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CELL THEORY AND MICROSCOPES Unit 1 – Matter and Energy for Life

BIOGENESIS VS. ABIOGENESIS Biogenesis Life is characterized by the fact that living things come only from other living things Abiogenesis The belief that living things can arise from

SPONTANEOUS GENERATION Before the invention of the microscope, people believed that living things could be produced from non-living things I.e. Spontaneous Generation or Abiogenesis For example: Maggots developing on a piece of rotting

SPONTANEOUS GENERATION The idea of abiogenesis was not contested for 2000 years Aristotle, the ancient Greek philosopher, concluded that abiogenesis was a reasonable explanation for the origin of life No one challenged the idea because people could make daily observations that seems to support the idea For example: during spring,

PARADIGM SHIFT A change in the way we think of the world We start to challenge modern thinking because we’re critical of present day ideas For example: The world is flat vs. round Abiogenesis vs.

FRANCESCO REDI Italian doctor who first challenged the idea of spontaneous generation Conducted one of the first controlled experiments that supported biogenesis Used meat in jars, half covered with mesh and half open.

ANTON VON LEEUWENHOEK Was one of the first to make and use microscopes In 1675, he first observed and described microorganisms (Bacteria) Working with solutions of broth, he discovered bacterial growth Suggested that the development of the microorganisms supported the arguments for abiogenesis (Life created

JOHN NEEDHAM Performed experiments that further supported abiogenesis Boiled meat broth to kill any microbes, sealed one container with a cork, another he left open Observed that microorganisms appeared in both containers He claimed that this proved that life can originate from the non-living Where did the microbes

LAZZARO SPALLANZANI Investigated the work done by Needham He repeated Needham’s experiment with two significant changes 1. 2. He boiled the broth longer He sealed his containers by melting the glass The result was that microorganisms did not grow in the sealed

LOUIS PASTEUR Conducted experiments that finally disproved abiogenesis Used broth that was heated in flasks with an S-Shaped stem Demonstrated conclusively that microorganisms did/do not spontaneously

ROBERT HOOKE Used a compound microscope to investigate slices of cork He observed empty structures which he names “cells”

OTHER SCIENTISTS Robert Brown Observed cells from a variety of organisms, noticed that each had a dark region within them, later known as the nucleus Matthias Schleiden Botanist who concluded that plants are also made of cells Theodor Schwann Proposed that all organisms, both plants and animals, are made of cells Alexander Braun Postulated that cells are the basic unit of life Robert Virchow

WHY IS THIS IMPORTANT? What’s the big deal?

CELL THEORY Cell theory states: 1. 2. 3. The cell is the basic living unit of organization for all organisms All organisms are made of cells or cell products All cells come from other cells Watch this http://www.youtube.co m/watch?v 4OpBylwH9

THE MICROSCOPE A SIGNIFICANT DISCOVERY

THE MICROSCOPE Revealed a whole new world to biologists Extended the limits of what could seen Changed the way scientists were able to study the world at a microscopic level

EARLY MICROSCOPES Often called Simple Microscopes Made of a single strongly curved lens Leeuwenhoek made simple microscopes that achieved magnifications as high as 400x

MODERN LIGHT MICROSCOPES Compound Microscopes Made of a series of lenses that allow you to magnify objects to about a max. magnification of 2000x Magnification is not enough to see all cells and certainly not all cellular organelles Resolution limited to about 0.2 µm Images appear upside

PARTS OF THE MICROSCOPE See page 16 in your textbook Condenser lens

MAGNIFICATION AND RESOLUTION Magnification How many times larger an object appears to be, compared to its actual size For example: 400x Resolution The ability of the eye, or other instrument, to distinguish between two objects that are close together I.e. Clarity Measured in micrometers

WHAT ABOUT GREATER DETAIL? WHAT CAN WE USE?

ELECTRON MICROSCOPES They use a beam of electrons to magnify objects Use electromagnets to focus beams instead of lens Can achieve resolutions better than 50 pm and magnifications of up to

TYPES OF ELECTRON MICROSCOPES 1. Transmission Electron Microscope Works on the same principle as the light microscope but uses electrons instead of light Magnifications up to 500,000x, Resolutions as low as 0.0002 µm First to observe cell structures Mitochondrion Rough ER – Notice the Ribosomes

TYPES OF ELECTRON MICROSCOPES 1. Transmission Electron Microscope Works on the same principle as the light microscope but uses electrons instead of light Magnifications up to 500,000x, Resolutions as low as 0.0002 µm First to observe cell structures Mitochondrion Rough ER – Notice the Ribosomes

ELECTRON MICROSCOPES 2. Scanning Electron Microscopes A narrow beam of electrons passes over the surface of a specimen Specimen is coated in a thin film of metal (Gold) which electrons scan to produce a 3D image Magnifications over 300,000x, Resolutions up

YOUR MICROSCOPES COMPOUND LIGHT MICROSCOPES

HANDLE WITH CARE! One hand on the arm, the other supporting the base Keep lenses clean, do not touch them! Do not adjust the focusing knobs until you’re ready to use them Always focus using the coarse adjustment knob first, with the low-power objective in position Do not use the coarse adjustment knob with the medium-power or high-power lenses in place

TOTAL MAGNIFICATION

CALCULATING FIELD OF VIEW 1. 2. 3. On low power, use a ruler and place one dash of the millimeter side of the ruler to the far left edge of your field of view On low power, the FOV is the distance read, in millimeters, on the ruler Use the following equations to calculate the field of view for medium power and high power objective lenses (also in mm)

CALCULATING FIELD OF VIEW Medium Power FOV Low Power FOV Magnification of Low Power Magnification of Medium Power High Power FOV Low Power FOV Magnification of Low Power Magnification of High Power Remember that FOV is originally measured in millimeters (mm). You will need to know how to covert the field of view to micrometers (μm) 1 mm 1000 μm or 1 μm 0.001 mm

VIEWING A PREPARED SLIDE 1. 2. 3. 4. 5. 6. 7. 8. Secure slide to stage with low power in place Adjust coarse adjustment Use fine adjustment to sharpen the focus Once in place, rotate to medium, make sure the objective lens does not come in contact with slide Adjust the fine adjustment, NOT COARSE Rotate to high power, be careful of the slide Adjust fine adjustment When done, rotate back to low

BIOGENESIS VS. ABIOGENESIS Biogenesis Life is characterized by the fact that living things come only from other living things Abiogenesis The belief that living things can arise from non-living things. SPONTANEOUS GENERATION Before the invention of the microscope, people believed that living things could be produced from non .