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Chapter 47

BIOL 1107 Chapter Notes - Chapter 47: Nutrient, Organic Compound, Overnutrition

Course Code
BIOL 1107
Thomas Abbot

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47.1 Feeding and Nutrition
βž”Plants only need sunlight and inorganic precursors (H2O, CO2, minerals) to make all organic molecules
βž”Animals require constant diet of organic molecules for energy and nutrients
βž”Herbivore: animal that obtains energy and nutrients primarily by eating plants
β—†Antelopes, horses, bison, giraffes
βž”Carnivore: animal that primarily eats other animals
β—†Cats, penguins, sharks, spiders
βž”Omnivore: animal that feeds at several trophic levels, consuming plants, animals, and other sources of
organic matter
β—†Crows, cockroaches, humans
βž”Organic molecules
β—†act as fuels for oxidative reactions that supply energy
β—†Are the building blocks for making complex biological molecules
βž”Energy in fuels is measured in calories
β—†In animal nutrition, food energy is presented as kilocalories
βž”Carbohydrates, proteins, fats are 3 main types of energy-rich food consumed by animals
β—†Fats provide 2x calories per gram as the carbs and proteins
βž”Malnutrition: condition resulting from a diet in which intake of organic fuels is inadequate or whose
assimilation of such fuels is abnormal or excessive
β—†Undernutrition: form of malnutrition, condition in which intake of organic fuels is inadequate or
assimilation of fuels is abnormal
●Animal is starving for 1+ nutrients, taking in fewer calories than needed
●Animals lose weight, use own body as fuels
●Mammals use stored fats and glycogen (animal starch) first, then proteins, which leads to
muscle wastage, organ and brain damage, and death
β—†Overnutrition: form of malnutrition, condition caused by excessive intake of specific nutrients
βž”Essential amino acids/fatty acids: any amino acid or fatty acid that is not made by the human body but
must be taken in as part of the diet
βž”Vitamin: organic molecule required in small quantities that the animal cannot synthesize for itself
β—†Many vitamins are coenzymes- nonprotein organic subunits associated with enzymes that assist
in enzymatic catalysis
βž”Essential mineral: any inorganic element such as calcium, iron, or magnesium that is required in the diet
of an animal
βž”Essential nutrient: any of the essential amino acids, fatty acids, vitamins, and minerals required in the
diet of an animal
βž”Animals fall into 1 of 4 groups according to overall feeding methods and physical state of the organic
molecules they consume
β—†Fluid feeder: animal that obtains nourishment by ingesting liquids that contain organic molecules
in solution
●Invertebrates- aphids, mosquitoes, leeches, spiders
●Vertebrates- hummingbirds, parasitic fishes (lampreys), bats

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β—†Suspension feeder: animal that ingests small food items suspended in water, such as bacteria,
archaea, single-celled protists, algae
●Aquatic invertebrates- clams, mussels, barnacles, fishes
●Some birds and whales
●Animals strain food in water through a body structure covered with sticky mucus or
through bristles
β—†Deposit feeder: animal that consumes particles of organic matter from the solid substrate on
which it lives
●Earthworms eat through soil, taking soil in and digesting any organic material it contains
●Fiddler crab picks up sediment with claw and moves it to mouth where contents are sifted
β—†Bulk feeder: animal that consumes sizable food items whole or in large chunks
●Most mammals, birds, and fishes
●All reptiles and adult amphibians
47.2 Digestive Processes
βž”Intracellular digestion: process in which cells take in food particles by endocytosis
β—†Endocytic vesicle containing food particles fuses with a lysosome (vesicle containing hydrolytic
β—†Molecular subunits produced by hydrolysis pass from vesicle to cytosol
β—†Sponges and some cnidarians break down food exclusively by intracellular digestion
●Sponges- water containing organic matter enters through pores, choanocytes (collar cells)
lining the body wall trap the food particles, take them in by endocytosis, and transport
them to amoeboid cells which digest them intracellularly
βž”Extracellular digestion: digestion that takes place outside body cells, in a pouch or tube enclosed within
the cell
β—†Epithelial cells lining pouch/tube secrete enzymes that digest the food
β—†Prevents animal from digesting its own body tissues
β—†Most invertebrates and all vertebrates digest food this way
β—†Greatly expands range of available food sources by allowing animals to digest much larger food
than single cells can take in
βž”Gastrovascular cavity: saclike body cavity with a single opening that serves as both entrance for food
and exit for undigested material, serves both digestive and circulatory functions
β—†Animals lack separate vascular system, water taken into digestive chamber serves to circulate
β—†Flatworms, cnidarians such as hydras, corals, sea anemones
●In flatworm Dugesia, food enters pharynx that protrudes from mouth, then enters
gastrovascular cavity
β—†Glands in cavity wall secrete enzymes that begin digestion
β—†Cells lining cavity take up partially digested material bty endocytosis and complete digestion
β—†Undigested matter is released through the pharynx
βž”Digestive tract: part of extracellular digestive system; tubeline with 2 openings that form a separate
mouth and anus

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β—†Digestive contents move in one direction through specialized regions of tube, from mouth to
βž”Lumen: inside of digestive tube, external to all body tissues
βž”Digestion mostly occurs in 5 successive steps
β—†Mechanical processing: chewing, grinding, tearing break food chunks into smaller pieces,
increasing mobility and surface area exposed to digestive enzymes
β—†Secretion: enzymes and other digestive aids (acids, emulsifies, lubricating mucus) are released
into the tube
β—†Enzymatic hydrolysis: food molecules are broken down through enzyme-catalyzed reactions into
absorbable molecular subunits
β—†Absorption: molecular subunits are absorbed from digestive contents into body fluids and cells
β—†Elimination: undigested materials are expelled through anus
βž”The earthworm is a deposit feeder
β—†Food entering mouth passes to muscular pharynx
β—†Contraction of the pharynx moves food through esophagus (connective passage of digestive
tube) into the crop (enlargement of digestive tube where digestive contents are stored and mixed
with lubricating mucus)
β—†Gizzard- grinds ingested material into fine particles by muscular contractions of the wall
β—†Pulverized mixture enters long intestine, where organic matter is hydrolyzed by secreted
●Molecular subunits are absorbed by cells lining the intestine as mixture is moved along
by muscular contractions of the intestinal wall
β—†Undigested residue is expelled through anus
βž”The grasshopper is an herbivorous insect
β—†Tears leaves and other plant parts into small particles with hard external mouth parts
β—†Particles enter mouth and pass through pharynx
β—†Salivary secretions moisten mixture before it enters the esophagus and passes into crop and then
gizzard (which grinds it into smaller pieces)
β—†Food particles enter stomach, where food is stored and digestion begins
β—†Gastric ceca- saclike outgrowths of insect stomachs, where enzymes hydrolyze digestive
●Products of digestion are absorbed through walls of ceca
β—†Undigested contents move into intestine for further digestion and absorption
β—†Water is absorbed from undigested matter and remnants are expelled through anus
βž”Pigeon picks up food (ex. seeds) with bill
β—†Food is moistened in mouth by mucus-filled saliva and swallowed whole (birds have no teeth)
β—†Food passes through pharynx into esophagus
β—†Anterior end of esophagus is tubelike, posterior end is the pouchlike crop where food can be
β—†Food passes from crop into anterior glandular portion of stomach (proventriculus) which secretes
digestive enzymes and acids
●Posterior end is the gizzard, where food is ground into fine particles, aided by ingested
bits of sand and gravel
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