Where they are and what they do
Before you read
Test yourself first: 5 questions
Question 1 of 5
The heart rate increases during exercise mainly to deliver more:
Answer: B. Exercising muscles need more oxygen, so the heart beats faster to deliver it.
Question 2 of 5
Exercise most directly strengthens the:
Answer: B. Regular exercise strengthens skeletal muscles and the heart muscle.
Question 3 of 5
The organ system that supports the body and allows movement (with muscles) is the:
Answer: A. The skeletal system provides structure and works with muscles for movement.
Question 4 of 5
The skeletal and muscular systems work together to allow:
Answer: B. Muscles pull on bones at joints to produce movement.
Question 5 of 5
Which gas makes up the majority of Earth's atmosphere?
Answer: B. Nitrogen makes up about 78% of the atmosphere; oxygen is about 21%.
Keep the streak going with more questions like these, each with a full rationale.
