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Biology. Chapter 7 Section 3. Key Ideas. What makes cells and organisms different? How are cells organized in a complex multicellular organism? What makes an organism truly multicellular?. Diversity in Cells. Prokaryotes are always unicellular and limited in size.
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Biology Chapter 7 Section 3
Key Ideas • What makes cells and organisms different? • How are cells organized in a complex multicellular organism? • What makes an organism truly multicellular?
Diversity in Cells • Prokaryotes are always unicellular and limited in size. • Eukaryotes are often larger and can be either unicellular or multicellular. • Different organelles and features of cells enable organisms to function in unique ways in different environments.
Diversity in Prokaryotes • They can vary in shape, the way they obtain and use energy, the makeup of their cell walls, and their ability to move. • To move they either use flagella (long, threadlike structure) or pili (short, thick outgrowths that allow them to attach to surfaces)
Diversity in Eukaryotes • Animal and plant cells • Have many of the same organelles, but plant cells also have chloroplasts, central vacuole, and cell wall. • Structure varies according to their function. • Their internal makeup of cells are specialized for certain functions. Example: muscle cells, which use large amounts of energy, have many mitochondria.
Levels of Organization • Plants and animals have many highly specialized cells that are arranged into tissues, organs, and organ systems.
Tissues • Tissue: a distinct group of cells that have similar structures and functions. • Example: muscle tissue is a group of many cells that have bundles of cytoskeletal structures.
Organs • Different tissues may be arranged into an organ, which is a specialized structure that has a specific function. • Example: the heart is an organ made of muscle, nerve, and other tissues.
Organ System • Various organs that carry out a major body function that make up an organ system. • Example: The circulatory system is made up of the heart, blood vessels, and blood.
Body Types • Single cells can not grow larger than a certain size, multicellular organisms can be large. • A multicellular organism is composed of many individual, permanently associated cells that coordinate their activities. • Distinct types of cells have specialized functions that help the organism survive.
Cell Groups • Some unicellular organisms can thrive independently, but others live in groups. • Cells that live as a connected group but do not depend on each other for survival are considered colonial organisms.
Multicellularity • True multicellularity occurs only in eukaryotes. • The cells of a multicellular body perform highly specific functions. • Most multicellular organisms begin as a single cell. • The specialized cells are arranged into tissues, organs, and organ systems, making up the entire organism.