Quiz 2

Animal Nutrition and Stages of Food Processing

• Four Stages of Food Processing:

  • Ingestion: The act of eating or feeding; taking food into the body.

  • Digestion: The process of breaking down food into molecules small enough for the body to absorb. Involves both mechanical breakdown (mastication, churning) and enzymatic chemical breakdown of polymers into monomers.

  • Absorption: The uptake of small nutrient molecules by an animal's body cells from the digestive lumen into body fluids or blood vessels.

  • Elimination: The passage of undigested or unabsorbed material out of the digestive tract in the form of feces.

• Modes of Ingestion:

  • Filter Feeding: Straining small organisms or food particles suspended in water (e.g., baleen whales filtering plankton).

  • Bulk Feeding: Eating relatively large pieces of food (e.g., snakes swallowing prey whole, humans eating meals).

  • Substrate Feeding: Living in or on the food source and eating through it (e.g., caterpillars burrowing through leaf tissue).

  • Fluid Feeding: Sucking nutrient-rich fluid from a living host (e.g., mosquitoes feeding on blood, aphids sucking plant sap).

• Mechanisms of Digestion:

  • Intracellular Digestion: Food particles are engulfed by endocytosis/phagocytosis, forming a food vacuole that fuses with lysosomes containing hydrolytic enzymes inside the cell (e.g., single-celled organisms, sponges).

  • Extracellular Digestion: Breakdown of food particles in compartments that are continuous with the outside of the animal's body, allowing animals to devour larger prey.

    • Gastrovascular Cavity: An incomplete digestive system with a single opening acting as both mouth and anus (e.g., Hydra, jellyfish, planarians).

    • Complete Gut (Alimentary Canal): A digestive tube extending between two distinct openings—a mouth and an anus.

Comparative Alimentary Canal Anatomy and Adaptations

• Advantages of Complete Digestive Systems:

  • Allows specialized anatomical compartments for step-by-step digestion and nutrient processing.

  • Enables continuous ingestion of food before previously ingested meals are fully digested.

• Comparative Invertebrate and Vertebrate Structures:

  • Earthworm (Annelida):

    • Mouth: Ingestion.

    • Pharynx: Pumps food in.

    • Esophagus: Transports food.

    • Crop: Soft storage organ.

    • Gizzard: Muscular organ containing sand granules for mechanical grinding.

    • Intestine: Extracellular digestion and nutrient absorption.

    • Anus: Elimination.

  • Grasshopper (Arthropoda):

    • Foregut: Includes esophagus and crop for food storage.

    • Midgut: Features gastric cecae (pouches extending from the gut that secrete digestive enzymes and absorb nutrients).

    • Hindgut: Includes rectum for water reabsorption and anus for elimination.

  • Bird (Aves):

    • Mouth: Ingestion (beak lacks teeth).

    • Esophagus & Crop: Food storage.

    • Stomach: Chemical digestion with enzymes.

    • Gizzard: Grinds tough food using swallowed stones/gravel.

    • Intestine: Digestion and absorption.

    • Anus: Elimination.

• Dietary Adaptations of the Alimentary Canal:

  • Carnivores: Have short digestive tracts and small, reduced cecums because meat is relatively easy to digest.

  • Herbivores (Non-ruminants): Require long digestive tracts and expanded, extremely large cecums or complex multi-chambered stomachs containing symbiotic microorganisms to break down cellulose and plant cell walls.

Mammalian Digestive System Pathway and Chemical Digestion

• Oral Cavity, Pharynx, and Esophagus:

  • Oral Cavity: Mechanical mastication by teeth increases surface area. Salivary glands release saliva containing salivary amylase, which initiates the chemical breakdown of carbohydrates (polysaccharides into smaller polysaccharides and maltose).

  • Swallowing Mechanism:

    • When not swallowing, the upper esophageal sphincter is contracted, the epiglottis is upright, and the glottis is open, allowing air into the trachea.

