The breathing rate of a goldfish can be measured by the number of times the goldfish opens its mouth. In an experiment, students placed a goldfish in a container of water at 26°C and counted the number of times the fish opened its mouth. They gradually lowered the water temperature and counted the number of times the fish opened its mouth at 20°C, 14°C, 8°C, and 2°C. The results are shown in the table below.

Which of these descriptions best explains the decrease in the breathing rate of the goldfish?

A student washes her hands with antibacterial soap and water. Then she touches the agar in a petri dish with her thumb. The agar contains nutrients that support the growth of bacteria. Other students repeat the procedure after washing their hands with three different kinds of antibacterial soap. The petri dishes are kept warm overnight to allow bacteria to grow. The next day the students count the number of bacterial colonies in each dish.

What should be the effect of the soap in this experiment?

Scientists wanted to study the effect of water temperature on the swimming speed of goldfish. They set up an experiment in which they raised populations of goldfish in two different aquariums. Population 1 was raised at 5°C. Population 2 was raised at 25°C. All other variables were constant in both aquariums. The results of this experiment are shown in the graph below.

If the temperature of the water increases from 5°C to 10°C, the goldfish in Population 1 would most likely

Which of these is an environmental factor that causes damage to chromosomes?

Botulism, a type of food poisoning, is caused when bacteria release a poisonous substance. Eating even a small amount of food that contains the poisonous substance can cause death.

This poisonous substance is called

A summer camp was built near a lake in the mountains. The campers used the lake for swimming, fishing, and boating. The relationships between three organisms found in the lake are shown below.

Which of these fish cell structures would be most directly affected by a change in the oxygen level of the lake?

A student is studying the relationship between a leafy plant and a species of beetle. He divided 20 plants into two groups. He planted each group in a separate planter box. He then released 50 beetles into one of the planter boxes. The beetles fed on the leaves and left a white substance around the plant, changing the pH of the soil. He recorded the average height of the plants at the end of three months. His data are shown below.

• How did the substance probably affect the growth of the plants in Group 1?
   
• Describe how changes in pH may affect the metabolic rates of cells.
   
• Describe how other environmental factors could affect growth in plants.