7 4 Homeostasis and Cells Unicellular vs multicellular

7. 4 Homeostasis and Cells

Unicellular vs. multicellular • Small one celled organisms – The cell does everything it needs to do and maintains homeostasis • Larger, multi-celled organisms – The cells work together with different functions and maintain homeostasis

What’s homeostasis again? ? • Maintaining relatively constant internal physical and chemical conditions • How do unicellular organisms do that? – Grow – Respond to environment – Change food or sunlight into useful energy – Reproduce

Multicellular Life • Cells need each other and work together

Specialized cells • k

Level of Organization

Definitions. Fun stuff. • Cell • Tissue – Group of similar cells that work together to do a particular job • Organ – Group of tissues that work together • Organ System – Group of organs that work together to do a job

Cellular Communication • Cells send chemical signals to communicate – “speed up” – “slow down!” – “change what you’re doing”, etc – How? • Connections – cellular junctions • Special “receptors” to receive signals

Cellular communication • http: //learn. genetics. utah. edu/content/begin/ cells/cellcom/

• Cell Signals – Sweat – Heart muscle contract – Stomach stop digesting, heart start pounding