Based on the tree in Figure 32.11, which statement is false?
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a. The animal kingdom is monophyletic.
b. Acoelomate flatworms are more closely related to echinoderms than to annelids.
c. Sponges are basal animals.
d. Bilaterians form a clade.

Which of the following was probably the least important factor in bringing about the Cambrian explosion?

a. The emergence of predator-prey relationships

b. An increase in the concentration of atmospheric oxygen

c. The movement of animals onto land

d. The origin of Hox genes

Bilateral symmetry in animals is best correlated with

a. An ability to see equally in all directions.

b. The presence of a skeleton.

c. Motility and active predation and escape.

d. Adaptation to terrestrial environments.

True or false?

New major animal body plans have continued to evolve since the Cambrian about 550 million years ago.

Which of the following combinations of phylum and description is correct?

a. Echinodermata—radial symmetry as a larva, coelom

b. Nematoda—roundworms, internal skeleton

c. Platyhelminthes—flatworms, gastrovascular cavity, no body cavity

d. Porifera—gastrovascular cavity, coelom

Select True or False for each statement.

Sister chromatids are homologous chromosomes.

Non-sister chromatids are found on two different homologs.

Crossing over occurs between sister chromatids.

A chiasma forms between two of the four molecules of double-stranded DNA on duplicated homologous chromosomes.

Why is it ecologically significant that animals are heterotrophic and multicellular?

Which of the following animal groups does not have tissues derived from mesoderm?

a. Annelids

b. Echinoderms

c. Cnidarians

d. Flatworms

If you followed a woman's cells through meiosis, at what stage of meiosis would the amount of DNA in one of these cells be equal to the amount of DNA in one of her G1 phase (before DNA replication) kidney cells?