The Cell Theory

The Cell Theory

• All living things are composed of cells

• Cells are the basic unit of structure and function of living things

• All cells are produced from other cells

The Cell Theory

• All living things are composed of cells– Plants and Animals are alive, therefore they

are made up of cells– Unicellular organisms are one celled organisms

• Ameoba (animal)• Algae (plant)

– Multicellular organisms are organisms with many cells

• Cats (animal)• Oak Tree (plant)

The Cell Theory

• Cells are the basic unit of structure and function of living things– Cells are organized into tissues– Tissues are organized into organs– Organs are organized into organ

systems– Organ systems are organized into

the organism

Cells>Tissue>Organ>Organ System>Organism

The Cell Theory

• All cells are produced from other cells– One cells grows and divides

• Now you have 2 cells

– 2 cells grow and divide• Now you have 4 cells

– 4 cells grow and divide• Now you have 8 cells

– New cells are needed for an organism to grow and also to replace cells that die

Closure Question

• What are the 3 statements made by The Cell Theory?– 1. All living things are made of cells.

– 2. Cells are the basic unit of structure and function in living things.

– 3. Cells come from other cells.

Diversity of Cellular Life

Cells

• Are the simplest form of life• Chemical elements organized into

cells become living matter.• All organisms are

made-up of cells• All the substances

of an organism are the products of its cells

– Some things are only one cell(unicellular)

– Some have many cells (multicellular)

Life is Cellular

Unicellular or Multicellular

• SINGLE CELL ORGANISM

• MULTI-CELL ORGANISM

Cells are small for 2 ReasonsReason 1: Limited in size by the RATIO between their Outer

Surface Area and Their Volume. 

A small cell has more SURFACE AREA than a large cell for a GIVEN VOLUME OF CYTOPLASM. 

Unicellular Organisms may be

Prokaryotic Eukaryotic

Remember? What does the Eukaryotic Cell have that Prokaryotic

Cells does not?

No nucleus Has a nucleusNo organelles Has organelles

Colonial Organisms Video:

• A colony of single-celled organisms is a colonial organism. It's likely that early colonial organisms were the first evolutionary step from single celled life to multicellular species.

Volvox releasing daughter colonies. Ref: volvox01

Synura: Three individual colonies. Ref: synura01.

Synura (above) and rotifer egg.  

Three Scenedesmus. Ref: scened00

Colonial Organisms• The difference between a

multicellular organism and a colonial organism is that individual cells from a colony can, if separated, survive on their own, while cells from a multicellular life form (e.g., liver cells) cannot.

Filamentous Algae

Colonial Organisms

• In a multicellular organism the cells have become specialized and taken on specific jobs to help out the whole organism

• In a colonial organism,there is little difference between cells.

Volvox carteri, a colonial freshwater alga. The small dots are regular cells and the large ones are asexual reproductive cells

• Cell differentiation- When cells take on a different shape, size, and chemistry, suitable for a certain function during development.

• Cells vary in size, shape, and internal components

• The variety of cell shapes include round, flat, long, rectangle, etc.

• Some cells have different extensions from the cell membrane

Cell Differentiation

• cell specialization- The characteristic of having separate roles for each type of cell in a multicellular organism; the cells is specifically designed for a certain function; it has a certain purpose or job.

• The size and shape of a cell is related to its function

Cell Specialization

• division of labor- A more efficient way of getting jobs done in a multicellular organism because the different tasks are dispersed to different cells, each of which is specialized to do that job.

• The organelles that make up a certain cell are also determined by the specific functions carried out by the cell

Division of Labor

• levels of organization- A system of hierarchy in which a group of things are arranged in order of rank, complexity, or size. Each group is made up of smaller parts and/or are a part of a larger group. (example- cells form tissues, which form organs, etc.)

Levels of Organization

Levels of Organization

• Cell• Tissue• Organ• Organ

system

Cells

Many different

types of cells are formed

during embryonic development.

Cells Continued

• Cells occur in many different shapes and sizes so they can perform many different functions.

Tissue

Many different cells work together to form a tissue.

Cartilage Muscle Nerves

Fat Skin Bone

Organ

Many tissues working together form an organ

Organ System

Each organ system is made up of several different organs that work together and enable the system to do its job.

Eleven Organ Systems

• Circulatory• Digestive• Endocrine• Excretory• Integumentary• Lymphatic

• Muscular• Nervous• Reproductive• Respiratory• Skeletal

Review of Organization

1. Cells – have a special job to do (i.e. cell from intestine)

Review of Organization

2. Tissues – a group of similar cells that work together to carry out a special job (i.e. group of lining cells in intestine)

Review of Organization

3. Organ – a group of tissues that work together to do a job (i.e. small intestine)

Review of Organization

4. Organ system – a group of organs that work together to do a certain job (i.e. digestive system)

Review of Organization

5. Organism – all organ systems working together (i.e. digestive, respiratory, circulatory, etc.)

Review of Organization

Review of Organization

• Some organisms are made up of only one cell but they have all the features of living things– The parts of their cell

still work together

• Other organisms have organs and organ systems like humans– Systems work together to keep us

alive