Basic Principles of Animal Form and Function

Chapter 40: Basic Principles of Animal Form and Function

Topics Covered

  • Cellular exchanges with the environment

  • Hierarchy of body plans

  • Epithelial, connective, muscle, and nervous tissues

  • Coordination of the endocrine and nervous systems

  • Homeostasis

  • Thermoregulation

  • Metabolic rate

Regulation of Internal State

  • Understanding how animals maintain their internal states in changing or harsh environments.

  • Role of adaptations in form, function, and behavior in maintaining internal environments.

    • Adaptations that limit variation in temperature and other internal variables are widespread and diverse.

    • Form (anatomy): Insulation reduces heat loss.

    • Function (physiology): Shivering produces heat.

    • Behavior: Packing together reduces exposure.

Correlation of Form and Function

  • 40.1 Form and Function Correlate at All Levels of Organization

    • Evolution of Animal Size and Shape:

    • Physical laws (gravity, heat, water properties) define the range of animal forms.

    • Evolutionary convergence reflects adaptations to similar environmental challenges.

    • Example species (Tuna, Penguins, Seals) exhibit:

      • Streamlined bodies for efficient swimming.

      • Mechanisms for buoyancy.

Exchange with the Environment

  • Dissolved substances must cross the plasma membrane of cells; the rate of exchange is proportional to membrane surface area.

  • The amount of material needing exchange is proportional to volume.

    • Example: A single-celled amoeba and hydra with two layers of cells demonstrate different scales of exchange.

  • Multicellular Animals:

    • Have branched or folded surfaces to facilitate substance exchange, utilizing interstitial fluid.

Hierarchical Organization of Body Plans

  • Four levels of organization:

    1. Cells: Basic unit of life.

    2. Tissues: Groups of cells with a common function.

    3. Organs: Functional units constructed from multiple tissue types.

    4. Organ Systems: Groups of organs that work collectively.

Structure and Function in Animal Tissues

  • Tissues Types:

    1. Epithelial Tissue:

    • Functions as covering/barrier.

    • Features: closely packed cells, distinct polarity (apical and basal surfaces).

    1. Connective Tissue:

    • Provides connection between body parts.

    • Has abundant extracellular matrix (ECM) and scattered cells.

    1. Muscle Tissue:

    • Responsible for body movement.

    1. Nervous Tissue:

    • Receives and processes information, facilitates responses.

Types of Epithelial Tissue

  • Stratified Squamous: Covers body surfaces, protection.

  • Pseudostratified Columnar: Secretion; found in respiratory tract.

  • Simple Squamous: Diffusion; seen in blood vessels and lungs.

  • Simple Columnar: Absorption; present in intestines.

  • Simple Cuboidal: Secretion; seen in renal tubules and glands.

Types of Connective Tissue

  • Loose Connective Tissue: Usually abundant in ECM and scattered cells.

  • Blood: Composed of red and white blood cells, plasma.

  • Cartilage: Contains chondrocytes and chondroitin sulfate.

  • Adipose Tissue: Stores fat droplets.

  • Bone: Structural support with osteons and central canals.

Types of Muscle Tissue

  • Skeletal Muscle: Voluntary, striated.

  • Smooth Muscle: Involuntary, non-striated; found in blood vessels.

  • Cardiac Muscle: Involuntary, striated; makes up the heart.

Nervous Tissue

  • Neurons: Responsible for impulse transmission.

    • Consists of dendrites, cell body, and axon.

  • Glial Cells: Support and insulate neurons.

Coordination and Control

  • Coordination among tissues, organs, and organ systems is essential.

    1. Endocrine System:

    • Hormones released into bloodstream, impacting distant cells with receptors.

    • Slow-acting but long-lasting effects.

    1. Nervous System:

    • Nerve impulses cause neurotransmitter release from neurons to various cells.

    • Fast-acting but short-lasting effects.

Feedback Control and Homeostasis

  • 40.2 Feedback Control Maintains the Internal Environment

    • Regulating: Maintains internal conditions despite external changes.

    • Conforming: Alters internal conditions in response to external changes.

    • Example: River otter (regulator) vs. Largemouth bass (conformer).

    • Homeostasis: A “steady state” or consistent internal balance despite external changes.

Mechanisms of Homeostasis

  • Set Point: Desired variable level.

