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 ?

#Question id: 361

#Unit 1. Molecules and their Interaction Relevant to Biology

Calculate the percentage of histidine that has its imidazole side chain protonated at pH 7.3. The pKa values for histidine are pK1 = 1.8, pK2 (imidazole) = 6.0, and pK3 = 9.2.

#Question id: 12402

#Unit 6. System Physiology – Plant

#Question id: 3403

#Unit 11. Evolution and Behavior

Balancing selection is a type of natural selection that balances two or more alleles in population allows maintaining genetic diversity. Which of the following allowed to this type of selection?

A- Heterozygote has the highest level of Fitness than normal homozygote

B- If rare phenotypes are favored over common phenotypes

C- Introduction of new allele in to a population by mutation and allowed to higher fitness in individuals

D- One homozygote has a highest level of fitness than heterozygote and another homozygote

#Question id: 7275

#Unit 5. Developmental Biology

The following experiment is designed to study the role of several hormones in the regulation of metamorphosis in frogs.

If the thyroid gland were removed from the tadpoles in Group 4, metamorphosis would

#Question id: 13184

#Unit 10. Ecological Principles

The MacArthur-Wilson equilibrium model of island biogeography predicts the number of species found on islands. The figure below depicts two volcanic islands located off a section of mainland coast.

According to  the  MacArthur-Wilson model, the  number of  bird  species present on  Island 2  at  any  one  time is  a function of the relative rates of