    • When a bolus of food reaches the pharynx, the swallowing reflex causes the larynx to move up, the epiglottis to tip downward over the glottis (preventing choking), and the upper esophageal sphincter to relax, allowing food into the esophagus.

• Stomach Structure and Secretions:

  • Stomach Functions: Stores food and performs mechanical churning via smooth muscle layers; converts food bolus into acid chyme.

  • Gastric Juices and Cell Types:

    • Mucous Cells: Secretes mucus to coat and protect the stomach epithelium from acid self-digestion.

    • Parietal Cells: Secretes hydrogen ions ($H^+$) and chloride ions ($Cl^-$) into the lumen via active transport, creating hydrochloric acid ($HCl$) with a highly acidic pH of approximately $pH = 2$.

    • Chief Cells: Secretes inactive pepsinogen.

  • Activation Mechanism:

    • $HCl$ converts inactive pepsinogen into active pepsin by cleaving a small portion of the molecule.

    • Active pepsin cleaves remaining pepsinogen molecules into active pepsin (positive feedback loop).

    • Pepsin breaks down proteins into small polypeptides.

• Small Intestine and Accessory Organs:

  • Duodenum: The first portion of the small intestine where acid chyme mixes with secretions from the pancreas, liver, gallbladder, and intestinal wall.

  • Pancreas: Produces alkaline pancreatic juice rich in bicarbonate ($HCO_3^-$) to neutralize acid chyme, as well as digestive enzymes:

    • Pancreatic Amylase: Digests starch/polysaccharides into disaccharides.

    • Pancreatic Trypsin and Chymotrypsin: Proteases activated in the duodenal lumen that break polypeptides into smaller polypeptides.

    • Pancreatic Carboxypeptidase: Cleaves amino acids from the carboxyl end of peptides.

    • Pancreatic Nucleases: Digests DNA/RNA into nucleotides.

    • Pancreatic Lipase: Digests fat triglycerides into glycerol, fatty acids, and monoglycerides.

  • Liver and Gallbladder:

    • Liver manufactures bile, which is stored in the gallbladder.

    • Bile salts act as detergents that emulsify fat droplets, increasing surface area for pancreatic lipase action.

  • Intestinal Epithelium (Brush Border Enzymes):

    • Disaccharidases, dipeptidases, carboxypeptidase, aminopeptidase, nucleotidases, nucleosidases, and phosphatases finish digestion into simple monosaccharides, amino acids, nitrogenous bases, sugars, and phosphates.

• Nutrient Absorption Mechanics:

  • Surface Area Enhancement: Large circular folds, villi (finger-like projections), and microvilli (microscopic projections on epithelial cell surface forming the brush border) create a massive surface area.

  • Hydrophilic Nutrients (Amino acids, sugars): Absorbed across epithelial cells via active transport or facilitated diffusion -> enter blood capillaries -> flow into the hepatic portal vein directly to the liver (for nutrient regulation and toxin detoxification) -> proceeds to the heart.

  • Hydrophobic Nutrients (Fats/Lipids): Fatty acids and monoglycerides are absorbed by epithelial cells, reassembled into triglycerides, coated with phospholipids/proteins to form chylomicrons -> exit into a lacteal (a lymphatic vessel inside each villus) -> travel through the lymphatic system -> enter veins directly near the heart.

• Large Intestine Anatomy and Gut Microbiome:

  • Anatomy: Consists of the cecum (blind pouch at junction), appendix (finger-like immunity/bacterial reservoir extension), colon (ascending, transverse, descending portions), rectum, and anus.

  • Primary Functions: Water reabsorption, ionic balance, bacterial fermentation, and feces storage/elimination.

• Gut Microbiome Functions:

  • Digestion of recalcitrant plant material (cellulose).

  • Synthesis of essential vitamins (e.g., vitamin K, biotin, B vitamins).

  • Regulation of intestinal epithelial development and immune system maintenance.

