The contraction of skeletal muscles is based on

• actin filaments coiling up to become shorter.

• myosin filaments coiling up to become shorter.

• actin and myosin filaments both coiling up to become shorter.

• myosin cross-bridges binding to actin and transitioning from a high-energy to a low-energy state.

Myasthenia gravis is a form of muscle paralysis in which

• the spinal cord is infected with a virus that attacks muscle stretch receptors.

• ATP production becomes uncoupled from mitochondrial electron transport.

• acetylcholine receptors are destroyed by an overactive immune system.

• motor neurons lose their myelination and the ability to rapidly fire action potentials.

A skeletal muscle with abnormally low levels of calcium ions would be impaired in

• initiating contraction.

• ATP hydrolysis.

• the initiation of an action potential.

• maintaining its resting membrane potential.

The muscles of a recently deceased human can remain in a contracted state, termed rigor mortis, for several hours, due to the lack of

• calcium ions needed to bind to troponin.

• sodium ions needed to fire action potentials.

• ATP needed to break actin-myosin bonds.

• phosphorylated myosin.

The hydrostatic skeleton of the earthworm allows it to move around in its environment by

• swimming with its setae.

• using peristaltic contractions of its circular and longitudinal muscles.

• alternating contractions and relaxations of its flagellae.

• crawling with its feet.

A female cat in heat urinates more often and in many places. Male cats are attracted to the urine deposits. Which of the following is a proximate cause of this increased urination?

• It announces to the males that she is in heat.

• Female cats that did this in the past attracted more males.

• It is a result of hormonal changes associated with her reproductive cycle.

• The female cat learned the behavior from observing other cats.

Animals use pheromones to communicate

• reproductive readiness.

• species recognition.

• gender recognition.

• All options are correct.

A mother goat can recognize its own kid by smell.

• operant conditioning

• altruistic behavior

• innate behavior

• imprinting

The evolution of mating systems is most likely affected by

• population density.

• territoriality.

• sexual dimorphism.

• certainty of paternity.

Which of the following statements about the evolution of behavior is correct?

• If a behavior is less than optimal, it will eventually become optimal through natural selection.

• Natural selection will favor behavior that enhances survival and reproduction.

• An animal may show behavior that minimizes reproductive fitness.

• Innate behaviors can never be altered by natural selection.