Cell theory

life 

The condition that distinguishes animals and plants from inorganic matter

life requirements

• movement

• reproduction

• sensitivity

• homeostasis

• excretion

• nutrition

• growth

• preceding death

living

• alive

• living creatures

non-living

• Inanimate

• inorganic "materials that come from nonliving sources"

spontaneous generation

• The idea that living things can come from nonliving matter

• based on seeing life appear in places that were thought to be lifeless

Zacharias Janssen

• 1590

• invented the first compound microscope

Robert Hooke

• 1665

• Used light microscope to look at thin slices of plant tissue (cork)

• Saw tiny chambers and made the name “cell”

Francessco Redi

• 1668

• He was the first person to challenge and disprove the theory of spontaneous generation

• demonstrated that maggots come from eggs of flies

Anton van Leeuwenhoek

• 1673

• First to see living microscopic organisms (in pond water).

• named these microorganisms animalcules.

Matthias Schleiden

• 1838

• "All living plants are made of cells".

• Credited for developing first two tenets of cell theory (with Schwann).

Theodore Schwann

• 1839

• "All living animals are made of cells".

• Credited for developing first two tenets of cell theory (with Schleiden).

Robert Remak

• 1852

• While looking at chicken embryos and frog spawn, discovered that all new cells come from pre-existing cells

Rudolph Virchow

• 1855

• "Where a cell exists, there must have been a pre-existing cell".

• Credited for developing the third tenet of the cell theory.

Robert Brown

• 1858

• discovery of the nucleus and its role helped to put together the cell theory

Louis Pasteur

• 1862

• experiment with the swan necked flask and broth led to the process of pasteurisation

• last person to challenge and disprove the theory of spontaneous generation

3 tenets of cell theory

• All organisms are composed of one or more cells.

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

• All cells come from pre-exsisting cells.

Redi’s meat experiment

• open jar: rotting meat attracted flies and maggots

• sealed jar: rotting meat was sealed from flies, no maggots produced

• gauze on jar: rotting meat scent attracted flies and maggots, but meat was untouched

Redi’s meat experiment outcomes

• life is produced from life

• flies produce flies, maggots do not spawn from rotting meat

Pasteur’s swan neck experiment

• sterile: nutrient broth is boiled to kill microbes

• sterile: broth remains sterile after cooling and sitting for extended amount of time (microbes trapped in the neck of flask)

• contaminated: microbes grow once neck is broken off

• contaminated: microbes multiply in broth

Pasteur’s swan neck experiment outcomes

• sterile environment free of airborne microorganisms, life will not naturally generate inside a sterile system

• “Life only comes from life“.

Cell theory

• the cell is the fundamental structural and functional unit of living matter

• organism is composed of independent cells with its properties being the sum of those of its cells