Animal Form and Function

Lecture Objectives

• Appreciate the role of physical laws and the environment in restricting animal size/shape.
• Recognize the different types of tissues that determine structure and function.
• Understand the basis of homeostasis.
• Compare the characteristics of ectotherms and endotherms.
• CLO 1, 2, 3

Natural Selection

• Natural selection can fit structure/anatomy to function/physiology over generations by selecting the variations in a population that work best.
• Physical laws and the environment limit animal size and shape.
• Physical laws and the need to exchange materials with the environment place limits on animal forms.

Evolutionary Convergence

• Evolutionary convergence reflects different species' independent adaptation to similar environmental challenges.

Exchange with the Environment

• An animal's size and shape directly affect how it exchanges energy and materials with surroundings.
• Exchange with the environment occurs as substances dissolved in the aqueous medium diffuse and are transported across cells' plasma membranes.

Single-celled Organisms

• Single-celled organisms living in water have sufficient plasma membrane surface area to service the entire volume of cytoplasm.

Multicellular Organisms

• Multicellular organisms exist with a sac body plan.
• Sac body plans have body walls only two cells thick, facilitating diffusion of materials.

Internal Exchange Surfaces of Complex Animals

• Organisms with complex body plans have highly folded internal surfaces specialized for exchanging materials.

Cells, Tissues, Organs

• Animal form and function are correlated at all levels of organization.
• Animals are composed of cells.
• Groups of cells with a common structure and function make up tissues.
• Different tissues make up organs, which together make up organ systems.

Tissue Structure and Function

• Different types of tissues have different structures suited to their functions.
• Tissues are classified into four main categories: epithelial, connective, muscle, and nervous.

Epithelial Tissue

• Epithelial tissue covers the body's outside, lines organs/cavities, and contains closely joined cells.
• Stratified squamous epithelium is multilayered, regenerates quickly, and has a protective function.
• Pseudostratified epithelium is a single layer of cells that lines the upper-respiratory tract, inner ear, vas deferens, prostate gland, epididymis, and endometrium.
• Simple squamous epithelium lines blood vessels/body cavities and regulates the passage of substances.
• Simple columnar epithelium is a single layer of tall/slender columnar epithelial cells with oval-shaped nuclei in the basal region; in humans, it lines most digestive tract organs.
• Cuboidal epithelium has equal width/height/depth in appearance and lines kidney tubules/bronchioles as well as secretory gland ducts like the pancreas, thyroid, salivary glands, ovaries, and testes.

Connective Tissue

• Connective tissue binds and supports other tissues.
• Contains sparsely packed cells scattered throughout an extracellular matrix.
• Bone, blood, loose connective tissue, fibrous connective tissue, adipose tissue and cartilage are all connective tissues.

Muscle Tissue

• Muscle tissue is composed of long cells called muscle fibers that contract in response to nerve signals.
• Muscle tissue in the vertebrate body consists of three types: skeletal, cardiac, and smooth.
• Nervous tissue senses and transmits stimuli/signals.

Organs and Organ Systems

• Tissues are organized into organs, which represents a higher level of organization among all but the simplest animals.
• Organ systems carry out the major body functions of most animals.

Organ Systems

• The digestive system's components are the mouth, pharynx, esophagus, stomach, intestines, liver, pancreas, and anus, and its main function is food processing from ingestion to elimination.
• The circulatory system's components are the heart, blood vessels, and blood.
• The function of the circulatory system is the internal distribution of materials.
• The respiratory system consists of lungs, trachea, and other breathing tubes which function in gas exchange.
• The Immune and lymphatic system's components are bone marrow, lymph nodes, thymus, spleen, and lymph vessels, which function in body defense.
• The excretory system consists of the kidneys, ureters, urinary bladder, and urethra, and functions in disposal of metabolic wastes and regulation of osmotic balance.
• The endocrine system includes the pituitary, thyroid, pancreas, adrenal, and other hormone-secreting glands to coordinate body activities such as digestion and metabolism.
• Reproductive systems include ovaries/testes and associated organs, to produce gametes, promote fertilization, and support embryo development.
• The nervous system includes the brain, spinal cord, nerves, and sensory organs, to coordinate body activities, detect stimuli, and formulate responses.
• The integumentary system includes the skin and its derivatives, such as hair, claws, and sweat glands for protection against injury/infection, dehydration, and thermoregulation.
• The skeletal system consists of the skeleton (bones, tendons, ligaments, cartilage) and its function is body support and protection of internal organs and movement.
• The skeletal muscles are the components of the muscular system, which functions in locomotion and other movement.

