If a cross produces a 3:1 phenotypic ratio in F2 offspring, what type of cross is it? How do you know that? 4. If a cross produces a 9:3:3:1 phenotypic ratio in F2 offspring, what type of cross is it? How do you know that?

What type of appendages do sponges cnidarians roundworms annelids mollusks arthropods echinoderms and vertebrate have? jointed, not jointed, absent  

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.

Which tool could you see a plant cell? a. a filter b. a microscope c. a microwave d. an electromagnet