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Three Categories of Animal Nutrition:
- Herbivores - Eat mainly autotrophs.
- Carnivores - Eat other animals.
- Omnivores - Consume animals and plants or algal.
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Stages of Food Processing:
- Ingestion > Digestion
- In chemical digestion, enzymatic hydrolysis splits bonds in molecules.
- Absorption is uptake of nutrients.
- Elimination is the passage of undigested material out.
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Types of Ingestion:
- Suspension
- Substrate
- Fluid
- Bulk
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Suspension Feeders:
- Many aquatic animals.
- Sift through particles in water.
- ex. Sponge
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Substrate Feeders:
- Animals that live in or on their food source.
- ex. Tapeworm
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Fluid Feeders:
- Suck nutrient-rich fluid from a living host.
- ex. Leeches
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Bulk Feeders:
- Eat relatively large pieces of food.
- ex. Snakes
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Digestive Compartments:
- Most animals process food in specialized compartments.
- Reduces risk of digesting its own cells and tissues.
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Intracellular Digestion:
Food particles engulfed by endocytosis and digested in vacuoles.
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Lysosomes:
Contains hydrolytic enzymes involved in intracellular digestion.
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Extracellular Digestion:
- Breakdown of food particles outside of cells.
- Occurs in compartments continuous with outside of body.
- Simple body plans have gastrovascular cavity that functions in digestion and Complex animals have a digestive tube with a mouth and anus. (Digestive Tube/Alimentary Canal)
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Alimentary Canal Regions:
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Foregut:
- Where food is physically broken up.
- Mouth cavity:
- Food may swallowed whole or fragmented/liquified.
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Stomach:
- Storage sac for food.
- Physically (and enzymatically) breaks down food.
- Some have crops that hold food and muscular gizzards that grind food.
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Midgut:
- A long, thin midgut is referred to as small intestine.
- The primary site of digestion and absorption.
- Hydrolytic enzymes secreted by intestinal cells and glands.
- Macromolecules broken down to monomers and absorbed into blood.
- Maximizing surface area increases ability to absorb.
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Hindgut:
- Is the final segment.
- Also called Large Intestine.
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Function of Large Intestine:
- Recover water and ions.
- Store feces.
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Cloaca:
Urinary and digestive wastes expelled through the same opening.
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Adaptations of Vertebrate Digestive Systems:
- Digestive systems are variations on a common plan.
- There are adaptations related to diet.
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Dental Adaptations:
- Dentition is a structural variation reflecting diet.
- Mammals have varying dentition adapted to their diet.
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Differences in dentition patterns:
- Carnivores - Tearing meat (large canines)
- Herbivores - Chewing tough plants (no or small canines, many molars)
- Omnivores - Balanced set of teeth for meat and plants.
- Snakes - Modified fangs to inject venom with unhingeable jaws.
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Stomach and Intestinal Adaptations:
- Herbivores have longer alimentary canals reflecting longer digestion times.
- Carnivores eat larger food pieces and store for a longer time due to fewer resources.
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Mutualistic Adaptations:
- Herbivores have fermentation chambers.
- Symbiotic microorganisms digest cellulose.
- Enzymes lacked in animal but present in microorganism.
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Ruminants:
- Herbivore with Elaborate adaptation.
- Multiple chambers to digest to a certain point.
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Animal Diet:
- Provides chemical energy.
- Need a source of organic carbon and nitrogen.
- Essential nutrients must be obtained from diet.
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Name the four classes of essential nutrients.
- Essential Amino Acids
- Essential Fatty Acids
- Vitamins
- Minerals
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Amino Acids:
- Require 20 amino acids.
- Can synthesize about half from diet.
- Remaining, essential amino acids, in preassembled form.
- Protein insufficient diet causes malnutrition called protein deficiency.
- Meat, eggs, and cheese are "complete" proteins.
- Most plant proteins are incomplete.
- Plant proteins need specific plant combinations.
- Adaptations help periods when demanding lots of protein.
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Essential Fatty Acids:
- Unsaturated fatty acids and obtained by diet.
- Animals can synthesize most fatty acids.
- Deficiencies in fatty acids are rare.
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Vitamins:
- Organic molecules required in small amounts.
- 13 vitamins essential to humans have been identified.
- Vitamins are either grouped fat-soluble and water-soluble.
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Minerals:
- Simple inorganic nutrients, required in small amounts.
- Calcium, Magnesium, Phosphorous, Iron
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Dietary Deficiencies:
Undernourishment is a diet that supplies less energy than required.
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An Undernourished Individual Will:
- Use up stored fat and carbohydrates.
- Break down its own proteins.
- Lose muscle mass.
- Suffer protein deficiency of the brain.
- Die or suffer irreversible damage.
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Malnourishment:
- Long-term absence from diet of essential nutrients.
- Cause deformities, disease, and death.
- Corrected by changes to diet.
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Energy Balance:
- Balances energy from metabolism, activity, and storage.
- ATP generation is based on oxidation of energy-rich molecules:
- Carbohydrates, Proteins, and Fats.
- Stores excess calories as glycogen in liver and muscles.
- Secondarily stored as adipose, or fat, cells.
- Fewer calories than expended leads to usage from storage and oxidized.
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Effect of Obesity:
- Diabetes (type 2)
- Cancer (colon, breasts)
- Heart Attacks
- Strokes
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Homeostatic Mechanisms:
- Feedback circuits controls storage and metabolism of fat long-term.
- Hormones regulate long-term and short-term affect a "satiety center".
- Complexity of weight control is evident from studies leptin. (hormone)
- Mice with defect in leptin gene become very obese.
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Problem of Maintaining Weight:
- From our past, when fat hoarding meant survival.
- A species of birds called petrels become obese as chicks.
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