Do Now: After you eat your food, how
does it get into the cells of your body?
Aim: What is digestion and how does it take
place in different organisms?
I. Digestion - The process by which food is
converted into substances that can be
absorbed and assimilated by the body.
A. Different types of digestion
1. Intracellular – when food particles are
broken down within the cell.
2. Extracellular – when food particles are
broken down outside the cell. Usually involves
digestive enzymes.
3. Mechanical digestion – when food is physically
broken down into smaller particles (increase the
surface area) so it can be digested easier.
4. Chemical digestion – when food is broken
down and turned into a different substance by
the use of digestive enzymes. Example: Starch
is broken down into disaccharides.
B. Digestion in different organisms
1. One -cell (Unicellular) Organisms (ex:
Ameba, paramecium)
Ameba
Paramecium
a. Ingest food – Ameba ingests (takes it into the
cell) food by the process of phagocytosis
(surrounds and engulfs food).
b. Food vacuole – temporarily stores food until
it is digested by the lysosome which releases
digestive enzymes to break down food.
Intracellular Chemical Digestion!!!!!!!!!!!!!!!
2. Digestion in the Hydra
a. Paralyzes its prey with stinging cells located
in tentacles.
b. Ingests food through mouth
c. Both intracellular and extracellular digestion
occurs within the hydra.
d. Wastes are released through the mouth
(2-way digestive tract).
3. Digestion in the Earthworm
a. Ingests food through mouth
b. Food is temporarily stored in the crop
c. Food is mechanically broken down
(grinded) by the gizzard.
d. Nutrients are chemically digested and
absorbed in the intestine.
i. Typhlosole – fold in intestine that
increases surface area for both digestion and
absorption.
e. Anus – where undigested material passes out
of Earthworm.
One – way digestive tract!!!!!
4. Digestion in the Grasshopper
a. Food is ingested through mouth and
sucked through the pharynx.
b. Food passes through esophagus.
c. Food is mechanically broken down by
mouth parts (mandible)
d. Food is temporarily stored in
the crop.
e. Has digestive glands (gastric caeca)
outside of intestine to help in chemical
digestion.
f. Wastes temporarily stored in
rectum and eventually egested
through anus.