Animal Bodies Interaction with the Environment Reference: Chapter 40

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9/15/14 BIOSC 041 Animal Bodies Interaction with the Environment Reference: Chapter 40 Animal

animal interacts with its environment Many different animal body plans have evolved and are

Physical laws constrain strength, diffusion, movement, and heat exchange As animals increase in

convergence reflects different species adaptations to a similar environmental challenge Surface

exchanged across the cell membranes of animal cells and then transported through the body Rate

has a sufficient SA of plasma membrane to service its entire vol.

1 9/15/14 BIOSC 041 Animal Bodies Interaction with the Environment Reference: Chapter 40 Animal form and function are correlated at all levels of organization Size and shape affect the way an animal interacts with its environment Many different animal body plans have evolved and are determined by the genome Evolution of Animal Size and Shape Exchange with the Environment Physical laws constrain strength, diffusion, movement, and heat exchange As animals increase in size, their skeletons must be proportionately larger to support their mass Evolutionary convergence reflects different species adaptations to a similar environmental challenge Surface Area : Volume Ratio Exchange with the Environment Nutrients, waste products, and gases must be exchanged across the cell membranes of animal cells and then transported through the body Rate of exchange is proportional to a cell s surface area A single-celled protist living in water has a sufficient SA of plasma membrane to service its entire vol. of cytoplasm Multicellular organisms with a saclike body plan have body walls that are only two cells thick, facilitating diffusion of materials 1

environment The nervous and endocrine interact in response to environmental stimuli to maintain the internal environment Nutrients 250 µm Blo Respiratory Heart Digestive Lining of small intestine

2 9/15/14 Exchange with the Environment Figure 40.4 External environment CO2 O Food 2 Mouth Feedback control maintains the internal environment in many animals Animals manage their internal environment by regulating or conforming to the external environment The nervous and endocrine interact in response to environmental stimuli to maintain the internal environment Nutrients 250 µm Blo Respiratory Heart Digestive Lining of small intestine (SEM) od Lung tissue (SEM) Cells Interstitial fluid Circulatory Excretory Anus Unabsorbed matter (feces) Metabolic waste products (nitrogenous waste) Blood vessels in kidney (SEM) 50 µm Animal body More complex organisms have highly folded internal surfaces for exchanging materials Increases available SA Increases SA/Vol In vertebrates, the space between cells is filled with interstitial fluid, which allows for the movement of material into and out of cells A complex body plan helps an animal living in a variable environment to maintain a relatively stable internal environment 100 µm Animals are Regulators and/or Conformers Regulator Uses internal control mechanisms to moderate internal change in the face of external, environmental fluctuation E.g., temperature control in mammals Conformer Allows internal condition to vary with certain external changes E.g., body temperature in most fish Animals may be both regulators and conformers for different characteristics E.g., Largemouth bass Conform with respect to body temperature Regulate solute concentrations in blood Figure 40.7 Homeostasis Homeostasis to maintain a steady state or internal balance, regardless of external environment In humans, body temperature, blood ph, and glucose concentration are examples of homeostatic processes Mechanisms of homeostasis moderate changes in the internal environment For a given variable, fluctuations above or below a set point serve as a stimulus; these are detected by a sensor and trigger a response The response returns the variable to the set point 2

shuts off the Reversible v Positive feedback amplifies a stimulus and does not usually contribute to homeostasis in animals Positive feedbacks are hard to control; often irreversible Occur in

birth) Alterations in Homeostasis 9b v Set points and normal ranges can change with age or show cyclic variation v In animals and plants, a circadian rhythm governs physiological changes that occur

3 Figure 40.8 Feedback Control in Homeostasis v The dynamic equilibrium of homeostasis is maintained by negative feedback, which helps to return a variable to a normal range Buildup of the end product slows or shuts off the Reversible v Positive feedback amplifies a stimulus and does not usually contribute to homeostasis in animals Positive feedbacks are hard to control; often irreversible Occur in situations where a process moves to completion (e.g. birth) Alterations in Homeostasis Figure 40.9b v Set points and normal ranges can change with age or show cyclic variation v In animals and plants, a circadian rhythm governs physiological changes that occur roughly every 24 hours v Homeostasis can adjust to changes in external environment, a process called acclimatization E.g., altitude, temperature Figure 40.9a Thermoregulation v Thermoregulation Homeostatic process by which animals maintain an internal temperature within a tolerable range v Endotherms Generate heat by metabolism; active at a greater range of external temperatures E.g., birds and mammals are endotherms v Ectotherms Gain heat from external sources; tolerate greater variation in internal temperature Ectotherms include most invertebrates, fishes, amphibians, and reptiles v Endothermy is more energetically expensive than ectothermy 3

body temp of a homeotherm is relatively constant Balancing Heat Loss and Gain v Organisms exchange heat

Conduction Heat regulation in mammals v Heat regulation in mammals often involves the integumentary :

Circulatory adaptations 3. Cooling by evaporative heat loss 4. Behavioral responses 5.

Insulation v Insulation is a major thermoregulatory adaptation in mammals and birds v Skin, feathers,

important in marine mammals such as whales and walruses 2.

