settle the question of whether orb webs evolved once or more than once
describe scientific speculation concerning an issue related to the evolution of orb webs
analyze the differences between the characteristic features of spiders in the Araneidae and Uloboridae families
question the methods used by earlier investigators of the habits of spiders
demonstrate that Araneidae spiders are not related to Uloboridae spiders
18. It can be inferred from the passage that all orb-weaving spiders belong to types of spiders that
lack venom glands
are included either in the Uloboridae or Araneidae families
share few characteristic features with other spider types
comprise less than a third of all known types of spiders
are more recently evolved than other types of spiders
19. According to the passage, members of the Araneidae family can be distinguished from members of the Uloboridae family by all of the following EXCEPT:
the presence of venom glands
the type of web they spin
the structure of their body hair
the arrangement of their eyes
their appearance
20. Which of the following statements, if true, most weakens Wiehles theory that complex behavior could evolve only once?
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