In bottom sediments of lakes and streams, organic matter is broken down by heterotrophic microorganisms and ammonia is released. Under aerobic conditions, specialized bacteria convert ammonia to nitrate (nitrification). This nitrate, together with nitrate from other sources, diffuses into the deeper sediments, where it may undergo anaerobic conversion to nitrogen gas (denitrification). These sediments typically contain oligochaete worms that live with their heads buried and their tails waving back and forth in the overlying water. Plastic columns were packed with freshly collected stream sediments and then  covered  with  layers  of  nitrate enriched  water.  A similar  set  of  columns  was packed with sediment that had been sterilized and then covered with either nitrate-enriched water or distilled water. Oligochaete  worms  were  collected  and  acclimated  to  20°(C)Following  acclimation,  worms  were  rinsed  in  distilled water and then added to three sediment columns. The columns were incubated in the dark at 20°C and monitored every three days for changes in the concentration of nitrate in the overlying water. Nitrate concentrations in each of the experimental treatments were plotted against time, as shown in the graph below

It can be concluded from the figure that

#Question id: 5302

#Unit 11. Evolution and Behavior

Using modern techniques of sequencing by synthesis and the shotgun approach, sequences are assembled into chromosomes by ________.

#Question id: 5232

#Unit 11. Evolution and Behavior

Using molecular clock, it was estimated that two species X and Y must have diverged from their common ancestor about 5 x 10^6 years ago. If the rate of divergence per base pair is estimated to be 0.06 per million years, what is the proportion of base pairs that differ between the two species now?

#Question id: 5225

#Unit 11. Evolution and Behavior

Homeotic genes contain a homeobox sequence that is highly conserved among very diverse species. The homeobox is the code for that domain of a protein that binds to DNA in a regulatory developmental process. Which of the following would you then expect?

#Question id: 5221

#Unit 11. Evolution and Behavior

Unequal crossing over during Prophase I can result in one sister chromosome with a deletion and another with a duplication. A mutated form of hemoglobin, known as hemoglobin Lepore, is known in the human population. Hemoglobin Lepore has a deleted set of amino acids. If it was caused by unequal crossing over, what would be an expected consequence?

#Question id: 5220

#Unit 11. Evolution and Behavior

In comparing the genomes of humans and those of other higher primates, it is seen that humans have a large metacentric pair we call chromosome #2 among our 46 chromosomes, while the other primates of this group have 48 chromosomes and any pair like the human #2 pair is not present; instead the primate groups each have two pairs of midsize acrocentric chromosomes. What is the most likely explanation?

#Question id: 5217

#Unit 11. Evolution and Behavior

Multigene families include two or more nearly identical genes or genes sharing nearly identical sequences. A classical example is the set of genes for globin molecules, including genes on human chromosomes 11 and 16. How might identical and obviously duplicated gene sequences have gotten from one chromosome to another?