Animal Form and Function Ch 40

A single-celled animal living in water Figure 40.3a Organisms must exchange matter and energy with the environment. Diffusion (a) Single cell Figure 40.3b Mouth Gastrovascular cavity Diffusion (b) Two cell layers Multicellular organisms with a sac body plan

External environment Food CO 2 O2O2 Mouth Animal body Respiratory system Circulatory system Nutrients Excretory system Digestive system Heart Blood Cells Interstitial fluid Anus Unabsorbed matter (feces) Metabolic waste products (urine) The lining of the small intestine, a diges- tive organ, is elaborated with fingerlike projections that expand the surface area for nutrient absorption (cross-section, SEM). 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). Inside a kidney is a mass of microscopic tubules that exhange chemicals with blood flowing through a web of tiny vessels called capillaries (SEM). 0.5 cm 10 µm 50 µm Figure 40.4

Energy intake is used for maintaining homeostasis Energy is used for maintenance and homeostasis first Any excess energy can go towards growth or reproduction Figure 40.7 Organic molecules in food Digestion and absorption Nutrient molecules in body cells Cellular respiration Biosynthesis: growth, storage, and reproduction Cellular work Heat Energy lost in feces Energy lost in urine Heat External environment Animal body Heat Carbon skeletons ATP

Body Size and Metabolic Efficiency Endotherms Ectotherm Annual energy expenditure (kcal/yr) 800,000 Basal metabolic rate Reproduction Temperature regulation costs Growth Activity costs 60-kg female human from temperate climate Total annual energy expenditures (a) 340,000 4-kg male Adélie penguin from Antarctica (brooding) 4, kg female deer mouse from temperate North America 8,000 4-kg female python from Australia Energy expenditure per unit mass (kcal/kgday) 438 Deer mouse 233 Adélie penguin 36.5 Human 5.5 Python Energy expenditures per unit mass (kcal/kgday) (b) Figure 40.10a, b Large animals require more energy overall, but have a lower energy expenditure per unit mass. Why? Surface area to volume ratio helps them conserve energy Ectotherms use less energy overall and per unit body mass Why? Do not waste energy heating body

A homeostatic control system has three functional components A receptor Control center An effector Positive vs negative regulation: see pogil Figure Response No heat produced Room temperature decreases Heater turned off Set point Too hot Set point Control center: thermostat Room temperature increases Heater turned on Too cold Response Heat produced Set point

Regulators and Conformers Regulators use physiological responses to maintain constant internal conditions Conformers are able to tolerate a range of a particular environmental condition In this example the Crab can tolerate a range of salt concentrations in the environment. Too low or too high leads to death Maintaining Homeostasis

Ectotherms Include most invertebrates, fishes, amphibians, and non- bird reptiles Endotherms Include birds and mammals Ectotherms and Endotherms an example of regulators vs. conformers Figure River otter (endotherm) Largemouth bass (ectotherm) Ambient (environmental) temperature (°C) Body temperature (°C)

Homeostatic control mechanisms support common ancestry Systems reach equilibrium and no further exchange takes place Systems do not reach equilibrium and exchange takes place along the entire length. More of the exchanged substance is transferred than in the previous example Countercurrent Exchange systems help animals maintain higher core temperatures in the cold- see diagrams for explanation of how. Countercurrent exchange systems are evolutionarily conserved-seen in terrestrial and aquatic animals

Reproductive strategies reflect energy availability in the environment When is the most energy available Which season is best to reproduce/ support young?

Type 1: relatively few young, more parental investment/ care, most survive past infancy and die after adulthood Type 3: have many young, young are small in size, few survive infancy, once adult or mature stage is reached most survive. Type 2: young are as likely to die as adults. Intermediate number of offspring and parental care.

Responses to the environment can be behavioral or physiological Behavioral responses: behaviors that maximize organisms chances of survival Seasonal Migration Nocturnal or crepuscular activity Reptiles (thermo-conformers) “sunning” when cold and seeking shade when hot This kangaroo is licking its forearms to cool itself by evaporation

Responses to the environment can be behavioral or physiological Physiological Responses Vasodilatation when hot, vasoconstriction when cold Insulation layer of body fat in marine mammals Torpor/ Hibernation during extended periods of energy deprivation Counter current exchange to reduce loss of heat Shivering in the cold/ sweating when hot

Hibernation is long term torpor Additional metabolism that would be necessary to stay active in winter Actual metabolism Body temperature Arousals Outside temperature Burrow temperature JuneAugustOctoberDecemberFebruaryApril Temperature (°C) Metabolic rate (kcal per day) Figure Torpor- Is a physiological state in which activity is low and metabolism decreases The body cools to near freezing temperatures Shivering warms body for brief intervals Saves energy during winter when food is not available

Circulation and Gas Exchange- a model of specialization, coordination, and adaptation Animals have specialized organs and organ systems for gas exchange and circulation The respiratory and circulatory systems reflect common ancestry and divergence due to different environments. Interaction and coordination between circulatory and respiratory systems allow the organism obtain nutrients and eliminate wastes

Circulatory systems in animals Gastrovascular cavity- open with the water Open circulatory systems in insects- fluid bathes internal organs and tissues Closed circulatory systems- blood is circulated, materials exchange by diffusion Figure 42.2 Circular canal Radial canal Mouth Heart Hemolymph in sinuses surrounding ograns Anterior vessel Tubular heart Lateral vessels Ostia (a) An open circulatory system Figure 42.3a Interstitial fluid Heart Small branch vessels in each organ Dorsal vessel (main heart) Ventral vessels Auxiliary hearts (b) A closed circulatory system

FISHES AMPHIBIANSREPTILES (EXCEPT BIRDS)MAMMALS AND BIRDS Systemic capillaries Lung capillaries Lung and skin capillariesGill capillaries Right Left RightLeft Right Left Systemic circuit Pulmocutaneous circuit Pulmonary circuit Systemic circulation Vein Atrium (A) Heart: ventricle (V) Artery Gill circulation A V V VVV A A A AA Left Systemic aorta Right systemic aorta Figure 42.4 Vertebrate Circulatory Systems: Common Ancestry and Divergence in different environments

Homeostatic Mechanisms represent common ancestry and divergence in different environments The heart is just one example of a structure that has diverged in organisms  Here is a phylogeny based on a heart structure. Source: Emergence of Xin Demarcates a Key Innovation in Heart Evolution. DOI: /journal.pone

Gas exchange systems all have large surface areas to maximize diffusion Figure 42.20b Gills in marine worms Salmon Gills Alveoli in Lungs

Interaction and coordination between circulatory and respiratory systems allow the organism obtain nutrients and eliminate wastes Countercurrent exchange!!! Figure Gill arch Water flow Gill filaments Oxygen-poor blood Oxygen-rich blood Water flow over lamellae showing % O 2 Blood flow through capillaries in lamellae showing % O 2 Lamella 100% 40% 70% 15% 90% 60% 30% 5% O2O2

Mammalian Respiratory Systems Branch from the pulmonary vein (oxygen-rich blood) Branch from the pulmonary artery (oxygen-poor blood) Alveoli Colorized SEM SEM 50 µm Heart