Transcript Chapter 6, lesson 1

Chapter 6, lesson 1
How animals get and digest
food.

Animals cannot make their own
food.
– Must get food from other
organisms

Different animals = different ways
of getting food
Filter feeding:

Filtering or straining food
particles from the water. Food
must be tiny.
– Many animals that live in water use
this method.
Animals that can’t move
to get food:
Sponges – filter through pores
 Barnacles – use legs (act like
screens)
 Mollusks – use gills

Animals that can move:

Whales – swim with mouth open,
capturing millions of tiny
organisms and filtering through
their baleen (combs of thick hair
in place of teeth).
Feeding on Fluids
(liquids):

Getting food from the fluids of
plants or other animals.
– Fluids are rich in nutrients.

Aphids and cicadas: have piercing
mouthparts to draw sap from
plants leaves, roots, and stem.

Bees, butterflies, and
hummingbirds: draw nectar from
flowers

Spiders and assassin bugs: suck
fluids from captured insects.

Leeches, mosquitoes, and horse
flies: suck blood from
vertebrates.
Consuming Large
Pieces of Food:

Most animals consume (eat) large
pieces of solid food.
– Use different kinds of body
structures to capture and consume
food.
Cnidarians:

use tentacles with stinging cells
to capture food and eat it whole.
Insects:

many have mouthparts suited for
cutting or chewing.
– Grasshoppers, termites, and beetles
feed on plants – herbivores

Herbivores: animals that eat
only plants or plant parts

Dragonflies and praying mantises
eat other insects – carnivores
– Carnivores: animals that eat only
other animals (meat).

Omnivores: animals that eat
both plants and animals.
(example: human and bears)
Vertebrates:

the only animals with teeth (not
all have them).
– Different shapes and sizes do
different jobs.
Teeth

Chisel-like at front of mouth: cut
food into pieces (incisors = the
ones you bite with)

Long, pointed teeth: grip and
pierce food (canines = “fangs”)

Flat surface: grind and crush
food (premolars and molars = the
ones you chew with).
Teeth type tell what kind
of food an animal eats:



Carnivores: long canine teeth and
sharp, pointed molars = tear flesh.
Herbivores: use incisors to clip plants,
large molars with flat surfaces =
grinding plants.
Omnivores: have a combination of the
types of teeth = tear flesh and grind
plants.
Herbivore
Carnivore
Omnivore
Digesting Food:

Food contains fats, proteins, and
carbohydrates.
– Provide energy an animal needs.
– Too large for most animal cells to
absorb
– Must be broken down into smaller
chemicals

This process is called digestion.
Digestion

Digestion occurs by secreting
digestive enzymes:
– Secreting = form and release.
– Enzymes = substance that speeds
up a chemical change in living
things
Digestion inside cells:

Sponges: cells trap food particles
and package them into vacuoles
(storage organelles inside the cell)
where digestive enzymes break down
the food and then the cell absorbs the
“food” chemicals from the vacuoles.
Digestion inside cell

Drawback: food must be small
enough to fit inside vacuoles 
tiny food particles.
Digestion outside cells:
Most other animals: eat food,
digestion occurs outside cells,
then “food” chemicals are
absorbed by the cells.
 Advantage: can eat much larger
foods.

Gastrovascular
Cavities: (cavity = open
space, like a cave)

(lower animals) Cnidarians and
flatworms digest food in a hollow
space  gastrovascular cavity.
– Only have one opening = the mouth.
– Food enters mouth  special cells in
cavity secrete digestive enzymes that
break down the food  cells absorb
particles.
– Material not digested leaves through the
mouth.
Gastrovascular
Cavities
Digestive Tracts:
(tract = path)

More developed (higher) animals
have a digestive tract.
– Tube-like digestive space with an
opening at each end.
– Food moves in one direction only 
entrance to exit direction.
Digestive tract

Different parts of tract carry out
different functions.
– Main functions:
 Storing
food
 Digesting food
 Absorbing nutrients
Most digestive tracts are
organized in the same way with
some differences.
 Example: Birds

Bird digestive tract




Food enters through the mouth.
Travels through the esophagus to the
crop: food storage.
Passes to stomach: food mixes with
acid and digestive enzymes.
Mixture moves to gizzard: grinds
food into watery paste.
Bird digestion cont.



Moves into intestines: more enzymes
added, nutrients absorbed through
intestine wall, and water is absorbed
(to make feces solid).
Digestion is completed here.
Anything that can’t be digested:
leaves body through the anus.
Humans

Humans and other mammals:
don’t have a crop or gizzard
– Stomach carries out the functions:
food storage, mixing with acids and
enzymes, and grinds food to watery
paste (chyme).