Review Sheet 41 Animal Nutrition
1) Organisms lose matter as waste (urine, shed skin, etc.) and usable energy when it is converted to feat.
For this reason, organims must acquire food, material containing nutrients and usable energy.
2) Animals are chemoheterotrophic and ingest food. They may be herbivorous, carnivorous, or
omnivorous. There are also more specialized terms for the various species diets (e.g. frugivorus (fruiteating), insectivorous, granivorous, etc.).
3) Methods of ingestion: 1) filter feeding: extract food particles from water (e.g. baleen whales, some
sharks, bivalve mollusks, sponges; 2) substrate feeders: animals lives on or in food and eats as it
moves (e.g. caterpillers on leaf, earthworms in soil, maggots on a carcass); 3) fluid feeders: drink fluid
from a host (aphids suck plant fluids; ticks, female mosquito drink blood; butterflies drink nectar; 4)
bulk feeding: most common, animals ingests large chunks of solid food using manidibles, tentacles,
etc.
4) First stage of eating: ingestion: food enters gut.
5) Second stage of eating: digestion. Two components: mechanical breakdown and chemical breakdown.
6) Mechanical breakdown is chewing and churning which breaks chunks of food into smaller pieces,
which increases the surface area giving digestive enzymes more surface on which to work. May be
achieved using jaws for chewing, others like birds have gizzards for “chewing”); chemical breakdown
of macromolecules into simple sugars, fats, and amino acids
7) Monogastric digestion: (e.g. human) stomach churns and acidifies foods, increasing surface area of
particles. Stomach acid also important for killing microorganisms in food.
8) Ruminant digestion: (e.g. cattle) four digestive chambers, 1) rumen, very large organ, contains
microorganisms that break down cellulose, food periodically regurgitated and chewed for increased
surface area, 2) reticulum, deteremines whether food particles are regurgitated or passed to omasum, 3)
omasum, various functions (e.g. absorption of water), 4) abomasum, functions like monogastric
stomach. Ruminants can digest low quality foods like grass indigestible to monogastric animals.
9) Third stage of eating: absorption: nutrients leave gut and enter organism’s bloodstream; usually
occurs in small intestine
10) Fourth stage of eating: elimination: unusable material expelled from gut (defecation)
11) Nutrition ties into the theme of homeostasis because energy must be taken in to replace lost energy
stores, and structures must be maintained with new material taken from food. Blood glucose is an
example of a nutritional characteristic that is under tight homoeostatic control.
12) Undernourishment means caloric intake has fallen below caloric expenditures. In vertebrates, blood
sugar homeostasis is maintained by mobilizing glycogen from the liver or lipids from the adipose
tissue to add glucose to the blood.
13) Overnourishment means caloric intake exceeds caloric expenditures. In this case, excess energy is
stored in glycogen in the liver, with has a limited storage capacity. When the liver is full, energy is
stored as lipid in the adipose tissue.
14) Essential nutrients are nutrients that cannot be synthesized by the body from other nutrients and
therefore they must be acquired in the animal’s diet. If an essential nutrient is absent from an animal’s
diet, it is said to be malnourished (note the distinction with undernourished).
15) Eight of the twenty amino acids are essential amino acids. Animal products normally provide all of
the essential amino acids. Vegetarian diets require the right mix of foods to get all of the essential
amino acids. A diet of grains (corn, rice, etc.) and legumes (beans) provides all of the essential amino
acids.
16) Some fatty acids are essential fatty acids. Deficiencies in essential fatty acids are rare, however.
17) Vitamins are organic molecules (other than proteins and lipids) that are essential nutrients. There are
thirteen known vitamins. They have a variety of functions.
18) Minerals are elements that are required in some form by the body for healthy functioning. Elements
cannot be synthesized by any chemical reaction (elements are the building blocks of molecules), so
elements that are nutrients are always essential nutrients.