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 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.