  • Microbiome composition dynamically shifts with age, diet (breastmilk vs. formula vs. solid food), antibiotic treatments, and physiological states (healthy vs. obese or malnourished).

Blood Glucose Homeostasis and Feedback Systems

• Homeostatic Set Point: Normal blood glucose range is $70\text{--}110\text{ mg glucose}/100\text{ mL blood}$.

• Hyperglycemic State (High Blood Glucose, e.g., after eating):

  • Stimulus: Blood glucose levels rise above set point.

  • Sensor/Control Center: Beta cells of the pancreas detect elevated glucose and secrete insulin into the blood.

  • Response: Insulin triggers transport of glucose into body tissue cells and stimulates the liver and skeletal muscle cells to store glucose as glycogen.

  • Result: Blood glucose levels fall back to set point.

• Hypoglycemic State (Low Blood Glucose, e.g., after fasting):

  • Stimulus: Blood glucose levels drop below set point.

  • Sensor/Control Center: Alpha cells of the pancreas detect low glucose and secrete glucagon into the blood.

  • Response: Glucagon stimulates liver cells to breakdown stored glycogen and release glucose into the bloodstream.

  • Result: Blood glucose levels rise back to set point.

• Diabetes Mellitus: A metabolic disease characterized by broken glucose homeostasis caused by lack of insulin production (Type 1) or reduced cellular response to insulin (Type 2).

Comparative Transport Systems in Animals and Plants

• Simple Exchange Systems: Very small or flattened animals (e.g., flatworms, sponges, Hydra) exchange gases and nutrients directly with the environment via simple diffusion across gastrovascular cavities or thin body layers.

• Comparison of Animal and Plant Transport Requirements:

• Transport Mechanisms in Animals:

  • Organ Level: Muscular pumps (hearts), muscular tubes (vessels), and muscular sheets (diaphragm).

  • Molecular Level: Diffusion, osmosis, and ATP-driven active transport.

  • Design Rules: Minimize diffusion distance because diffusion time is proportional to the square of the distance ($\text{Diffusion time} \thicksim \text{distance}^2$); maximize surface area at exchange sites.

• Transport Mechanisms in Plants (No Muscles):

  • Xylem: Transports water and inorganic mineral ions upward from roots to leaves by passive bulk flow driven by negative transpirational pull.

  • Phloem: Transports sucrose sap from source to sink tissues via bulk flow driven by positive hydrostatic pressure created by active loading of sugar and osmotic movement of water.

Comparative Circulatory System Architecture

• Open Circulatory Systems:

  • Circulating fluid (hemolymph) is continuous with interstitial fluid and bathes organs directly in body sinuses.

  • A tubular heart pumps hemolymph through open-ended vessels into sinuses; relaxation draws hemolymph back through pores with valves.

  • Found in arthropods (e.g., grasshoppers) and most mollusks (gastropods, bivalves).

  • Trade-off: Low energy cost, but lower pressure and velocity.

• Closed Circulatory Systems:

  • Circulating fluid (blood) is confined strictly to blood vessels and is distinct from interstitial fluid.

  • One or more muscular hearts pump blood through a continuous network of branching vessels.

  • Found in annelids (e.g., earthworms), cephalopod mollusks (e.g., squids, octopuses), and all vertebrates.

  • Trade-off: Higher energy expenditure, but high blood pressure supports larger body sizes, high metabolic activity, and selective blood delivery to specific tissues.

• Vertebrate Circulatory Circuit Variations:

  • Single Circulation (Fish):

    • Heart Structure: 2-chambered heart (1 atrium, 1 ventricle).

    • Pathway: Deoxygenated blood from ventricle -> gill capillaries (gas exchange) -> oxygen-rich blood proceeds directly to systemic body capillaries -> atrium.

    • Limitation: Blood pressure drops drastically in gill capillaries, slowing delivery to systemic tissues.

