1. Learning Goal 2 – Gas Exchange and Circulation
Plants Gas Exchange Stomata – Guard Cells – Circulation Xylem – Phloem – Invertebrates Aquatic Invertebrates – Terrestrial Invertebrates – Open Circulatory Systems – Closed Circulatory Systems – Vertebrates Gills – Lungs – Fish – Amphibians and Reptiles – Crocodilians, Birds, and Mammals –

2. Unit II Organs and Organ Systems
Learning Goal 2
Describe components of various organisms that function in gas exchange and in circulation of essential substances.

4. Plants
Gas Exchange
Openings on the underside of leaves, called stomata, allow plants to take in carbon dioxide and give off oxygen during photosynthesis.

5. Cells called guard cells surround the stomata and cause them to open and close in response to water pressure within the guard cells.

6. Circulation
Water and food are transported throughout plants in tube-like vascular tissue called xylem and phloem.
Xylem
Water moves through xylem from the roots.

7. Phloem
Sugars made by the plant for food are moved from the leaves where photosynthesis takes place into other parts of the plant in the phloem.

8. Invertebrates Gas Exchange Aquatic invertebrates
Most exchange oxygen and carbon dioxide through gills. They are feathery structures that expose a large surface area to the water. Examples: mollusks, arthropods.

9. Terrestrial invertebrates
Have respiratory surfaces covered with water or mucus. They range from book lungs in spiders to spiracles (openings) that open into tracheal tubes in insects.

10. Circulation
Open Circulatory System
Blood contained in vessels and sinuses (large spaces) pumped by one or more heart-like organs. Examples: arthropods and most mollusks

11. Closed Circulatory System
A heart-like organ forces blood through vessels that extend throughout the body. Examples: annelids and some mollusks

12. Vertebrates Gas Exchange Aquatic Vertebrates
Gills in fish and amphibian larvae (tadpoles).

13. Terrestrial
Lungs in terrestrial vertebrates like mature amphibians, reptiles, birds, and mammals.
Both gills and lungs consist of moist surfaces containing many tiny blood vessels through which oxygen and carbon dioxide move.

14. Circulation
Single Loop Circulatory System Found in fish. Contains a two chambered heart.

15. Double Loop System
One loop carrying blood between the heart and lungs and the other loop carrying blood between heart and rest of body. Heart has three chambers in amphibians.

16. Reptiles
Most reptiles have a double loop system with a three chambered heart, but the heart is partitioned so that there is less mixing of oxygen-poor and oxygen-rich blood than in amphibians.

17. Crocodilians, Birds, and Mammals Have a four-chambered completely divided heart in a double loop system.