Ok so in science im taking a test and a question is which statement describes natural selection?
A it is the primary mechanism.
B it must act on structural traits.
C it acts to cause overpopulation.
D it causes learned skills to become heritable traits.

2. sketch the inside of the bean nodule, and describe or label what you observed with the hand lens.

Which greenhouse gas is emitted when burn fossil fuels for energy? a.nitrogen b.oxygen c.carbon dioxide d.helium

Refer to this portion of a dichotomous key for fish identification to answer the question. 1. (a) has a single dorsal fin ® 5 (b) has a double dorsal fin ® 2 2. (a) one fin is spiny, the other is smooth ® 3 (b) one fin is not spiny or smooth ® 4 5. (a) has small fin on back near tail ® 6 (b) has no fin on back near tail ® 7 6. (a) has barbs near the mouth ® catfish (b) does not have barbs near the mouth ® 10 7. (a) tail is asymmetrical ® 8 (b) tail is symmetrical ® 9 10. (a) scales are small ® trout (b) scales are large ® whitefish what is the next step to complete to identify a fish that has a single dorsal fin, no fin on the back near the tail, and no barbs near the mouth? step 2 step 5 step 7 step 10