Basic Principles of Animal Form & Function Chapter 40 Basic Principles of Animal Form & Function

Anatomy & Physiology anatomy – the study of the structure of an organism physiology – the study of the functions an organism performs natural selection can fit structure to function by selecting, over many generations, what works best among the available variations in a population

relationship between structure & environment

Exchange with the Environment an animal’s body plan must allow all of its living cells to be bathed in an aqueous medium to main the fluid integrity of the plasma membrane this is easy for… a single-celled organism (ie: protist) because its entire surface area is in contact with water a simple animal (ie: a hydra or flatworm) that has a 2-layered sac or flat body plan that puts a large surface area in contact with the environment

continued… complex animals require extensively folded or branched internal surfaces to facilitate exchange with the environment

levels of organization in animals form & function are correlated at all levels of organization

Tissues tissues are groups of cells with a common structure and function different types of tissues have different structures that are suited to their function 4 main types of tissues: epithelial connective muscle nervous

Epithelial Tissue covers the outside of the body and lines organs & cavities within the body sheets of tightly packed cells enables the epithelium to function as a barrier against mechanical injury, microbes, & fluid loss criteria for classifying epithelial tissue: # of cell layers: simple (single layer) or stratified (multiple layers) shape of cells: cuboidal (like dice), columnar (like bricks standing on end), or squamous (like floor tiles)

Connective Tissue functions mainly to bind & support other tissues consists of a sparse population of cells scattered through an extracellular matrix 3 kinds of connective tissue fibers: collagenous – made of collagen; nonelastic & do not tear easily when pulled lengthwise elastic – made of elastin; provide a rubbery quality that complements the nonelastic strength of collagenous fibers reticular – made of collagen; thin & branched; continuous with collagenous fibers; form a tightly woven fabric that joins connective tissue to adjacent tissue

continued… major types of connective tissue: loose connective tissue adipose tissue fibrous connective tissue cartilage bone blood 2 predominant types of cells in loose connective tissue: fibroblasts – secrete protein ingredients of the extracellular fibers macrophages – amoeboid cells that roam the maze of fibers, engulfing foreign particles & the debris of dead cells by phagocytosis continued…

Muscle Tissue composed of long cells called muscle fibers that are capable of contracting arranged in parallel within the cytoplasm of muscle fibers are large numbers of contracting units called myofibrils made of the proteins actin and myosin most abundant tissue in most animals muscle contractions account for much of the energy-consuming cellular work in an active animal 3 types: skeletal, cardiac, & smooth

Nervous Tissue senses stimuli & transmits signals in the form of nerve impulses from one part of the animal to another functional unit = neuron concentrated in brain

Organs & Organ Systems tissues are organized into organs many of the organs of vertebrates are suspended by sheets of connective tissue called mesenteries mammals have two body cavities separated by a sheet of muscle called the diaphragm: thoracic cavity – houses lungs & heart abdominal cavity – most other organs organs work together in organ systems to carry out the major body functions of most animals

11 Organ Systems

bioenergetics the flow of energy through an animal

Energy & Allocation animals harvest energy from the food they eat food is digested by enzymatic hydrolysis & energy-containing molecules are absorbed by body cells most of these molecules are used to generate ATP after energetic needs are met, any remaining molecules from food can be used in biosynthesis (body growth & repair, synthesis of storage materials such as fat, and gamete production)

Quantifying Energy Use metabolic rate = amount of energy an animal uses in a unit of time can be measured by: monitoring an animal’s rate of heat loss determining the amount of O2 consumption or CO2 production by cellular respiration estimating the rate of food consumption & the energy content of the food consumed energy is measured in calories (cal) or kilocalories (kcal) metabolic rate is closely related to an animal’s bioenergetic strategy: endothermic or ectothermic in general, endotherms have higher metabolic rates than ecototherms

Influences on Metabolic Rate size it’s been shown that the amount of energy it takes to maintain each gram of body weight is inversely related to body size (explanation is still unclear) activity minimum rate powers the basic functions that support life endotherms  basal metabolic rate (BMR) non-growing, resting, fasting, non-stressed ectotherms  standard metabolic rate (SMR) resting, fasting, non-stressed @ a particular temperature maximum rate is inversely related to the duration of activity many factors influence metabolic rate between these extremes: age, sex, size, body & environmental temperatures, quality & quantity of food, activity level, oxygen availability, hormone balance, and time of day

