B5 7th

Researchers are investigating processes that happen during digestion. Which answer choice describes only a physical change during digestion?

• 
  Enzymes in saliva start the digestion of starches before food is swallowed.

• Hydrochloric acid in the stomach breaks down proteins.

• Bacteria in the intestines convert dietary fiber into fats

• Chewing in the mouth breaks food into small pieces.

When an animal is thirsty, it responds by-

• Eating food

• Drinking water

• Blinking rapidly

• Sweating Excessively

Which statement BEST describes the primary role of perspiration in humans?

• Perspiration eliminates bacteria from the skin

• Perspiration rids the body of excess water

• Perspiration helps to maintain a stable body temperature.

• Perspiration opens skin pores to absorb more oxygen

Both the esophagus and the small intestine are involved in the digestion of food. The esophagus squeezes food into the stomach by wave-like muscle contractions. Peptidase enzymes in the small intestine break food molecules into smaller molecules. Which statement best describes changes to food during digestion?

• 
  The muscle contractions result in physical changes, while the action of the peptidase results in chemical changes.

• 
  The muscle contractions and the action of the peptidase both result only in physical changes.

• The muscle contractions result in chemical changes, while the action of the peptidase results in physical changes.

• 
  The muscle contractions and the action of the peptidase both result only in chemical changes.

A person experiences a flight or fight response to danger. Which statement explains what takes place in the human body as a result?

• The heart muscle contracts faster, increasing blood flow through blood vessels.

• The heart valves close, increasing the blood volume

• Breathing slows down, allowing the blood to absorb oxygen

• Blood vessels relax

When a plant wilts, or begins to lose too much water, the stomata close. How does this help the plant

• A. Increase light absorption
  

• B. Reduces water intake by roots

• C. Increase photosynthesis

• D. Reduces the amount of water lost

Which environmental stimulus causes leaves on certain trees to change color in autumn?

• Loss of nutrients in the forest soil

• Lower air humidity

• Changes in the amount of light

• Competition for survival

When an animal is infected with a virus, the body responds by creating conditions that are not favorable for the virus. It does this by -

• Inhabiting the sense of balance

• Increasing sensitivity to sound

• Creating a sensation of hunger

• Raising the core body temperature

Which example shows a chemical change to food during digestion?

• Enzymes breaking down food

  
  

• Teeth chewing food

• Food moving through the instetine

• Food churning the in stomach

A student kept a notebook during an investigation. Which recorded observation was MOST likely a physical change?

• The solution was heated for two minutes until it boiled.

• A solid was heated for two minutes until it boiled together.