1. C. external
2. A. Small blood vessels pass next to the air sacs of the lung, and gases are exchanged across a thin membrane.
3. A. allow movement.
4. C. Organs are made up of cells and tissues.
5. B. a structure composed of a number of tissues that work together to perform a specific task
6. A. birds
7. D. The muscles in her leg relax and contract to move the bones.
8. B. thigmotropism
9. D. cell tissue organ organ system
10. C. digestive and excretory
11. D. a tiny blood vessel that delivers oxygen to tissues
12. C. The circulatory system transports nutrients and oxygen brought in by the respiratory system throughout the body.
13. B. phloem
14. D. 3,5,1,4,2
15. D. The heart pumps blood to the blood vessels, and the vessels transport the blood throughout the human body.
16. C. cells.
17. D. The plant grows toward or away from the sunlight.
18. C. lose water through their leaves.
19. C. Some; most
20. C. hydrotropism
1.
2.
Most gills are internal and require water to be drawn into the body for oxygen exchange to occur. However, some insects and some amphibians have external gills. These structures stick into the water and absorb oxygen from it.
After empty blood with no oxygen returns from the body, it moves through the right atrium and right ventricle of the heart and is pumped through the pulmonary artery to the lung. In the lung, the pulmonary artery divides into small capillaries. Here, small blood vessels pass next to the air sacs of the lung, and gases are exchanged across a thin membrane. Oxygen crosses the membrane into the blood, while carbon dioxide leaves the blood through this same membrane.

3. The muscular system consists of all the muscles in the human body, including skeletal muscles that are attached to bones. The skeletal system is made up of all of the bones in the human body. The muscles of the muscular system relax and contract to move the bones of the skeletal system. This allows the human body to move.
The muscular system and the skeletal system of the human body work together to
allow movement.
4. All multicellular organisms are made of cells. Specialized cells group together to form tissues, and groups of tissues come together to form organs. Therefore, organs are
made up of both tissues and cells.
5.
6.
7.
The most basic unit of life is the cell. Cells may be grouped into tissues, which may, in turn, be grouped into organs.
An organ is made of different tissues working together to carry out a certain function.
Organs may be grouped together into systems.
Birds need a greater amount of oxygen than most animals. To obtain more oxygen, most birds have four air sacs attached to one lung and five air sacs attached to the other. Air that enters the lung is drawn into the air sacs, and this increases the amount of oxygen that is exchanged.
The muscular system consists of all the muscles in the human body, including skeletal muscles that are attached to bones. The skeletal system is made up of all of the bones in the human body. The muscles of the muscular system relax and contract to
move the bones of the skeletal system. This allows the human body to move.
8.
9.
The way that a plant grows in response to touch is called thigmotropism.
Sometimes plants respond by growing toward objects that touch them. For example, the tendrils of a vine wrap around nearby objects that touch the vine. Plants can also grow away from objects that touch them. For example, plant roots tend to grow away from rocks in the soil.
The basic building block of any organism is the cell. A group of similar cells working together form a tissue. A group of tissues working together form an organ. A group of organs working together form an organ system. cell tissue organ organ system
Interacting organ systems make up a whole organism.
10. The digestive system takes in food, digests it to extract energy and nutrients and expels the remaining matter. The mouth, esophagus, and stomach are only a few components of this system.
The excretory system removes excess, unnecessary or dangerous materials from the body. The skin is a part of the excretory system by eliminating sweat to keep the body cool. The liver is a member of the digestive system as well as the excretory system by

excreting waste from the body.
The excretory system removes the materials consumed by the digestive system and therefore are in direct interaction with each other.
11. Capillaries are tiny blood vessels that deliver oxygen to tissues. They can only be seen under a microscope because they are about one-tenth the width of a human hair.
Capillaries have thin walls that allow oxygen and nutrients from the blood to move through them to the tissues. Carbon dioxide and other wastes leave the tissue cells, cross through the capillary walls, and enter the blood for the trip back to be purified by the heart.
12. Oxygen and carbon dioxide are exchanged in the body when the respiratory and circulatory systems interact.
The circulatory system transports nutrients and oxygen brought in by the
respiratory system throughout the body. Without the circulatory system, oxygen would not be able to move through the body to the extremities and organs.
In many organisms, oxygenated blood is pumped from the lungs to the rest of the body.
Then, the blood transports the oxygen and nutrients to the organs and brings the deoxygenated blood back to the lungs. Once the blood returns to the lungs, carbon dioxide is expelled from the blood, so more oxygen can be brought in.
13. Plants absorb nutrients and water from the soil into their roots. The nutrients and water are then transported by the xylem to the leaves. In the leaves, the plant undergoes photosynthesis and makes food for itself which is transported to the rest of the plant by the phloem.
14. During digestion, the food moves from the mouth to the esophagus to the stomach to the small intestine and finally to the large intestine. Each body part plays a role in breaking down the food and absorbing nutrients from the food.
15. A system is made up of interrelated parts that work together to perform a single task.
There are thousands of systems at work every day in society, in machines, and in our own bodies.
An example of a system is the circulatory system. In the circulatory system, the heart pumps blood to the blood vessels, and the vessels transport the blood
throughout the human body. This provides the human body with nutrients and oxygen. All of the parts of the circulatory system work together to perform this task.
16. Multicellular organisms are made up of differentiated cells that are organized in specific ways to perform specialized functions. Interconnected cells known as tissue can perform specialized functions as a group. Examples of specific kinds of tissue are muscle tissue, nervous tissue, and epithelial tissue.
17. Phototropism is the way a plant moves or grows in response to light. Growing toward
or away from the sunlight would be a phototropic response of Elizabeth's plant to its environment.

18. Through the process of transpiration, plants lose water through their leaves. Water evaporates from small holes in the leaves called stomata, which must open up to let carbon dioxide enter the plant.
Plants open and close their stomata at different times to control water loss and the intake of carbon dioxide. If plants could not control transpiration, they would wither up and die.
19. Some of the water absorbed by plant roots is used for photosynthesis. Most of the water, however, is lost through the leaves of the plant in a process called transpiration.
20. Hydrotropism is a plant's response to water. In a time of drought, the plant roots can move to an area where water is stored. The roots can grow deeper if the water source is below the plant, and they can grow sideways, if that is where the source is located.
Phototropism is growth in a direction that is determined by the direction of the light source.
Geotropism and gravitropism are growth responses due to gravity.