most deer mouse populations inhabit regions with dark soils. these deer mice have dark brown fur. populations of deer mice found in the sand hills region of nebraska, which has tan colored sand instead of dark soil, have tan fur. which statement best explains why the sand hills population of deer mice have tan fur, rather than the dark brown fur found in other populations of deer mice?

a- multicellular

b-eukaryotic

c-no cell wall

d-heterotrophic

e-autotrophic

the answer is: the „power stroke“ step.

muscle contraction can be divided into a few steps:

1. the release of ach (acetylcholine) in the synaptic cleft, binding of ach for its receptor and consequently opening of the ca channels.

2. the release of ca, binding of ca for the troponin

3. troponin shifting the tropomyosin, which was blocking the active site on the actin

4. myosin heads attaching to actin by breaking down atp to adp+ pi

5.   formation of the ‘cross-bridge’ on the active site of the actin filament by myosin head

6. “power stroke” -the cross bridge pulls actin, which slides over the myosin

9.     7. the release of adp completes the cross-bridge movement and atp attaches to myosin, breaking the actin-myosin cross bridge.