The earliest organisms were completely heterotrophic in nature. why?
a. the primitive atmosphere lacked sunlight. primitive organisms did not have a system complex enough to use for other sources for photosynthesis.
b. the primitive atmosphere lacked oxygen. primitive organisms did not have a way to break down the oxygen in water.
c. the primitive atmosphere lacked carbon dioxide. primitive organisms did not have a way to obtain carbon dioxide for photosynthesis.

the correct answer is: b. pantala flavescens, because these organisms would have a high level of genetic variation due to sexual reproduction.  

because involves two organisms (parents) whose genetic material combines, sexual reproduction leads to genetic variation in new generations of offspring. the offspring is an unique organism, with new genome, more protected with the higher ability to adapted. this process is fundamental to evolution.

b. climate change will cause an increase in biodiversity of all ecosystems.

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