7.4 Homeostasis and Cells

CellsCells 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.

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Types of Unicellular Organisms__________________

Protozoa (picture on previous slide)Algae – have chloroplasts, found in waterYeast (a unicellular fungi) – break down nutrients

_________________Bacteria – highly adaptive and can live almost

anywhereBoth prokaryotes and eukaryotes, though

unicellular, ______ __________ _______ _____________ ________________.

Multi-cellular OrganismsCells have a certain job in the body and are specialized for

their taskAnalogy: cells work together like members of a baseball

team-are interdependentMembers of a baseball team have different jobs – coach,

catcher, pitcher, fielders, trainersNeed 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.

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

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 CommunicationCells 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 messengerEx: 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?