People who are heterozygous for sickle cell disease are generally healthy because they (1 point) are resistant to many different diseases have some normal hemoglobin in their red blood cells are not affected by the gene until they are elderly produce more hemoglobin that they need

Even though the ostrich is a flightless bird, ostriches still possess wings that stretch approximately two meters across when fully extended. scientists speculate that when dinosaurs became extinct, some of the birds that lived during that time became land dwellers since they were able to consume the food that the dinosaurs once ate. over time, these species grew larger and heavier. eventually, the ostrich species became too big to fly. the wings found on ostriches are known as a. analogous structures. b. homologous structures. c. vestigial structures. d. symmetrical structures.