Download Animal Nutrition

Animal Nutrition
We need to eat! 
 Since we as animals
cannot produce our own
food, we must EAT it.
 Classifying organisms by
what they eat…
 Herbivores: eat
autotrophs
 Carnivores: eat other
animals
 Omnivores: eat both
autotrophs and animals
Classifying Animals by HOW They Get
Their Food
 Suspension feeders:
 Sift small food particles
from the water
 Examples: clams, oysters,
whales
 Substrate feeders:
 Live on (or in) their food
source
 Example: leaf miners, eat
their way through leaves
 Deposit feeders:
 A type of substrate feeder
 Eat partially decayed
organic material in soil
Classifying Animals by HOW They Get
Their Food
 Fluid-feeders
Suck nutrient-rich fluids
from a living host
Example: mosquitoes,
hummingbirds
 Bulk-feeders
Eat relatively large
pieces of food
That’s us! 
The 4 Stages of Food Processing
1. Ingestion
The act of eating
2. Digestion
The process of breaking down food into
molecules small enough for the body to
absorb
This involves hydrolysis, which you should
know well 
This has to occur in a specialized
compartment… why??
The 4 Stages of Food Processing
3. Absorption
 The animal’s cells absorb the small molecules
broken down during digestion
4. Elimination
 Undigested material passes out of the
digestive compartment
Gastrovascular Cavities
 Gastrovascular
cavities are the
digestive systems in
simple animals
 GCs have only one
opening, and there is
only one “part” of a
GC
Digestion in Alimentary Canals
Complex animals use alimentary canals, a
digestive tube extending between two
openings, a mouth and an anus
An “Entrance” and an “Exit”
Food travels in one direction only
Mouth = site of ingestion
Anus = site of elimination
Alimentary Canals
The Mammalian Digestive System
The Mammalian Digestive System
 Consists of:
Oral cavity (mouth)
Pharynx
Esophagus
Stomach
Small Intestine
Large Intestine
 Food moves through the digestive system by
peristalsis, rhythmic waves of contraction by the
smooth muscles
Oral Cavity
The mouth
Chewing cuts, smashes, and grinds food
to facilitate swallowing
Saliva is secreted into the mouth by the
salivary glands
Saliva contains salivary amylase
This enzyme breaks down starch and glycogen
into smaller pieces
Pharynx
 The pharynx is the intersection that leads to both
the esophagus (digestive system) and the
trachea (respiratory system)
 The epiglottis makes sure that food doesn’t enter
the trachea
Esophagus
 The esophagus
carries food from the
pharynx into the
stomach
Stomach
 Our stomachs are stretchy – they expand to fit
our food! 
 The inside of the stomach contains gastric
juice, which has a pH of about 2
HCl – kills most bacteria swallowed with food
- breaks down cells in meat and plant material
Pepsin – breaks down proteins
 Because the smooth muscle of the stomach and
enzymes churn and break up your meal, the
food becomes a nutrient broth known as acid
chyme
Stomach
 The pyloric
sphincter closes off
the stomach from the
small intestine, the
next stop on our tour
 The pyloric sphincter
lets in small amounts
of acid chyme at a
time
Small Intestine
Most digestion and absorption occurs in
the small intestine
In humans, the small intestine is about 6
meters long
It’s called the “small intestine” because it has a
small diameter
Small Intestine
First section of the small intestine is the
duodenum  responsible for digestion
Acid chyme enters from the stomach
Pancreatic enzymes (hydrolytic) enter
Bile (produced in the liver, stored in the gall
bladder) enters
Bile contains bile salts which aid in digestion and
absorption of fats
Small Intestine
Carbohydrates are broken down
(digested) by amylases from the pancreas
Proteins are broken down (digested) by
trypsin
DNA and RNA are broken down by
nucleases
Fats are broken down by bile salts from
the liver and lipase
Small Intestine
The digestion occurs in the duodenum
The absorption of nutrients occurs in the
jejunum and ileum
In order to be useful to an organism, the
nutrients that have been broken down must be
absorbed
The jejunum and ileum (sections 2 and 3 of the
small intestine) are responsible for absorbing
what the duodenum digested
Small Intestine
The jejunum and ileum have a brush
border
The jejunum and ileum have villi (that look like
fingers) and microvilli
This gives them more surface area, which
facilitates absorption of nutrients
More doors = faster access
The Small Intestine
Large Intestine (Colon)
 The major function of the colon is to reabsorb
water that entered the digestive system as a
solvent
 The wastes of the digestive tracts are called
feces, and they become more solid as they are
moved along the colon
If it moves through too quickly, not enough water is
reabsorbed  diarrhea
If it moves through too slowly, too much water is
reabsorbed  constipation
 The waste is stored in the rectum until it can be
eliminated through the anus
The Mammalian Digestive System
Evolutionary Adaptations
Evolutionary adaptations of the digestive
system exist among animals, primarily
based on their diet
Herbivores have less specialized teeth
than do carnivores
Herbivores have longer alimentary canals
than carnivores…why??
Evolutionary Adaptations
Food is our Fuel
 Undernourished:
Someone whose diet is
deficient in calories
 Malnourished:
Someone whose diet is
missing one or more
essential nutrients
 However, obesity is a
more common dietary
problem in America