Answer:
Natural selection is the process through which populations of living organisms adapt and change. Individuals in a population are naturally variable, meaning that they are all different in some ways. ... Individuals with adaptive traits—traits that give them some advantage—are more likely to survive and reproduce.
The blood is collected in heparinized capillary tubes to prevent clotting. Heparin is a blood thinner and this anticoagulant is produced naturally by mast cells and basophils. But heparin can not dissolve or break the preformed clots.
A seals flippers has finger bones when a birds wing is just a bone connected to other joints.