Tertiary means 3rd. So why is it the fourth link?

Which direction does the energy flow in this energy pyramid ?

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

Ascientist is designing an investigation to study the impact of invasive bird populations on local, native bird populations at backyard bird feeders. what population is most likely to be a control group for the investigation? amount of food number of bird feeders invasive bird populations local backyard birdfeeders without food