Chpts 42 Lecture Notes In biology structure has a profound influence on function Biologists analyze the structure and function of animals at a variety of levels molecules cells tissues organs and organ systems Body size has a strong influence on how animals work in large part because a body s volume increases faster than its surface area as body size increases Animals use an array of methods to maintain a relatively constant environment inside their bodies homeostasis They have systems that sense changes in internal conditions and trigger responses that return conditions to normal Some animals have sophisticated systems for generating and conserving heat and regulating body temperature Anatomy is the study of an organism s physical structure Physiology is the study of how the physical structures in an organism function Tissues Organs and Systems If a structure found in an animal is adaptive The structure s size shape or composition will correlate with its function If a mutant allele alters the size and shape of a structure to make function more efficient individuals with that allele produce more offspring Allele will increase in frequency over time Correlations between form and function begin at the molecular level For example protein shape correlates with their role as enzymes structural components of the cell or transporters Similar function between structure and function occur at the cellular level For example cells that secrete digestive enzymes contain a lot of rough ER and Golgi Absorptive cells have a large surface area A tissue is a group of similar cells that function as a unit Adult tissue types are Connective Nervous Muscle and Epithelial Connective Tissue Consists of cells loosely arranged in a liquid jellylike or solid matrix secreted by the connective tissue cells themselves The nature of the matrix determines the nature of the connective tissue Types of connective tissue Loose connective tissue contains an array of fibrous proteins in a soft matrix ie reticular tissue and adipose tissue Dense connective tissue found in the tendons and ligaments connects muscles bones and organs Supporting connective tissue has a firm extracellular matrix ie bone and cartilage Fluid connective tissue cells surrounded by a liquid extracellular matrix ie blood Nervous tissue consists of nerve cells or neurons and several types of supporting cells Most neurons have two distinct types of projections from the cell body where the nucleus is located Short branching dendrites which transmit electrical signals from other cells to the cell body Long axons which carry electrical signals from the cell body to other cells Muscle tissue was a key innovation in the evolution of animals like nervous tissue it appears in no other lineage Muscle tissue functions in movement There are three types of muscle tissue 1 Skeletal muscle 2 Cardiac muscle 3 Smooth muscle Epithelial Tissue epithelia are tissues that cover the outside of the body line the surfaces of organs and form glands An organ is a structure that serves a specialized function and consists of several tissues A gland is a group of cells that secrete specific molecules or solutions Epithelia carry out several functions Protection Transport of water and nutrients Epithelial cells typically form layers of closely packed cells All epithelial tissue have polarity The apical side faces away from other tissues The basolateral side faces the animal s interior The basal lamina connects the epithelial to the connective tissue The apical and basolateral sides of an epithelium have distinct structures and functions apical side of an epithelium generally lines organs and secretes mucus ie lining of the esophagus basolateral side cements the apical to the basal lamina Surface Area Volume Relationships Theory The cell surface area determines the rate at which gases and nutrients diffuse across the membrane The cell volume determines the rate of diffusion As a cell gets larger its volume increases much faster than its surface area does The area volume affect the animal s overall physiology The physiological activity can be measured as the metabolic rate http www youtube com watch v xuG4ZZ1GbzI Surface Area Volume Relationships Data Metabolic rate is the overall rate of energy consumption Consumption of energy is measured as the basal metabolic rate The BMR is the rate at which an animal consumes oxygen while at rest with an empty stomach under normal temperature and moisture conditions measured in mL of O2 consumed per gram of body mass per hour 1 On a per gram basis small animals have higher BMRs than do large animals As an organism s size increases its mass specific metabolic rate must decrease or the surface area available for exchange of materials would fail to keep up with the metabolic demands of the organism Adaptations That Increase Surface Area Increases in surface area relative to its volume are achieved in three ways 1 Flattening ie fish gills have flattened sheetlike structures called lamellae 1 Folding ie mammal small intestine has folds called villi 1 Branching ie small blood vessels called capillaries are highly branched Homeostasis is the maintenance of relatively constant internal environment Internal chemical and physical states are kept within a tolerable range Constancy of physiological state can be achieved by conformation and or regulation Each variable has a set point a normal or target value A homeostatic system is based on three general components A sensor is a structure that senses some aspect of the external or internal environment An integrator is a component of the nervous system that evaluates the incoming sensory information and decides if a response is necessary to achieve homeostasis An effector is any structure that helps restore the desired internal condition Homeostatic systems are based on negative feedback in which effectors reduce or oppose the change in internal conditions ie changes in blood pH blood pressure How Do Animals Regulate Body Temperature Overheating can cause proteins to denature Protein denature can lead to dehydration Low body temperatures can slow down enzyme function and energy production Mechanisms of Heat Exchange All animals exchange heat with their environment in four ways 1 Conduction 2 Convection 3 Radiation 4 Evaporation Many animals can control their body temperature through the process of thermoregulation which includes 2 factors 1 How animals obtain heat An endotherm produces adequate heat