Answer and Explanation:
In rest, attraction strengths between myosin and actin filaments are inhibited by the tropomyosin. When the muscle fiber membrane depolarizes, the action potential caused by this depolarization enters the t-tubules depolarizing the inner portion of the muscle fiber. This activates calcium channels in the T tubules membrane and releases calcium into the sarcolemma. At this point, tropomyosin is obstructing binding sites for myosin on the thin filament. When calcium binds to the troponin C, the troponin T alters the tropomyosin by moving it and then unblocks the binding sites. Myosin heads bind to the uncovered actin-binding sites forming cross-bridges, and while doing it ATP is transformed into ADP and inorganic phosphate which is released. Myofilaments slide impulsed by chemical energy collected in myosin heads, producing a power stroke. The power stroke initiates when the myosin cross-bridge binds to actin. As they slide, ADP molecules are released. A new ATP links to myosin heads and breaks the bindings to the actin filament. Then ATP splits into ADP and phosphate, and the energy produced is accumulated in the myosin heads, which starts a new binding cycle to actin. Z-bands are then pulled toward each other, thus shortening the sarcomere and the I-band, and producing muscle fiber contraction.
That should be the cell membrane. The cell membrane acts as a filter in and out.
8. Arteries carry oxygenated blood from the heart to the rest of the body, while veins carry deoxygenated blood from the body, back to the heart. Arteries are thick and muscular, while veins aren't as thick, and they have valves.
Answer:
1) A mutation appeared in one weed plant that made that weed not susceptible to the herbicide ( B )
2) The weed will survive long enough to reproduce ( B )
Explanation:
1) The most likely reason the weed remained is : A mutation appeared in one weed plant that made that weed not susceptible to the herbicide
The weed plant must have undergone some mutation in order to be resistant to the herbicide which would kill the weed before now
2) The most likely thing that will happen if the weed stays in place in that farm is : The weed will survive long enough to reproduce
The trait or mutation of the weed cannot just spread to other weeds nearby it can only spread by reproducing more weeds of same mutation
Phylogenetic species concept (PSC) The concept of a species as an irreducible group whose members are descended from a common ancestor and who all possess a combination of certain defining, or derived, traits (see apomorphy). ... "phylogenetic species concept." A Dictionary of Biology. .
Or
The biological species concept has its limitations (although it works well for many organisms and has been very influential in the growth ofevolutionary theory). ... In thisexample, Ensatina salamander lineages A and B are separate species.Each has a common ancestor that individuals of other species do not.
I hope that this helps you out
