-
Heterotrophs
Organisms that must acquire nutrients in the form of organic material from their environment.
-
Three Dietary
Categories of Animals
- 1. Herbivores
- 2. Carnivores
- 3. Omnivores
-
Herbivores
Plant eaters, Cattle, gorillas, etc
-
Carnivores
Meat eaters, Sharks, lions, etc
-
Omnivores
Plant & meat eaters, crows, bears, etc
-
Chemical Digestion
Chemical break-down of food by digestive enzymes. Breaks down food into smaller molecules for reassembly as required by the body.
-
Mechanical Digestion
- Physical processes such as chewing.
- 1. Homodont dentition
- 2. Heterodont dentition
-
Homodont dentition
Teeth are identical in shape; used for grasping and swallowing prey whole. Examples – fish, amphibians, reptiles.
-
Heterodont dentition
- Teeth are different in shape; used for tearing and chewing, breaking food down into smaller pieces. Examples – mammals.
-
Four Stages of Food Processing
- 1. Ingestion
- 2. Digestion
- 3. Absorption
- 4. Elimination
-
Ingestion
Act of eating. Nutrients are taken into the body
-
Digestion
Breakdown of food into small nutrient molecules. Carbohydrates, lipids, and proteins
-
Absorption
Uptake of small nutrient molecules by the lining of the digestive tract.
-
Elimination
Disposal of undigested materials left over from eating.
-
Food Vacuole
Intracellular organelles filled with digestive enzymes. Example: Amoeba
-
Gastrovascular Cavity
Compartments with a single opening that functions as both entrance for food and exit for undigested wastes. Example: Hydra
-
Digestive Tube
Tube with two separate openings extending between mouth and anus. Examples: invertebrates – mammals.
-
Oral Cavity
Food is mechanically (teeth) and chemically (salivary glands) broken down.
-
Saliva
Protects the lining of mouth from abrasion, lubricates food for easy swallowing. Salivary amylase breaks down starch, glycogen. Antibacterial agents kill germs. Buffers neutralize acids.
-
Tongue
Tastes food, manipulates it during chewing, shapes it into a ball (bolus). During swallowing, the tongue pushes the bolus to the back of the oral cavity and into the pharynx.
-
Pharynx
Junction that opens to both the esophagus and the trachea. Epiglottis - covers the glottis (opening in trachea) when swallowing
-
-
Peristalsis
Rhythmic waves of contraction by involuntary smooth muscles in the wall of the tract that pushes food along.
-
Stomach
Stores food and continues the process of digestion. Stretches to accommodate about 2L. Secretes: Gastric juice, Pepsin, HCl (pH 2). 1. Preventing self-digestion
-
Preventing self-digestion
- 1. Delaying activation of enzymes until in lumen of stomach.
- 2. Secreting a coating of mucus from cells lining the stomach.
- 3. Constantly regenerating stomach lining cells by mitosis.
-
Small Intestine
- Site of enzymatic hydrolysis of macromolecules and absorption of nutrients into the blood stream. Longest section of the digestive tract (6 m).
- 1. Site of most nutrient absorption, also, some in stomach and large intestine.
- 2. Large surface area (300 m2) due to villi (fingerlike projections) & microvilli (microscopic finger-like projections).
- 3. Pancreas: Produces hydrolytic enzymes and bicarbonate which acts as a buffer.
- 4. Liver: Produces bile which contains bile salts that act as detergents that aid in digestion and fat absorption.
-
Pancreas
Produces hydrolytic enzymes and bicarbonate which acts as a buffer
-
Liver
Produces bile which contains bile salts that act as detergents that aid in digestion and fat absorption.
-
Large Intestine
- (colon) Primary site of water absorption. Along with small intestine, reabsorbs about 90% of water in digestive tract.
- 1. Feces are formed here, becoming more solid as they move along by peristalsis. Takes between 12 and 24 hours to cover the distance of the colon (1.5 m).
- 2. Viral or bacterial infections irritate lining of small intestine, reducing water absorption, resulting in diarrhea.
- 3. Too slow, too much water is absorbed resulting in constipation.
- 4. Many organisms, mostly harmless bacteria, live inside large intestine (methanogens). Live on unabsorbed organic material. Byproducts include CH4 and H2S.
- 5. Rectum: Endpoint of the colon; stores feces until they can be eliminated.
- 6. Sphincters: (2) located between the rectum and anus – one voluntary and the other in-voluntary.
-
Rectum
Endpoint of the colon; stores feces until they can be eliminated.
-
Sphincters
(2) located between the rectum and anus – one voluntary and the other in-voluntary.
-
Essential Nutrients
Materials that must be obtained in preassembled form – can’t be manufactured by body. Example: ascorbic acid (orange juice). Required for metabolic reactions.
-
Essential Amino Acids
Animals require 20 AA for proteins; 12 AA can be made from diet while 8 AA must be obtained from food preassembled. Animal products are best sources of proteins - cheese, eggs, meat
-
Vitamins
Organic molecules required in small amounts preventing deficiencies which may result in severe problems. 13 essential vitamins for humans. Balanced diets prevent deficiencies.
-
Minerals
Simple inorganic nutrients required in small amounts preventing deficiencies which may result in severe problems. Ca, P – bone construction, maintenance Fe – component in cellular respiration and hemoglobin in blood I – thyroid hormones for metabolism Na, K, Cl – nerve functioning, maintaining osmotic balance in cells
-
Essential Fatty Acids
- Certain fatty acids required by animals to construct cell membranes.
- Sources = plant-based oils
-
Undernutrition
- Stores of glycogen and fat are depleted and the body begins breaking down proteins for metabolism. Muscles decrease in size.
- Brain becomes protein deficient. Death will eventually result. Causes: starvation, anorexia.
-
Malnutrition
- Deficiency of one or more of the essential nutrients. Protein deficiency = #1 problem.
- Causes: inadequate intake, metabolic or digestive abnormalites.
-
-
Obesity
Body hoards fat – storing fat in-stead of using it for fuel producing an inappropriately high weight to height ratio. Results in: Diabetes, Colon, breast cancer, Cardiovascular disease. Causes: Diet, sedentary lifestyle, genetics.
-
Stomach and Intestine
- 1. Expandable stomach Allows for more eating at one time - in between time may be lengthy.
- 2. Long intestine allows for more surface area for absorption of hard to digest plant material.
-
Symbiosis
- 1. Herbivores house symbiotic bacteria (methanogens) which contain enzymes to assist them in breaking down cellulose.
- 2. Location of symbiotic bacteria in digestive tract varies from species to species.
|
|
