What is the term for a specialized structure in a cell

Which organism is the producer in this food web? 7th grade question. a) arthropods b) birds c) fungi d) plants

Hemoglobin is a proton that carries oxygen around your body what is hemoglobin made from

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.