Why is it important that an expeirement include a control group

Identify the type of energy used in each action. the flexing of an arm muscle: a signal transduction process by a neuron: a ball at the top of a hill: 1. electrical energy 2. mechanical energy 3. gravitational potential energy

What percentage of light hits earth's surface directly?

The bacteria inside a tube worm would be analogous to what organism in the ocean ecosystem near the waters surface? a. photosynthetic algae b. shrimp c. clown fish d. parasitic lamprey