Every cell in a flatworm of phylum Platyhelminthes must get its oxygen directly from the environment around it because flatworms lack a ________ system.

Which of the following traits are not shared by all chordates at some point in their lives: notochord, dorsal nerve cord, exoskeleton, pharyngeal slits, sessile living, post-anal tail?

The sponges in phylum Porifera are outliers in the animal kingdom in that, almost alone among animals, their bodies are not composed of ____________ and their body structure lacks the quality of ____________.

All animal phyla except sponges and cnidarians exhibit __________ symmetry in their body plans, meaning a symmetryin which ______ of their body are mirror images of one another.

A coelom is an internal ___________ possessed by almost all animals except sponges, jellyfish, and flatworms.

A feature common only to animals is that all animals pass through a ____________ stage in their ____________ development.

Four other features that all animals share are that they are ____________ for at least part of their lives, ____________, __________, and their cells do not have

Vertebrates make up a ____ portion of the animal kingdom.

One of the distinguishing features of animals is that their cells do not have the thick outer lining known as a cell wall. Plant cells have a cell wall, as do fungi cells. Why would a feature such as this be advantageous to plants but disadvantageous to animals?

Animals (select all that apply):

a. go through a blastula stage in development.

b. have cells with cell walls.

c. can be single-celled.

d. are heterotrophs.

e. are mostly vertebrates.

Plants can have elaborate defense systems, and they can respond in sophisticated ways to their environment—for example, in preserving resources, they can go into a dormant state in winter. Given this, can plants have intelligence? Or is it only animals that have this trait, to one degree or another?