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Exchange with the Environment An animal’s size and shape directly affect how it exchanges energy and materials with its surroundings Exchange occurs as.

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Presentation on theme: "Exchange with the Environment An animal’s size and shape directly affect how it exchanges energy and materials with its surroundings Exchange occurs as."— Presentation transcript:

1 Exchange with the Environment An animal’s size and shape directly affect how it exchanges energy and materials with its surroundings Exchange occurs as substances dissolved in the aqueous medium diffuse and are transported across the cells’ plasma membranes A single-celled protist living in water has a sufficient surface area of plasma membrane to service its entire volume of cytoplasm

2 Diffusion Mouth Diffusion Two cell layers Single cell Diffusion Gastrovascular cavity

3 Multicellular organisms with a sac body plan have body walls that are only two cells thick, facilitating diffusion of materials More complex organisms have highly folded internal surfaces for exchanging materials

4 Digestive system Circulatory system Excretory system Interstitial fluid Cells Nutrients Heart Animal body Respiratory system Blood CO 2 Food Mouth External environment O2O2 50 µm A microscopic view of the lung reveals that it is much more spongelike than balloonlike. This construction provides an expansive wet surface for gas exchange with the environment (SEM). 10 µm Inside a kidney is a mass of microscopic tubules that exchange chemicals with blood flowing through a web of tiny vessels called capillaries (SEM). The lining of the small intestine, a digestive organ, is elaborated with fingerlike projections that expand the surface area for nutrient absorption (cross-section, SEM). Unabsorbed matter (feces) Metabolic waste products (urine) Anus 0.5 cm

5 Tissues make up organs, which together make up organ systems Different tissues have different structures that are suited to their functions Tissues are classified into four main categories: epithelial, connective, muscle, and nervous Tissue Structure and Function

6 EPITHELIAL TISSUE Stratified columnar epithelium Simple columnar epithelium Pseudostratified ciliated columnar epithelium Columnar epithelia, which have cells with relatively large cytoplasmic volumes, are often located where secretion or active absorption of substances is an important function. Stratified squamous epithelia Simple squamous epithelia Cuboidal epithelia Basement membrane 40 µm

7 CONNECTIVE TISSUE Collagenous fiber Elastic fiber 120 µm 100 µm Chondrocytes Chondroitin sulfate Cartilage 150 µm Adipose tissue Fat droplets Blood Red blood cells White blood cell 55 µm Plasma Bone Central canal 700 µm Osteon 30 µm Fibrous connective tissue Nuclei Loose connective tissue

8 MUSCLE TISSUE Multiple nuclei 100 µm Skeletal muscle Cardiac muscle Smooth muscle Neuron Muscle fiber Sarcomere Intercalated disk Nucleus 50 µm Nucleus 25 µm Muscle fibers Process Nucleus 50 µm Cell body NERVOUS TISSUE

9 Epithelial tissue covers the outside of the body and lines the organs and cavities within the body Connective tissue mainly binds and supports other tissues Muscle tissue consists of long cells called muscle fibers, which contract in response to nerve signals It is divided in the vertebrate body into three types: skeletal, cardiac, and smooth Nervous tissue senses stimuli and transmits signals throughout the animal

10 Lumen of stomach Mucosa: an epithelial layer that lines the lumen Submucosa: a matrix of connective tissue that contains blood vessels and nerves Muscularis: consists mainly of smooth muscle tissue Serosa: a thin layer of connective and epithelial tissue external to the muscularis 0.2 mm

11 Metabolic rates are affected by many factors besides whether an animal is an endotherm or ectotherm Two of these factors are size and activity Amphibians and reptiles other than birds are ectothermic: They gain their heat mostly from external sources Ectotherms generally have lower metabolic rates Influences on Metabolic Rate

12 The basal metabolic rate (BMR) is the metabolic rate of an endotherm at rest Activity greatly affects metabolic rate Different species use energy and materials in food in different ways, depending on their environment Use of energy is partitioned to BMR, activity, homeostasis, growth, and reproduction Activity and Metabolic Rate

13 A = 60-kg alligator A = 60-kg human Key Existing intracellular ATP ATP from glycolysis ATP from aerobic respiration Time interval 1 second 1 minute 1 hour 1 day 1 week Maximum metabolic rate (kcal/min; log scale) AH A H A H A H A H

14 800,000 Endotherms 340,000 Annual energy expenditure (kcal/yr) Basal (standard) metabolism Reproduction Temperature regulation Growth Activity 60-kg female human from temperate climate 4-kg male Adélie penguin from Antarctica (brooding) 4, kg female deer mouse from temperate North America 4-kg female python from Australia 8,000 Ectotherm Total annual energy expenditures. The slices of the pie charts indicate energy expenditures for various functions. Energy expenditures per unit mass (kcal/kgday). Comparing the daily energy expenditures per kg of body weight for the four animals reinforces two important concepts of bioenergetics. First, a small animal, such as a mouse, has a much greater energy demand per kg than does a large animal of the same taxonomic class, such as a human (both mammals). Second, note again that an ectotherm, such as a python, requires much less energy per kg than does an endotherm of equivalent size, such as a penguin. Energy expenditure per unit mass (kcal/kgday) Python Human Deer mouse Adélie penguin

