Lesson Overview 7.4 Homeostasis and Cells

THINK ABOUT IT All living cell are not the same. Differences arise from the ways in which cells are specialized Cells also have to associate with one another in multicellular organisms. How do they communicate?

The Cell as an Organism A single-celled-unicellular -Do everything a living thing needs to do. unicellular organisms must achieve homeostasis Homeostasis-relatively constant internal physical and chemical conditions. To maintain homeostasis, unicellular organisms: grow respond to the environment transform energy reproduce.

The Cell as an Organism Unicelluar organisms dominate life on Earth. Unicellular organisms include both prokaryotes and eukaryotes. Prokaryotes ( no nucleus), especially bacteria, are remarkably adaptable and live almost everywhere— soil on leaves in the ocean in the air even within & on the human body.

The Cell as an Organism Many eukaryotes(with Nucleus) also spend their lives as single cells. Algae, which contain chloroplasts and are found in oceans, lakes, and streams around the world, are single celled. Yeasts, or unicellular fungi, are also widespread.

The Cell as an Organism Whether prokaryote or a eukaryote, homeostasis is an issue for each unicellular organism. Every unicellular organism needs to: - find sources of energy or food -keep concentrations of water & minerals within certain levels -respond quickly to changes in its environment

The Cell as an Organism How do individual cells maintain homeostasis?

The Cell as an Organism How do individual cells maintain homeostasis? To maintain homeostasis, unicellular organisms grow, respond to the environment, transform energy, and reproduce.

Multicellular Life Multi-Many Cellular Cells Multicellular-Oranism made up of many cells The cells of multicellular organisms are interdependent *like the members of a team, they work together. Cells take on a particular roles The cells of multicellular organisms become specialized for particular tasks. Cells communicate with one another in order to maintain homeostasis. I am a multicellular creature!

Cell Specialization The cells of multicellular organisms are specialized -different cell types playing different roles. Some cells are specialized to move Other Cells are specialized to react to the environment Other Cells are specialized to produce substances that the organism needs. Specialized cell contributes to the overall homeostasis of the organism.

Levels of Organization The specialized cells of multicellular organisms are organized into Cell Tissues, Organs organ systems.

Levels of Organization A cell is the basic unit of living things

Levels of Organization A tissue 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 organ. 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 organ system.

Levels of Organization The organization of the body’s cells, tissues, organs, and organ systems creates a division of labor among those cells that allows the organism to maintain homeostasis.

Cellular Communication Cells in a large organism communicate by chemical signals that are passed from one cell to another. Signals can speed up or slow down the activities of the cells that receive them, and can cause a cell to change what it is doing.

Cellular Communication Some cells form connections, or cellular junctions, to neighboring cells. Some junctions hold cells firmly together.

Cellular Communication Other junctions allow chemical messages to pass directly from one cell to the next. Receptor are places where signaling molecule can bind. Sometimes receptors are on the cell membrane Sometimes receptors are inside the cytoplasm.

Multicellular Life How do the cells of multicellular organisms work together to maintain homeostasis?

Multicellular Life How do the cells of multicellular organisms work together to maintain homeostasis? The cells of multicellular organisms become specialized for particular tasks and communicate with one another to maintain homeostasis.