A substance that enters Earth's cycles and does harm to living things is

a. a pollutant.

b. hydrogen.

c. freshwater.

d. oxygen.

Compare sex chromosomes with autosomes

Name the three stages of cellular respiration. what happens in each stage?

Suan has to make an important phone call. Unfortunately, his cell phone is not charged so he has to use his parents' old landline, which does not store phone numbers.

Type the correct answer in the box. A humming bird flits from flower to flower. Over a period of 10 minutes, it travels 40 meters. The average speed of the humming bird is m/min.

What are two of the products of the Krebs cycle? O A. NADH and H20 O B. NADH and FADHz O C. Acetyl CoA and NADH O D. Pyruvate and H2O

A soccer player has been sprinting up and down the field. She is breathing very hard and has a burning sensation in her muscles. Which of the following is the most likely cause of her symptoms? A.

The hydra has an incomplete digestive system. How does the hydra remove undigested food? A. It pushes out food through an opening, which is also used to bring in food. B. It pulls food out with its tentacles. C.

The absolute threshold is the: A. decreasing sensitivity to a stimulus over time. B. intensity of a stimulus that can be detected in the presence of noise. C. minimal intensity needed to just barely detect a stimulus. D.

Aquatic organisms in lakes and ponds are often able to survive the water underneath a layer of ice because the water underneath the ice remains liquid.

On an evolutionary tree, what is the intersection and common ancestor known as?