Transcript 7.4 Homeostasis and Cells

Cells
 Cells have the same basic composition, and the same
kinds of organelles, but not all living things are the same
 Cells are ___________________ and associate with other
cells in special ways
Unicellular Organisms
 _________________ –
relatively constant internal
physical and chemical
conditions
 Single-celled organisms
are living too.
-
Types of Unicellular Organisms
 __________________
 Protozoa (picture on previous slide)
 Algae – have chloroplasts, found in water
 Yeast (a unicellular fungi) – break down nutrients
 _________________
 Bacteria – highly adaptive and can live almost
anywhere
 Both prokaryotes and eukaryotes, though
unicellular, ______ __________ _______
_____________ ________________.
Multi-cellular Organisms
 Cells have a certain job in the body and are specialized
for their task
 Analogy: cells work together like members of a baseball
team-are interdependent
 Members of a baseball team have different jobs – coach,
catcher, pitcher, fielders, trainers
 Need to communicate effectively
 So do cells!
The cells of multicellular organisms become
specialized for particular tasks and
communicate with one another to maintain
homeostasis.
Some specialized cells, pg 215
Fig 7-22 Human trachea
epithelial cells 
Fig 7-23 Pollen grains from pine
tree
Levels of Organization
 The specialized cells of multicellular organisms are
organized into tissues, then into organs, and finally
into organ systems.
Levels of Organization
 A ______________ is a group of similar cells that
performs a particular function.
Levels of Organization
 To perform complicated tasks, many groups of tissues
work together as an _____________.
 Each type of tissue performs an essential task to help
the organ function.

In most cases, an organ completes a series of
specialized tasks.
Levels of Organization

A group of organs that work together to perform a
specific function is called an ________________.

For example, the stomach, pancreas, and intestines
work together as the digestive system.
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.
Levels of Organization: review
 Cells make…
 Tissues, which make…
 Organs, which make…
 Organ systems,
which make…
 Organisms
Cellular Communication
 Cells are specialized, but
interdependent
 Cells MUST
________________
___________________
 Some cells form a
connection to another
cell, called cellular
junctions
 Signals pass through junctions, but only if they
have the right _____________ (like a receiver)
= specific protein that has specific shape that
molds to a specific molecular messenger
 Ex: junctions in the heart – electrical signals pass
through junctions to make heart contract and pump
blood
In your Notes, answer these:
1. What is homeostasis?
2. What do unicellular organisms do to maintain
homeostasis?
3. What is cellular specialization?
 Cellular specialization describes how, in
multicellular organisms, groups of cells play
different, specific roles.
 Ex: Cilia on trachea cells
4. What are 2 things that help cells
communicate and maintain homeostasis?