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Questions and Answers
What is the primary function of salivary amylase in the oral cavity?
What is the primary function of salivary amylase in the oral cavity?
What is the main component of gastric juice that kills bacteria and denatures proteins?
What is the main component of gastric juice that kills bacteria and denatures proteins?
What is the function of the tongue in the oral cavity?
What is the function of the tongue in the oral cavity?
What is the primary function of the parietal cells in the stomach?
What is the primary function of the parietal cells in the stomach?
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What is the role of mucus in the stomach?
What is the role of mucus in the stomach?
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What is the function of the chief cells in the stomach?
What is the function of the chief cells in the stomach?
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What is the function of the sphincters in the stomach?
What is the function of the sphincters in the stomach?
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What is the primary location of enzymatic hydrolysis of ingested food in humans?
What is the primary location of enzymatic hydrolysis of ingested food in humans?
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Which of the following is NOT a stage of feeding in the digestive process?
Which of the following is NOT a stage of feeding in the digestive process?
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What is the primary function of the gastrovascular cavity in simple animals?
What is the primary function of the gastrovascular cavity in simple animals?
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Which of the following organs is responsible for producing bile that aids in fat digestion?
Which of the following organs is responsible for producing bile that aids in fat digestion?
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What is the term for the process by which cells engulf and digest food particles?
What is the term for the process by which cells engulf and digest food particles?
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Which of the following is a characteristic of extracellular digestion?
Which of the following is a characteristic of extracellular digestion?
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What is the primary function of the oral cavity in the digestive process?
What is the primary function of the oral cavity in the digestive process?
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Which of the following enzymes is responsible for breaking down proteins into smaller peptides and amino acids?
Which of the following enzymes is responsible for breaking down proteins into smaller peptides and amino acids?
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Which of the following statements is true about the complete digestive tract?
Which of the following statements is true about the complete digestive tract?
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What is the primary function of essential nutrients in an animal's body?
What is the primary function of essential nutrients in an animal's body?
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What is the consequence of an undernourished individual breaking down their own proteins?
What is the consequence of an undernourished individual breaking down their own proteins?
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Which of the following macronutrients provides the most energy per gram?
Which of the following macronutrients provides the most energy per gram?
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What is the primary difference between gastrovascular cavities and complete digestive tracts?
What is the primary difference between gastrovascular cavities and complete digestive tracts?
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What is the primary role of enzymatic digestion in the stomach?
What is the primary role of enzymatic digestion in the stomach?
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Which of the following is NOT a characteristic of essential amino acids?
Which of the following is NOT a characteristic of essential amino acids?
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What is the primary function of the oral cavity in the digestive process?
What is the primary function of the oral cavity in the digestive process?
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What is the primary site of absorption in the large intestine?
What is the primary site of absorption in the large intestine?
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What is the primary function of coanocytes in sponges?
What is the primary function of coanocytes in sponges?
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In which animals does extracellular digestion occur?
In which animals does extracellular digestion occur?
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What is the primary function of the gizzard in birds?
What is the primary function of the gizzard in birds?
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In which animals is the digestive process initiated through ingestion?
In which animals is the digestive process initiated through ingestion?
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What is the primary function of the intestine in bilaterally symmetrical animals?
What is the primary function of the intestine in bilaterally symmetrical animals?
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In which animals is the digestive process facilitated by the release of enzymes through exocytosis?
In which animals is the digestive process facilitated by the release of enzymes through exocytosis?
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What is the primary function of the crop in birds?
What is the primary function of the crop in birds?
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In which animals does the digestive process occur entirely within cells?
In which animals does the digestive process occur entirely within cells?
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What is the primary function of macronutrients in animals?
What is the primary function of macronutrients in animals?
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Which of the following is NOT a characteristic of proteins in animals?
Which of the following is NOT a characteristic of proteins in animals?
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Why is energy efficiency important for animals?
Why is energy efficiency important for animals?
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What is the primary function of vitamins and minerals in animals?
What is the primary function of vitamins and minerals in animals?
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What determines the nutrient requirements of different animals?
What determines the nutrient requirements of different animals?
