The Next Few Questions Refer to the Following Description

question 56

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 behavior 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

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Definitions:

Death Rate

The number of deaths per unit of population in a specific time period, used as an indicator of the health of a population.

Age Intervals

Defined periods or spans of time between specific age milestones used in studies or demographic surveys.

Highly Developed Countries

Nations with advanced economic systems, high standards of living, and well-developed infrastructure as compared to other countries.

Fertility Rates

The average number of children born to a woman over her lifetime in a specific population.