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What type of limiting factor affects a large population more then it affects a small population

Awic dietitian is meeting with a client who has an infant and a young child. the mother says that the young child is a very picky eater and will only eat crackers and juice. the health worker notices that the child's hair is brittle, his nails tear easily, and the skin inside his lower eyelids is very pale. these are all signs of iron deficiency.

Which group of chordates does  notpossess true backbones?                 a.  birds      b.  frogs and toads      c.  lampreys      d.  crocodilians