The term protostome refers to the animals, which are mostly invertebrates, having a mouth that is formed by the blastophore.

B. mouth

The evolutionary trend in invertebrates involves specialization, body symmetry, cephalization, segmentation, coelom formation, and embryological development. This means that the loss of true coelom didn’t happen during the evolution of invertebrates.

B. loss of a true coelom

Sponges do not exhibit body symmetry. They have asymmetrical body shape.

A. sponges

The excretory system of an organism is in charge of getting rid of the metabolic wastes in its body.

B. to rid the body of metabolic wastes

Muscles are the specialized tissues that are involved in the movement, respiration, circulation of blood, and other life functions of an organism.

D. muscles

Arthropods and some mollusks, such as snails and clams, have an open circulatory system that contains a heart that pumps blood into blood vessels that lead to an open cavity. In this type of circulation, the blood surrounds the tissues and organs.

D. arthropods and most mollusks

Cephalization means that the concentration of sensory organs and nerve cells are located in the anterior part of the body.

A. cephalization

Cnidarians such as jellyfishes developed from two germ layers that include ectoderm and endoderm. They are lacking a mesoderm.

A. jellyfishes

The experiment contains two set-ups in which Sample A worms are placed in water at the same temperature as their soil environment and Sample B is placed in iced water–relatively very different from their usual habitat temperature. Therefore, we can conclude that Sample A serves as the control set-up in these two sets.

A

According to the results of the experiment, the heart rate of worms in sample A is faster than sample B. This indicates that the body temperature and heart rate have a positive relationship. If the body temperature goes down, the heart rate decreases too; and if the temperature increases, the heart rate increases too.

D. A decrease in body temperature corresponds to a decrease in heart rate.