Basic Principles of Animal Form & Function Ch 40 – 7 th ed Campbell’s Biology

Diverse Forms, Common Challenges Diverse forms have evolved to meet some common needs including… –Procuring nutrients –Obtaining oxygen –Removing wastes –Etc. There is an intimate relationship between form and function

Structure-Function Correlates Anatomy = study of structure Physiology = study of function Natural selection can fit structure to function by selecting over many generations what works best among the available variations in a population

Constraints on Animal Size & Shape Physical laws and the need to exchange materials with the environment place certain limits on the range of animal forms (size & shape) –Ex: laws of physics dictate that mythical dragons would not have generated enough lift to get off the ground –Hydrodynamics constrain the shapes of aquatic animals that swim rapidly/all use a fusiform body shape / an example of convergent evolution

Evolutionary convergence in fast swimmers

Constraints on Animal Size & Shape, cont’d Body size and shape affect interactions with the environment –Each cell of a multicellular animal must have access to an aqueous environment –2-Layered sacs and flat shapes maximize exposure to surrounding medium –Complex plans have highly folded internal surfaces specialized for exchange (gills, mitochondria, etc)

Animal form and function are correlated at all levels of organization Hierarchical levels of organization, each with emergent properties cells → tissues → organs → organ systems

Structure and Function in Animal Cells Tissues –Groups of cells with common structure and function Four Tissue Classes –Epithelial (diagrams p. 824 in 7 th ed.) –Connective (diagrams p. 825 in 7 th ed.) –Nervous (diagrams p. 826 in 7 th ed.) –Muscle (diagrams p. 826 in 7 th ed.)

Epithelial Tissues Tightly packed sheets of cells that cover the outside of the body or line internal organs and cavities Function as a protective barrier against mechanical injury, fluid loss, and invasive microorganisms Free surface exposed to air or fluid Cells at base are attached to a basement membrane Glandular epithelia are specialized for absorption and secretion –Secretions of mucous membranes serve to moisten and lubricate

Epithelial Tissue Simple = single layer of cells Stratified = multiple tiers of cells Cuboidal = dice-shaped Columnar = rectangular brick-shaped Squamous = flat

Figure 40.1 The structure and function of epithelial tissues

Epithelial Tissue, cont’d Simple squamous –Thin, leaky, function in exchange of material by diffusion, lining of blood vessels and lungs Stratified squamous –Regenerate rapidly, commonly found on surfaces that are subject to abrasion, ex: skin Simple columnar –Secrete digestive juices and absorb nutrients, intestinal lining Stratified columnar –Line surface of urethra Simple cuboidal –Specialized for secretion, make up kidney epithelia and many glands

Connective Tissue Bind and support other tissues Loosley packed/ Sparse population of cells scattered throughout an extracellular matrix which is often secreted by connective tissue Three types of connective tissue fibers: –Collagenous fibers –Elastic fibers –Reticular fibers

Connective Tissue, cont’d Collagenous fibers –Made of collagen (may be most abundant protein in the animal kingdom) –Nonelastic, do not tear easily Elastic fibers –Made from elastin –Rubbery quality, restore shape Reticular fibers –Collagen –Tightly woven fiber fabric that joins connective tissues to other tissues

Figure 40.2 Some representative types of connective tissue

Types of Connective Tissue Loose Connective Tissue – binds epithelia to underlying tissue and functions as a packing material and holds organs in place, contains all three types of fibers –Fibroblasts secrete protein ingredients of extracellular matrix –Macrophages are amoeboid, phagocytic cells Adipose Tissue –stores fat for padding, insulation, energy

Connective Tissue, cont’d Fibrous Connective Tissue –Dense, primarily collagenous fibers –Tendons attach muscle to bones –Ligaments attach bones together at joints Cartilage –Strong, flexible support material composed of chondroitin sulfate and collagen Bone –mineralized connective tissue –Collagen, calcium, magnesium, and phosphate Blood –cells suspended in plasma, the extracellular matrix

