Chapter 7 Section 4

• 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)

• SINGLE CELL ORGANISM

• MULTI-CELL ORGANISM

Prokaryotic Eukaryotic

No nucleus Has a nucleusNo organelles Has organelles

• 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

• 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

• 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 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

• division of labor- A more efficient way of getting jobs done in a multicellular organism because the different tasks are given 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

• 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.)

• Cell

• Tissue

• Organ

• Organ system

Many different types of cells are formed during embryonic development.

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

Many different cells work together to form a tissue.

Cartilage Muscle Nerves

Fat Skin Bone

Many tissues working together form an organ

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

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

• Muscular• Nervous• Reproductive• Respiratory• Skeletal

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

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

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

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

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

• 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