CP p.86-89
Unicellular
 No Digestive system
 Intracellular digestion


Example: Amoeba
Pseudopods engulf food
 Food vacuole formed
 Lysosome fuses with vacuole
 Hydrolytic enzymes released into food
vacuole to digest food
 Nutrients absorbed into cytoplasm

Bag system
 Extracellular digestion, followed
by intracellular digestion


Example: Hydra, Jellyfish
Tentacles bring prey to mouth
 Prey is stuffed into gastrovascular
cavity


Different types of cells line gastrovascular
cavity:
◦ Some cells release digestive enzymes to
breakdown food (extracellular digestion)
◦ Other cells with flagella keep contents of cavity
moving
◦ Still other cells engulf food particles for
intracellular digestion
Lining cells can absorb nutrients
 Nutrients diffuse to outer layer of
cells
 Waste is expelled through the
mouth


Tube system
◦ Digestive tract allows the separation of
processed (ingestion, digestion,
absorption, and egestion) into different
regions
◦ Extracellular digestion
◦ Example: Earthworm, Bird, Cow
Muscular pharynx sucks food and soil
into mouth
 Muscles in wall of esophagus push
food to crop
 Crop stores and moistens food

Food is broken down by small
particles of sand and gravel in the
muscular gizzard (physical digestion)
 Food is broken down chemically and
absorbed in the intestine (chemical
digestion)
 Waste is eliminated through the anus

Esophagus carries food to crop
 Crop stores food
 Small pebbles in muscular gizzard
grinds food
 Stomach begins chemical digestion
 Intestine absorbs food
 Waste removed through anus

abomasum
omasum
Stomach has four chambers to help
digest cellulose
 Food travels first to rumen then to
reticulum of stomach where bacteria
start to help break down cellulose

Cow regurgitates and re-chews food
to help soften and break down plant
fibres
 Food then travels to last two chambers
of stomach and onto the intestine
 Waste removed through anus
