Staphylococcus aureus is a species of bacteria that have invaded the human body for a long time. Humans scientifically created an antibiotic, methicillin, to fight off the bacteria, but in return, the
Staph bacteria developed resistance to the methicillin and are now considered a new strain called
methicillin-resistant Staphylococcus aureus (or MRSA.) Therefore, humans had to develop even
stronger antibiotics to fight it. What pattern of evolution does this exhibit?

this might

answer; /// the shaft of the hair consists of dead cells;

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.