Animal Biology Notes

Animal Form and Function

  • Animals have distinct body plans limiting size and shape.
  • Anatomy (structure) and physiology (function) are studied in relation to the environment.

Body Plans

  • Symmetry types: asymmetrical, radial, bilateral.
  • Asymmetrical: no symmetry (e.g., sponges).
  • Radial: up-and-down orientation, equal halves along longitudinal axis (e.g., sea anemone).
  • Bilateral: right and left sides (e.g., goats).
  • Anterior (front), posterior (rear), dorsal (back), ventral (stomach).
  • Bilateral symmetry enables high mobility.

Limits on Animal Size and Shape

  • Aquatic animals: fusiform shape reduces drag.
  • Land animals: constrained by gravity.
  • Exoskeleton: hard covering for protection and muscle attachment; limits growth due to molting; made of chitin and calcium carbonate.
  • Apodemes: ingrowths for muscle attachment
  • Endoskeleton: muscles attached on the outside, more efficient for increased mass; size determined by skeletal and muscle mass.

Limiting Effects of Diffusion on Size and Development

  • Diffusion limits cell size; surface-to-volume ratio decreases with increasing size.
    • Surface Area = 4πr^2
    • Volume = (4/3)πr^3
    • Surface-to-volume ratio = 3/r
  • Multicellularity and specialization solve diffusion limits.
  • Circulatory and respiratory systems enhance nutrient and waste exchange.

Animal Bioenergetics

  • Energy from food converted to ATP.
  • Energy stored as glycogen or triglycerides.
  • Metabolism produces heat.
  • Endotherms (warm-blooded) conserve heat with insulation; ectotherms depend on environment.
  • Metabolic rate measured in joules, calories, or kilocalories.
  • BMR (basal metabolic rate) for endotherms; SMR (standard metabolic rate) for ectotherms.

Energy Requirements Related to Body Size

  • Smaller endotherms have higher BMR per body weight due to greater surface area.

Energy Requirements Related to Levels of Activity

  • More activity requires more energy.

Energy Requirements Related to Environment

  • Torpor: decreased activity and metabolism to survive adverse conditions.
  • Hibernation: long-term torpor during winter.
  • Estivation: torpor during summer.
  • Daily torpor: conserves energy during coldest parts of the day.

Animal Body Planes and Cavities

  • Sagittal plane: divides body into right and left.
  • Midsagittal plane: equal right and left halves.
  • Frontal (coronal) plane: separates front and back.
  • Transverse (horizontal) plane: divides into upper and lower.
  • Dorsal cavity: contains cranial and vertebral cavities.
  • Ventral cavity: contains thoracic (pleural and pericardial) and abdominopelvic cavities.

Animal Tissues

  • Four primary types: epithelial, connective, muscle, nervous.

Epithelial Tissues

  • Cover organs and line lumens.
  • Classified by cell shape and number of layers.
  • Simple: single layer; stratified: multiple layers.
  • Types: squamous, cuboidal, columnar, transitional.
  • Squamous: flat, irregular; diffusion (e.g., lungs, capillaries); protection (e.g., skin, mouth).
  • Cuboidal: cube-shaped; secretion and absorption (e.g., glands, renal tubules).
  • Columnar: tall, narrow; absorption (e.g., digestive tract); pseudostratified (e.g., respiratory tract).
  • Transitional: changes thickness (e.g., urinary bladder).

Connective Tissues

  • Matrix of living cells and ground substance (organic and inorganic).
  • Fibroblasts produce fibers.
  • Collagen: strength.
  • Elastic: flexibility.
  • Reticular: support network.
  • Types: loose/areolar, fibrous, cartilage, bone, adipose, blood.
  • Loose/Areolar: around blood vessels, organs; tough and flexible.
  • Fibrous: dense collagen; irregular (e.g., skin), regular (e.g., tendons, ligaments).
  • Cartilage: chondrocytes in lacunae; hyaline, elastic, fibrocartilage.
  • Bone: osseous tissue; organic and inorganic matrix; osteoblasts, osteocytes, osteoclasts.
  • Compact bone: osteons with Haversian canals.
  • Spongy bone: trabeculae.
  • Adipose: adipocytes store fat; insulation and cushioning.
  • Blood: matrix (plasma); erythrocytes, leukocytes, platelets.

Muscle Tissues

  • Three types: smooth, skeletal, cardiac.
  • Smooth: no striations, involuntary; visceral organs.
  • Skeletal: striations, voluntary; skeletal muscles.
  • Cardiac: striations, involuntary; heart; intercalated discs.

Nervous Tissues

  • Neurons transmit electrical impulses.
  • Cell body, dendrites (receive), axon (transmit).
  • Glial cells: astrocytes (chemical environment), oligodendrocytes (insulation).

Homeostasis

  • Maintaining dynamic equilibrium.
  • Set point: target value.
  • Stimulus, receptor, control center, effector.

Negative Feedback Mechanisms

  • Reverses the stimulus.
  • Example: blood glucose (insulin and glucagon) and blood calcium (PTH) levels.

Positive Feedback Loop

  • Maintains the direction of the stimulus.
  • Examples: blood clotting, uterine contractions (oxytocin).

Set Point

  • Can be adjusted (e.g., blood pressure).
  • Acclimatization: changes in organ systems to maintain set point (e.g., altitude, seasonal coats).

Homeostasis: Thermoregulation

  • Body temperature affects enzyme activity.

Endotherms and Ectotherms

  • Ectotherms: body temperature varies with environment.
  • Endotherms: maintain constant body temperature.
  • Heat exchange: radiation, evaporation, convection, conduction.

Heat Conservation and Dissipation

  • Insulation (fur, fat, feathers).
  • Vasodilation and vasoconstriction.
  • Countercurrent heat exchange.
  • Behavioral changes.
  • Metabolic waste heat and shivering.
  • Brown fat.

Neural Control of Thermoregulation

  • Hypothalamus maintains set point.
  • Endogenous pyrogens cause fever.