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What is the primary function of carbohydrates in animals?
What is the primary function of carbohydrates in animals?
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What is the primary function of lipids in animals?
What is the primary function of lipids in animals?
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What is the primary function of the digestive system in animals?
What is the primary function of the digestive system in animals?
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What is the characteristic that distinguishes the mammalian digestive system from that of other vertebrates?
What is the characteristic that distinguishes the mammalian digestive system from that of other vertebrates?
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Which of the following is NOT a component of saliva?
Which of the following is NOT a component of saliva?
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What is the primary function of the epiglottis?
What is the primary function of the epiglottis?
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What is the pH of the stomach due to the secretion of which acid?
What is the pH of the stomach due to the secretion of which acid?
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What is the main function of the pancreas in the small intestine?
What is the main function of the pancreas in the small intestine?
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What is the process by which triglycerides are broken down into fatty acids and glycerol in the small intestine?
What is the process by which triglycerides are broken down into fatty acids and glycerol in the small intestine?
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What is the function of villi in the small intestine?
What is the function of villi in the small intestine?
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What is the type of vessel that transports fats and other lipids from the small intestine to the bloodstream?
What is the type of vessel that transports fats and other lipids from the small intestine to the bloodstream?
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Which type of plankton is characterized by being plant-like?
Which type of plankton is characterized by being plant-like?
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What is required for suspension feeding?
What is required for suspension feeding?
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What distinguishes filter feeding from other feeding strategies?
What distinguishes filter feeding from other feeding strategies?
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What is a key point to remember about deposit feeding?
What is a key point to remember about deposit feeding?
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Which of the following is an example of an animal that uses suspension feeding?
Which of the following is an example of an animal that uses suspension feeding?
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Which of the following is NOT a type of feeding strategy mentioned in the content?
Which of the following is NOT a type of feeding strategy mentioned in the content?
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Which feeding strategy involves collecting small particles with minimal effort?
Which feeding strategy involves collecting small particles with minimal effort?
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What is the primary benefit of mutualism in symbiotic relationships?
What is the primary benefit of mutualism in symbiotic relationships?
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Which feeding strategy involves using fake or misleading signals to attract prey?
Which feeding strategy involves using fake or misleading signals to attract prey?
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What is the primary benefit of group feeding?
What is the primary benefit of group feeding?
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Which of the following animals is an example of tool use?
Which of the following animals is an example of tool use?
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What is the primary difference between bulk feeding and particle feeding?
What is the primary difference between bulk feeding and particle feeding?
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Which of the following feeding strategies is used by filter feeders?
Which of the following feeding strategies is used by filter feeders?
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What is the primary advantage of using traps and deception in feeding?
What is the primary advantage of using traps and deception in feeding?
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Study Notes
The First Stage of Digestion
- Mechanical digestion occurs in the oral cavity.
- Salivary glands deliver saliva to lubricate food and initiate breakdown of glucose polymers.
- Saliva contains mucus, a viscous mixture of water, salts, cells, and glycoproteins.
- Teeth chew food into smaller particles, and the tongue shapes food into a bolus and provides help with swallowing.
- The throat, or pharynx, is the junction that opens to both the esophagus and the trachea.
- The esophagus conducts food from the pharynx down to the stomach by peristalsis.
Digestion in the Stomach
- Gastric juice has a low pH of about 2, which kills bacteria and denatures proteins.
- Gastric juice is made up of hydrochloric acid (HCl) and pepsin.
- Pepsin is a protease, or protein-digesting enzyme, that cleaves proteins into smaller peptides.
- Parietal cells secrete hydrogen and chloride ions separately into the lumen of the stomach.
- Chief cells secrete inactive pepsinogen, which is activated to pepsin when mixed with hydrochloric acid in the stomach.
- Mucus protects the stomach lining from gastric juice.
- Coordinated contraction and relaxation of stomach muscle churn the stomach's contents.
Stages of Feeding
- Ingestion: taking in food.
- Digestion: breaking food into small pieces for absorption.
- Absorption: nutrient uptake by cells.
- Elimination: expulsion of undigested material.
