The Hierarchy of Structure in Animals

Hierarchy with in Animals’ Bodies There are levels of organization within each animal with the most complex at the top and least complex at the bottom. Starts with cell, groups of cells with the same specialty make the tissue, in different organs different types of tissues are involved, different organ systems are made of different organs.

Levels of Organization All animals (incl. humans) have bodies made up of cells organized in a hierarchy (levels of organization of increasing or decreasing complexity). The Hierarchy: Cells- the most basic unit of living things. Tissue- any group of similar cells that performs the same specific function (eg. Muscle, bone, blood, skin, nerve tissue). Organ- A structure made up of two or more types of tissue that work together to complete a specific task. Organ System – One or more organs and other structures that work together to perform a body function. Organism – A complex individual that can perform functions such as eat, breathe, move and reproduce.

Any animal tissue belongs to one of four main tissue types Epithelial tissue Connective tissue Muscle tissue Nerve tissue

Tissue Types Tissues: groups of similar cell types that perform a common function. Histology: the study of tissues.

Ex.: skin and lining of digestive tract. Function: protect surfaces from dehydration and make low friction surfaces. Thin sheets of tightly packed cells covering surfaces and lining internal organs. Single layered or multi-layered.

Ex.: bones and tendons and blood Function is to support and insulate, and protect internal organs. Various types of cells and fibers held together by a liquid, a solid, or a gel, known as a matrix.

Ex.: brain and sensory organs. Nerve Tissue Ex.: brain and sensory organs. Function is to communicate with the body and environment, coordinate body functions Long, thin cells with fine branches at the ends capable of coducting electricity impulses.

Ex.: muscles that make bones move, surround digestive tract, and heart. Some contract voluntarily, some involuntarily. Function is movement. Bundles of long cells called muscle fibers. They are capable of shortening and contracting

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