Organisms are made of tiny cells that perform the basic life functions and keep the organism alive. Many organisms (for example yeast, algae) are single-celled, and many organisms (for example plants, fungi and animals) are made of millions of cells that work in coordination.

Students should understand that…..

Compare and contrast living organisms that are single celled with multicellular organisms.

Students should be able to….

All living things are made of cells

• The cell is the smallest unit that can perform the basic activities of life.

Sizes of cells, viruses, and other small things

Unicellular Organisms

• Unicellular organisms are those that contain just one single cell.

• Single-celled organisms have been on Earth for 3.8 billion years.

• Although they are only one cell, they are complex.

bacteriaUnicellular Organism

protozoaUnicellular Organisms

unicellular algaeUnicellular Organisms

unicellular fungi= yeastsUnicellular Organisms

Multicellular OrganismsMulticellular organisms are those that are made up of more than one cell. They have specialized cells that, together, meet the basic needs Animals Multicellular Algae

Multicellular Fungi

Plants

The microscope led to the discovery of the cell (1660s-1670s)

Robert Hooke

Anton Van Leeuwenhoek

Anton Van Leeuwenhoek was the first to see and describe bacteria (1674), yeast plants, the teeming life in a drop of water, and the circulation of blood corpuscles in capillaries.

1660s-1670s

On September 17, 1683, Leeuwenhoek wrote to the Royal Society about his observations on the plaque between his own teeth, "a little white matter, which is as thick as if 'twere batter." He repeated these observations on two ladies (probably his own wife and daughter), and on two old men who had never cleaned their teeth in their lives. Looking at these samples with his microscope, Leeuwenhoek reported how in his own mouth: "I then most always saw, with great wonder, that in the said matter there were many very little living animalcules, very prettily a-moving. The biggest sort. . . had a very strong and swift motion, and shot through the water (or spittle) like a pike does through the water. The second sort. . . oft-times spun round like a top. . . and these were far more in number." In the mouth of one of the old men, Leeuwenhoek found "an unbelievably great company of living animalcules, a-swimming more nimbly than any I had ever seen up to this time. The biggest sort. . . bent their body into curves in going forwards. . . Moreover, the other animalcules were in such enormous numbers, that all the water. . . seemed to be alive." These were among the first observations on living bacteria ever recorded.

First look at bacteria

Schleiden, Schwann and Virchow 1850s Cell Theory

"all living things are composed of living cells"

"All living cells arise from pre-existing cells". 

Virchow

Virchow: Discovered that cells only come from other cells.

Schleiden: Announced that all plants are composed of cells.

Schwann: Discovered that all animals are made up of cells.

Louis Pastuer He was able to demonstrate that organisms such as bacteria were responsible for souring wine and beer (he later extended his studies to prove that milk was the same).

The bacteria could be removed by heating wine, beer, milk, or vinegar briefly, thereby sterilizing—or 'pasteurizing'—the substances.

• scientists believed living things could spontaneously generate.

Louis Pasteur helped prove there was no spontaneous creation of cells from

non-living matter

people believed that mice can arise in the pot with grain, shut by dirty shirt.

Spontaneous Generation? Or Not?

Heat- kills bacteria

Left open- bacteria appear conclusion: spontaneous generation is true

Stoppered – No bacteria grow = no spontaneous generation

Argument – Hey! Nothing grows with no air!

How do we resolve this question?

Pasteur's Experiment

Flask changed into a long S shape= prevented microorganisms in the air from easily entering the flask, yet allowed some air interchange.

If the swan neck was broken, microbes readily entered the flask and grew.

Trying to prove the living organisms that grew came from outside, as spores on dust, rather than spontaneously generated within the broth.

Pasteur & Vaccinations

The principle of vaccination or immunization is based on the property of 'memory' of the immune system.

A vaccine is defined as an inoculation containing germs in dead, weakened or virulent form or modified toxins which when injected inside the body, stimulates the defensive system of the body to produce antibodies. This creates an immunity inside the body of an organism against that particular disease.

Germ Theory

• Beverage contamination led Pasteur to the idea that micro-organisms infecting animals and humans cause disease.

Scientists Trash Talk

Cell Theory

1. All living organisms are composed of one or more cells.

2. The cell is the basic unit of structure, function, and organization in all organisms.

3. All cells come from preexisting cells.

Light Microscopemicroscope The light microscope has a limit of resolution of about 200 nm (0.2 µm). This limit is due to the wavelength of light (0.4-0.7 µm). Cells observed under a light microscope can be alive, or fixed and stained

The Transmission Electron Microscope (TEM)

The Transmission Electron Microscope (TEM) The Transmission Electron Microscope (TEM) has a limit of resolution of about 2nm. This is due to limitations of the lens used to focus electrons onto the sample. A TEM looks at replicas of dead cells, after fixation and heavy metal ion staining. Electrons are scattered as they pass through a thin section of the specimen, and then detected and projected onto an image on a fluorescent screen.

Images UsingTransmission Electron Microscope

The Scanning Electron Microscope (SEM)

The Scanning Electron Microscope (SEM) The Scanning Electron Microscope (SEM) also has a limit of 2nm. Like the TEM, the SEM allows you to look at replicas of dead cells, after fixation and heavy metal ion staining. With this technique, electrons are reflected off the surface of the specimen.

Scanning electron micrograph of a sipunculan pelagosphera larva

Gills of a fish, the mudskipper (Periophthalmus argentilineatus)lung trachea epithelium

pollen grains from a variety of common plants

Comparing TEM and SEMTransmission Electron Microscopes• The transmission electron microscope (TEM), the first type of EM, has many commonalities with the optical

microscope and is a powerful microscope, capable of producing images 1 nanometer in size.• They require high voltages to increase the acceleration speed of electrons, which, once they pass through

the sample (transmission), increase the image resolution.• The 2-d, black and white images produced by TEMs can be seen on a screen or printed onto a photographic

plate.• Although recent innovations in software help to minimize, TEM resolution is hampered by spherical and

chromatic aberrations.• The TEM is a popular choice for nanotechnology as well as semiconductor analysis and production.

Scanning Electron Microscopes• Reflecting light microscopes are the optical counterpart to scanning electron microscopes (SEM) and

produce similar data.• SEMs are primarily used to obtain topographical information.• In this type of EM, a series of solenoids pulls the beam back and forth across the sample, systematically

scanning the surface; it detects secondary electrons emitted from the surface and produces an image.• Although SEMs are approximately 10 times less powerful than TEMs, they produce high-resolution, sharp,

black and white 3D images.