Lesson Overview

1. Lesson Overview 7.4 Homeostasis and Cells

2. 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?

3. 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.

4. 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.

5. 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.

6. 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

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

8. 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.

9. 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!

10. 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.

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

14. Levels of Organization • A cell is the basic unit of living things

15. Levels of Organization A tissue is a group of similar cells that performs a particular function.

16. 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.

17. Levels of Organization • A group of organs that work together to perform a specific function is called an organ system.

18. 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.

19. 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.

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

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

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

23. 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.