Why would a shark need to regulate its internal salt concentration?

How did the research presented in the article affect scientists' understanding of the evolution of eukaryotes

Getting out of bed is the first goal i tackle each day. 2several small goals are achieved by me as the day progresses. 3when i am riding the bus home or walking the dog, i think about the bigger goals i have for my life. which statement correctly describes the verb tense, aspect, and voice in this paragraph? a.sentences 1 and 2 contain present progressive verbs. sentence 3 contains both present progressive and simple present verbs. sentence 2 uses passive voice. b.sentences 1 and 2 contain simple present verbs. sentence 3 contains present progressive verbs. all three sentences use active voice. c.sentences 1 and 2 contain present progressive verbs. sentence 3 contains simple present verbs. all three sentences use active voice. d.sentences 1 and 2 contain simple present verbs. sentence 3 contains both present progressive and simple present verbs. sentence 2 uses passive voice.

In general, characteristics that an organism survive and reproduce become more common over time. what mechanism of evolution causes this?