Unit C - Biology Study of Life

Early microscopes & lenses a better understanding of cells and the structure of living things came hand-in-hand with the development of microscope technology before the 1500s, scientists could only observe what they could see with the naked eye

A little history on the microscope Hans and Zacharias Janssen Invented the microscope in 1595 2 lens system (ocular lens & objective lens) Magnifying power of 20x considered to be a compound microscope because it used more than one lens

Robert Hooke 1665 Improvement by adding: a third lens (beam of light through a water filled flask) A light to illuminate the objects

Robert Hooke Hooke observed a cross-section of cork, which he thought was non-living observing that it was full of empty air chambers, he called these tiny chambers “cells” (latin for: small compartment) these chambers turned out to be the remnants of living cells

Antoni Van Leeuwenhoek Leeuwenhoek’s microscope only had a single lens – called a simple microscope the lenses were of much higher quality, and allowed him to magnify objects up to 250X the first person to observe the movement of living single- celled organisms (such as bacteria, sperm, unicellular protozoa etc)

Labeling the Microscope Eyepiece Body tube Coarse adjustment knob Fine adjustment knob Revolving Nosepiece Arm Objective lenses Stage Stage clips Base Diaphragm Light Source

Use your textbook to define the function of the microscope parts Eyepiece or Ocular Coarse adjustment knob Fine adjustment knob Revolving nosepiece Objective lenses Stage Stage clips Diaphragm Lamp or Mirror Arm Base

How to focus a microscope Ensure that the low power lens is in position Watch from the side as you use the coarse adjustment knob to lower the lens until it is as close as possible to the stage. Look through the eyepiece while using the coarse adjustment knob to move the lens upward Once the image appears almost sharp, use the fine adjustment knob to finish focusing

High Power focusing Move the objective upward with the coarse adjustment knob enough to revolve the high power objective lens into position. Watch from the side as you lower it close to the slide Use only the fine adjustment knob to fine tune the focusing

Skills in microscopy Magnification: how many times larger the image is compared to the original magnification = (power of the objective lens) x (power of the eyepiece) eyepiece lens – always 10X objective lens low power: 4X medium power: 10X high power: 40X

Magnification – practice problems What is the magnification of a microscope with a 10X ocular (eyepiece) lens, and a 10X objective lens? magnification = (10X)(10X) = 100X How much more powerful is the magnification on high power compared to low power? magnification high = (10X)(40X) = 400X magnification low = (10X)(4X) = 40X the high powered magnification is 10 times more powerful

Field of view the area that can be seen through the microscope with a particular objective lens field of view can be described in terms of field diametre or field area when the lens power increases, field of view decreases

Field of view the field diameter on low power can be measured by placing a ruler under the microscope the field diameter on high power can be calculated using this formula: high-power field diameter = low-power magnification low-power field diameter high-power magnification

Field of view – practice problems The image to the right is the view through low power. What is the field diameter of this microscope? 29 mm What is the field diameter on high power? 2.9mm How many times smaller is the field diameter on high power as on low power? one tenth

Scale a comparison between the size of a drawing and the actual size of the object to calculate it, compare the diameter of the circle in the drawing with the diameter of the field of view you calculated previously e.g. a drawing with a diameter of 90mm done from low power would roughly have a scale of 90mm:29mm or 3:1.

Actual size once you know the field diameter, you can estimate an object’s size by noting how much of the field of view it occupies this can be done by estimating how many times across the object would fit e.g. if it would fit 10 times across, it takes up 1/10th of the field of view e.g. if the field of view is 29mm and a cell takes up about 1/3 of the field of view, it’s actual size is about 10mm

Actual size – practice problem our field of view on high power was found to be 2.9mm. What is the actual size of this cell, as viewed under high power? (2.9mm)(1/2)=1.45mm what is its size in micrometers? (hint: 1 mm = 1000 µm) 1.45mm = 1450 µm

Distance Units x1012 x109 x106 x103 x102 x101 pm nm µm mm cm dm m centi meter nano milli micro pico deci x1012 x109 x106 x103 x102 x101 x100 pm nm µm mm cm dm m

Microscope Lab

C1.2 Development of cell theory Brain cells of a rat.

