Explain why atmospheric concentrations of carbon dioxide are expected to increase in the future.

Explain how paleontologists use trilobite fossils as index fossils for various geologic time periods.

Which statements about a food chain are true? choose all answers that are correct. a.plants are the first living organisms in food chains on land. b. the plants in a food chain are called herbivores. c. all food chains on land begin with energy from the sun. d. carnivores in a food chain eat only plants.

The picture below shows two galaxies. spiral galaxy and elliptical galaxy which of these statements best describes a similarity between the two galaxies? (2 points) both have elongated centers. both have centers shaped like bars. both change their shape from time to time. both are held together by gravitational forces.