4-3 Multicellular Organization

4-3 Objectives

• Distinguish between tissues, organs and organ systems.

• Describe the features of a colonial organism.

Tissues, Organs, and Organ Systems

• Most multicellular organisms are organized into tissues.

• Tissues- groups of cells that carry out a specific function.

Tissues, Organs, and Organ Systems

• Ex: epithelial tissue, connective tissue, muscle tissue.

Blood Tissue

• Human Red Blood Cells, Platelets and T-lymphocyte (erythocytes = red; platelets = yellow; T-lymphocyte = light green) (SEM x 9,900). This image is copyright Dennis Kunkel at www.DennisKunkel.com, used with permission.

Tissues, Organs, and Organ Systems (cont.)

• Organ- several types of tissues that interact to perform a specific function.

Tissues, Organs, and Organ Systems (cont.)

• Ex: stomach contains epithelial, muscle, nervous and connective tissue

Tissues, Organs, and Organ Systems (cont.)

• Organ system – group of organs that work together to perform a set of related tasks.

• Systems interact to carry out life processes.

Tissues, Organs, and Organ Systems (cont.)

• Digestive system includes, mouth, esophagus, stomach, intestines, etc.

Tissues, Organs and Organ Systems (cont.)

• Plant cells include parenchyma, sclerenchyma, collenchyma, xylem, and phloem cells.

• Plant tissues include dermal, ground, and vascular tissue.

• Plant organs include flowers, stems, leaves, and roots.

• Plant organ systems include shoots and roots.

Evolution of Multicellular Organisms

• Colonial Organizations– Colonies- temporary groups of eukaryotic

cells of the same kind– Colonial organism – a collection of genetically

identical cells that live together in a connected group.

Evolution of Multicellular Organisms

• Individual cells of a colonial organism may have specific functions.

• Ex: Outside cells of Volvox colonies have flagella that propel the colony through the water.

Evolution of Multicellular Organisms

• Volvox exhibits specialization but lacks tissues and organs; therefore it is a unicellular colony and not a multicellular organism.

Volvox

Evolution of Multicellular Organisms

• Research indicates that multicellular organisms evolved from colonial organisms.