When science contradicts belief: sometimes, despite scientific evidence to the contrary, people find it hard to accept new ideas as a result, scientific advancement is sometimes slowed Galileo imprisoned in 1630s by the Catholic Church for claiming that the Earth revolved around the Sun the Church took exception to this idea because they believed that since God created man, he should be at the centre of the Universe despite being correct, Galileo was forced to recount his findings and spent his last years on house arrest October 31, 1992 – Pope John Paul II issued a papal pardon, 350 years after Galileo’s death

Spontaneous Generation another idea that was believed for hundreds of years despite scientific evidence to the contrary spontaneous generation is the belief that living things can emerge from non-living matter widely accepted until the 19th century people believed there was a life force that caused non-living things to “birth” living things

Spontaneous Generation To the left we have two photos the first is the imprint of a fossilized plant in a rock the second is a moldy sandwich How do we explain these two photos? the plant: trapped between the rock and the layers of dirt and sediment above it as it decomposed, it wore out a pattern in the rock the sandwich: microscopic spores of fungus landed on the bread over time, the fungus spread across the surface of the bread, giving it the moldy appearance

Spontaneous Generation prior to the 19th century, people would have explained these two situations differently the plant: they would assume the plant had grown out of the rock the sandwich: the sandwich, a non-living thing, would give the mold a life force, allowing it to grow

Francisco Redi set up an experiment to illustrate that maggots, (a living thing) did not grow spontaneously out of raw meat (a non- living thing) set out two flasks one with access to air one without access to air only the flask open to air (and flies) had evidence of maggots Redi thought this disproved spontaneous generation, but other scientists said it proved that air was a necessary ingredient in life force

John Needham performed another experiment, and claimed that it proved the existence of life forces boiled chicken broth (to kill bacteria) put it in a sealed flask found that microorganisms still appeared likely because broth wasn’t heated for long enough or at a high enough temperature

Lazzaro Spallanzani repeated Needham’s experiment, but in a vacuum this removed all the air from the flask before it was sealed no microorganisms appeared despite this evidence, Needham still maintained this only proved air was an ingredient in life force

Louis Pasteur his experiment in 1864 was finally the decisive proof the scientific community needed to reject spontaneous generation once and for all

Louis Pasteur Pasteur set up two flasks, each with the same meat broth he heated them both to sterilize them and remove the bacteria the flasks he used had bent necks, so that they were open to the air but protected from dust initially, neither broth became cloudy with microbial growth

In experiment 1, Pasteur broke off the neck of the flask, giving it access to air In experiment 2, he left the neck intact

dust now had access to flask 1, while it got trapped in the neck of flask 2 over time, microorganisms appeared in flask 1, but not in flask 2 this proved that microorganisms are not generated by the broth, but rather carried in the air, and simply too small to see

Experimental variables whenever performing an experiment, a scientist must decided what he or she is testing for some variables will change from trial to trial, and the results analyzed some variables will stay the same so the scientist knows that these variables are not the cause of any differences between trials

Manipulated variable the variable that is altered between trials in Pasteur’s experiment, the manipulated variable was whether the flask’s neck was broken or left intact

Responding variable the responding variable is the results of the changes made in Pasteur’s experiment, the responding variable was the presence of microbial growth

Controlled variables the controls are all the things that could have been changed, but were deliberately kept constant in Pasteur’s experiment, the controls were: the temperature and duration of heating the shape and size of flasks before they were broken the type of broth the amount of broth etc.

