7.4 Homeostasis and Cells

Cells have the same basic composition, and the same kinds of organelles, but

not all living things are the sameCells are specialized and associate with

other cells in special ways

How do unicellular organisms maintain homeostasis?

• Homeostasis – relatively constant internal physical and chemical conditions

• What workbook question deals with the definition of homeostasis?

• #1• What’s the answer to #6?

#6. Unicellular Organisms• Single-celled organisms:• Maintain homeostasis• Grow• Respond to the environment• Transform energy• Reproduce

7. Why is that important to single-celled organisms?

• They consist of only ONE cell, so homeostasis is vital to their life. If they lose the ability to keep their internal conditions stable, they face immediate death

What are the types of unicellular organisms?

• Look at #2 - 5

Types of Unicellular Organisms• Eukaryotes

– Protozoa (picture on p214), – Algae – have chloroplasts, found in water– Yeast (a unicellular fungi) – used in baking bread

and other foods• Prokaryotes

– Bacteria – highly adaptive and can live almost anywhere

• Both prokaryotes and eukaryotes, though unicellular, ARE alive and maintain homeostasis

#8. How are cells of multicellular organisms like a baseball team?

Multi-cellular Organisms• Cells have a certain job in the body and are

specialized for their task• Members of a baseball team have different

jobs – coach, catcher, pitcher, fielders, trainers

• Need to communicate effectively – So do cells!

#9. How does a multicellular organism maintain homeostasis?

• Specialized cells from various parts of the body work together and communicate effectively

• Cooperate with each other for survival of the organism

Some specialized cells - • Fig 7-22 p.215 – Human trachea epithelial

cells - have cilia to catch debris when you breathe in air

• Fig 7-23 – Pollen grains from pine tree– Tiny, lightweight, protective covering – Float in the wind until they land on seed cone

#10. What are the levels of organization that make up a multicellular organism?

• Most basic level is…

Levels of Organization• Cells make…• Tissues, which make…• Organs, which make…• Organ systems,

which makes…• Organisms• Where would you

put organism?Another organ?

STOP HERE

• The following slides are from LAST YEAR. We aren’t doing this part!

Cellular Communication• Cells are specialized, but interdependent

• Cells MUST communicate effectively

• Some cells form a connection to another cell, called cellular junctions

• Signals pass through junctions, but only if they have the right receptor – 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

Pop Quiz!

1. What is homeostasis?

The relatively constant internal physical and chemical conditions that occurs in both unicellular and multicellular organisms

2. What do unicellular organisms do to maintain homeostasis?

Grow, respond to the environment, transform energy, and reproduce

3. What does it mean that cells are “specialized”?

• Cells have different tasks or roles to carry out that require them to have a specific structure

• Ex: Cilia on trachea cells

4. What are 2 things that help cells communicate and maintain homeostasis?

• Cellular junctions (connections to other cells)• Receptors (molecule that other cells can bind to)