Which statement best describes a cause and its effect that occurs during the process of muscle contraction? A.
The shortening of the sarcomere causes the release of calcium around the myofibrils.
B.
The presence of calcium ions within nerve cells causes the sarcomere to shorten.
C.
The release of calcium ions causes myosin and actin to attach to each other.
D.
The pull of myosin on actin causes the motor neuron to send a nerve impulse.

Examine the two squirrel populations in the accompanying figure. the populations are separated by a geographic barrier. if after a long period of time the two species are no longer separated, what evidence is needed to determine if speciation has occurred? the figure shows two populations of squirrels separated by a geographic barrier. examine the two squirrel populations in the accompanying figure. the populations are separated by a geographic barrier. if after a long period of time the two species are no longer separated, what evidence is needed to determine if speciation has occurred? the figure shows two populations of squirrels separated by a geographic barrier. polyploidy is creating new species. the two populations are not interbreeding freely. hybrid offspring of the two populations begin to appear. one species will increase into a population size twice as large as the other species.

2. how does the miller-urey experiment fall short of demonstrating that life can arise from inorganic molecules? explain. a. it doesn't show a leap between a collection of amino acids and a single-celled organism. b. it recreates the conditions that existed at the earth's beginning, but no molecules form as a result. c. it doesn't provide evidence of the formation of amino acids. d. it doesn't show how multicellular organisms developed from unicellular organisms

The carbon cycle is best defined as a process in which a. carbon changes from inorganic forms to organic forms and back b. carbon is changed into other elements such as oxygen or nitrogen c. carbon is continually created from the sun’s energy by plants d. carbon is consumed and regenerated from other elements such as oxygen and nitrogen