It's something to do with the fact that having sickle cell anaemia reduces the chances of contracting malaria, obviously a very common disease in Africa. I'm not quite sure what the link is but hopefully this helps a little bit?
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do you know some people have golden blood
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The answers would be likely be to a.) improve the environment and b.) cut costs.
Correct matching of invertebrates and its characteristics are as follows:
Sponges are animals which have many cell but no mouth, muscles , heart or brain. They are sessile and can not move from place to place like other animals do, filter feeding animals with an asymmetrical body plan.
Cnidarians are the animals with radial symmetry and stinging cnidocyte cells. These animals consists a special cell cnida which functions in preying catch and defense. example- jellyfish, anemone.
Flatworms are the worm like animal which do not consist a body cavity or coelom. example- fluke and tapeworms.
Roundworms or threadworms are segmented worms that can live in water or land. They consist a body cavity and internal organs. examples- pinworms and hookworms.
Mollusks are the animals which consist mentle, foot and and sometimes a shell. example- octopus, squids.
Echinoderms are the animals which have radial symmetry and an endoskeleton made out of calcareous plate. These animals live only in marine environment.These animals lack circulatory and excretory systems.
Arthopods are the animals with jointed legs and an exoskeleton made out of chitin. example- spiders, shrimps and crabs.
