The figure above represents a late zebrafish gastrula. The following concepts may be proposed during further development of the embryo.

A. The concentration of FGF decreases from the yolk towards the epidermis, along with the increase of BMP activity from the dorsal to the ventral axis.

B. Increase in FGF activity in the epidermis with concomitant decrease in BMP activity towards the ventral axis.

C. Neural induction in zebrafish is independent of the organizer and depends on activation of BMP signalling.

D. In comparison, both Xenopus and chick embryos require activation of FGF for neural induction to occur in addition to BMP inhibition.

Which of the above statements are incorrect?

#Question id: 4955

#Unit 11. Evolution and Behavior

If relatively small carbonaceous chondrites from space were a significant source of Earthʹs original amino acids, then which two of these would have been most important in permitting their organic materials to survive impact with Earth?

I. Carbonaceous chondrites must contain no D-amino acids.

II. Earthʹs early atmosphere must have had little free oxygen.

III. The chondrites must have arrived on Earth before 4.2 billion years ago.

IV. Earthʹs early atmosphere must have been dense enough to dramatically slow the chondrites before they impacted.

V. The chondrites must have impacted land, rather than a large body of water.

#Question id: 4956

#Unit 11. Evolution and Behavior

Which measurement would help determine absolute dates by radiometric means?

#Question id: 4957

#Unit 11. Evolution and Behavior

How many half-lives should have elapsed if 6.25% of the parent isotope remains in a fossil at the time of analysis?

#Question id: 4958

#Unit 11. Evolution and Behavior

What is true of the fossil record of mammalian origins?

#Question id: 4959

#Unit 11. Evolution and Behavior

If a fossil is encased in a stratum of sedimentary rock without any strata of igneous rock (e.g., lava, volcanic ash) nearby, then it should be

#Question id: 4960

#Unit 11. Evolution and Behavior

Letʹs say that a hypothetical submersible robot was used to collect samples of sedimentary rock from the sea floor along the section illustrated. The robot moved back and forth along the transect, collecting first from site A, then site III, then site B, then site II, and lastly site D. Assuming that sedimentation has occurred at a constant rate along the transect over the past million years, rearrange the sites mentioned above on the basis of the thickness of the sediments overlying the igneous rock, from thickest to thinnest.