  • Stimulus: Trigger inducing change.

  • Sensor: Detects stimulus and sends information.

  • Response: Action taken to return variable to set point.

    • Example: Thermostat mechanism regulating room temperature.

Feedback Control in Homeostasis

  • Most systems utilize Negative Feedback, where responses dampen the stimulus and restore balance.

  • Positive Feedback loops amplify stimulus and drive processes to completion but do not contribute to homeostasis.

Cyclic Alterations in Homeostasis

  • Circadian Rhythms: Physiological changes occurring every 24 hours, such as variations in body temperature and hormone concentration (e.g., melatonin).

    • Example: Fluctuations in core body temperature throughout the day.

Acclimatization vs. Adaptation

  • Acclimatization: Temporary adjustments to environmental changes (e.g., increased red blood cell production at high altitudes).

  • Adaptation: Long-term changes influenced by natural selection over many generations.

Thermoregulation

  • 40.3 Homeostatic Processes for Thermoregulation

  • Process by which animals maintain an internal temperature within acceptable limits.

  • Consequences of temperature imbalance:

    • Protein denaturation, altered reaction speeds, decreased enzyme activity, and impaired oxygen binding by hemoglobin.

Endothermy and Ectothermy

  • Endotherms: Generate heat mainly through metabolic processes, often maintaining constant internal temperatures (e.g., mammals).

  • Ectotherms: Obtain heat from external sources, leading to temperature variation with the environment (e.g., reptiles).

Mechanisms of Heat Exchange

  • Heat flows from warmer to cooler areas; methods of exchange include:

    1. Radiation: Emission of electromagnetic waves.

    2. Evaporation: Heat loss from liquid surfaces.

    3. Conduction: Heat transfer between contact objects.

    4. Convection: Heat transfer via air movement over a surface.

Balancing Heat Loss and Gain

  1. Insulation: Examples include hair, feathers, and fat.

  2. Circulatory Adaptations:

    • Vasodilation: Increases blood flow for heat dissipation.

    • Vasoconstriction: Decreases blood flow for heat conservation.

    • Countercurrent exchange: Heat transfer between fluids in opposite directions.

  3. Cooling Mechanisms:

    • Evaporation (e.g., sweating, panting).

  4. Behavioral Responses:

    • Seeking cooler or warmer environments etc.

  5. Metabolic Heat Production Adjustments:

    • Shivering Thermogenesis: Involuntary muscle contractions generate heat.

    • Nonshivering Thermogenesis: Metabolic processes producing heat without muscle contractions.

Acclimatization in Thermoregulation

  • Adaptations to seasonal changes (e.g., thicker fur in winter, altered plasma membrane composition).

  • Cryoprotectants: Like urea and glucose in wood frogs to prevent cell damage during freezing.

Physiological Thermostats

  • The hypothalamus acts as a thermostat controlling body temperature, responding to infection-induced fevers by activating cooling mechanisms.

Energy Requirements Related to Size and Activity

  • 40.4 Energy Requirements Are Related to Animal Size, Activity, and Environment

  • Bioenergetics: Overall flow and transformation of energy in an animal.

  • Nutrient molecules needed for ATP formation, which drives cellular work.

Measuring Metabolic Rate

  • Metabolic Rate: Amount of energy use in a unit of time, identifiable through heat loss, oxygen consumption, or carbon dioxide production measurements.

    • Basal Metabolic Rate (BMR): Energy use by endotherms at rest in comfortable conditions.

    • Standard Metabolic Rate (SMR): Energy use by ectotherms at rest at a specific temperature.

    • Ectotherms generally exhibit lower metabolic rates compared to similarly sized endotherms (e.g., average human male BMR = 1,600-1,800 kcal/day).

Influences on Metabolic Rate

  • Factors include: age, sex, activity level, body size, temperature, and nutrition.

    • Larger animals have higher metabolic energy needs, but per gram, this requirement decreases with size.

Energy Budgets

  • Energy allocation varies among species based on behavior, environment, and thermoregulatory needs, including BMR, activity, reproduction, and growth.

Torpor and Energy Conservation

  • Torpor: A physiological state conserving energy by lowering metabolic inactive periods; can last overnight or longer (e.g., hibernation).

  • Example: Arctic ground squirrel exhibits significant metabolic adjustments during winter.