Choose all the answers that apply. Connective tissue
D covers the outside of an organism
hold organs and other tissue in place
lines the inside of holow organs
D cushions the body and stores energy
attaches muscle to bone
joins bones together

the skeletons of most mammals reach a certain size and then stop growing. however, many animals, including some mammals, keep growing throughout their lives. kangaroos, for example, just keep growing and growing until they die. also, the longer an animal lives the greater the chance it might catch some deadly disease.

causes

fossil fuels burn

cities become more industrialized

human population grows worldwide