Animal Anatomy and Physiology

Diverse Forms, Common Challenges

• Anatomy refers to the biological form of an organism.
• Physiology refers to the biological functions an organism performs.
• Comparative animal studies reveal a close correlation between form and function.
• Many structures are specialized for particular functions.

Animal Size and Shape Evolution

• Physical laws govern strength, diffusion, movement, and heat exchange.
• Properties of water limit possible shapes for fast-swimming animals.
• Convergent evolution leads to similar adaptations in diverse organisms facing the same challenge.
• Thicker skeletons are required as animals increase in size for support.

The Body Plan

• Size and shape affect the way an animal interacts with its environment.
• The body plan is programmed by the genome.

Exchange with the Environment

• Materials like nutrients, waste products, and gases are exchanged across cell membranes.
• The rate of exchange is proportional to a cell's surface area.
• The amount of exchange material is proportional to a cell's volume.
• A single-celled organism in water has sufficient surface area for exchange.
• Multicellular organisms with a saclike body plan have thin body walls for diffusion.
• Complex organisms adapt specialized structures for sufficient exchange.
• Interstitial fluid links exchange surfaces to body cells in animals.
• A complex body plan helps maintain a stable internal environment.

Hierarchical Organization

• Most animals' cells are organized into tissues with different functions
• Tissues form organs, which create organ systems
• Some organs, like the pancreas, belong to multiple organ systems.

Tissue Types

• There are four main tissue types: epithelial, connective, muscle, and nervous.

Epithelial Tissue

• Epithelial tissue covers the body's exterior and lines organs and cavities.
• Epithelial cells are closely joined
• Epithelial cells' shape can be cuboidal, columnar, or squamous.
• Epithelial cell arrangements can be simple, stratified, or pseudostratified.

Connective Tissue

• Connective tissue binds and supports other tissues.
• Connective tissue contains sparsely packed cells in an extracellular matrix.
• The matrix is of fibers in a liquid, jellylike, or solid foundation.
• Collagenous fibers give strength and flexibility.
• Reticular fibers connect it to adjacent tissues.
• Elastic fibers allow stretching and snapping.
• Fibroblasts secrete proteins of extracellular fibers.
• Macrophages are involved in the immune system.
• Loose connective tissue binds epithelia and holds organs.
• Fibrous connective tissue is in tendons and ligaments.
• Bone is mineralized and supports the skeleton.
• Adipose tissue stores fat.
• Blood has cells and fragments in plasma.
• Cartilage provides strong, flexible support.

Muscle Tissue

• Muscle tissue enables nearly all body movement with actin and myosin filaments.
• Skeletal muscle enables voluntary movement.
• Smooth muscle enables involuntary activities.
• Cardiac muscle contracts the heart.

Nervous Tissue

• Nervous tissue accepts, processes, and transmits information.
• Neurons transmit nerve impulses.
• Glial cells or glia, support cells.

Coordination and Control

• Control and coordination depend on the endocrine and nervous systems
• The endocrine system releases hormones into the bloodstream.
• A hormone may affect multiple regions.
• Hormones have long-lasting effects and coordinate gradual changes.
• The nervous system transmits information between specific locations.
• Conveyed information depends on pathway, not signal type.
• Nerve signal transmission is fast, involving nerve impulses and chemical signals.
• The endocrine and nervous systems coordinate rapid responses.

Feedback Control

• Manage internal environment by regulating or conforming to environmental fluctuations.
• Regulators use internal mechanisms to control fluctuations.
• Conformers allow internal conditions to vary.
• Animals may regulate some variables while conforming to others.

Homeostasis

• Organisms use homeostasis to maintain a steady state or internal balance.
• Body temperature, blood pH, and glucose concentration are regulated
• Fluctuations from a set point trigger a response.
• A control center generates a response, returning the variable to the set point.
• Acclimatization enables adaptation in external environments.
• Acclimatization is a temporary change.

Thermoregulation

• Thermoregulation maintains internal temperature.
• Endothermic animals generate heat; birds and mammals are endotherms.
• Ectothermic animals gain heat from external sources.
• Endotherms maintain stable body temperatures even with large environmental fluctuations.
• Endothermy is more energy expensive than ectothermy.
• Ectotherms tolerate greater internal temperature variation.
• Poikilotherm body temperature varies with its environment.
• Homeotherm body temperature is constant.

Heat Exchange

• Organisms exchange heat through radiation, evaporation, convection, and conduction.

Heat Regulation

• Mammal heat regulation involves the integumentary system: skin, hair, and nails.
• Insulation reduces heat flow, important in marine mammals.
• Blood flow regulation affects thermoregulation.
• Vasodilation increases blood flow and heat loss.
• Vasoconstriction decreases blood flow and heat loss.
• Countercurrent exchange transfers heat between fluids flowing in opposite directions.
• Arteries and veins are adjacent with opposite flow.
• Evaporation cools bodies by sweating or bathing.
• Panting increases cooling.
• Ectotherms/endotherms use behavior to control body temperature.
• They seek warm places or orient towards heat sources to warm up in the cold.
• They bathe, move, huddle, or change orientation to cool down when warm.
• Thermogenesis adjusts heat production.
• Increased by muscle activity/shivering and in birds/reptiles.
• Nonshivering thermogenesis activates mitochondria.
• Brown fat is specialized for rapid heat production and is found in infants and hibernating specimens.
• Acclimatization has varied insulation
• Lipid composition changes.
• Some ectotherms produce "antifreeze" compounds.
• The hypothalmus regulates temperature.
• Fever increases a biological thermostat.
• Some ectotherms increase temperature

Energy Requirements

• Bioenergetics transforms it in an animal.
• Determines nutritional needs
• Relates to size, activity, and environment
• Organisms harvest food as energy source.
• Autotrophs harness light energy into energy-rich molecules.
• Heterotrophs, harvest food as chemical energy.
• Metabolism provides ATP for body/cell function and work.
• Remaining molecules create biosynthesis, growth, repair, stores and gametes

Quantifying Energy Use

• Metabolic rate sums energy use; can be determined by:
  • Heat loss (calorimetry)
  • Oxygen/carbon dioxide (indirect calorimetry)
  • Amount of food vs. wasted energy content used
• Basal metabolic rate (BMR): endotherm rate when resting.
• Standard metabolic rate (SMR): ectotherm rate when resting
• Must be non-growing, fasting, non-stressed specimen.
• Ectotherms have lover rates than endoderms of comprable size
• Adult male BMR: 1600-1800 kcal/day.
• Adult female: 1300-1500 kcal/day
• Alligator SMR at 20C is 60 kcal/day

Influences on Rate

• Activity affects metabolic rate of any specimen, with a inverse duration relationship
• Terrestrial's use 2x-4x their BMR/SMR
• Activity uses a fraction of energy based on size, thermoregulation, environment, etc.
• Torpor reduces activity
• It saves animals energy from dangerous conditions
• long-term winter is known as hibernation

size and metabolic rate

• It is proportional to body mass to .75 power
• smaller are animals have higher metabolic rates and oxygen/blood volume comparative to larger animals