Question

Based on the tree in Figure 32.11, which statement is false?

(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.

Short answer

(A) The statement “the animal kingdom is monophyletic” is false.

(B) The statement “acoelomate flatworms are more closely related to echinoderms than to annelids” is true.

(C) The statement “sponges are basal animals” is false.

(D) The statement “bilaterians form a clade” is false.

Step-by-step solution

Animal phylogeny

The phylogeny of animal groups helps in understanding the pattern in which the diverse groups of the animal kingdom branched from an ancestral group. It also depicts the closeness of one group to another and the lineage pattern of animal clades.

Explanation of option ‘(A)’

The phylogenetic tree of animals reveals that it forms a monophyletic group as the diversified animal groups share a common organism as the ancestral organism that lived approximately 770 million years ago.

Thus, this statement given in this option is accurate with regards to the phylogenetic tree in figure 32.11.

Therefore, the given statement is false.

Explanation of option ‘(B)’

Animal phylogeny depicts that the clade of bilaterian is broadly divided into two groups; one is acoelomate, and the other is divided into three lineages. The group of echinoderms and annelids are part of the lineages formed by one of the bilaterian groups, and so both will have the same closeness to acoelomates.

Thus, the statement in this option is not in accordance with information present in the phylogenetic tree.

Therefore, the given statement is true.

Explanation of option ‘(C)’

In phylogeny, the term basal is used for describing the group or organism which lies closest to the root or the most ancestral group. In this phylogenetic tree, the Porifera, which contain sponges, comprise the basal position.

Thus, sponges (a Porifera organism) are basal animals.

Therefore, the given statement is false.

Explanation of option ‘(D)’

The clade is a term that describes a portion of a phylogenetic tree in which an ancestral lineage is grouped with all the lineages that descended from it. Bilaterian is an ancestral lineage of eumetazoans that comprises all the descended lineages.

Thus, bilaterian is a clade of animal phylogeny.

Therefore, the given statement is false.