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TLS Online TPP Program

#Question id: 7109

What observation might explain how somites originally become specified to form structures appropriate to their position along the antero-posterior axis?

#Unit 5. Developmental Biology
  1. If pre-somitic mesoderm is rotated, the somites form in a reversed order.
  2. Somites in the anterior of the embryo form before somites in the more posterior regions.
  3. A gradient of retinoic acid exists that emanates both anteriorly and posteriorly from the somites.
  4. Periodic waves of c-hairy1 are expressed in the presomitic mesoderm, such that cells in the more anterior somites will have been exposed to fewer waves of c-hairy1 than the cells in more posterior somites.
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TLS Online TPP Program

#Question id: 12246

#Unit 10. Ecological Principles

The graphs below show that the relationship between atmospheric CO2 and mean global temperature is
TLS Online TPP Program

#Question id: 12247

#Unit 10. Ecological Principles

Which of the following is NOT a hypothesis explaining the advantage of group living? 
TLS Online TPP Program

#Question id: 12248

#Unit 10. Ecological Principles

The graphs below show the survivorship and fecundity curves for two congeneric species, X and  Y, that are found in different habitats. Of the two species, Y is more likely to
TLS Online TPP Program

#Question id: 12249

#Unit 10. Ecological Principles

In Batesian mimicry, a harmless species mimics a harmful or toxic model species. Increasing the relative abundance of the mimic will:
TLS Online TPP Program

#Question id: 12250

#Unit 10. Ecological Principles

Two islands, P and Q, are similar in habitat and other features. They are 100 and 200 km2 in size respectively, but have the same number of species. Which of the following statements can independently explain this observation?
(i)    P is closer to the mainland than Q
(ii)   P is further away from the mainland than Q
(iii)  P has higher speciation rates than Q
(iv) P has lower speciation rates than Q
TLS Online TPP Program

#Question id: 12251

#Unit 10. Ecological Principles

A plant produces flowers that are open through the day and the night. An experimenter places pollen on the stigmas of freshly opened flowers and covers them after pollination to prevent natural pollinators from having access to the flowers. When experimental pollination was carried out during the day, 40% of the flowers yielded fruit. When experimental pollination was carried out during the night, 80% of the flowers yielded fruit. However, when flowers were  kept  open  to  natural  pollination  during  the  day  (covered  at  night),  35%  of  flowers  produced  fruit.  20%  of flowers exposed to natural pollination during the night (covered during the day) produced fruit. Which of the following statements is NOT a plausible explanation of these results ?