Multicellular Organization

Submitted By JKracke77
Words: 3772
Pages: 16

Multicellular Organization * Some organizations are unicellular * Bodies of plants, and especially animals, are organized on the basis of tissues, organs, and organ systems
* Composed of many cells that are similar in both structure and functional unit in organisms

Organ * Is a group of various tissues that form a structural and functional unit in organisms
Organ Systems * Group of interacting organs that form a functional complex and the life of the organisms
* Chloroplast (autotrophs) * Cell wall * Large vacuole * Few cell types * Cells not organ specific * Indeterminate growth * Growth restricted to certain zones – meristems
* No chloroplast (heterotrophs) * No cell wall * Small vacuole * Many cell types * Cells organ specific * Determinate growth * Growth nonspecific
Plants Tissues * Hard to classify because different cell types are often similar and one type of cell can change into another type of cell * 2 major categories: * Meristematic tissues * Permanent tissues
Meristematic Tissues * Composed of immature, undifferentiated cells * Region of active cell division * Cells tend to be small, have thin cell wall, and rich in cytoplasm * In very young plant almost all cells are meristematic, as plant grows meristematic differentiates into permanent tissue * Mature plants 2 regions of meristematic activity * Apical meristems – at tips of roots and stems and causes increase in life * In woody plants there is also a lateral meristem (cambium) – at bottom of stems and roots and causes increase in girth of plant * Basal meristem * E.g. grasses
Permanent Tissues * Composed of mature, differentiated cells * May go back to meristematic activity under certain conditions * 3 subcategories * Surface tissue * Forms the protective outer covering of plant, covers stems, leaves, and roots * Epidermis – surface tissue in all young plants and adult herbaceous plants * Surface tissue of all leaves * May be one cell thick or many cells thick * Cells are flat with large vacuoles so there is little cytoplasm * Arial epidermis may have a waxy outer layer called a cuticle * Periderm * Eventually replaces the epidermis in plants with an active lateral meristem * Commonly known as bark * Cells are actually dead, only cell walls remain * Fundamental tissue * Any tissue that isn’t surface tissue or vascular tissue * Parenchyma * Thin cell walls and a large vacuole * Loosely packed * Unspecialized vegetative cells – still divide and differentiate * Collenchyma * Similar to parenchyma but cell walls are thickened at corners * Provide support for the plant

* Sclerenchyma * Dead at maturity, very thick cell walls * One type is elongated and other is irregular * Elongated is fiber * Irregular is sclereid * Endodermis (inner skin) * Layer surrounding vascular tissue of roots and sometimes stems * Similar to parenchyma but has a casparian strip – prevents follow of water between cells * Vascular tissue * Only found in the higher plants (more advanced) * Moves water and nutrients around in the plant * Xylem * Transports water and nutrients upward in plant * Several types of cells involved, so it’s a complex tissue * Some cells are dead but others are living * Phloem * Moves water and nutrients upward and downward * Especially…