Digestion Part I
Heterotrophic organismsOrganisms that can not make their own high
energy, organic compounds. Must get their
nutrition from the environment.
Nutrition is needed for
1. Energy
2. Building blocks for their own organic
molecules
Plants are autotrophs
Bacteria-Absorptive
heterotrophs (some are
autotrophs)
Fungi-Absorptive
heterotrophs
Animals-Ingestive
heterotrophs
Protista can vary (algae are autotrophs, others are heterotrophs)
Terms
Saprophytes- Heterotrophs that get their nutrition from dead
organisms
Parasites-Heterotrophs that get their nutrition from living tissue.
Digestion-nutrients are taken in and broken down. The basic plan
is a tube within a tube of higher organisms.
Herbivores-use only plant material for nutrition
Carnivores-use only animal materials for nutrition
Omnivores- nutrition from animal and plant materials
Nutrients-Organic compounds need for life (carbohydrates, fats,
proteins, and vitamins)
Nutritional Requirements varies from species to species for
example some bacteria only require carbohydrates and inorganic
minerals, while other bacteria need all 3 organic nutrients.
Carbohydrates are needed mainly as a source of energy. Glucose
levels in the blood remain relatively constant. When it decreases,
glycogen in the liver and muscles are broken down into glucose.
Some carbohydrates are also used for structure and lubricants.
Carbohydrates are called empty calories because in general they
are needed only for energy.
Proteins are needed as a source of amino acids so that the
organism can generate their own proteins as needed and dictated
by their DNA. Some organisms can make their own amino acids,
however, essential amino acids are amino acids that an organism
cannot make and must have in their diet. These vary from species
to species. Most have at least nine essential amino acids. Animal
material rather than plant material is the most reliable source of
protein. Humans that rely on only one plant nutrient (rice or corn)
may be deficient in amino acids resulting in kwashiorkor disease
(degeneration of liver anemia and inflammation of skin)
Fats are needed for cell membranes. Also fats are the most
efficient way to store energy. Gram for gram, there is twice as
much energy in a gram of lipid as carbohydrates. Lipids are
stored in the liver and in adipose tissue. This is because lipids are
so highly reduced. Carbohydrates have more oxygen than lipids.
Essential fatty acids-are
those fatty acids that an
organism needs but can not
make. Usually not as
severe a problem as
essential amino acids
because animals have the
ability to make carbohydrates into fatty acids.
Vitamins- organic compounds that are needed by an organism in
their diet. Not a carbohydrate, protein or fat. Usually used as a
coenzyme.
Water soluble-Can't be stored vitamins(C+Complex B)
Fat soluble-can be stored vitamins A, E, K and D
Scurvy- lack of vitamin C connective tissue, bleeding gums,
anemia, delayed wound healing
Beriberi- lack of vitamin B causes muscle atrophy, paralysis,
mental confusion, congestive heart failure.
Xerophthalmia-lack of vitamin A keratinization of tissues of the
eye which can lead to blindness.
Rickets-lack of vitamin D results in soft bones so a growing
skeleton can become deformed.
Lack of K- slow blood clotting
Lack of E-malfunction of muscular nervous systems
Minerals are inorganic nutrients essential for the organism but
cannot be made by the organism.
Survey of how nutrition is procured.
Nutrient Procurement Fungi- Uses extracellular digestion as fungi
secretes digestive enzymes which break down the organic
compounds, and then absorb nutrients. Can be saprophytic (bread
mold) or parasitic (athlete's foot).
Animation
Paramecium
Amoeba- phagocytosis or intercellular digestion in vacuoles. *Food
must be digested before it crosses a cell membrane.
Animation
Paramecium
Paramecium- intracellular is similar
Cnidarian nutrient procurement (Jelly fish and hydra)
-Radial symmetry
-2 layers of cells with jelly layer between called mesoglea
1. Food is paralyzed by tentacles with nematocysts
2. Food brought inside gastrovascular cavity via tentacles
3. Digestive juices released by specialized digestive glands
(extracellular digestion). Phagocytosis takes place with the other
cells.
Flat worm- bilateral symmetry
1. Anterior (front) and posterior (rear) end
2. Ventral(tummy side) dorsal (upper) sides
Food enters and wastes exit (the same tube )
mouth
Pharynx- muscular tube which leads to the
gastrovascular cavity
The G.V.C. (gastro vascular cavity) branched extensively this
helps in greater absorptive surfaces.
Digestion in the G.V.C. is some extracellular but mainly
intracellular
note- Tape worm- parasite has lost its digestive system because it
is bathed in nutrients
Some examples of
actual flatworms
Complete digestive tracts- one way tube with a mouth and an anus.
Advantage-Tube can be differentiated into digestive organs to treat
the food in various ways to maximize nutritional value.
Pharynx- Forces food down the tube
Esophagus- tube connects to the crop
Crop- storage area
Gizzard- muscular organ that mechanically grinds food
Intestine- enzymes released more digestion occurs- Nutrients
are absorbed- also has fold called typhlosole which increases
surface area.
Different types of
Annelids
Insects- Very diversified digestive tracts
Mouth parts also very diversified.
Foregut- mouth esophagus, pharynx-moves food into tract
crop- storage of food
ceca- secretes digestive enzymes into midgut
Midgut- chemical digestion occurs
Hindgut- nutrient absorption, water absorption, and cellular
wastes secreted out.
Vertebrates
Shark- replaceable teeth
Intestine-Spiraled valve slows down food and increase surface area
Fish
Herbivore fish intestine: long and winding
Carnivore fish intestine: short (animal matter easier to digest)
Amphibian digestive tract like herbivore fish but tongue
moveable
Reptiles- mostly carnivores
Snakes- unhinge jaws and swallow food whole releasing very
powerful digestive enzymes- some poisonous
Jacobson organ- smell food via tongue; heat sensory organs
Turtles lack teeth but have a razor sharp bill
Alligators- have many unspecialized teeth
Birds- specialized beaks for food procurement
Teeth Adaptations
incisors- gnawing
canine- tearing
molars- grinding
premolars- grinding
Number and type depend on
nutrition
Carnivores- well developed
canines
Herbivores- well developed
molars and premolars
Omnivore- in between
The digestive tract of an
herbivore is usually longer than
the digestive tract of a carnivore
as plant matter is more difficult
to digest. The cecum in
herbivores is more fully
developed as it serves a chamber
where bacterial
Cow has a four chambered
stomach
Rumen- bacteria aids in
digestion and allows
regurgitated and chewed again
Reticulum-removes indigestible material
Omasum-absorbs water and nutrients
Abomasum-true stomach
The End