The blastopore is a structure that first becomes evident during
A) fertilization.
B) gastrulation.
C) the eight-cell stage of the embryo.
D) coelom formation.
E) cleavage.
Answer: B
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Biology
- Which of the following is descriptive of protostomes?
- The blastopore denotes the presence of an endoderm-lined cavity in the developing embryo, a cavity that is known as the
- You have before you a living organism, which you examine carefully. Which of the following should convince you that the organism is acoelomate?
- What distinguishes a coelomate animal from a pseudocoelomate animal is that coelomates
- At which developmental stage should one be able to first distinguish a protostome embryo from a deuterostome embryo?
- At which developmental stage should one be able to first distinguish a diploblastic embryo from a triploblastic embryo?
- A researcher is trying to construct a molecular-based phylogeny of the entire animal kingdom. Assuming that none of the following genes is absolutely conserved, which of the following would be the best choice on which to base the phylogeny?
- Soon after the coelom begins to form, a researcher injects a dye into the coelom of a deuterostome embryo. Initially, the dye should be able to flow directly into the
- An adult animal that possesses bilateral symmetry is most certainly also
- Arthropods invaded land about 100 million years before vertebrates did so. This most clearly implies that
- What is the probable sequence in which the following clades of animals originated, from earliest to most recent? 1. tetrapods 2. vertebrates 3. deuterostomes 4. amniotes 5. bilaterians
- Fossil evidence indicates that the following events occurred in what sequence, from earliest to most recent? 1. Protostomes invade terrestrial environments. 2. Cambrian explosion occurs. 3. Deuterostomes invade terrestrial environments. 4. Vertebrates become top predators in the seas.
- Whatever its ultimate cause(s), the Cambrian explosion is a prime example of
- Which of the following genetic processes may be most helpful in accounting for the Cambrian explosion?
- Which statement is most consistent with the hypothesis that the Cambrian explosion was caused by the rise of predator-prey relationships?
- Evidence of which structure or characteristic would be most surprising to find among fossils of the Ediacaran fauna?
- The last common ancestor of all animals was probably a
- In individual insects of some species, whole chromosomes that carry larval genes are eliminated from the genomes of somatic cells at the time of metamorphosis. A consequence of this occurrence is that
- The Hox genes came to regulate each of the following in what sequence, from earliest to most recent? 1. identity and position of paired appendages in protostome embryos 2. anterior-posterior orientation of segments in protostome embryos 3. positioning of tentacles in cnidarians 4. anterior-posterior orientation in vertebrate embryos
- What do animals as diverse as corals and monkeys have in common?
- Which of the following is (are) unique to animals?
- The larvae of some insects are merely small versions of the adult, whereas the larvae of other insects look completely different from adults, eat different foods, and may live in different habitats. Which of the following most directly favors the evolution of the latter, more radical, kind of metamorphosis?
- Both animals and fungi are heterotrophic. What distinguishes animal heterotrophy from fungal heterotrophy is that only animals derive their nutrition by
- The adaptive advantage associated with the filamentous nature of fungal mycelia is primarily related to
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