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Biology: Chapter 6, lesson 2: Respiration and Circulation notes
 In order to
(get) energy in food, animals must carry
out chemical reactions:
 Food molecules join with
(O2).
 Energy is
when molecules are
apart (bonds broken).
 Carbon dioxide (CO2) is a
product
 Animals must take in (
) oxygen and eliminate
(
) carbon dioxide.
 Process of gas exchange =
.
 Formula for cellular respiration: respiration that occurs
inside the cell to
apart molecules with
oxygen to release
that can be used by the
cell to do
.
C6H12O6 + 6O2  6CO2 + 6H2O + energy
1 Glucose + 6 oxygens yields (=) 6 carbon dioxides + 6 waters +
energy
 Respiration happens differently for different animals.
 How does the oxygen get in and the carbon dioxide get out?
 Gas Exchange in Simple Animals:

and cnidarians = simple animals
 Body wall is
cell layers thick.
 Water outside touches one layer, water inside (the animal)
touches the other layer.
 Both layers get oxygen (O2) and get rid of carbon dioxide
(CO2) by
. (known as simple
diffusion)
 Diffusion = movement of molecules from an area of
concentration to an area of
concentration.
 O2 outside is at higher
in the
water than inside the cells  O2 diffuses from water
cells.
 CO2is at a higher concentration
the
cells than in the water  CO2 diffuses
the
cells into the water.
Biology: Chapter 6, lesson 2: Respiration and Circulation notes
 Diffusion also happens in flatworms because they also
have 2 cell layers.
 Gas Exchange in Other Animals:
 Most animals contain
cells (many layers
thick)
 Cannot simply exchange gases with environment.
 They have special
for respiration.
 Animals that live in water 
.
 Gills =
structure that provides a
large
that allows diffusion to
happen quickly.
 O2 in and CO2 out.
 Examples: fish, tadpoles, lobsters, clams.
 Land animals: exchange gases with the
.
 Insects  system of
that carry air
into and out of body.
 Air enters and leaves through small
(spiracles) scattered over the
body.
 Other land animals 
.
 Lungs =
like structure inside
body.

= breathe in, draws air into lungs

= breathe out, pushes air out of
lungs.
 Lungs provide a large surface area for O2 to diffuse
bloodstream and CO2 to diffuse
the bloodstream.
 How does the Oxygen get to the rest of the body and the carbon
dioxide get back to the lungs from the cells?
 Circulatory Systems:
 Animals must
(move) O2 from the gills or
lungs to the rest of the body and transport CO2 from the body to
the gills or lungs.
 This is the job of the
sytem:
 “circulatory” = flowing in a
.
Biology: Chapter 6, lesson 2: Respiration and Circulation notes
 Moves blood through the body
 As blood circulates it
O2 and
up CO2 .
 Blood also carries
from the digestive
tract to the cells to be broken down by cellular
respiration.
 Oxygen is carried by hemoglobin (made of iron) inside a
red blood cell.
 Red blood = oxygenated (with oxygen)
 Blue blood = deoxygenated (without oxygen)
 All circulatory systems have:
 A set of tubes =
.
 Carries the blood.
 One or more pumps =
.
 When heart
(squeezes),
blood through blood vessels.
 Two types of circulatory systems:
 1. Open circulatory system:
 blood
the vessels and enters the
around organs. (leaks out and
surrounds organs)
 blood flows
and makes direct contact
with cells.
 Examples: arthropods and most mollusks.
 2. Closed circulatory system:
 blood stays
the vessels at all times.
 Smallest vessels (capillaries) have very
so the O2 can diffuse out of blood
and into the cell and CO2 can diffuse out of the cell
and into the blood.
 Blood cells don’t cross, just the gases and nutrients.
 Examples: Annelids, vertebrates, and some mollusks.
 Vertebrate Circulatory Systems:

heart.
 Divided into
= enclosed spaces.

(atrium = singular)= chambers that
receive blood that
to the heart (enter only).

= chambers that pump the blood
of the heart (exit only).
Biology: Chapter 6, lesson 2: Respiration and Circulation notes
 Different classes = different # of chambers
 Fish: one atrium and one ventricle.
 Amphibians and most reptiles: two atria and one ventricle.
 Birds, mammals, and some reptiles: two atria and two
ventricles.
 How does blood circulate through the body of a bird or
mammal?
 Left
: receives blood from the lungs that
is rich in oxygen with very little carbon dioxide (red blood =
oxygenated).
  Left
: pumps blood to rest of body
(arteries carry oxygenated blood away from the heart).
  the oxygen rich blood (in capillaries)
the oxygen to the cells and
carbon
dioxide from the cells (waste from cellular respiration)
 the oxygen poor blood (blue blood = deoxygenated) or
carbon dioxide rich blood
to the heart
(veins carry blood to the heart)
  blood returns to and enters the right
:
very little oxygen but a lot of carbon dioxide.
  Right
: pumps the blood to the
lungs.
  at the
, the deoxygenated blood gets rid
of carbon dioxide (the waste) and picks up more oxygen.
  the oxygenated blood returns to the left
and
begins the cycle again.