How can you decipher between a parental type and a nonparental type?

What do scientists need to look at before developing an argument

Which of the following is a reason why early living organisms on earth could not have survived on the surface? 1. the lack of an ozone layer 2. the lack of oxygen in the atmosphere 3. the fact that these organisms were single-celled

Some steps in cell division are shown below: 1. chromosomes condense and pair up 2. segments of dna of sister chromatids twist and cross 3. exchange of dna occurs between chromosomes 4. four daughter cells are created that are haploid which of the following steps is least likely to occur during meiosis 1?