15 Animals regulate their internal environment within relatively narrow limits The internal environment of vertebrates is called the interstitial fluid and is very different from the external environment Homeostasis is a balance between external changes and the animal’s internal control mechanisms that oppose the changes

16 A homeostatic control system has three functional components: a receptor, a control center, and an effector Most homeostatic control systems function by negative feedback, where buildup of the end product shuts the system off In positive feedback, a change in a variable triggers mechanisms that amplify rather than reverse the change Mechanisms of Homeostasis

17 Response No heat produced Room temperature decreases Room temperature increases Set point Too hot Set point Heater turned off Too cold Set point Control center: thermostat Heater turned on Response Heat produced

18 Thermoregulation is the process by which animals maintain an internal temperature within a tolerable range Ectotherms include invertebrates, fishes, amphibians, and reptiles Endotherms include birds and mammals In general, ectotherms t olerate greater variation in internal temperature than endotherms Ectotherms and Endotherms

19 River otter (endotherm) Largemouth bass (ectotherm) Ambient (environmental) temperature (°C) Body temperature (°C)

20 Endothermy is more energetically expensive than ectothermy It buffers the animal’s internal temperatures against external fluctuations It also enables the animal to maintain a high level of aerobic metabolism Organisms exchange heat by four physical processes: conduction, convection, radiation, and evaporation

21 Radiation Evaporation Conduction Convection

22 Balancing Heat Loss and Gain In thermoregulation, physiological and behavioral adjustments balance heat loss and gain Five general adaptations help animals thermoregulate: – Insulation – Circulatory adaptations – Cooling by evaporative heat loss – Behavioral responses – Adjusting metabolic heat production

23 Insulation Insulation is a major thermoregulatory adaptation in mammals and birds It reduces heat flow between an animal and its environment Examples are skin, feathers, fur, and blubber In mammals, the integumentary system acts as insulating material

24 Epidermis Dermis Hypodermis Adipose tissue Blood vessels Hair Sweat pore Sweat gland Muscle Nerve Oil gland Hair follicle

25 Many endotherms and some ectotherms can alter the amount of blood flowing between the body core and the skin In vasodilation, blood flow in the skin increases, facilitating heat loss In vasoconstriction, blood flow in the skin decreases, lowering heat loss Circulatory Adaptations

26 Many marine mammals and birds have an arrangement of blood vessels called a countercurrent heat exchanger Countercurrent heat exchangers are important for reducing heat loss Some bony fishes and sharks also have countercurrent heat exchangers

27 Blood flow Vein Artery Pacific bottlenose dolphin Canada goose Vein Artery 33° 27° 18° 9° 35°C 30° 20° 10°

28 Vein Artery Skin Capillary network within muscle Blood vessels in gills Heart Artery and vein under the skin Dorsal aorta Great white shark

29 Cooling by Evaporative Heat Loss Many types of animals lose heat through evaporation of water in sweat Panting augments the cooling effect in birds and many mammals Bathing moistens the skin, helping to cool an animal down

30 Both endotherms and ectotherms use behavioral responses to control body temperature Some terrestrial invertebrates have postures that minimize or maximize absorption of solar heat

31 Adjusting Metabolic Heat Production Some animals can regulate body temperature by adjusting their rate of metabolic heat production Many species of flying insects use shivering to warm up before taking flight

32 Mammals regulate body temperature by negative feedback involving several organ systems In humans, the hypothalamus (a part of the brain) contains nerve cells that function as a thermostat Feedback Mechanisms in Thermoregulation

33 Thermostat in hypothalamus activates cooling mechanisms. Increased body temperature (such as when exercising or in hot surroundings) Body temperature decreases; thermostat shuts off cooling mechanisms. Sweat glands secrete sweat that evaporates, cooling the body. Blood vessels in skin dilate: capillaries fill with warm blood; heat radiates from skin surface. Body temperature increases; thermostat shuts off warming mechanisms. Decreased body temperature (such as when in cold surroundings) Blood vessels in skin constrict, diverting blood from skin to deeper tissues and reducing heat loss from skin surface. Skeletal muscles rapidly contract, causing shivering, which generates heat. Thermostat in hypothalamus activates warming mechanisms. Homeostasis: Internal body temperature of approximately 36–38°C

34 Adjustment to Changing Temperatures In acclimatization, many animals adjust to a new range of environmental temperatures over a period of days or weeks Acclimatization may involve cellular adjustments or (as in birds and mammals) adjustments of insulation and metabolic heat production

35 Torpor and Energy Conservation Torpor is a physiological state in which activity is low and metabolism decreases 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

36 Actual metabolism Additional metabolism that would be necessary to stay active in winter Arousals Body temperature Outside temperature Burrow temperature –5 –10 –15 Temperature (°C) JuneAugustOctoberDecemberFebruaryApril Metabolic rate (kcal per day)

37 Estivation, or summer torpor, enables animals to survive long periods of high temperatures and scarce water supplies Daily torpor is exhibited by many small mammals and birds and seems adapted to feeding patterns

38 Animations and Videos Bozeman – Thermoregulation Bozeman - Anatomy and Physiology Bozeman - Organ Systems Chapter Quiz Questions – 1 Chapter Quiz Questions – 2


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