The earliest land plants were liverworts, mosses and ferns. Using the information that you learned in the section, why do you think that these plants were successful in the humid and moist ancient environment? What about these plants makes them unable to thrive in areas with drier climates today? What makes angiosperms and gymnosperms more successful in these climates?

Which type of organism is missing from the food web seen in the illustration? primary consumers decomposers primary producers secondary consumers

What sentence best supports the statement that hormones are involved in the regulation of homeostasis? a. the hormone erythropoeitin increases the production of red blood cells when oxygen levels are low. b. the hormone oxytocin promotes labor contractions of the uterus during childbirth. c. the hormone melatonin induces sleep and its production is slowed by exposure to light. d. the hormone cortisol suppresses the immune system and is produced when the body is under stress.

Ascientific idea becomes valid when it is what?