Digestion Forms
- Intracellular digestion: food particles are engulfed by phagocytosis, and food vacuoles fuse with lysosomes containing hydrolytic enzymes.
- Extracellular digestion: breakdown of food particles outside of cells, occurring in compartments that are continuous with the outside of the animal's body.
Mammalian Digestive System
- The mammalian digestive system consists of an alimentary canal and accessory glands that secrete digestive juices through ducts.
- Accessory glands are the salivary glands, the pancreas, the liver, and the gallbladder.
Animal Nutrition
- Macronutrients: carbohydrates, lipids, and proteins.
- Essential nutrients: those the animal body cannot synthesize, including essential amino acids, essential fatty acids, vitamins, and minerals.
- Undernutrition: results when a diet does not provide enough chemical energy, leading to protein deficiency, loss of muscle mass, and potentially death or irreversible damage.
Digestive Strategies in Animals
- There are four stages of feeding: ingestion, digestion, absorption, and elimination.
Sponges
- Sponges are filter feeders, benefiting from small particles of food in the water that comes into their bodies through incurrent canals.
- Coanocytes capture food particles through phagocytosis and digestion occurs when enzymes in vesicles fuse with food vacuoles, breaking down food into smaller molecules.
- Absorption occurs when these molecules are used by the cell or packaged into vesicles for sharing with other cells.
- Wastes are eliminated through exocytosis.
Cnidarians
- Cnidarians, such as jellyfish and sea anemones, have extracellular digestion in the gastrovascular cavity.
- Cells produce enzymes in vesicles, which are released through exocytosis for digestion.
- Absorption occurs in cells lining the gastrovascular cavity.
- Wastes are eliminated through the mouth, which also serves as the anus.
Bilaterally Symmetrical Animals
- Bilaterally symmetrical animals, such as segmented worms and arthropods, have a complete digestive system with a mouth and anus.
- Ingestion occurs through the mouth, followed by mechanical digestion through chewing mandibles or a gizzard.
- Digestion occurs in the stomach, aided by digestive enzymes.
- Absorption occurs along the intestine.
- Wastes are eliminated through the anus.
Birds
- Birds have a crop for storing food, which is then broken down in the gizzard with the help of digestive enzymes and mechanical grinding.
- Absorption occurs in the intestine.
- Wastes are eliminated through the cloaca, which also serves as the reproductive and excretory system.
Mammals
- Mammals have a complex digestive system with well-developed teeth for mechanical digestion.
- Ingestion occurs through the mouth, followed by chemical digestion with enzymes in the stomach.
- Absorption occurs in the small intestine, and water is recycled in the large intestine.
- Wastes are eliminated through the anus.
Energy Sources for Animals
- Carbohydrates, lipids, and proteins are macronutrients that provide energy for animals.
- Fruits, vegetables, and meat are examples of food sources that contain large amounts of macronutrients.
Importance of Energy for Animals
- Energy is necessary for daily activities, growth, and maintenance of bodily functions.
- Animals require energy to move, find food, and respond to their environment.
Macronutrients and their Functions
- Carbohydrates provide energy for the body and are found in fruits, vegetables, and grains.
- Lipids provide energy, are found in fatty foods, and are essential for brain function.
- Proteins build and repair tissues, and are found in meat, fish, and eggs.
Digestion and Absorption
- Digestion breaks down macronutrients into smaller molecules.
- The digestive system absorbs these molecules, which are then used by the body for energy and growth.
Importance of Vitamins and Minerals
- Vitamins and minerals are essential nutrients that help the body function properly.
- They are found in small amounts in food sources and are crucial for maintaining health.
Energy Efficiency
- Animals use energy efficiently to conserve energy.
- Energy efficiency is vital for survival, especially in environments where food is scarce.
Nutrient Requirements
- Different animals have unique nutrient requirements based on their size, age, and environment.
- A balanced diet meeting an animal's nutrient needs is necessary for maintaining health and function.
