5.40 Animal form and function

• How animals regulate their internal state in changing or harsh environments


  • Adaptation in form, function and behavior help maintain an animal's internal environment
  • Adaptations that limit variation in temperature and other internal variables are widespread and diverse
• Form (anatomy)


  • Insulating reduces heat loss
• Function (physiology)


  • Shivering produces heat
• Behavior


  • Packing together reduces exposure
• Animal form and function are correlated at all levels or organization
• What all animals must do


  • Obtain nutrients and oxygen
  • Fight off infection
  • Survive to produce offspring
• Anatomy


  Biological structure (form)
• Physiology


  Biological function
• Biological structure and function are correlated
• Size and shape


  • Affect the way an animal interacts with its environment
  • The body plan (pattern of development) of an animal is programmed by the genome, itself the product of millions of years of evolution
• Evolution of Animal size and shape


  • Physical laws that govern strength, diffusion, movement, and heat exchange limit the range of animal forms
  • Convergent evolution often results on similar adaptations of diverse organisms facing the same challenge
  • Physical laws influence max size. At some point mobility becomes limited
• Exchange with the Environment

  • Materials such as nutrients, waste products, and gases must be exchanged across the plasma membranes of animal cells
  • Single-celled organism living in water has sufficient surface are to carry out all necessary exchange
  • Multicellular organisms with a cylindrical body plan have body walls that are only two cells thick, facilitating diffusion of materials
  • Exchange occurs at the outer surface and inside the gastrovascular cavity
  • In flat animals (I.e tapeworms) most cells are in direct contact with their environment
• Exchange with the Environment


  • Evolutionary adaptions such as specialized, extensively branched or folded structures enable sufficient exchange with the environment
  • The exchange surfaces are usually internal but are connected to the environment via openings
  • A complex body plan helps an animal living in a variable environment to maintain a relatively stable internal environment
• Hierarchical Organization of Body Plans


  • Animal body is composed of cells organized into tissues that have common functions
  • Different tissues are organized into functional units called organs, which together make up the organ system
  • Sponges lack organs or true tissue
  • Some organs have more than one physiological functions
• Four main types of animal tissues


  • Epithelial
  • Connective
  • Muscle
  • Nervous
• Epithelial Tissue


  • Epithelial cells are closely packed, act as tight junctions, and can function as a barrier
  • The shape of epithelial cell may be cuboidal, columnar or squamous
  • The arrangement of epithelial cells may be simple, stratified or pseudostratified
  • All epithelia are polarized (have 2 different sides)
• Connective tissue


  • Connective tissue mainly holds many tissues and hold organs in place
  • It contains sparsely packed cells scattered throughout
  • There are three types of connective tissue fiber, all made of protein
• Six major types of connective tissue in vertebrates


  • Loose connective tissue
  • Fibrous connective tissue
  • Bone
  • Adipose tissue
  • Cartilage
  • Blood
• Muscle


  • Muscle tissue is responsible for nearly all types of body movement
  • Muscles cells consist of filaments of the protein's actin and myosin, which together enable muscles to contract
  • Skeletal muscle, Smooth muscle, Cardiac muscle
• Nervous tissue


  • Nervous tissue functions in the receipt, processing, and transmission of information
  • Nervous tissue contains neurons and glial cells
• Coordination and control


  • Animals have two major systems for coordinating and controlling responses to stimuli: the endocrine and the nervous system
  • The endocrine system releases signaling molecules called hormones into the bloodstream
  • The nervous system transmits information between specific locations
  • The endocrine system is well adapted for coordinating gradual changes that affect the entire body
  • The nervous system is well adapted for directing immediate and rapid responses to the environment
  • Both systems work in close coordination to maintain a stable internal environment
• Feedback control maintains the internal environment in many animals


  • Regulator uses internal control mechanisms to control internal change in the face of external fluctuation
  • Conformer allows its internal condition to change in accordance with external changes
  • Homeostasis in animals relies largely on negative feedback, which helps return a variable to normal range
  • Positive feedback amplifies a stimulus and does not usually contribute to homeostasis in animals
• In humans, body temperature (37C), blood pH (~7.4), and glucose concentration are each maintained at a constant level
• Hyperglycemia can damage the vessels that supply blood to vital organs, which can increase the risk of heart disease and stroke, kidney disease, vision problems and nerve problems
• Positive feedback helps drive a process (such as childbirth) to completion. Oxytocin stimulate
• Conformer


  Allows its internal condition to change in accordance with external changes
• Homeostasis


  Maintaining a "steady state" or internal balance regardless of external environment
• Homeostasis in animals relies largely on negative feedback, which helps return a variable to normal range
• Hyperglycemia


  Can damage the vessels that supply blood to vital organs, which can increase the risk of heart disease and stroke, kidney disease, vision problems and nerve problems
• Positive feedback


  Amplifies a stimulus and does not usually contribute to homeostasis in animals
• Positive feedback helps drive a process (such as childbirth) to completion. Oxytocin stimulates the muscles contractions that push the baby through the birth canal
• Thermoregulation


  Process by which animals maintain an internal temperature within a normal range
• Endothermic animals


  Generate heat by metabolism; birds and mammals are endotherms
• Endotherms


  Can maintain a stable body temperature even in the face of large fluctuations in environmental temperature
• Ectothermic animals


  Gain heat form external sources (i.e. sunlight, heated rock surfaces)
• Ectotherms include most invertebrates, fishes, amphibians, and nonavian reptiles (turtles, snakes)
• In general, ectotherms tolerate greater variation in internal temperature
• Thermoregulation


  • Depends on animal's ability to control the exchange of heat with its environment
• Exchange of heat


  1. Radiation

  2. Evaporation

  3. Convection

  4. Conduction
• Adaptations that help animals thermo-regulate


  • Insulation (insulating layers)
  • Circulatory adaptations (blood flow)
  • Cooling by evaporative heat loss (sweat glands, panting)
  • Behavioral responses
  • Adjusting metabolic heat production