Question

3% 8% Percent increase Percent increase Percent increase fluorescence fluorescence fluorescence over background over background over background Tissue when dye is when dye is when dye is injected in the injected in the injected in the ectoderm mesoderm endoderm Nerve ring 40% 5% Intestinal 6% 70% lining Nerve cords 59% 6% 7% Water vascular 7% 40 40% system Tube feet 10% 60% 9% Epidermis covering 47% 8% 6% endoskeleton

Fluorescence Mapping of Blastomere in Sea Urchins

Fate mapping is a technique that allows determination of the fate of cells from the three germ layers. In worms, the endoderm gives rise to the cells that line the intestines. The ectoderm gives rise to cells of the nervous system and body covering. The mesoderm gives rise to the muscles and other organs between the ectoderm and mesoderm. A researcher is tracing the fate of a particular cell (blastomere) from its position in one of the three germ layers of sea urchin blastulae by injecting a fluorescent tag in cells of the ectoderm, mesoderm, and endoderm. Several weeks later, the sea urchin embryos were analyzed for the presence of fluorescence in specific tissues. The following results were obtained.

Use the passage to answer the question.

1. Based on the results, which conclusion is correct?

A. In sea urchins, only the fate of the ectodermal cells is conserved.

B. In sea urchins, only the fate of the endodermal cells is conserved.

C. In sea urchins, the fate of the ectodermal and mesodermal cells is conserved.

D. In sea urchins, the fate of the three gem layers is conserved between the two clades.

2. Which of the following statements is the MOST compelling argument that fungi are more closely related to animals than plants?

A. Plants have chloroplasts whereas fungi and animals cells do not.

B. Plants fix carbon dioxide from the air; fungi and animals use pre-existing organic molecules.

C. The DNA sequences of ribosomal RNA of fungi share more homology with ribosomal RNA from animals than plants.

D. Both animal and fungal cells are eukaryotic.

3. If you were to build a phylogenetic tree of living animals, which of the following derived characters would appear first?

A. deuterostome development

B. true tissues

C. protostome development

D. bilateral symmetry

Answer 1

1-D (because in sea urchin fate of Ectoderm, endoderm and mesoderm pre determined)

2-C (DNA sequence of r-RNA can be studied to trace phylogeny)

3-B (True tissue because the most premitive animals i.e. sponges are parazoa and rest other phylums comes under catagory of eumetazoa)