Lesson Overview Homeostasis and Cells

Lesson Overview7.4 Homeostasis and Cells

Lesson Overview Homeostasis and Cells

THINK ABOUT IT

What’s the smallest part of any living thing that still counts as being

“alive?”

Can we just keep dividing living things into smaller and smaller parts,

or is there a point at which what’s left is no longer alive?

As you will see, there is such a limit. The smallest living unit of any

organism is the cell.

Lesson Overview Homeostasis and Cells

The Cell Theory

Soon after the invention of the microscopek, observations were made

by scientists that made it clear that cells were the basic units of life.

In 1838, German botanist Matthias Schleiden concluded that all plants

are made of cells.

The next year, German biologist Theodor Schwann stated that all

animals were made of cells.

In 1855, German physician Rudolf Virchow concluded that new cells

could be produced only from the division of existing cells, confirming a

suggestion made by German Lorenz Oken 50 years earlier.

Lesson Overview Homeostasis and Cells

The Cell Theory

These discoveries are summarized in the cell theory, a fundamental

concept of biology.

The cell theory states:

-All living things are made up of cells.

-Cells are the basic units of structure and

function in living things.

-New cells are produced from existing cells.

Lesson Overview Homeostasis and CellsTHINK ABOUT IT

The diversity of life is so great that

you might have to remind

yourself that all living things are

composed of cells, use the same

basic chemistry, and even

contain the same kinds of

organelles.

This does not mean that all living

things are the same. Differences

arise from the ways in which

cells are specialized and the

ways in which cells associate

with one another to form

multicellular organisms.

Lesson Overview Homeostasis and Cells

Multicellular Life

The cells of multicellular organisms are

interdependent, and like the members of a successful baseball

team, they work together.

In baseball, players take on a particular role, such as pitcher, catcher,

infielder, or outfielder. Messages and signals are sent and understood by

teammates and coaches to play the game effectively.

Cells in a multicellular organism work the same way.

The cells of multicellular organisms become

specialized for particular tasks and communicate

with one another in order to maintain homeostasis.

This is referred to as Division of Labor.

Lesson Overview Homeostasis and Cells

Cell Specialization

The cells of multicellular organisms are specialized, with different cell

types playing different roles.

Some cells are specialized to move, others to react to the environment,

and still others to produce substances that the organism needs.

No matter what the role, each specialized cell contributes to the overall

homeostasis of the organism.

Lesson Overview Homeostasis and Cells

Specialized Animal Cells

Particles of dust, smoke, and bacteria are part of even the cleanest air.

Specialized animal cells act like street sweepers to keep the particles

out of the lungs.

These cells are full of mitochondria, which provide a steady supply of

the ATP that powers the cilia on their upper surfaces.

Lesson Overview Homeostasis and Cells

Levels of Organization

1.Cell

Lesson Overview Homeostasis and Cells

Levels of Organization

The specialized cells of multicellular organisms are organized into

tissues, then into organs, and finally into organ systems.

Cell: The smallest living unit of any organism

Lesson Overview Homeostasis and Cells

2. Tissue

Lesson Overview Homeostasis and Cells

Levels of Organization

Tissue: a group of similar cells that performs

a particular function.

Lesson Overview Homeostasis and Cells

3. Organ

Lesson Overview Homeostasis and Cells

Levels of Organization

Organ: many groups of tissues work together

to perform complicated tasks.

Each type of tissue performs an essential task to help the organ

function.

In most cases, an organ completes a series of specialized tasks.

Lesson Overview Homeostasis and Cells

4. Organ System

Lesson Overview Homeostasis and Cells

Organ system: a group of organs that work

together to perform a specific function

For example, the stomach, pancreas, and intestines work together as

the digestive system.

Levels of Organization

Lesson Overview Homeostasis and Cells

5.Organism

Lesson Overview Homeostasis and Cells

Levels of Organization

The organization of the body’s cells into

tissues, organs, and organ systems creates a

division of labor among those cells that allows

the organism to maintain homeostasis.