Animals and Energy

• Animals use the chemical energy in food to maintain form and function.
• All organisms require chemical energy for growth, repair, physiological processes, regulation, and reproduction.

Bioenergetics

• Bioenergetics refers to the flow of energy through an animal to determine its behavior, growth, and reproduction.
• Studying an animal's bioenergetics tells us a lot about its adaptations and how much food it needs.

Energy Sources and Allocation

• Animals harvest chemical energy from food.
• After the digestion of food, energy-containing molecules generate ATP for powering cellular work.

Bioenergetics of an Animal

• Food is digested via enzymatic hydrolysis, and nutrients are absorbed by body cells.
• ATP produced by respiration and fermentation powers cellular work to enable cells, organs, and organ systems to perform the functions that keep an animal alive.

Quantifying Energy Use

• An animal's metabolic rate is the amount of energy it uses in a unit of time.
• Metabolic rate can be measured in a variety of ways.

Endotherms and Ectotherms

• Birds and mammals are mainly endothermic, generating body heat through metabolism and typically have higher metabolic rates.
• Amphibians and reptiles are mostly ectothermic, gaining heat from external sources and have lower metabolic rates.

Influences on Metabolic Rate

• Metabolic rates are affected by many factors.
• Metabolic rate per gram is related to body size among similar animals, such that Is inversely related to body size among similar animals

Activity and Metabolic Rate

• Basal Metabolic Rate (BMR) indicates the metabolic rate of an endotherm at rest.
• Standard Metabolic Rate (SMR) indicates the metabolic rate of an ectotherm at rest.
• Activity impacts metabolic rate for both endotherms and ectotherms.

Energy Budgets

• Different species of animals use energy and food materials derived from food in different ways, which depends on their environment.

Homeostasis

• Animals regulate their internal environment within relatively narrow limits.
• The internal environment of vertebrates is called the interstitial fluid.
• Homeostasis achieves a balance between external changes and the animal's internal control mechanisms.

Regulating and Conforming

• Regulating and conforming are two extremes in how animals cope with environmental fluctuations.
• Regulators, use internal mechanisms to control internal change.
• Conformers allow their internal condition to vary with external changes.

Homeostatic Control System

• A homeostatic control system has three functional components: a receptor, the control center, and an effector.

Types of Feedback for Homeostatic Control

• Negative feedback loops occur in most homeostatic control systems where the accumulation of the end products slows the process.
• Positive feedback is when a change in a variable triggers mechanisms that amplify the change.

Thermoregulation

• Thermoregulation contributes to homeostasis and involves anatomy, physiology, and behavior.
• Thermoregulation is the process by which animals maintain an internal temperature within a tolerable range.

Types of Thermoregulation

• Ectotherms include most invertebrates, fishes, amphibians, and non-bird reptiles.
• Endotherms include birds and mammals.

Ectotherms vs Endotherms

• Ectotherms tolerate greater variation in internal temperatures than endotherms
• Endothermy is energetically more expensive than ectothermy.
• Endothermy buffers animals' internal temperatures against external fluctuations and enables them to maintain a high level of aerobic metabolism.

Modes of Heat Exchange

• Radiation: Emission of electromagnetic waves by all objects warmer than absolute zero.
• Evaporation: Removal of heat when a liquid vaporizes.
• Convection: Transfer of heat by movement of air or liquid past a surface.
• Conduction: Direct transfer of thermal motion (heat) between objects in contact.

Balancing Heat Loss and Gain

• Thermoregulation involves physiological and behavioral adjustments that balance beat gain and loss.
• Insulation reduces the flow of heat between an animal and its environment and may include feathers, fur, or blubber.
• The integumentary system acts as an insulating material in mammals.

Circulatory Adaptations

• Animals can alter bloodflow between the body core and the skin.
• Vasodilation increases blood flow to the skin, facilitating heat loss.
• Vasoconstriction decreases blood flow to the skin, lowering heat loss.

Countercurrent Heat Exchangers

• Marine mammals and birds often have arrangements of blood vessels called countercurrent heat exchangers that reduce heat loss.

Cooling by Evaporative Heat Loss

• Many animals lose heat through the evaporation of water in sweat or by panting.
• Bathing moistens the skin and helps to cool animals down.
• Some terrestrial invertebrates have postures that help them minimize or maximize their absorption of heat from the sun.
• Some animals can regulate body temperature by adjusting their rate of metabolic heat production.