Figure 40.2x Connective tissue

Nervous Tissue Neurons are functional units Neurons are composed of a cell body with dendrites and axons that transmit electrical signals called impulses

Figure 40.3 The basic structure of a neuron

Muscle Tissue Composed of long cells containing parallel fibrils of contractile proteins Most abundant tissue in most animals Accounts for much of the energy consumption in an active animal Contains contractile proteins actin and myosin Three types which differ in shape, striation, and nervous control –Skeletal –Cardiac –Smooth

Figure 40.4 Three kinds of vertebrate muscle

Muscle –Skeletal Elongated, striated (striped pattern) Voluntary movements of the body Fixed number of muscle cells/can increase in size not number when bodybuilding –Cardiac Striated, branch via intercalated discs –Smooth Spindle-shaped cells, lack striations Contract more slowly than skeletal or cardiac muscle Involuntary movements (digestive tract for example)

Figure 40.4x Three kinds of vertebrate muscle

Organs & Organ Systems In all but the simplest organisms, different tissues are organized into organs Tissues may be arranged in layers Example: stomach –Thick epithelium for stomach lining surrounded by a layer of connective tissue surrounded by a layer of smooth muscle surrounded by another layer of connective tissue

Tissue Layers of the Stomach

Organs & Organ Systems, cont’d Organ systems are interdependent Body functions as a whole, not the sum of its parts Activities of tissues, organs, and organ systems are coordinated

40.3 Animals use the chemical energy in food to sustain form and function Animals are heterotrophs that harvest chemical energy from the food they eat –The chemical energy is required for growth, repair, physiological processes, regulation, and reproduction –Animal’s ability to function is dependent on cellular work being powered by chemical energy in ATP.

Bioenergetics of Animals Bioenergetics –the flow of energy through an organism –limits an animal’s behavior, growth, and reproduction –determines how much food the organism needs to consume to survive

Bioenergetics Energy Sources & Allocation –As mentioned previously, animals harvest chemical energy from the food they eat –Most energy-containing molecules are used to generate ATP by respiration & fermentation –ATP powers cellular work/heat produced –After basic survival needs are met, remaining molecules in food can be used for biosynthesis, storage, and reproduction

An overview of bio- energetics in animals

Bioenergetics - Quantifying Energy Use Metabolic rate = amount of energy an animal uses in a unit of time = sum of all energy-requiring biochemical reactions Energy typically measured in kilocalories Note: 1000 calories = 1 kcal = 1 Calorie Can be measured by monitoring rate of heat loss using a calorimeter, the rate of O 2 consumed or the rate of CO 2 produced

Bioenergetics of Animals, cont’d Metabolic rate provides clues to an animal’s bioenergetic strategy Metabolic rates for birds and mammals (endotherms) is generally higher than those of most fishes, amphibians, reptiles, and invertebrates (ectotherms) –Endotherm = constant body temperature –Ectotherm = body temperature similar to that of the surroundings

Bioenergetics of Animals, cont’d Influences on Metabolic Rate Influences on Metabolic Rate Let’s make some predictions as to how other factors besides endothermy/ectothermy influence metabolic rate… –Size –Activity

Figure 40.13a Annual energy budgets for four animals: Total annual energy expenditures

Figure 40.13b Annual energy budgets for four animals: Energy expenditure per unit mass

Bioenergetics of Animals, cont’d Metabolic rate per gram is inversely related to body size among similar animals Animals adjust their metabolic rates as conditions change –Activity increases metabolic rate above the BMR (endotherms) or SMR (ectotherms) Energy budgets reveal how animals use energy and materials –Animal’s use of energy is partitioned to BMR (or SMR), activity, homeostasis, growth, and reproduction

