The Next Few Questions Refer to the Following Description

question 43

Multiple Choice

The next few questions refer to the following description.
Healthy individuals of Paramecium bursaria contain photosynthetic algal endosymbionts of the genus Chlorella. When within their hosts, the algae are referred to as zoochlorellae. In aquaria with light coming from only one side, P. bursaria gathers at the well-lit side, whereas other species of Paramecium gather at the opposite side. The zoochlorellae provide their hosts with glucose and oxygen, and P. bursaria provides its zoochlorellae with protection and motility.? P. bursaria can lose its zoochlorellae in two ways: (1) if kept in darkness, the algae will die; and (2) if prey items (mostly bacteria) are absent from its habitat, P. bursaria will digest its zoochlorellae.
-Which term accurately describes the behaviour of Paramecium species that lack zoochlorellae in an aquarium with light coming from one side only?

• A)positive chemotaxis
• B)negative chemotaxis
• C)positive phototaxis
• D)negative phototaxis

---

Definitions:

Parasympathetic Nervous System

Part of the autonomic nervous system responsible for conserving energy as it slows the heart rate, increases intestinal and gland activity, and relaxes sphincter muscles in the gastrointestinal tract.

Sympathetic Nervous System

A division of the autonomic nervous system that controls the body's responses to perceived threats by activating the fight-or-flight response.

Parasympathetic

The part of the autonomic nervous system responsible for rest and digestion, counterbalancing the sympathetic system.

Nervous System

The part of an animal's body that coordinates its actions and transmits signals to and from different parts of its body, including the brain, spinal cord, and nerves.