Question 1

Which of the following statements best describes the evolutionary conservation of circadian rhythms (CR) in animals?

Accepted Answer

Circadian rhythms are present in both simple and complex animals, including those without a central nervous system.

Question 2

Which gene is rhythmically expressed in sea anemones but is missing its PER orthologue, according to the study materials?

Accepted Answer

CLOCK

Question 3

What behavioral evidence supports the presence of a sleep-like state in the upside-down jellyfish Cassiopea spp.?

Accepted Answer

They show quantifiable pulsing behavior and periods of quiescence, especially at night.

Question 4

Which experimental result indicates that sleep in jellyfish is homeostatically regulated?

Accepted Answer

Jellyfish decrease subsequent activity after being perturbed at night, proportional to the amount of sleep deprivation.

Question 5

Which molecule is evolutionarily conserved in Cnidarians and is known to induce a decrease in activity in Cassiopea jellyfish during the day?

Accepted Answer

Melatonin

Question 6

What does the presence of sleep-like states in jellyfish suggest about the evolution of sleep?

Accepted Answer

Sleep evolved prior to the evolution of a central nervous system.

Question 7

In the context of cavefish populations, what is the genetic basis for sleep loss?

Accepted Answer

Sleep loss genes are dominant to the surface population’s ‘sleep’ genes.

Question 8

Which pharmacological treatment was shown to rescue the decreased-sleep phenotype in cavefish?

Accepted Answer

Beta blocker (propranolol)

Question 9

What is the effect of the HCRTR2 pharmacological inhibitor TCSOX229 on cavefish?

Accepted Answer

It rescues the decreased-sleep phenotype in cavefish.

Question 10

Which of the following best explains why cavefish populations have evolved reduced sleep compared to surface populations?

Accepted Answer

Reduced sleep in cavefish is likely an adaptive trait with a genetic basis.

Question 11

A researcher perturbs Cassiopea jellyfish at night and observes a decrease in activity the following day. What does this result most likely indicate?

Accepted Answer

Jellyfish compensate for lost sleep, indicating homeostatic regulation.

Question 12

Which of the following is NOT a requirement for a sleep-like state as observed in Cassiopea jellyfish?

Accepted Answer

Central nervous system involvement

Question 13

Which of the following best describes the effect of melatonin on Cassiopea jellyfish?

Accepted Answer

It induces a decrease in activity during the day.

Question 14

Which of the following statements about the conservation of circadian clock genes is supported by the phylogenetic table in the study materials?

Accepted Answer

Some early-diverging animals, like sponges and ctenophores, lack several core clock genes.

Question 15

A student claims that sleep requires a brain. Based on the evidence from Cassiopea jellyfish, how should you respond?

Accepted Answer

Incorrect, because Cassiopea jellyfish lack a central nervous system but still exhibit sleep-like states.

Question 16

Which of the following best explains the significance of finding sleep-like states in ancient metazoan phyla?

Accepted Answer

It suggests that the ancestral role of sleep is rooted in basic requirements conserved across the animal kingdom.

Question 17

If a cavefish population is treated with a beta blocker, what is the expected outcome based on the study materials?

Accepted Answer

An increase in total sleep duration.

Question 18

Which of the following is a plausible reason why surface-cave hybrids show intermediate sleep phenotypes?

Accepted Answer

Sleep loss is genetically based and the alleles from both populations interact to produce an intermediate phenotype.

Question 19

Which of the following best describes the role of hypocretin/orexin in the evolution of sleep loss in Mexican cavefish?

Accepted Answer

Increased hypocretin/orexin signaling is associated with reduced sleep in cavefish.

Evolutionary Conservation of Sleep and Circadian Rhythms in Animals: Insights from Cnidarians and Cavefish

Study Guide - Practice Questions