Regulating the Internal Environment Mechanisms of homeostasis moderate changes in the internal environment –Internal environment surrounding cells is often very different than that of the external environment –Interstitial Fluid = fluid which fills spaces between our cells, exchanges nutrients and wastes with blood

Homeostasis Homeostasis depends on feedback circuits –Negative feedback Commonly used to maintain homeostasis Reverse the change/Ex: low blood glucose, try to raise it –Positive feedback Amplify the change/Ex: contractions during childbirth

Figure 40.9a An example of negative feedback: Control of room temperature

Figure 40.9b An example of negative feedback: Control of body temperature (Layer 2)

40.5 Thermoregulation contributes to homeostasis and involves anatomy, physiology, and behavior Thermoregulation = process by which animals maintain an internal temperature within a tolerable range Q 10 –the factor by which a process changes when temperature changes by 10 degrees –Most enzymatic reactions have a Q 10 of 2 or 3, ie. If temperature is increased 10 degrees, rate of reaction will double, etc.

Figure 44.4 The relationship between body temperature and ambient (environmental) temperature in an ectotherm and an endotherm

Ectotherm vs Endotherm Ectotherm –Body temperature is the same as the temperature of the environment –Low metabolic rates –Most invertebrates, fishes, amphibians, and reptiles

Ectotherm vs Endotherm Endotherm –Maintain a constant internal temperature despite temperature of the surroundings –Have high metabolic rates and therefore need a higher food intake than ectotherms –Sustain intense activity better than ectotherms –Most mammals, birds, some fishes, a few reptiles, many insects

Heat exchange between an organism and its environment ( Figure 40.13)

Modes of Heat Exchange, cont’d Conduction –Direct transfer of heat between objects in direct contact with each other –Heat moves from an object with higher temperature to an object of lower temperature –Rate of transfer depends on the materials Convection –Transfer of heat by movement of air or liquid past a surface –Ex: breeze contributes to heat loss

Modes of Heat Exchange, cont’d Radiation –Emission of electromagnetic waves by all objects warmer than absolute zero Evaporation –Removal of heat from the surface of a liquid that is losing some of its molecules as gas –Has a strong cooling effect –The reason why we sweat!

Heat exchange between an organism and its environment ( Figure 40.13)

Adaptations for Thermoregulation Adjust the rate of heat exchange between the animal and its surroundings –Insulation such as fur, feathers, hair, fat –Circulatory System Adaptations Vasodilation increase blood flow and heat exchange Vasoconstriction reduce blood flow and heat exchange Countercurrent exchange/arteries and veins run in close proximity to one another/warmer blood from arteries helps warm cooler blood of veins

Figure 44.5 Countercurrent heat exchangers

Adaptations for Thermoregulation, cont’d Adjust the rate of heat exchange between the animal and its surroundings: Cooling by Evaporative Heat Loss Behavioral Adaptations

Thermoregulation in Various Animals Mammals and Birds –High metabolic rates –Shiver when cold/Sweat when hot –Vascular adjustments –Insulation by hair, fat, and/or feathers Amphibians and Reptiles –Control body temperature mainly by behavior –Seek cool or warm places depending on outside temperature

Thermoregulation in Various Animals Fishes –Most are conformers –Regulators use circulatory adaptations to maintain core body temperature Invertebrates –Aquatic invertebrates are mainly conformers –Terrestrial invertebrates are either conformers or regulators –Regulators use flight muscles or shivering to increase temperature

Figure The thermostat function of the hypothalamus and feedback mechanisms in human thermoregulation

Feedback Mechanisms in Thermoregulation Hypothalamus as the thermostat Temperature sensed by skin and hypothalamus itself Acclimatization –Adjustment to a new range of temperatures over a period of days or weeks –Ex: grow thicker fur coat in colder temperatures

Feedback Mechanisms in Thermoregulation Torpor –A physiological state in which activity is low and metabolism decreases –Hibernation is an ex of long term winter torpor –Estivation is a summer torpor –Daily Torpor/Biological clock