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?

Which of the following lists the parts of a reflex are in the corret order? A) receptor, sensory neuron, interneuron, motor neuron, effector B) receptor, effector, sensory neuron, interneuron, motor neuron C) receptor, sensory neuron, effector,

A life science student uses a compound microscope to look at a slide of human tissue. He is not sure what part of the body the tissue is from, but makes an educated guess based on the cells he sees on the slide.

Which of the following increases as an object becomes warmer? A. elastic potential energy. B. nuclear energy. C. chemical energy. D. thermal energy.

Why are the Miller-Urey experiments essential to the theory of evolution? A) They showed that life can only come from life. B) They showed that electricity can create life.

How are living things classified in the environment where they live?

Which of the following is not true about cells? 1) All living thing begins life as a single cell. 2) The cell is the basic unit of the structure and function of life. 3) It takes many cells to make a complex organism.

Is mold that grows on bread a decomposer a producer or a consumer

In the Atlantic which part of the oceanic crust is older

Item 2 Put the following in order from smallest to largest: Organism Tissue Organelle Organ Organ System Cell

you looked at a cross section of a bone. Describe how you could model theinterior structure of an entire body?