Biology 201 Dr. Edwin DeMont St. Francis Xavier University Cells, Tissues, Organs, and Organ Systems of Animals

Hierarchy St. Francis Xavier University Multicellular animals are organized in a complex manner which starts with small single cells and builds into a large living entity.

Cells St. Francis Xavier University Cells are the basic functional units of all animals. Cell size ~ 10 μm

Tissues St. Francis Xavier University Tissues are specialized groups of cells adapted for a particular function. Tissue size ~ 100 μm to 10 cm

Tissues St. Francis Xavier University Four types of tissues: 1.Epithelial tissue: Many forms and functions 2.Connective tissue: Connection and support 3.Nervous tissue: Communication 4.Muscle tissue: Movement

Tissues St. Francis Xavier University Epithelial tissue Structure: Covers or lines structures and is bounded by a basement membrane. Function: Absorption, transport, excretion, protection and sensory reception. Simple columnar epithelium Location: Lines digestive tract Function: Absorption, enzyme secretion. (Arrow shows a goblet cell that secretes mucus.)

Tissues St. Francis Xavier University Connective tissue Structure: Cells are embedded in an extracellular matrix, usually with many fibers. Function: Support and bind other tissues. Fibrocartilage Location: Intervetebral disks Function: Absorbs compressive shock. (Arrow shows a fibroblast)

Tissues St. Francis Xavier University Nervous tissue Structure: Composed of neurons and glial cells which support the neurons. Function: Transmits electrical signals from sensory receptors to the spinal cord or brain. Nervous tissue Location: Brain and spinal cord

Tissues St. Francis Xavier University Muscle tissue Three kinds of muscle tissue: 1.Skeletal 2.Smooth 3.Cardiac Function: Allows movement Cardiac muscle tissue Location: The walls of the heart (Arrow shows intercalated disks which allow rapid transmission of action potentials.)

Organs St. Francis Xavier University Organs are function units composed of different types of tissues. Organ size ~ 0.1 to 100 cm

Organ systems St. Francis Xavier University An organ system is a group of organs with a particular function. Organ system size ~ to 10 m?

Animals St. Francis Xavier University All parts of the animal body function to create an individual. Complex control systems maintain a constant internal environment. This state is called homeostasis.

Homeostasis St. Francis Xavier University Many physiological systems operate around a Set Point, in which the organ systems monitor and maintain the body at the Set Point. Control systems operate with a feedback loop. Temperature regulation in houses is an example of a feedback loop.

Body Temperature St. Francis Xavier University Animals which maintain a relatively constant core body temperature are called homeotherms. The hypothalamus is the temperature-regulating center that functions as a thermostat with a fixed set point. Why do homeotherms control body temperature?

Body Temperature St. Francis Xavier University How do animals generate (or maintain) heat if body temperature drops below the Set Point?

Body Temperature St. Francis Xavier University How do animals release heat if body temperature rises above the Set Point?

Animal Size St. Francis Xavier University The range of sizes of animals is very large GroupLength RangeFactor Insects to m1000 Fish to m1000 Does this size range impact the biology of animals?

Animal Size St. Francis Xavier University YES!!!! Almost every aspect of animal biology that we talk about for the rest of class is impacted by animal size.

Animal Size St. Francis Xavier University SA → l 2 V → l 3 SA/V → 1/l Isometric objects: Increase in size but do not change shape. The “geometric” problem that impacts much of animal biology.

Animal Size St. Francis Xavier University CatElephant Animals are allometric (change shape as they grow).

Allometry St. Francis Xavier University SA → l 2 V → l 3 SA/V → 1/l Y = a X b log Y = log a + b log X For a set of isometric objects (like the spheres) the slope of the line will be 2 (SA) and 3 (V).