microscope magnification = 400x Copyright Pearson Prentice Hall

7-1 Life Is Cellular Slide 20 of 31 A drawing’s magnification can be calculated using the formula: M = DSwhere, M = drawing magnification FD DS = Drawing size (in mm) FD = Field diameter (diameter of object viewed based on the microscope viewing area) Copyright Pearson Prentice Hall

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Slide 22 of 31 Copyright Pearson Prentice Hall 7-1 The cell theory states that new cells are produced from a.nonliving material. b.existing cells. c.cytoplasm. d.animals.

Slide 23 of 31 Copyright Pearson Prentice Hall 7-1 The person who first used the term cell was a.Matthias Schleiden. b.Lynn Margulis. c.Anton van Leeuwenhoek. d.Robert Hooke.

Slide 24 of 31 Copyright Pearson Prentice Hall 7-1 Electron microscopes are capable of revealing more details than light microscopes because a.electron microscopes can be used with live organisms. b.light microscopes cannot be used to examine thin tissues. c.the wavelengths of electrons are longer than those of light. d.the wavelengths of electrons are shorter than those of light.

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