Characteristics of Mammalian Digestive System
- Has fewer compartments compared to other vertebrates
- Lacks crop and gizzard
Mouth and Saliva
- Initial digestion occurs in the mouth
- Saliva contains amylase to break down polysaccharides into smaller polysaccharides and disaccharides
- Saliva also contains mucous, water, salts, and glycoproteins to aid food passage through the esophagus
- Formation of bolus occurs during chewing
- Epiglottis prevents food from entering the respiratory tract
Stomach
- Stomach pH is 2 due to hydrochloric acid
- Gastric pits contain:
- Parietal cells that secrete hydrogen and chloride ions
- Chief cells that secrete pepsinogen, which is converted to pepsin by hydrochloric acid
- Mucous cells that produce mucus to protect the stomach lining
- Stomach muscles mix food with digestive enzymes through churning action
Small Intestine
- Main site of chemical digestion
- Divided into three regions: duodenum, jejunum, and ileum
- Pancreas secretes various enzymes, such as trypsin, chymotrypsin, and amylase, into the duodenum
- Bile from liver and gallbladder aids in fat digestion and absorption
- Epithelial cells lining the intestine produce digestive enzymes, such as amylase and carboxypeptidase
- Villi increase the surface area for nutrient absorption
- Fats are broken down into fatty acids and glycerol, then formed into chylomicrons with phospholipids, cholesterol, and proteins for transport to the blood and distribution to the body
Particle Feeding
- Particle feeding involves feeding on fine particles in aquatic environments, such as plankton.
Types of Plankton
- Phytoplankton are plant-like plankton, including microscopic algae like diatoms, found in freshwater and oceans.
- Zooplankton are animal-like plankton, including larvae of animals and protists, found in aquatic environments.
Suspension Feeding
- Suspension feeding involves generating water currents to move water towards the mouth and trapping food particles in mucus.
- Two conditions required for suspension feeding are:
- A mechanism for guiding water with suspended food particles towards the mouth.
- The ability to secrete mucus to trap food particles.
- Examples of animals that use suspension feeding include clams and tunicates.
Filter Feeding
- Filter feeding involves using a straining mechanism to trap small particles from the water.
- Animals that use filter feeding must have a straining mechanism to mechanically pick up food particles from the water.
- Examples of animals that use filter feeding include baleen whales, spoonbills, flamingos, and ducks.
Deposit Feeding
- Deposit feeding involves feeding on depositors or larvae that settle to the bottom of a lake or ocean.
- Animals that use deposit feeding must wait for food particles to settle to the bottom before collecting them.
- Examples of animals that use deposit feeding include worms, snails, limpets, and clams.
Feeding Strategies
- Particle feeding involves collecting small particles, including dead organisms, with minimal effort, but may not be satisfying.
- Filter feeders and deposit feeders are examples of particle feeding.
Bulk Feeding
- Bulk feeding involves consuming large items, such as prey, which requires more effort and investment.
- It provides a lot of energy at once, allows selection of food items, but needs greater effort to find, capture, and consume prey.
Symbiotic Relationships
- Mutualism involves both organisms benefiting, such as aphids and ants, where aphids feed on plant sap and ants provide protection in exchange for honeydew.
- Aphids benefit from protection, and ants benefit from honeydew.
Traps and Deception
- Some animals set up traps, like spider webs or larval ant lions, to catch prey.
- Deception involves using fake or misleading signals, such as the angler fish's lure or spider's pheromone imitation, to attract prey.
- Lantern fly, spider, and angler fish are examples of traps and deception.
Tool Use
- Some animals use tools, like chimps using sticks to extract termites or Egyptian vultures using rocks to crack open ostrich eggs, to obtain food.
- Chimpanzees and Egyptian vultures are examples of tool use.
Group Feeding
- Group feeding increases food capture efficiency, reduces search area, and lowers predation risk.
- Examples of group feeding include lions, hyenas, wild dogs, dolphins, grey whales, and Harris Hawks.
- Strategies include coursing, stalking, ambushing prey, and using group hunting tactics like bubble nets or driving prey towards the shore.
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Description
Learn about the first stage of digestion, including mechanical digestion in the oral cavity, the role of salivary glands, and the process of swallowing.
