The birds shown above have beaks with three different shapes and sizes. these genetic variations in the beak each appeared initially due to environmental factors mutations natural disasters conscious choice by the birds

a time line cause it goes from 685 to 978

straight or amphibians are homeothermic to thermal

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.