Question

what was one side effect of oxygen reacting with methane in the atmosphere?
o a oxygen levels dropped to zero.
o b the earth entered its first major ice age.
o c earths oceans evaporated.
o d volcanoes became more active.
question 13 (1 point)
what did some ancient microbes gain when they swallowed cyanobacteria?
o a the ability to perform photosynthesis.
o b the ability to live underwater.
o c the ability to make nitrogen gas.
o d the power to move faster.
question 14 (1 point)
what organelle in modern plant cells is descended from cyanobacteria?
o a ribosomes
o b mitochondria
o c chloroplasts
o d nucleus

Explanation:

• For the first question: When oxygen reacted with methane, methane (a greenhouse gas) was reduced. This led to a cooling effect, and the Earth entered its first major ice age. Oxygen levels did not drop to zero as there were other sources. Oceans did not evaporate. Volcano activity was not a direct side - effect.
• For the second question: Cyanobacteria are capable of photosynthesis. When ancient microbes swallowed cyanobacteria (endosymbiosis theory), they gained the ability to perform photosynthesis. The ability to live underwater was not a new gain (many ancient microbes already lived in water). Cyanobacteria are not primarily related to nitrogen - making in this context. There is no indication of increased movement speed.
• For the third question: Chloroplasts are the organelles in plant cells that are involved in photosynthesis. According to the endosymbiotic theory, chloroplasts are descended from cyanobacteria. Ribosomes are involved in protein synthesis. Mitochondria are related to energy production (ATP synthesis) and are descended from a different type of bacteria. The nucleus is the control center of the cell and has a different evolutionary origin.

Answer:

• First question: b. The Earth entered its first major ice age.
• Second question: a. The ability to perform photosynthesis.
• Third question: c. Chloroplasts.