8. Valves prevent blood from flowing backwards. Valves are located in the O
veins
heart
heart and arteries
heart and veins

Choose one animal (cheetas) and research on the internet what has contributed to this animal becoming "endangered" or "threatened." what animal you have chosen? how long has the animal been endangered or threatened? what has contributed to this animal’s endangered or threatened status? why is it important to save this animal from extinction? after researching and gathering facts, write a 350-word letter from the point of view of an animal rights' activist. be sure to include at least five facts that you learned from your research.

What is it called when part of a cell membrane closes around a molecule to allow the molecule to enter the cell? a. passive transport b. diffusion c. endocytosis d. exocytosisc. endocytosis

18. over time, how do sand dunes tend to migrate? a. perpendicular to the movement of the wind b. in the same direction as the wind blows c. toward the wind d. in random directions