Question

Which of the following statements about the abilities to move and to sense the environment is incorrect?

a. Both are observed in single-celled as well as multiple-celled organisms
b. A brain is not required to sense and respond to the environment
c. They allow resources to be found and obstacles to be avoided
d. At the molecular level they are based on very different mechanisms in single- vs. multiple-celled organisms.

Answer 1

The incorrect statement is the one claiming a fundamental difference between single-celled and multicellular organisms regarding movement and environmental sensing at the molecular level. Multicellular organisms tend to have more complex communication systems due to the need for signaling across multiple cells, involving more time for signal transduction, partly due to compartmentalization.

Step-by-step explanation:

The statement 'At the molecular level they are based on very different mechanisms in single- vs. multiple-celled organisms' is incorrect. Both single-celled and multicellular organisms can move and sense their environment, but the mechanisms at the molecular level are not necessarily fundamentally different; rather, they are often scalable or more complex in multicellular organisms. For instance, both may use chemical signaling, but multicellular organisms coordinate these signals across many cells and may require more time for signal transduction due to compartmentalization, which is not typically found in single-celled organisms that tend to communicate with nearby cells through direct contact such as fusion of the plasma membrane.

Animals, which are multicellular organisms, detect environmental stimuli through specialized sensory nerve cells and respond with the coordination of muscles and nerves. Single-celled organisms have simpler mechanisms, like utilizing flagella for movement and sensing chemicals in their environment to navigate toward food or away from harm.