Exam 27: The Rise of Animal Diversity

Figure 27.2 Fishes that have swim bladders can regulate their density and thus their buoyancy. There are two types of swim bladder: physostomus and physoclistus. The ancestral version is the physostomus version, in which the swim bladder is connected to the esophagus via a short tube (Figure 27.2). The fish fills this version by swimming to the surface, taking gulps of air, and directing them into the swim bladder. Air is removed from this version by "belching." The physoclistus version is more derived, and has lost its connection to the esophagus. Instead, gas enters and leaves the swim bladder via special circulatory mechanisms within the wall of the swim bladder. -Rank the following fish, from most to least, in terms of the amount of energy each must use to maintain its position (depth) in the water column over the long term. 1. physoclistus fish 2) physostomus fish 3) chondrichthyan fish

Which extant chordates are postulated to be most like the earliest chordates in appearance?

If nudibranch rhinophores are located at the anteriors of these sea slugs, then they contribute to the sea slugs'

The last common ancestor of all bilaterians is thought to have had four Hox genes. Most extant cnidarians have two Hox genes, except Nematostella (of β-catenin fame), which has three Hox genes. On the basis of these observations, some have proposed that the ancestral cnidarians were originally bilateral and, in stages, lost Hox genes from their genomes. If true, this would mean that

During chordate evolution, what is the sequence (from earliest to most recent) in which the following structures arose? 1. amniotic egg 2) paired fins 3) jaws 4) swim bladder 5) four-chambered heart

An adult animal that possesses bilateral symmetry is most certainly also

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

Some researchers claim that sponge genomes have homeotic genes, but no Hox genes. If true, this finding would

Which of the following belong to the lobe-fin clade?

Placozoan evolutionary relationships to other animals are currently unclear, and different phylogenies can be created, depending on the character used to infer relatedness. Sponges have no tissues, but about 20 cell types. Tp (Trichoplax adhaerens) produces a neuropeptide almost identical to one found in cnidarians. The genome of Tp, although the smallest of any known animal, shares many features of complex eumetazoan (even human!) genomes. The next three questions refer to the phylogenetic trees that follow. I. II. III. -Which phylogeny has been created by emphasizing the structural simplicity of placozoans?

Which characteristic(s) is (are) shared by both cnidarians and flatworms?

If a multicellular animal lacks true tissues, then it can properly be included among the

What is true of the feeding stage of cycliophorans? 1. It is chemoheterotrophic. 2) It is sessile. 3) It captures food in a manner similar to that of animals with lophophores. 4) It has radial symmetry.

The members of which clade in the phylum Cnidaria occur only as polyps?

Which graph properly depicts the relationship between the amount of gas in the swim bladder and the density of the fish?

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

If all of the animals died in a large region of an ocean, we would expect an increase in the

The last common ancestor of all animals was probably a

Which group's members have had both lungs and gills during their adult lives?

Lampreys differ from hagfishes in