7.1 The Discovery of Cells

Chapter 7A View of A CellPages 171 - 174

Eggs are giant cells.

Some are more giant than others. This is a replica of the egg from an Elephant Bird Egg Aepyornis maximus

It became extinct around 400 years ago. They were found on Madagascar, Africa.

This egg is 15 times the bulk of an Ostrich egg and is believed to be the largest egg that has ever existed.

The brown egg is a chicken egg.

The tiny white one is a hummingbird, the smallest bird that lives on our planet today.

Egghead

A man poses with the alleged largest egg in the world during a photocall in central London. The egg was laid in the early 17th century, by the now extinct Great Elephant Bird of Madagascar.

(AFP/Shaun Curry)

This was what we believe the elephant bird looked like!

They had eggs, up to three feet in circumference. They were the eggs of a bird that would later come to be known as the Elephant Bird, or Vouron Patra (Aepyornis maximus). The eggs that the Elephant Bird laid were larger than the largest dinosaur eggs, and, in fact, I have heard that some mathmetician-types somewhere have calculated that they were as large as a structurally functional egg could possibly be...the largest single cells to have ever existed on Earth.

The flightless bird grew to around ten or eleven feet tall, and is estimated to have weighed up to 1100 pounds. By comparison, a BIG Ostrich will go eight feet and 300 pounds. Only the largest of the New Zealand Moas were taller, some reaching thirteen feet, but they weren't as massively built.

All were extinct by 1700.

The History of the Cell Theory

• Cells are the basic unit of living organisms

Light microscopes

• Anton van Leeuwenhoek used a simple microscope in the 1600’s

• Compound light microscopes use series of lenses to magnify objects up to 1500 times

• In our classroom, 40X, 100X, 400X

Anton van Leeuwenhoek(1632-1723)

• Dutch microscopist who was born and died in Delft, the Netherlands.

• He was the finest lens grinder of his time.

• He made his own microscopes.

• He was the first to observe sperm, bacteria, and red blood cells.

• His observations laid the foundations for the sciences of bacteriology and microbiology.

• Called the protists he saw ”wee beaties”.

Anton van Leeuwenhoek(1632-1723)

• Leeuwenhoek made over 500 "microscopes," but fewer than ten have survived to the present day.

• Most of Leeuwenhoek's instruments were really powerful magnifying glasses, not compound microscopes of the type used today.

• A drawing of one of Leeuwenhoek's "microscopes" is shown at the right.

• Compared to modern microscopes, it is an extremely simple device, using only one lens, mounted in a tiny hole in the brass plate that makes up the body of the instrument.

• The specimen was mounted on the sharp point that sticks up in front of the lens, and its position and focus could be adjusted by turning the two screws.

• The entire instrument was only 3-4 inches long, and had to be held up close to the eye; it required good lighting and a lot of patience to use.

MirrorFine adjustment knobCourse adjustment knobEye pieceNose pieceObjective lensesStage clipsStageDiaphragm

The Cell Theory

• Robert Hooke used a compound light microscope to look at cork

• He gave box like structures the name cells because it reminded him of the rooms monks lived in at the monastery

Robert Hooke (1635-1703) • There are no known pictures of

Robert Hooke.

• Some say his name is not as well known today because he did not get along with Sir Isaac Newton.

• An experimental scientist from the seventeenth century.

• He studied physics and astronomy, chemistry, biology, and geology, to architecture and naval technology.

• He worked with or corresponded with scientists as diverse as Christian Huygens, Antony van Leeuwenhoek, Christopher Wren, Robert Boyle, and Isaac Newton.

Robert Hooke (1635-1703) • Some of his accomplishments include:

– the universal joint, – the iris diaphragm, – an early prototype of the respirator; – invented the anchor escapement – the balance spring, which made more

accurate clocks possible; – served as Chief Surveyor and helped rebuild

London after the Great Fire of 1666; – worked out the correct theory of

combustion– devised an equation describing elasticity

that is still used today ("Hooke's Law")– assisted Robert Boyle in studying the

physics of gases– invented or improved meteorological

instruments such as the barometer, anemometer, and hygrometer

– he made important contributions to biology and to paleontology.

• Hooke's reputation in biology is from his book Micrographia, published in 1665.

The Cell Theory

• In the 1830’s two German scientists made some cell observations.

• Matthias Schleiden studied plants.

• Theodor Schwann studied animals.

Matthias Schleiden (1804-1881)

• German botanist • Master microscopist • studied primarily cells in plants. • He observed that all plants seemed

to be made of cells.• Schleiden observed various cell

activities such as protoplasmic streaming.

• Schleiden also found that certain fungi live on or within the roots of some plants.

• This relationship between fungi and plants, called mycorrhiza ("fungi roots"), has since been shown to be very common and extremely beneficial to both organisms.

Theodor Schwann (1810 -1882)

• In 1839 Schwann proposed that all organisms are made of cells.

• Together with Matthias Schleiden he formulated the cell theory of life.

• Schwann also discovered the cells, now known as Schwann cells, that form a sheath surrounding nerve axons.

• He conducted experiments that helped disprove the theory of spontaneous generation.

• He was the person who came up with the word “metabolism” to define the chemical changes that take place in cells.

• He demonstrated that yeast organisms cause fermentation of sugar solutions.

• I remember that Schwann is the animal part of this duo because “Schwann” sounds like ”swan”.

Teddy Bear Swan

Schwan sounds like swan which is an animal

The Cell Theory

• Both Schleiden & Schwann came up with the ideas that we now know as the cell theory.

Cell Theory

1. All organisms are composed of one or more cells

Unicellular organismMulti-cellular organisms

The Cell Theory

• 2. The cell is the basic unit of structure and organization of organisms.

• The same type of cells make tissue

• The same type of tissue make an organ

• The organs doing the same type of job make an organ system

• Many organ systems make an organism

Cell Theory

2. The cell is the basic unit of organization within an organism-

The cell is the simplest part of any living thing.

Cell Theory

3. All cells come from preexisting cells

Electron Microscopes

• Electron microscopes can magnify more than 150,000 times actual size

• Developed in the 1930’s

• Uses a beam of electrons instead of light

Electron Microscopes

• Specimens must be examined in a vacuum because the electrons can collide with air particles

• Two types; SEM scanning & TEM transmission

SEM scanning

• Scanning shows 3-d image of the outside

TEM transmission

• Transmission shows what the inside looks like

Soil microbe

Leaf cutter ant eye

Leaf cutter ant head with jaw

Fly’s head

SEM (Scanning Electron Microscope) image of a white blood cell, platelet and red blood cell. White blood cells or leucocytes (far right) fight infection by producing antibodies or devouring invading bacteria. Red blood cells or erythrocytes (far left) carry oxygen from the lungs to the rest of the body. Platelets (middle) are cell fragments that play a role in the ability of blood to clot.

Two Basic Cell Types

• Two Groups of cells ~ Those with membrane bound organelles and those without membranes around organelles.

• Prokaryotes• Pro = first ,like prototype• Most bacteria are prokaryotes• Eukaryotes• Eu = true, more advanced• Some unicellular and all multicellular are

eukaryotes