  • Double Circulation - 3-Chambered Heart (Amphibians & Reptiles):

    • Heart Structure: 3 chambers (2 atria, 1 shared ventricle).

    • Circuits: Pulmocutaneous circuit (picks up $O_2$ at lungs and skin) + Systemic circuit.

    • Feature: Allows repumping of blood after gas exchange; partial mixing of oxygenated and deoxygenated blood occurs in the single ventricle.

  • Double Circulation - 4-Chambered Heart (Mammals, Birds, Crocodilians):

    • Heart Structure: 4 chambers (2 atria, 2 completely separated ventricles).

    • Circuits: Pulmonary circuit (right side) + Systemic circuit (left side).

    • Advantage: Completely eliminates mixing of oxygenated and deoxygenated blood, maintaining high blood pressure to meet massive metabolic demands.

• Cephalopod Circulation (Squids):

  • Features a closed double circulation system powered by three hearts: two branchial hearts (which pump deoxygenated blood through the gills) and one systemic heart (which pumps oxygenated blood to the body tissue).

Mammalian Cardiovascular System Anatomy and Hemodynamics

• Complete Step-by-Step Path of Blood Flow:

  1. Deoxygenated blood enters the Superior Vena Cava (from upper body) and Inferior Vena Cava (from lower body).

  2. Blood empties into the Right Atrium.

  3. Blood passes through the right tricuspid atrioventricular (AV) valve into the Right Ventricle.

  4. The right ventricle pumps blood through the pulmonary semilunar valve into the Pulmonary Artery.

  5. Pulmonary arteries transport blood to the Capillaries of Left and Right Lungs (gas exchange: release $CO_2$, load $O_2$).

  6. Oxygen-rich blood returns via Pulmonary Veins.

  7. Blood enters the Left Atrium.

  8. Blood passes through the left mitral/bicuspid AV valve into the Left Ventricle.

  9. The thick muscular left ventricle pumps blood through the aortic semilunar valve into the Aorta.

  10. Aorta distributes blood to Systemic Arteries.

  11. Arteries branch into Arterioles.

  12. Arterioles feed into Capillaries of head, forelimbs, abdominal organs, and hind limbs (delivers $O_2$, picks up $CO_2$).

  13. Capillaries drain into Venules.

  14. Venules combine into Veins, returning to the venae cavae.

• Heart Valves and Prevention of Backflow:

  • Atrioventricular (AV) Valves: Located between atria and ventricles (Tricuspid valve on right, Mitral/Bicuspid valve on left). Closed during ventricular contraction to prevent backflow into atria.

  • Semilunar Valves: Located at exits of ventricles (Pulmonary valve on right, Aortic valve on left). Closed during ventricular relaxation to prevent backflow into ventricles.

• Vessel Structure Comparisons:

  • Arteries: Thick walls composed of endothelium, heavy smooth muscle layer, and outer connective tissue with elastic fibers to withstand high pressure generated by ventricular systole.

  • Capillaries: Extremely thin walls consisting of only an endothelium layer and basal lamina; optimized for rapid molecular diffusion.

  • Veins: Thinner walls with smaller smooth muscle layers under low pressure. Contain one-way internal valves to prevent backflow of blood as it returns to the heart.

• Hemodynamics across Vessel Types:

  • Total Cross-Sectional Area: Extremely low in aorta and arteries, dramatically rises to a peak of $5,000\text{ cm}^2$ in capillaries, and decreases in veins.

  • Blood Velocity: Fastest in aorta ($40\text{--}50\text{ cm/sec}$), drops to near $0\text{ cm/sec}$ ($< 1\text{ cm/sec}$) in capillaries to allow adequate time for gas/nutrient exchange, and speeds up slightly in veins ($20\text{--}25\text{ cm/sec}$).

  • Blood Pressure:

    • Systolic Pressure: Peak pressure ($120\text{ mm Hg}$) in arteries during ventricular contraction.