Energy Budgets different animals use the energy and materials in food in different ways, depending on: environment behavior size basic strategy of endothermy or ectothermy

homeostasis (internal balance)

Coping with Environmental Fluctuations regulators – animals that use internal control mechanisms to moderate internal change in the face of external fluctuation conformers – animals that allow their internal condition to vary with certain external changes no organism is a perfect regulator or conformer

Mechanisms of Homeostasis 3 functional components of a homeostatic control system: receptor – detects a change in some variable of the animal’s internal environment control center – processes info it receives from receptor & sends appropriate response to effector effector - initiates response to reverse the change control circuits exhibit negative feedback: change triggers the control mechanism to counteract further change in the same direction, which prevents small changes from becoming too large a large portion of the energy from food is used to maintain homeostasis

example of negative feedback

thermoregulation the process by which animals maintain an internal temperature within a tolerable range

Ectotherms common misconception: ectotherm means an animal has variable body temperature & are “cold-blooded” (ie: have low body temperatures) ectotherms are animals that use heat from the environment as the source of heat for maintaining body temperature

Endotherms common misconception: endotherm means an animal has constant body temperature & are “warm-blooded” endotherms are animals that use metabolic heat to regulate their body temperature advantages of endothermy: enables animals to perform vigorous activity for longer periods of time enables animals to maintain stable body temperature on land where temperature fluctuations are generally more severe disadvantages: cannot tolerate large fluctuations in internal temperatures like ectotherms energetically expensive

Modes of Heat Exchange 4 processes: conduction – transfer of heat between 2 objects in direct contact convection – transfer of heat by the movement of air or liquid past a surface radiation evaporation heat is always transferred from an object of higher temperature to one of lower temperature

Adaptations for Thermoregulation insulation reduces the flow of energy between an animal & its environment and lowers the energy cost of keeping warm hair, feathers, fat layers (ie: adipose tissue) raising fur or feathers traps a thicker layer of air, reducing heat loss circulatory adaptations vasodilation – increase in diameter of superficial blood vessels; helps release heat by radiation, conduction, & convection vasoconstriction – decrease in diameter of superficial blood vessels; reduces heat loss countercurrent heat exchanger traps heat in the body core to reduce heat loss by direct transfer of heat in arterial blood to venous blood

continued… evaporative heat loss behavioral responses loss of water by evaporation across skin & via breathing cools the body because the water absorbs a considerable amount of heat when it evaporates adaptations that promote evaporative heat loss include panting & sweating behavioral responses simple behaviors like moving between sun & shade more complex behaviors like hibernation & migration adjusting metabolic heat production shivering nonshivering thermogenesis (NST) hormones cause mitochondria to increase their metabolic activity and produce heat instead of ATP in some mammals, a tissue called brown fat in the neck & between the shoulders is specialized for NST continued…

Feedback Mechanisms in Thermoregulation nerve cells that control thermoregulation are concentrated in the region of the brain called the hypothalamus responds to changes in body temperature above or below the normal range by activating mechanisms that promote heat loss or gain functions as a thermostat warm receptors signal hypothalamus when temperature increases cold receptors signal hypothalamus when temperature decreases

Adjusting to Changing Temps. acclimatization – adjustment to a new range of environmental temperatures over a period of days or weeks in endotherms, may include adjusting amount of insulation in ectotherms, often includes adjustments at the cellular level such as increasing the production of certain enzymes or producing enzyme variants that have the same function but different optimal temperatures

Torpor torpor = a physiological state in which activity is low & metabolism decreases enables animals to save energy while avoiding difficult or dangerous conditions 3 examples: hibernation = long-term torpor that is an adaptation to winter cold & food scarcity estivation = summer torpor that enables animals to survive long term periods of high temperatures and scare water supplies daily torpor – exhibited by small mammals & birds; based on feeding patterns