Hi!
The selection in this case would be natural selection.
Natural selection is a process that involves organisms with favorable characteristics having a higher chance of reproductive success, and passing on their traits onto the offspring. This process, as opposed to artificial selection, does not involve human intervention and is a natural phenomenon.
In our case, whales with maximum length (the favorable trait) are mating on accord of their own, without external factors governing the process; hence, the selection is natural.
Hope it helps!
A) remain in the body after production
B) flag antigens for destruction
C) are an important part of the immune system
D) all of the above
D) ALL ARE CORRECT!!
Answer:
1. nerve stimulus
4. calcium channels open
10. acetylcholine vesicles move to endplate
7. exocytosis occurs releasing acetylcholine into synaptic cleft
3. acetylcholine binds to receptor
6. impulse rides along sarcolemma
9. impulse enters the cells via the t-tubule
5. sarcoplasmic reticulum releases calcium
8. calcium binds to troponin moving tropomyosin out of the way
2. myosin attaches to actin causing a twitch
Explanation:
The central nervous system generates an action potential (<u>1</u>) that travels to the muscle fiber activating the calcium channels (<u>4</u>). Calcium triggers vesicles fusion to the presynaptic membrane (<u>10)</u> releasing acetylcholine (Ach) into the synaptic space (<u>7</u>). Once there, Ach binds to its receptors (<u>3</u>) on the postsynaptic membrane of the skeletal muscle fiber, causing ion channels to open. Positively charged sodium ions cross the membrane to get into the muscle fiber (sarcoplasm) and potassium leaves the cell. The difference in charges caused by these ions transport charges positively the muscle fiber membrane (<u>6</u>). It depolarizes. The action potential enters the t-tubules (<u>9</u>) depolarizing the inner portion of the muscle fiber.
Contraction initiates when the action potential depolarizes the inner portion of the muscle fiber. Calcium channels activate in the T tubules membrane, releasing calcium into the sarcolemma (<u>5</u>). At this point, the muscle is at rest, and the tropomyosin is inhibiting the attraction strengths between myosin and actin filaments. <em>Tropomyosin is obstructing binding sites for myosin on the thin filament</em>. When calcium binds to troponin C, troponin T alters the tropomyosin position by moving it and unblocking the binding sites (<u>8)</u>. Myosin heads join to the uncovered actin-binding points forming cross-bridges <u>(2</u>), and while doing so, ATP turns 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 (<u>2</u>). 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. Finally, Z-bands are pulled toward each other, shortening the sarcomere and the I-band, producing muscle fiber contraction.
U will need to actually post a question, i dont see one
