Chapter 40 Basic Principles of Animal Form and Function Diverse Forms Common Challenges Anatomy Biological Form Natural Selection is why organisms vary extensively in organization and appearance Physiology Biological Function 40 1 ANIMAL FORM AND FUNCTION ARE CORRELATED AT ALL LEVELS OF ORGANIZATION An animals size and shape are fundamental aspects of form that significantly affect the way the animal interacts with its environment The body plan of the animal is the result of programming by the genome which is a product of evolution EVOLUTION OF ANIMAL SIZE AND SHAPE Physical laws that govern strength diffusion movement and heat exchange limit the range of animal forms For example the properties of water limit the possible shapes for animals that are fast swimmers because water is 1000 times denser than air Aquatic Environments tend to select for organisms that lack bumps Swimmers have adapted through convergent evolution In addition physical laws also influence animal body plans with regard to maximum size As body dimensions increase thicker skeletons are required for support This also affects internal skeletons Muscle mass must also increase with size EXCHANGE WITH THE ENVIORNMENT Animals need to exchange nutrients waste products and gasses with their environments and this requirement impose an additional limitation on body plans Exchange occurs as substances dissolved in an aqueous solution move across the plasma membrane of each cell Each cell has a plasma membrane across which diffusion can occur The rate of exchange is proportional to surface area of the membrane Flat Shapes help maximize surface area In addition a gastrovascular cavity can help maximize surface area because it is open to the external environment Humans and other animals are composed of compact masses of cells with an internal organization that is complex Increasing the number of cells decreases the ratio of outer surface area to volume Each cell must be bathed by fluid for diffusion to occur Failure to do so would result in death of a cell To maximize surface area mammals have developed specialized surfaces that are branched or folded to maximize exchange with the surrounding environment by increasing surface area Internal body fluids link exchange surfaces to body cells The spaces between cells are filled with fluid in many animals called INTERSTITIAL FLUID Complex body plans also include circulatory fluid such as blood to obtain nutrients and get rid of wastes Complex Bodies offer the following advantages External skeleton can protect against predators Sensory Organs provide details Internal digestive organs can break food down and control release of energy Specialized filtration can maintain a stable living environment by bathing animals body cells with fluid Really Important to land organisms where external environments may vary highly HIERARCHIAL ORGANIZATION OF BODY PLANS Cells form a working animal body through emergent properties which arise from successive levels of structural and functional organization Cells are organized into TISSUES which are organized into ORGANS which form ORGAN SYSTEMS which make up the ORGANISM Many organs contain tissues with distinct physiological roles sometimes one organ can belong to many systems PANCREAS The specialized and complex organ systems of animals are built from a limited set of cell and tissue types There are 4 main types of animal tissues Epithelial o Cover outside of body and lines organs and cavities o Closely packed in tight junctions This means they function as a barrier against mechanical injury pathogens and fluid loss o Polarity means they have 2 different sides Apical and Basal Cuboidal Simple Columnar Simple Squamous Pseudo stratified Connective Stratified Squamous o Consist of a sparse population of cells scattered through extracellular matrix and holds many tissues and organs together o Within matrix are numerous cells called fibroblasts which secrete fiber proteins and macrophages o 3 kinds Collagenous flexibility and strength Elastic elasticity Reticular Fibers join connective tissue to adjacent tissues o Major types of Connective Tissue formed from mixtures of the 3 kinds Loose Connective Fibrous Connective Bone Blood Adipose Cartilage Muscle o Responsible for movement Skeletal Smooth Cardiac Skeletal attached to bones via tendons Smooth lack striations and found in walls of digestive tract urinary bladder and other internal organs Cardiac forms contractile wall of heart Striated like skeletal Nervous o Responsible in receipt processing and transmission of information Contain neurons or nerve cells which transmit nerve impulse as well as support cells called gilal cells or gilia Concentration of nervous tissue forms brain Neurons Basic units of nervous system Receives impulses via dendrites Axons transmit impulses COORDINATION AND CONTROL Tissues organs and organ systems act in concert with one another and the endocrine and nervous system aid in this The ENDOCRINE SYSTEM has signaling molecules released into the bloodstream by endocrine cells and are carried to all locations of the body The endocrine system uses hormones to broadcast messages The effects of hormones can be long lasting because they can remain in the bloodstream for a long time The NERVOUS SYSTEM has neurons transmitting signals along dedicated routes connecting specific locations in the body Nerve impulses travel to specific target cells along communication lines consisting primarily of axons THE NERVOUS SYTEM CONVEYS INFORMATION ON A PARTICULAR PATHWAY UNLIKE THE ENDOCRINE SYSTEM WHICH USE THE BLOODSTREAM The variation in signal type transmission speed and duration make the 2 systems adapted to different functions The endocrine system is better suited for coordinating gradual changes across the entire body growth development while the nervous system is suited for rapid responses THE 2 SYSTEMS MAY VARY IN FUNCTION BUT WORK IN COHESION 40 2 FEEDBACK CONTROL MAINTAINS THE INTERNAL ENVIRONMENT IN MANY ANIMALS REGULATING AND CONFORMING An animal is a REGULATOR for an environmental variable if it uses internal mechanism to control internal change in the face of external fluctuation For example the Otter controls its own body temperature An animal is a CONFORMER if it allows internal condition to change in accordance with external changes in the variable Reptiles and their blood HOMEOSTASIS Organisms must perform homeostasis maintain a stable living environment for it to survive