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I think that birds have different bill lengths because of their habitats and their diet. Also natural selection and evolution has also played a factor due to the fact that birds have not always looked the way that they do now, for example the Archaeopteryx a bird that lived around the time of the dinosaurs had a shorter and more powerful bill to grind insects and small mammals
Explanation:
Answer:
Bacteria cells have no nucleus.
Answer:
where are the choices????
A........................
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Active transport requires energy input from the cell.