Chapter 6, lesson 2 Respiration and Circulation

In order to obtain (get) energy in food, animals must carry out chemical reactions: Food molecules join with oxygen (O 2 ). Energy is released when molecules are broken apart (bonds broken). Carbon dioxide (CO 2 ) is a waste product

Animals must take in (respire) oxygen and eliminate (give off) carbon dioxide. Process of gas exchange = respiration.

Cellular respiration Respiration that occurs inside the cell to break apart molecules with oxygen to release energy that can be used by the cell to do work. Formula for cellular respiration: C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + energy 1 Glucose + 6 oxygens yields (=) 6 carbon dioxides + 6 waters + energy

Cellular respiration

Respiration happens differently for different animals. How does the oxygen get in and the carbon dioxide get out?

Gas Exchange in Simple Animals: Sponges and cnidarians = simple animals Body wall is two cell layers thick.  Water outside touches one layer, water inside (the animal) touches the other layer. Both layers get oxygen (O 2 ) and get rid of carbon dioxide (CO 2 ) by diffusion. (known as simple diffusion)

Diffusion Diffusion = movement of molecules from an area of high concentration to an area of low concentration.

O 2 outside is at higher concentration in the water than inside the cells  O 2 diffuses from water into cells. CO 2 is at a higher concentration inside the cells than in the water  CO 2 diffuses from the cells into the water.

Diffusion also happens in flatworms because they also have 2 cell layers.

Gas Exchange in Other Animals: Most animals contain many cells (many layers thick) Cannot simply exchange gases with environment. They have special organs for respiration.

Animals that live in water  gills. Gills = feathery structure that provides a large surface area that allows diffusion to happen quickly. O 2 in and CO 2 out. Examples: fish, tadpoles, lobsters, clams.

Land animals: exchange gases with the air. Insects  system of tubes that carry air into and out of body. Air enters and leaves through small openings (spiracles) scattered over the body.

Other land animals  lungs. Lungs = balloon like structure inside body. Inhale = breathe in, draws air into lungs Exhale = breathe out, pushes air out of lungs.

Lungs provide a large surface area for O 2 to diffuse into bloodstream and CO 2 to diffuse out of 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 transport (move) O 2 from the gills or lungs to the rest of the body and transport CO 2 from the body to the gills or lungs. This is the job of the Circulatory sytem:  “circulatory” = flowing in a circle.

Moves blood through the body As blood circulates it delivers O 2 and picks up CO 2. Blood also carries nutrients 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 = blood vessels. Carries the blood. One or more pumps = hearts. When heart contracts (squeezes), pushes blood through blood vessels.

Two types of circulatory systems: Open circulatory system Closed circulatory system

1. Open circulatory system: blood leaves the vessels and enters the spaces around organs. (leaks out and surrounds organs) blood flows slowly and makes direct contact with cells.  Examples: arthropods and most mollusks.

2. Closed circulatory system: blood stays inside the vessels at all times. Smallest vessels (capillaries) have very thin walls so the O 2 can diffuse out of blood and into the cell and CO 2 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.

OpenClosed

Vertebrate Circulatory Systems: Single heart. Divided into chambers = enclosed spaces.  Atria (atrium = singular)= chambers that receive blood that returns to the heart (enter only).  Ventricles = chambers that pump the blood out of the heart (exit only).

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 atrium: receives blood from the lungs that is rich in oxygen with very little carbon dioxide (red blood = oxygenated).  Left ventricle: pumps blood to rest of body (arteries carry oxygenated blood away from the heart).  the oxygen rich blood (in capillaries) delivers the oxygen to the cells and picks up carbon dioxide from the cells (waste from cellular respiration)

 the oxygen poor blood (blue blood = deoxygenated) or carbon dioxide rich blood returns to the heart (veins carry blood to the heart)  blood returns to and enters the right atrium: very little oxygen but a lot of carbon dioxide.  Right ventricle: pumps the blood to the lungs.

 at the lungs, the deoxygenated blood gets rid of carbon dioxide (the waste) and picks up more oxygen.  the oxygenated blood returns to the left atrium and begins the cycle again.