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

Below are the three main organs that make up the plant body. what is the main function of the structure that is identified as b in the picture above? it anchors the plant. it produces food. it absorbs nutrients. it supports the plan

The kidney filters potentially toxic substances in the blood, and thus “clears” the blood of those substances. this clearance function is dependent upon and proportional to the diffusion gradient of the substance across filtering capillaries, i. e. if the concentration of the substance is doubled, twice as much will be cleared from each ml of blood that is filtered. suppose that the body produces a constant amount of a substance x per unit of time. the kidneys eliminate substance x at a rate directly proportional to the concentration of the substance and the volume of blood cleared each minute (c): elimination = c × [x], where [x] is the steady-state concentration of substance x. imagine an individual with an initial concentration of x equal to [x]0 who develops kidney disease. her baseline clearance c0 drops to one half of the original (½c0). what is the new steady state concentration of x? (for simplicity, assume that substance x is 100% filtered by the kidney).

Cladistics is a way of classifying organisms by examining the characteristics of their ancestors and descendants and depicting the relationships in a cladogram. which of the following best describes a challenge in classifying organisms this way? a. there are millions of species on earth, and a cladogram is not a practical means for classifying all of them. b. it is impossible to tell which organisms are most closely related to each other using a cladogram. c. cladograms are detail-oriented and do not provide a useful understanding of evolutionary relationships. d. there is a limited number of ways to organize the information, so most cladograms end up looking very similar.