The study of how living and extinct organisms are related to one another is simple. This study is called evolution.
Taphonomy
By the way they look, (their bone structure, body weight) and DNA too.
All the ones not extinct.
all extinct organisms more closely related to the crown group than to any other living group. = Paraphyletic group.
what happen when some living organisms in food phyramid become extinct
"Biota" is another term for living organisms in a specific region or habitat.
Few organisms have become extinct. Few organisms are rare species.
evolution
Living organisms depend on one another and on their environment for survival.
No, all living organisms have a slightly different to a very different DNA pattern. No living organism is alike. Not even people or animals related to another.
Pathogen means "disease-causing" (pathos-: suffering, disease; -gen: begetting) Therefore: "harmful to living organisms" For the other answers: beneficial organisms are not pathogens; harmful only to plants are specifically plant pathogens; "nearly extinct" has no relevance in this question.
Another name for the classification system for classifying living things is taxonomy. This system organizes organisms into groups based on their shared characteristics and evolutionary relationships.
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