In angiosperms, pollen grains are

diploid, and are made when haploid gametes join in fertilization.
diploid, and are made when haploid gametophytes join in pollination. **i think
haploid, and are made when haploid spores undergo mitosis.
haploid, and are made when haploid ovules undergo meiosis.

Which of the following statements is true about the relationship between genetic variation and natural selection? a. genetic variation must be present in a population before natural selection can act on it. b. genetic variation arises in a population as a result of natural selection. c. natural selection can act on a population whether there is genetic variation within the population or not. d. after natural selection acts on a population, the amount of genetic variation in the population always increases.

Why has two different alleles for the same trait?

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