Animal Form and Function at All Levels of Organization

Overview of Animal Structure and Function

• All organisms obtain nutrients and oxygen, fight infection, and reproduce.

• Anatomy: Biological structure of organisms.

  • Varies due to natural selection and adaptations.

  • Form fits function (physiology).

  • Convergent adaptation: Similar solutions to similar environmental challenges in unrelated species.

• Physical laws constrain physical shape.

  • Example: Law of maximum size – thicker skeletons, larger muscles, slower movement in large animals.

Animal Exchange with Environment

• Animals exchange nutrients, waste, and gases with the environment.

• Rate of exchange is proportional to membrane surface area.

• Amount of material to be exchanged is proportional to total volume.

• Multicellular organisms must have access to aqueous environment for exchange.

• Highly folded organs increase surface area for exchange.

• Types of fluids:

  • Interstitial fluid: Fluid in the space between cells.

  • Circulatory fluid: Blood.

  • Exchange with interstitial fluid allows body to take in nutrients and rid itself of wastes.

Homeostasis and Body Systems

• Complex body systems regulate homeostasis (internal balance).

• Cells → tissues → organs → organ systems.

• Organs may have multiple roles (e.g., pancreas: digestive and endocrine).

Types of Animal Tissue

• Epithelial tissue: Covers organs and cavities, forms barriers.

  • Polarized: Different sides have different functions.

• Connective tissue: Holds tissues and organs together.

  • Cells in extracellular matrix (fibroblasts, reticular fibers, macrophages).

  • Examples: Tendons, bone, adipose tissue, cartilage, blood.

• Muscle tissue: Body movement (actin and myosin filaments).

• Nervous tissue: Neurons transmit signals; glial cells nourish and support neurons.

Feedback Control and Homeostasis

Regulation of Internal Environment

• Regulator: Uses internal mechanisms to control internal change despite external changes.

• Conformer: Internal change in accordance with external changes.

Homeostasis Mechanisms

• Maintains variables (e.g., temperature) within a set point.

• Stimulus (fluctuation above/below set point) detected by a sensor.

• Control center signals response to return variable to set point.

• Negative feedback: Counters stimulus (e.g., temperature regulation).

• Positive feedback: Amplifies stimulus (e.g., childbirth).

Set Points and Biological Rhythms

• Set points for homeostasis can change (regulated changes).

• Circadian rhythm: Physiological changes that occur every 24 hours.

• Acclimatization: Adjustment to external environment (e.g., low oxygen at mountain → higher blood O2).

Thermoregulation in Animals

Heat Exchange and Temperature Regulation

• Endothermic: Heat from metabolism (mammals, birds).

  • Stable body temperature even if environment changes.

• Ectothermic: Heat from external environment (reptiles, amphibians, fish).

  • Consume less food, tolerate bigger changes.

• Homeotherm: Constant body temperature (temporary in some species).

• Exchange heat with environment:

  • Radiation: Electromagnetic waves (e.g., sun).

  • Evaporation: Removal of heat during evaporation.

  • Convection: Movement of air or liquid (breeze).

  • Conduction: Transfer of heat during contact (e.g., hot rock).

Heat Gain and Loss Mechanisms

• Integumentary system: Outer covering of body (skin, hair, feathers, fat, secreted oils).

• Insulation: Raises hair/feathers, blubber.

• Vasodilation/vasoconstriction: Blood vessel diameter changes to regulate heat loss.

• Countercurrent exchange: Arteries and veins exchange heat to minimize loss.

• Evaporative cooling: Sweat glands, panting, fluttering pouch in mouth.

• Thermogenesis: Shivering, increased metabolic activity to produce heat.

• Acclimation: Changing enzymes, shedding fur, adjusting membrane lipids.

• Hypothalamus: Sensor for thermoregulation; can induce fever.

Energy Requirements and Metabolic Rates

Bioenergetics

• Flow of energy in an animal.

• ATP: Cellular work, biosynthesis, growth, repair, gamete production.

Metabolic Rate

• Metabolic rate: Energy an animal uses in a given time interval.

• Basal metabolic rate (BMR): Minimum metabolic rate of a nongrowing endotherm at rest, empty stomach, no stress.

• Standard metabolic rate (SMR): Metabolic rate of fasting, nonstressed ectotherm at a particular temperature.

• Proportional to body mass:

• Smaller animals have higher metabolic rate per gram.

• Maximum metabolic rates: Peak activity.

Torpor and Hibernation

• Torpor: Physiological state of decreased activity and metabolism.

• Hibernation: Long-term torpor (winter cold and food scarcity).

• Estivation: Summer torpor (high temp and scarce water).

Animal Nutrition

Animal Diet and Essential Nutrients

• Animals require chemical energy, organic building blocks, and essential nutrients.

• Carbs, proteins, lipids.

• Vitamins: Required in small amounts (13 for humans).

• Minerals: Inorganic nutrients (iron, sulfur).

• Herbivores: Eat plants; Carnivores: Eat other animals; Omnivores: Eat both.

• Malnutrition: Diet lacking one or more essential nutrients.

• Essential amino acids: Amino acids that organisms cannot produce; must be consumed.

Food Processing

• Ingestion: Eating or feeding.

• Digestion: Food broken into molecules small enough to absorb.

  • Mechanical: Chewing or grinding.

  • Chemical: Cleaves large molecules (hydrolysis).

• Absorption: Animal cells absorb small molecules.

• Elimination: Undigested material passes out of digestive system.

Organs for Digestion

• Oral cavity: Mouth, where food processing begins (chewing).

• Salivary glands: Release saliva for lubrication, protection, and taste.

• Pharynx and esophagus: Food passage to stomach.

• Peristalsis: Muscle contractions move food through digestive tract.

• Stomach: Storage (2L), processes food into liquid (chyme), secretes gastric juice (acidic, pH 2), contains protease (pepsin).

• Small intestine: Most enzymatic hydrolysis of macromolecules; first 25 cm is duodenum (receives digestive juices from pancreas, liver, gallbladder).

• Liver: Produces bile (stored in gallbladder), detoxifies blood.

• Large intestine: Recovers water, forms feces, includes cecum (fermentation), appendix (minor immune function).

Digestive System Adaptations

• Teeth adapted for animal's diet.

• Large expandable stomachs in carnivores.

• Longer digestive tracts in herbivores for plant digestion.

Summary Table: Types of Animal Tissue

Summary Table: Types of Animal Diets

Key Equations

• Metabolic rate proportionality:

Additional info:

• Some context and terminology were expanded for clarity and completeness.

• Tables were inferred and constructed to summarize tissue and diet types.