Topic 20: Origin of Animals Flashcards

• Kingdom Animalia includes a great diversity of what and an even greater diversity of what?

  a great diversity of living species and an even greater diversity of extinct species.
• Molecular phylogenetic analyses suggest that what two things evolved 700-670 mya?

  sponges and the common ancestor to other animal phyla
• Morphological and molecular data suggest that the common ancestor was a what?

  was a flagellated eukaryote.
• what did the common ancestor of Animalia may have resembled?

  modern choanoflagellates
• what are modern choanoflagellates

  opisthokont protists that are the closest living relatives of animals
• are choanoflagellates heterotrophic or autotrophic?

  heterotrophic
• what do choanoflagellates look like? (as in, what makes up their body structure)

  Single flagellum surrounded by a collar of microvilli-looks like a sperm wearing a skirt
• Choanoflagellates can be one of what two kinds of social behaviours?

  solitary or colonial
• if Choanoflagellates are colonial, what two kinds of colonies can they form?

  stalked or ball-like colonies
• what is the hypothesis for how Choanoflagellates became a multicellular animal? why is it only a hypothesis?


  -ball-shaped colonial choanoflagellates evolved into a simple multicellular animals-only a hypothesis because there is no fossil evidence
• what are the 3 lines of evidence that choanoflagellates are closely related to animals?

  1. Cell morphology. 2. Cell morphology unique to animal cells.3. DNA sequence homology.
• how is cell morphology one of the three lines of evidence that choanoflagellates are closely related to animals?

  Choanoflagellate cells and the collar cells of sponges are almost indistinguishable.
• how is the fact that cell morphology unique to animal cells is one of the three lines of evidence that choanoflagellates are closely related to animals?

  Similar collar cells have been identified in other animals, but never in non-choanoflagellate protists, plants, or fungi.
• how is DNA sequence homology one of the three lines of evidence that choanoflagellates are closely related to animals?

  DNA sequence data indicate that choanoflagellates and animals are sister groups.
• Evolution of eukaryotic cells allowed for a greater range of what

  of unicellular forms-e.g. protists.
• A second wave of diversification occurred when? (1) what did it give rise to? (4)

  -when multicellularity evolved in multiple lineages-gave rise to: algae, plants, fungi, and animals.
• Oldest known fossil of a multicellular eukaryote is of what? how old is it?

  algae ~1.2 bya
• DNA clock places multicellular eukaryote origin at how many years ago?

  ~1.7 bya
• Whole-body animal fossils date from how many mya?

  ~560 mya
• in what era did the first whole-body animal fossils appear in?

  Neoproterozoic era, late Proterozoic
• early members of animal fossil record include what kind of biota

  Ediacaran biota
• when does ediacaran biota date back to?

  from 565 to 550 mya
• what is Ediacaran Hills named for? where are they located?

  -after Ediacaran biota-in south Australia
• what was the first known group of animals called?

  Ediacaran biota
• what are Ediacaran biota?


  Diverse soft-bodied, mostly non-motile (sessile) marine organisms.
• Ediacaran biota largely disappeared by what era


  Cambrian
• when did the Cambrian explosion occur

  during the Palaeozoic era 535 to 525 mya
• Most of the fossils from the Cambrian explosion are animals with what kind of body plan?

  bilaterians
• Most of the fossils from the Cambrian explosion are bilaterians with what two traits?

  -Bilaterally symmetrical body plan-Complete digestive tract with one-way digestive system
• what three animal phyla appeared prior to the Cambrian explosion?

  sponges, cnidarians, and molluscs.
• what are the three hypotheses for the cause of the Cambrian explosion

  −New predator-prey relationships. − A rise in atmospheric O 2 supported greater body size and more energetic lifestyles. − Evolution of the Hox gene complex.
• Animal diversity increased through Paleozoic but was punctuated by what

  mass extinctions.
• Animals began to make an impact on land by how long ago

  460 mya
• Vertebrates made the transition to land around how many mya

  365 mya
• 95% of known animal species are classified as what

  invertebrates
• Invertebrates occupy almost every what

  every habitat on Earth
• invertebrates are diverse in what way?

  morphologically diverse: microscopic to huge
• Invertebrates does not refer to a what

  specific taxon
• what kind of classification are invertebrates

  Anatomical classification
• invertebrates are what kind of group

  paraphyletic