Variables - Practice problems In each of the experiments described below, identify the manipulated, responding, and at least two controlled variables: a science student wants to know if the amount of water given to a plant affects how tall it will grow a pharmaceutical company wants to know if a new drug is effective in treating migraines a car company wants to know if the type of brake pads in a car affects stopping distance

Robert Brown with improvements in lens technology came a new understanding of the cell in 1833, identified the nucleus of the cell as being responsible for controlling cell function

Schleiden & Schwann made observations on plant and animal cells together, proposed that all plant and animals are composed of cells described cells as the basic unit of life for all organisms

Rudolf Virchow Expanded on Schleiden and Schwann’s theories on cells theorized that all cells arise only from pre-existing cells

Summary of cell theory The three points of cell theory are: all living things are made up of one or more cells and the materials produced by these cells all life functions take place in cells, making them the smallest unit of life all cells are produced from pre-existing cells through the process of cell division, also called mitosis

Development in Imaging Technology & Staining 1.3 – 1.4

The quality of the image Three factors affect the quality of an image in microscopy: magnification contrast resolution Skin cells of a frog

Magnification improved with advancements in lens-making light microscopes used in labs today can now magnify between 1000-2000X

Contrast refers to the variation of shadow and colour it is contrast that allows the human eye to focus on different aspects of the image and to register depth cells by themselves are mostly colourless image quality has improved with: new stains and staining techniques new methods of illuminating the specimen

Contrast a cell with low contrast a cell with high contrast a cell with phase contrast illumination

Resolution the ability to distinguish between two structures that are very close together the human eye is capable of resolving objects that are 0.1mm or larger the higher the resolution of a microscope, the more clearly you can see the magnified image similar to the resolution capabilities of a digital camera

Resolution the picture on the left has low resolution, and appears pixelated the picture on the right has a higher resolution and is therefore a clearer image

Fluorescent microscopy fluorescent stains called GFP (green fluorescent protein) are introduced to the specimen different cell structures absorb stains in different amounts the specimen is subjected to UV light depending on the type of dye, the cell glows either yellow, orange or green unlike conventional staining, GFP does not kill the cell, and allows for observation of living specimens

Brightfield microscopes light passes through the specimen fixing and staining process kills the specimen you can’t view living tissues limited resoloution you can’t get any higher resolution than 0.2µm

Confocal technology uses lasers and computers to focus the light the later reflects off the object and back to the eyepiece you see a thin section with high resolution computer software can be used to build up a 3D image fluorescent stains work better with confocal microscopes because they eliminate the blurriness of the reflected light

Confocal technology traditional optical microscope confocal microscope

Electron microscopy uses a fine beam of electrons instead of light the electrons pass through different materials at different rates, due to differences in density instead of lenses, EMs use magnetic fields to focus the image Canadian invention

Transmission Electron Microscope (TEM) electrons pass through the specimen 100X better magnification and resolution than light microscope difficult to produce 3D images specimens are fixed and stained, so living specimens cannot be observed

Scanning Electron Microscope (SEM) good for observing surface features of specimens the specimen is fixed, and coated in gold the electrons reflect off the gold and produce a 3D image 2X better image quality than the TEM uses computes to move the specimen and view it from different angles new SEMs permit the use of live material

Eye of a Fruit Fly

Pollen

Salt

Gene mapping with new imaging techniques comes new possibilities for research at the cellular level gene mapping refers to decoding of a species’ genome an organism’s genome refers to all the information contained within its DNA in 2001, the Human Genome Project published a complete map of the entire human genome

Gene mapping could help us understand where cancer and other diseases come from and how to treat them more effectively also allows us to create new varieties of plants ethical arguments arise about the dangers of genetically modified food

Cell communication cells are open systems, meaning they must interact with their environment to survive hormones are chemicals produced in one part of your body that act on a different part for example, the hormone adrenaline is produced in your brain, but acts all over your body in times of stress or excitement hormones and other transmitter chemicals form part of your cells’ communication system

Cell communication receptors on the surface of the cells allow transmitters to attach to the cell and carry out their function only transmitters with the correct shape can dock at a particular receptor similar to a lock and key method

Cell communication certain viruses and bacteria can trick the cells by mimicking the shape of a harmless molecule in order for your immune system to fight off invaders, it must first identify them, based on the markers on their cell membranes

Cell communication better understanding of cell communication allows scientists and research companies to: diagnose diseases carried by viruses and bacteria diagnose diseases of the immune system make more targeted, and more effective medications