1)which structure regulates breathing rate in humans?
a)diaphragm
b)lungs
c)hypothalamus
d)medulla

2)the first forms of life on earth
a)appeared about 10,000 years ago
b)could easily maintain a stable internal environment
c)were single-celled
d)depended on the hypothalamus for thermo regulation .

in an embryo , the tissues that receive a nerve produce sprouting factor, which encourages nerves to grow and branch , while the nerve produces anti sprouting factor ,which inhibits grow.

a. positive feedback
b. negative feedback
c. thermoreglation
d. homeostasis