    • Diastolic Pressure: Lowest pressure ($80\text{ mm Hg}$) in arteries during ventricular relaxation.

    • Pressure drops continuously due to resistance in arterioles and reaches near $0\text{ mm Hg}$ in venae cavae.

• Venous Return Mechanisms: Venous blood flow under low pressure relies on rhythmic contraction of surrounding skeletal muscles squeezed against veins and one-way venous valves that force blood toward the heart.

Comparative Respiratory Systems

• Specialized Respiratory Surfaces:

  • Common features: Moist epithelial surfaces, large surface area, short diffusion distances, and close association with circulatory systems.

  • Four main types: Gills, Tracheae, Lungs, and Skin (cutaneous respiration).

• Gills and Countercurrent Exchange Mechanism:

  • Gills are outfoldings of the body surface specialized for aquatic gas exchange.

  • Invertebrate Gills: Marine worms use parapodia; crayfish have internal branchial chambers; sea stars use dermal branchiae and tube feet.

  • Vertebrate Gills (Fish): Water enters the mouth, passes over gill arches, filaments, and microscopic lamellae, exiting through the operculum.

  • Countercurrent Exchange Process:

    • Blood flows through lamellae capillaries in the opposite direction to the flow of water over the gills.

    • Maintains a concentration gradient favorability for $O_2$ diffusion from water to blood along the entire length of the capillary bed.

    • Allows fish gills to extract over $80\text{\%}$ of dissolved oxygen from water (compared to low oxygen availability in aquatic environments).

• Tracheal Systems in Insects:

  • A branched network of internal chitinous tubes (tracheae) that divide into microscopic tracheoles penetrating every cell.

  • Air enters via external openings called spiracles.

  • Delivers $O_2$ directly to body tissue cells and mitochondria without using the circulatory system.

• Avian Unidirectional Respiratory System:

  • Lungs feature tiny air tubes called parabronchi surrounded by capillaries.

  • Utilizes anterior and posterior air sacs acting as bellows to ensure unidirectional, continuous airflow through lungs.

  • Two-Cycle Passage Mechanism:

    1. First Inhalation: Air passes through trachea into posterior air sacs.

    2. First Exhalation: Posterior air sacs contract, pushing air into parabronchi of lungs (gas exchange occurs).

    3. Second Inhalation: Air moves out of lungs into anterior air sacs.

    4. Second Exhalation: Anterior air sacs contract, expelling air out of the body.

  • No mixing of fresh and stale air occurs, maximizing metabolic efficiency for flight.

• Mammalian Respiratory System (Bidirectional / Tidal):

  • Airway Path: Nasal cavity -> Pharynx -> Larynx -> Trachea -> Left/Right Bronchi -> Bronchioles -> Alveoli.

  • Alveoli: Microscopic air sacs wrapped in a dense mesh of pulmonary capillaries; site of gas exchange.

• Amphibian Positive Pressure Ventilation:

  • Amphibians use buccal pumping to force air down into lungs.

  • Floors of buccal cavity lowers with nostrils open, drawing in air -> nostrils close and glottis opens -> mouth floor raises, pushing air under positive pressure into lungs.

• Mammalian Negative Pressure Ventilation:

  • Inhalation (Active): Skeletal rib muscles contract (expanding rib cage upward/outward) and the diaphragm contracts (moving downward). Sealed thoracic cavity volume increases, lowering intra-alveolar pressure below atmospheric pressure, pulling air into lungs.

  • Exhalation (Passive): Rib muscles relax (rib cage drops) and diaphragm relaxes (moves upward). Thoracic volume decreases, increasing internal pressure, forcing air out.

Blood Composition and Respiratory Gas Transport

• Components of Whole Blood:

  • Plasma ($55\text{\%}$ of total volume):

    • Water: Acts as a solvent ($90\text{\%}$ of plasma).

