A crystal contains a radioactive isotope that has a half-life of 20,000 years. You analyze a sample and find that one-eighth of the isotope remains (12.5%). How old is the sample? How many half-lives have passed?

What is a herbivore? A. an animal that gets energy from eating other animals B. an organism that gets energy from eating only plants C. an animal that gets energy by eating both plants and other animals D. an animal that eats only herbs

a group of of scientists is studying the internal parts of a cell. which microscope is most appropraite for these scientist to use

A student was given a task to observe a bacterial specimen made from dilute yoghurt and sketch the shape of bacteria seen. He drew circular shapes. What kind of bacteria could these be? Cocci Bacilli Spirilla

How does evolution need to occur

Plants make glucose using energy from the sun and two molecules. Which two molecules do they use?

In a population of deer mice, the allele for white hair is recessive and the allele for brown hair is dominant.

What makes a molecule a saturated fat?

Muscles or nerves or hormones control (s) the functioning of organs

How are Australia's fires relevant to today's vocabulary word "Succession"?

Water moves between the ocean, atmosphere, and land. In which form does water enter the atmosphere?