What Constitutes a Species?

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I. Typological Species Concept
    - by Charles Darwin
    - categorized by look
II. Biological Species Concept
    - if two similar organisms will breed, they are the same species
    - in some cases of breeding a hybrid is produced
    - some species can mate to create intergrades
    - problem with the concept is asexual organisms and when females reproduce when no males are present
III. Ecological Species Concept
    - separated by niche
    - depends on interactions within the environment and eating habits
    - environmental preference between organisms can make a difference
IV. Evolutionary History Species Concept
    - structured according to evolution
    - refers to genetic trees
    - caused by geographic separation
    - ex: species A evolves into species A and B. later species A creates another offshoot to create species C.
V. Phylogenetic Species Concept
    - says that one species evolves in to two completely new species leaving the old species extinct
    - ex: species A evolves into species B and C and A no longer exists

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