Which effect of the weather would most likely be studied by biologists who work in this location?

Which of the following was not a major animal on land during the carboniferous period? amphibians insects both a and b none of the above

Which one is an advantage of external fertilization a. the offspring are genetically identical to the parents b. more eggs can be fertilzed at one time c. more sperm can be released at one time d. more protection is available for developing plz

Abird flies by moving its wings up and down. which two systems are most directly responsible for the movement of a bird's wings? a. skeletal and muscular systems b. respiratory and muscular systems c. skeletal and digestive systems d. respiratory and digestive systems