What is the role of the effector in a feedback loop?
a. it detects a change due to a stimulus.
b. it causes a response to a stimulus
c. it is the respone to a stimulus

The nervous system interacts with the endocrine system by a. using hormones as connections b. sending nerve impulses directly to glands c. using neuroendocrine cells as connections d. sending neurotransmitters directly to neurons

Which statement describes characteristics of planarians? a they live in oceans, are parasites, and reproduce only sexually. b they live in fresh water, are parasites, and reproduce only asexually. c they live in oceans, are free living, and reproduce sexually and asexually. d they live in fresh water, are free living, and reproduce sexually and asexually.

When the oxygen produced by photosynthetic plants in the water dissolves in the water, which of these is being formed?