4 Figure Variation in Body Temperature v The body temp of a poikilotherm varies with its environment v The body temp of a homeotherm is relatively constant Balancing Heat Loss and Gain v Organisms exchange heat by four physical processes: 1. Radiation 2. Evaporation 3. Convection 4. Conduction Heat regulation in mammals v Heat regulation in mammals often involves the integumentary : skin, hair, and nails v Five adaptations help animals thermoregulate: 1. Insulation 2. Circulatory adaptations 3. Cooling by evaporative heat loss 4. Behavioral responses 5. Adjusting metabolic heat production 1. Insulation v Insulation is a major thermoregulatory adaptation in mammals and birds v Skin, feathers, fur, and blubber reduce heat flow between an animal and its environment v Insulation is especially important in marine mammals such as whales and walruses 2. Circulatory Adaptations v Regulation of blood flow near the body surface significantly affects thermoregulation v Many endotherms and some ectotherms can alter the amount of blood flowing between the body core and the skin v In vasodilation, blood flow in the skin increases, facilitating heat loss v In vasoconstriction, blood flow in the skin decreases, lowering heat loss 4

2. Circulatory Adaptation - Countercurrent Exchange Figure 40.

Countercurrent heat exchangers transfer heat between fluids flowing in opposite directions and reduce heat

countercurrent heat exchangers that help maintain a high temperature in the thorax 3.

skin v Panting increases the cooling effect in birds and many mammals v Sweating or bathing moistens the

Behavioral Responses v Both endotherms and ectotherms use behavioral responses to control body temperature

Adjusting Metabolic Heat Production Figure 40.

5 2. Circulatory Adaptation - Countercurrent Exchange Figure v The arrangement of blood vessels in many marine mammals and birds allows for countercurrent exchange v Countercurrent heat exchangers transfer heat between fluids flowing in opposite directions and reduce heat loss v Some bony fishes and sharks also use countercurrent heat exchanges v Many endothermic insects have countercurrent heat exchangers that help maintain a high temperature in the thorax 3. Cooling by Evaporative Heat Loss v Many types of animals lose heat through evaporation of water from their skin v Panting increases the cooling effect in birds and many mammals v Sweating or bathing moistens the skin, helping to cool an animal down 4. Behavioral Responses v Both endotherms and ectotherms use behavioral responses to control body temperature v Some terrestrial invertebrates have postures that minimize or maximize absorption of solar heat 5. Adjusting Metabolic Heat Production Figure v Thermogenesis Adjustment of metabolic heat production to maintain body temperature Increased by muscle activity such as moving or shivering Nonshivering thermogenesis takes place when hormones cause mitochondria to increase their metabolic activity Some ectotherms can also shiver to increase body temperature 5

Acclimatization in Thermoregulation Physiological Thermostats and Fever v Birds and mammals can vary their insulation to acclimatize to seasonal temperature changes

controlled by a region of the brain called the hypothalamus v The hypothalamus triggers heat loss or heat generating mechanisms v Fever is the result of a change to

16 Energy requirements v Bioenergetics is the overall flow and transformation of energy in an animal v Bioenergetic requirements Determine how much food an animal

6 Acclimatization in Thermoregulation Physiological Thermostats and Fever v Birds and mammals can vary their insulation to acclimatize to seasonal temperature changes Winter coats in mammals v When temperatures are subzero, some ectotherms produce antifreeze compounds to prevent ice formation in their cells v Thermoregulation is controlled by a region of the brain called the hypothalamus v The hypothalamus triggers heat loss or heat generating mechanisms v Fever is the result of a change to the set point for a biological thermostat Figure Energy requirements v Bioenergetics is the overall flow and transformation of energy in an animal v Bioenergetic requirements Determine how much food an animal needs Relate to an animal s size, activity, and environment Figure Quantifying Energy Use v Metabolic rate is the amount of energy an animal uses in a unit of time v Metabolic rate can be determined by An animal s heat loss The amount of oxygen consumed or carbon dioxide produced 6

7 Minimum Metabolic Rate and Thermoregulation v Basal metabolic rate (BMR) is the metabolic rate of an endotherm at rest at a comfortable temperature v Standard metabolic rate (SMR) is the metabolic rate of an ectotherm at rest at a specific temperature v Both rates assume a nongrowing, fasting, and nonstressed animal v Ectotherms have much lower metabolic rates than endotherms of a comparable size Influences on Metabolic Rate v Metabolic rates are affected by many factors besides whether an animal is an endotherm or ectotherm v Two of these factors are size and activity Size and Metabolic Rate Figure v Metabolic rate is proportional to body mass to the power of three quarters (m 3/4 ) v Smaller animals have higher metabolic rates per gram than larger animals v The higher metabolic rate of smaller animals leads to a higher oxygen delivery rate, breathing rate, heart rate, and greater (relative) blood volume, compared with a larger animal Figure Activity and Metabolic Rate v Activity greatly affects metabolic rate for endotherms and ectotherms v In general, the maximum metabolic rate an animal can sustain is inversely related to the duration of the activity 7

Torpor and Energy Conservation v Torpor is a physiological state in which activity is low and metabolism decreases v Torpor enables animals to save energy while avoiding difficult and dangerous

8 Torpor and Energy Conservation v Torpor is a physiological state in which activity is low and metabolism decreases v Torpor enables animals to save energy while avoiding difficult and dangerous conditions Hibernation is long-term torpor that is an adaptation to winter cold and food scarcity Puskatawny Phil (groundhog) Estivation enables animals to survive long periods of high temperatures and scarce water Earthworms in summer Daily torpor is exhibited by many small mammals and birds and seems adapted to feeding patterns hummingbirds Energy Budgets v Different species use energy and materials in food in different ways, depending on their environment v Use of energy is partitioned to BMR (or SMR), activity, thermoregulation, growth, and reproduction 8

Basic Principles of Animal Form and Function Anatomy/Physiology Animal form and function are correlated at all levels of organization

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Basic Principles of Animal Form and Function Anatomy/Physiology Form and function are related Animal form and function are correlated at all levels of organization Evolution