Development of the Cell Theory

Biology 11

History

Middle ages - magnifying lenses

1590 – first compound microscopeRequired to view microscopic organisms

1665 – Hooke discovered cells

Spontaneous Generation

Living organisms could suddenly arise from non-living materials

Believed until 19th century

Maggots on rotting meatFrogs & salamanders appear in mudMushrooms on logsMice from a dirty shirt & wheat

Four Parts of the Cell Theory

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

2. Cells are the basic units of structure and function in all organisms.

3. All cells are derived from pre-existing cells.

4. In a multicellular organism, the activity of the entire organism depends on the total activity of its independent cells.

Asking Questions

500 BCAncient Greece supports scholars

Ask questions about life & natureSeek answers through observations & thought

Not experiments

Aristotle

Greek philosopher 384 – 322 BC

334 BCClassified all living things

Plant or animal

Believed in spontaneous generation

Roger Bacon

English philosopher1214 – 1294

1268First wrote about eyeglasses

Magnifying Images

1590Dutch eyeglass makers

Hans & Zaccharias Janssen

Invented first compound microscopeUsed two lensesMagnified 10x

King Charles II

English monarch

1602Founded “Royal Society of London for the Promotion of Natural Knowledge”Shared & debated knowledge

Used books, letters, meetings

Robert Hooke

English scientist1635 – 1703

1665Published book – Micrographia

Illustrated cork images from microscope

Coined term “cells”Empty room-like compartments

Antony van Leeuwenhoek

Dutch scientist1632 – 1723

1666/1667Read Hooke’s bookDesigned microscopes

Six times more magnifying power

Francesco Redi

Italian scientist1629 – 1697

1668Experiments disproved spontaneous generation

Maggots do not appear in meat if no contact with flies

Redi’s Experiment

van Leeuwenhoek (… again!)

Wrote letters to Royal Society

1673/1674 Described “animalcules” in water

Bacteria & protozoa

Hooke later confirmed findings

… van Leeuwenhoek (… again!)

1683Examined plaque from teeth

“Many very little living animalcules, very prettily a-moving”Discovered bacteria

John Needham

English naturalist & priest1713 – 1781

1748Experiments supported spontaneous generation

John Needham’s Experiment

Lazzaro Spallanzani

Italian biologist1729 – 1799

1748Experiments disproved Needham & spontaneous generation

Boiled broth longer

1770’s

Microscope mechanical advancements

Sturdier & easier to use

Not as advanced or clear as van Leeuwenhoek’s

Jane Haldiman

English science writer

1809Developed textbooks about scienceUsed terms “cell”, “cellular system”, “cell tissue”

Robert Brown

Scottish botanist1773 – 1858

1831All cells contain a nucleus

Matthias Jacob Schleiden

German botanist1804 – 1881

1838Wrote “All plants are made of cells”

Theodor Schwann

German physiologist

1810 – 1882

1839Wrote “All animals are made of cells”

Alexander Carl Henrich Braun

German botanist1805 – 1877

1845Wrote “The cell is the basic unit of life”

Jugo von Mohl

German biologist1805 – 1872

1846/1847Described protoplasm (cytoplasm) and cell membrane

William Henry Perkin

English chemistry student1838 – 1907

1856Developed a purple dye

Used to stain slide specimens

Rudolph Virchow

German physiologist1821 – 1902

1858Stated (in short) … “All cells come from pre-existing cells”

Disagree with spontaneous generation

Louis Pasteur

French biologist1822 – 1895

1860Finally disproved spontaneous generation

Living organisms DO NOT come from non-living matterPrize from Paris Academy of Sciences

Louis Pasteur’s Experiment

Cell Theory Scientists

1. SchleidenPlants are made up of cells

2. SchwannAnimals are made up of cells

3. VirchowAll cells come from other cells

Indirect Credit:Hooke

Discovery of cells

van Leeuwenhoek

Microscope improvements