Concept Check Multiple Choice

Excited by your discovery, you send genetic samples back to your lab. The results confirm what a team of researchers suspected in 1999 — these Giardia groups have genetic differences so significant that they might actually be different species! The lab provides you with a phylogenetic tree showing their evolutionary relationships.

Now it’s up to you, the top scientist, to classify Giardia intestinalis based on the tree. Is this group Paraphyletic, Monophyletic, Polyphyletic, Parsimonious, or Extinct?

Paraphyletic

As you continue analyzing the Giardia phylogenetic tree, you stumble upon a curious species — G. microti. It seems to have a complicated relationship with other Giardia species. You scratch your head, take a sip of your jungle expedition coffee, and try to make sense of it all. What does the tree tell you about G. microti?

The Loyal Clan Member — it belongs to the same group as G. intestinalis, making it part of the Giardia family tree’s VIP section.

Which statement best explains why natural selection cannot “plan ahead”?

Selection requires heritable variation that already exists.

Which event most directly removed the energetic constraint that had previously limited the evolution of large, metabolically expensive body plans?

The great oxygenation event.

Which combination correctly matches archeal lineages to the traits listed in the table?

Archea, Euryarchaeota, Thaumarchaeota, Crenarchaeota.

Why does horizontal gene transfer complicate phylogenetic reconstruction in prokaryotes?

It allows traits to spread across unrelated lineages.

A bacterium that forms endospores is most likely adapted to —

Surviving extreme, unpredictable stress.

Which statement best explains why oxygen was initially toxic to many early prokaryotes?

Oxygen forms highly reactive molecules that damage cellular components.

Which combination correctly matches protist lineages to the traits listed in the tables?

Alveolata, Rhizaria, Stramenopila, Excavata.

Why do protists exhibit a wider diversity of feeding strategies than most multicellular eukaryotes?

Compartmentalization enables specialization of ingestion, digestion, and metabolism.

Protists are considered evolutionarily essential primarily because they —

Include the ancestors of all multicellular lineages and pioneered key eukaryotic innovations.

Which feature most directly allowed protists to overcome the diffusion-based constraints that limit prokaryotic size and shape?

Compartmentalization of cellular processes within membrane-bound organelles.

the shift from gametophyte-dominant to sporophyte-dominant life cycles primarily reflects:

Greater production of the diploid stage.

Angiosperms radiated so extensively because:

Flowers and fruit increased pollination specificity and speed dispersal.

Which evolutionary innovation most directly allowed plants to increase height without proportionally increasing the risk of hydraulic failure?

Lignified vascular tissue.

Which interference about early land plant evolution is best supported by fossil, morphological, and phylogenetic evidence?

Early land plants likely faced trade-offs between gas exchange and water conservation.