    • Plasma Electrolytes/Ions: $Na^+$, $K^+$, $Ca^{2+}$, $Mg^{2+}$, $Cl^-$, $HCO_3^-$ (Maintain osmotic balance, pH buffering, regulate membrane permeability).

    • Plasma Proteins: Albumin (osmotic balance, pH buffering), Immunoglobulins/Antibodies (immune defense), Apolipoproteins (lipid transport), Fibrinogen (blood clotting).

    • Transported Substances: Nutrients, metabolic waste products, respiratory gases, and hormones.

  • Cellular Elements ($45\text{\%}$ of total volume):

    • Leukocytes (White Blood Cells, 5,000\text{--}10,000\text{ /̢L}): Basophils, Lymphocytes, Eosinophils, Neutrophils, Monocytes. Perform immune defense and destruction of pathogens.

    • Platelets (250,000\text{--}400,000\text{ /̢L}): Cell fragments involved in blood clotting.

    • Erythrocytes (Red Blood Cells, 5,000,000\text{--}6,000,000\text{ /̢L}): Biconcave non-nucleated discs optimized for transporting oxygen and carbon dioxide.

• Respiratory Pigments across Animal Taxa:

• Hemoglobin Oxygen Transport Mechanics:

  • Human hemoglobin molecule consists of 4 polypeptide subunits, each bound to a heme group containing an iron atom at its center.

  • Each iron atom binds one molecule of $O_2$; thus, one hemoglobin molecule carries up to $4\text{ }O_2$ molecules.

• Carbon Dioxide Transport Mechanics in Blood:

  • $10\text{\%}$ transported dissolved directly in blood plasma as gas $CO_2$

  • $30\text{\%}$ transported bound to amino acid chains of hemoglobin as carbaminohemoglobin ($Hb\text{-}CO_2$).

  • $60\text{\%}$ chemically modified and transported as bicarbonate ions ($HCO_3^-$) in plasma:

    • In Systemic Tissue Capillaries: $CO_2$ produced by cellular respiration diffuses into red blood cells. Carbonic anhydrase converts $CO_2 + H_2O \rightleftharpoons H_2CO_3 \rightleftharpoons H^+ + HCO_3^-$.

    • Chloride Shift: $HCO_3^-$ diffuses out of red blood cells into plasma, balanced by $Cl^-$ entry into red blood cells. Free $H^+$ is buffered by binding to hemoglobin ($Hb\text{-}H^+$).

    • In Pulmonary Lungs Capillaries: Reactions reverse ($H^+ + HCO_3^- \rightarrow H_2CO_3 \rightarrow CO_2 + H_2O$); $CO_2$ diffuses into alveoli and is exhaled.

Osmoregulation and Excretion of Nitrogenous Wastes

• Nitrogenous Waste Categories and Trade-offs:

  • Protein and nucleic acid breakdown generates toxic nitrogenous waste.

  • Ammonia ($NH_3$): Extremely toxic; requires huge amounts of water for excretion; produced primarily by aquatic organisms.

  • Urea: Low toxicity; requires energy to synthesize from ammonia; conserves water; produced by mammals, adult amphibians, and sharks.

  • Uric Acid: Non-toxic; semi-solid paste; requires high energy expenditure to synthesize; maximum water conservation; excreted by insects, land snails, reptiles, and birds.

• Osmosis and Membrane Principles:

  • Osmosis: The passive diffusion of free water molecules across a selectively permeable membrane from a hypoosmotic solution to a hyperosmotic solution.

  • Hyperosmotic Solution: Higher solute concentration, lower free $H_2O$ concentration -> cell shrivels as water flows out.

  • Hypoosmotic Solution: Lower solute concentration, higher free $H_2O$ concentration -> cell swells and lyses as water flows in.

  • Isoosmotic Solution: Equal solute concentration -> zero net movement of water.

• Osmoregulation Strategies:

  • Osmoconformers: Internal body fluid osmolarity changes in direct linear proportion to match external environmental osmolarity (isoosmotic; e.g., jellyfish, marine invertebrates).

