A van de graaff generator is a device for generating a large electric potential by building up charge on a hollow metal sphere. A typical classroom-demonstration model has a diameter of 30 cm.

In the image, layer a is the topmost layer. layer c contains fossils from the precambrian era. layer b contains dinosaur fossils, and layer a contains fossils of mammals. which two statements are supported by this evidence? 1. mammals lived before the precambrian era. 2. dinosaurs and mammals existed in the precambrian era. 3. dinosaurs evolved after precambrian organisms. 4. precambrian organisms evolved after dinosaurs. 5. precambrian organisms were the first life-forms to become fossilized, according to this sample.

These two squirrels live in the same ecosystem. what type of interaction do the images represent? a. direct competition b. mutualism c. interference competition d. symbiotic e. indirect competition

In this food web, which group would increase in number if snakes were eliminated? a. producers b. decomposers c. primary consumers d. secondary consumers e. tertiary consumers