Powers Unit 3 - Homeostasis and Cells

Unit 3 - Homeostasis and Cells

Homeostasis and Cells

● The cell as an organism

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Maintaining homeostasis

● Multicellular Life

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Cell specialization

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Levels of organization

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Cellular communication

The Cell as an Organism

● Unicellular organisms need to go through some of the same

processes as multicellular organisms
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Prokaryotes
■bacteria

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Eukaryotes
■Amoeba, algae, yeasts, fungi

● Unicellular organisms must maintain homeostasis

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To maintain homeostasis, unicellular organisms grow,
respond to the environment, transform energy, and
reproduce.

The Cell as an Organisms

● Every unicellular organism needs to maintain homeostasis

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Needs to find sources of food

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Needs to keep concentrations of water and minerals at
certain levels

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Needs to respond quickly to changes in environments

Multicellular Life

● Humans, animals, plants, etc.

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Cells do not live on their own

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They are interdependent
■

They work together

■

Communicate by sending and receiving signals

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The cells of multicellular organisms become specialized for
particular tasks and communicate with one another to maintain
homeostasis

Multicellular Life - Cell Specialization

● As cells in organisms multiply and divide,

they become specialized
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Special jobs
■To move

■React to environment

■Produce substances

● Each cell contributes to maintaining

homeostasis

Multicellular Life - Levels of Organization

● Specialized cells are organized into tissues, then organs, and

finally organ systems

● Specialization and interdependence are the main attributes

of living things

Levels of Organization

● Tissue: a group of similar cells that perform a particular

function
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Ex: muscle tissue

● Organ: many groups of tissues work together

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Ex: bicep

● Organ System: a group of organs that work together to

perform a special function
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Ex: muscular system

Cellular Communication

● Cells in large organisms need to

communicate!
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They use chemical signals

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Speed up or slow down the
activities of the cells that receive
them

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Could cause cells to change
what they are doing

Cellular Communication

● Cells have junctions to neighboring

cells to pass signals back and forth
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Receptor: a specific protein to
whose shape fits a specific
molecular messenger, such as a
hormone
■Some are on the cell or in the
cytoplasm

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Nerve cell impulses