Nutrition & Digestion System *Extended Version*

Overview & Important Concepts

—

Autotrophs (Primary Producer) #1

organisms that produce their own food from inorganic materials (CO2) and either light or chemical energy

Overview & Important Concepts

—

Autotrophs (Primary Producer) #1

organisms that produce their own food from inorganic materials (CO2) and either light or chemical energy

Species type #1a

Plants, protists (algae), and some bacteria and archaea

Heterotopic #2

cannot manufacture their own food; derives nutrition from other sources of organic carbon

Species type #2a

Carnivores, herbivores, omnivores, insectivores, decomposers

Nutrition #3

All processes by which an animal ingests, digests, absorbs, stores and uses food to meet metabolic needs

Digestion:

—

What is Digestion? #1

the chemical and/or mechanical breakdown of food into particles that individual cells of an animal can absorb/use

#2

Digestion can occur inside a cell (intracellular), outside a cell (extracellular), or in both places

Intracellular Digestion:

—

#!

Cells take in whole food particles directly from the environment by diffusion, active transport and/or endocytosis and break them down with enzymes to obtain nutrients

#2

Circumvents the need for mechanical and/or chemical breakdown of food, but also limits animal’s size and complexity (only very small pieces of food can be used)

#3

Common in simpler life forms such as sponges and protists

Extracellular Digestion:

—

#1

Development of a complete digestive tract –with separate mouth and anus—first seen in Aschelminths (ancestors of modern roundworms)

Extracellular Digestion #2

enzymatic breakdown of larger pieces of food into smaller molecules (usually in a special organ or cavity); nutrients from the food then pass into the body and are used in energy metabolism or biosynthesis

#3

Found in some invertebrates and all vertebrates

Types of Feeding:

—

Continuous Feeding #1

food is continuously passed through movement of water as small particles; digestive specializations absent

Found in #1a

Common in slow moving or sessile animals (ex. sponges)

Discontinuous Feeders #2

eat large meals at specific times/periodically; digestive specializations common

Found in #2a

Found commonly in active, faster-moving animals (ex. herbivores/carnivores)

Feeding Strategies:

—

Suspension Feeding #1:

capture and ingestion of food particles that are suspended in water

#1a

Sponges, crustaceans, mollusks, some whales

Deposit Feeding #2

obtaining food from the sediments of ocean beds or moist soil

#2a

Polychaetes, echinoderms

Surface nutrient absorption #3

absorbing food through the general body surface

#3a

Endoparasites

Fluid Feeding #4

sucking plant fluids, or animal fluid/blood

#4a

Leeches, ticks, mosquitos, hummingbirds

Predation #5

an interaction in which one organism (predator) captures and eats all or part of the body of another organism (prey)

#5a

Herbivory, carnivory, parasitism

Nutrients & Animal Dietary Requirements

—

#1

Nutrients in the food an animal consumes provides the necessary chemicals for growth, maintenance, and energy production

#2

Enzymes break down these molecules into components used for energy production or as sources of “building blocks”

#3

The types of nutrients that heterotrophs ingest are divided into macronutrients & micronutrients:

Macronutrients #3a

are needed in large quantities and include carbohydrates, lipids & proteins

Micronutrients #3b

are needed in small quantities and include organic vitamins & inorganic minerals

Carbohydrates:

—

#1

Includes sugars, starch & cellulose

#2

Monosaccharides (simple), disaccharides, polysaccharides (starch; complex)

#3

Functions:

#3a

Sugars and starches broken down into glucose— major dietary source of energy

#3b

Provides carbon source for incorporation into important organic compounds (building blocks of most cells; cellular respiration  ATP)

#3c

Cellulose can not be digested, but it is important as fiber to help move food through the digestive tract

Lipids:

—

Classes #1

fats, oils, waxes, phospholipids & sterols

#2

Functions

#2a

Long-term energy storage

#2b

Insulation

#2c

Precursor to hormones (steroids)

#2d

Major constituents of plasma membrane (cholesterol)

Proteins:

—

#1

Made up of amino acids, which heterotrophs use to build their own proteins

#2

Can be used as energy when in excess

#3

Types of proteins

#3a

Structural

#3b

Enzymes

#3c

Antibodies

#3d

Motor

#3e

Transport

#3f

Receptors

#3g

Regulatory

Micronutrients:

—

#1

Usually small ions, organic vitamins, inorganic minerals, molecules used repeatedly in enzymatic reactions or as parts of certain proteins

#2

Needed in much smaller quantities

Minerals:

—

Essential #1

are those minerals required by the body; includes macrominerals and trace minerals (microminerals)

Macrominerals #2

are those needed in greater amounts

Trace mineral #3

also essential, but needed only in very small amounts for various enzymatic functions

Copper #3a

component of many enzymes, essential for melanin and hemoglobin synthesis; part of cytochrome

Iodine #3b

component of thyroid hormones

Iron #2c

component of hemoglobin, myoglobin, enzymes and cytochromes

Zinc #2d

component >70 enzymes; needed for wound healing

Steps of Digestion:

—

Ingestion #1

Eating

Peristalsis #2

the involuntary, sequential muscular contractions that move ingested nutrients along the digestive tract

Segmentation #3

mixing the contents in the digestive tract (mechanical digestion)

Secretion #4

the release of hormones, enzymes, and specific ions and chemicals that take part in (chemical) digestion

Digestion #5

the conversion of large nutrient particles or molecules into small particles or molecules

Absorption #6

the passage of usable nutrient molecules from the small intestine into the bloodstream and lymphatic system for the final passage to body cells

Defecation #7

The elimination from the body of undigested and unabsorbed material as waste

Oral Cavity:

—

#1

A pair of lips protects the oral cavity (mouth); highly vascularized, skeletal muscle tissue that help retain food as it is being chewed; also play a role in phonation

#2

Within the oral cavity are the tongue and teeth

#3

Mammals can mechanically process wide ranges of food because their teeth are covered with enamel (the hardest material in the body) and because their jaws and teeth exert a strong force

Anatomy of Vertebrate Teeth:

—

Enamal #1

outermost layer; hardest and most mineralized substance in the human body

Dentin #2

covered by enamel; surrounds entire pulp; makes up the majority of the tooth’s structure

#2a

Dentinal Tubules

Cementum #3

Covers the roots

Pulp #4

innermost portion; contains blood vessels and nerves

Type & Arrangement of Vertebrate Teeth:

—

#1

Different vertebrates (herbivore, carnivore, omnivore) have evolved specific patterns and variations from a generalized pattern of dentition depending on their nutritional source

Dentition #2

homodont (majority of verts— fish, amphibia, reptiles), heterodont (mammals)

Attachment to Jawbone #3

acrodont (fish & amphibians), pleurodont (lizards), thecodont (mammals)

Crown height #4

brachydont (humans), hypsodont (herbivores)

Digestion Begins in the Oral Cavity:

—

#1

The oral cavity is continuously bathed by saliva, a watery fluid excreted by (at least) three pairs of salivary glands