  • Osmoregulators: Maintain a constant internal body fluid osmolarity despite fluctuations in external environmental osmolarity (e.g., mammals, terrestrial animals, freshwater fish). Requires metabolic energy.

Questions & Self-Assessment Discussions

• Digestive Systems Quiz Questions:

  • Question 1: A complete digestive tract, or alimentary canal, differs from a gastrovascular cavity in that only the complete tract _____.

    • A. permits extracellular digestion

    • B. has teeth and tentacles to help with ingestion

    • C. uses its surface area for nutrient absorption

    • D. has specialized compartments

    • E. allows elimination of undigested wastes

    • Correct Answer: D

  • Question 2: Which of the following organisms is most likely to have an extremely large cecum?

    • A. carnivore

    • B. nonruminant herbivore

    • C. insectivore

    • D. omnivore

    • Correct Answer: B

  • Question 3: Hydrochloric acid in the stomach _____.

    • A. splits proteins into individual amino acids

    • B. activates pepsinogen into pepsin

    • C. initiates the development of stomach ulcers

    • D. inhibits the production of epithelial cells

    • Correct Answer: B

  • Question 4: The primary reason the hepatic portal vein delivers blood containing the products of digestion directly to the liver is in order to _____.

    • A. recover excess water and ions

    • B. detoxify foreign molecules

    • C. allow toxic substances to circulate broadly

    • D. conduct blood from the gastrointestinal tract to the heart

    • Correct Answer: B

  • Question 5: Which of the following organs or structures is NOT part of the large intestine?

    • A. cecum

    • B. colon

    • C. appendix

    • D. duodenum

    • E. rectum

    • Correct Answer: D

• Circulation and Gas Exchange Quiz Questions:

  • Question 6: Why is the net movement by diffusion slow for distances greater than a few millimeters?

    • A. Beyond a few millimeters substances need to be actively transported.

    • B. Diffusion time is proportional to the square of the distance.

    • C. Every body cell is within a few millimeters of every other body cell.

    • D. Except for cnidaria and flatworms, most animal cells are in direct contact with surrounding media.

    • Correct Answer: B

  • Question 7: Which of these is transported by animal but not plant vascular systems?

    • A. Macronutrients

    • B. Micronutrients

    • C. Hormones

    • D. Gases

    • Correct Answer: D

  • Question 8: Which of these circulatory architectures would you expect in a large, very active, fully terrestrial animal?

    • A. Open circulatory system

    • B. Closed circulatory system with single circulation

    • C. Closed circulatory system with double circulation and 3-chambered heart

    • D. Closed circulatory system with double circulation and 4-chambered heart

    • Correct Answer: D

  • Question 9: Which of the following is a disadvantage of a closed circulatory system compared with an open circulatory system?

    • A. A closed circulatory system uses more energy.

    • B. Higher pressures in a closed circulatory system support increased size and more activity.

    • C. Closed vessels allow fluid to be directed to specific body regions.

    • D. Exchange of gas and nutrients is faster in a closed circulatory system.

    • Correct Answer: A

  • Question 10: After blood enters the right atrium, it then enters the _____.

    • A. right ventricle

    • B. left atrium

    • C. left ventricle

    • D. aorta

    • Correct Answer: A

  • Question 11: Which of the following have valves within them to prevent blood backflow?

    • A. arteries

    • B. veins

    • C. capillaries

    • D. arterioles

    • Correct Answer: B

  • Question 12: Which of these ventilation mechanisms lacks air sacs and relies on unidirectional flow?

    • A. Lungs of birds

    • B. Lungs of mammals

    • C. Gills

    • D. Tracheae

    • Correct Answer: C

  • Question 13: Negative-pressure ventilation requires which of these?

    • A. A strong muscle to push air into lung

    • B. Sealed internal cavity

    • C. Unidirectional flow

    • D. High concentration of oxygen

    • Correct Answer: B