The activity of all human body systems is coordinated by (1) the secretion of hormones and the nervous system
(2) the interaction of nerve impulses with the excretory system
(3) the movement of digested food by the circulatory system
(4) the secretion of hormones and the circulatory system

Which of the following occurs after a natural or unnatural disturbance in an ecosystem

The large increase in atmospheric carbon dioxide in the last 50 years most likely comes from a. an increase in cellular respiration b. increased decomposition by bacteria c. an increase in the burning of fossil fuels d. an increase in photosynthesis

Parthenogenesis is a type of reproduction that does not require a mate. it’s rarely seen in birds and higher vertebrates. parthenogenesis involves the formation of a zygote. but this zygote is formed without fertilization. in parthenogenesis, in the absence of a male gamete, the ovum develops directly in the zygote.