<span>The climate and the situation of the country or city that they live in.</span>
The dissolved oxygen content in water
Answer:
In osmosis, water moves from areas of low concentration of solute to areas of high concentration of solute.So osmosis only occurs with a semipermeable membrane, and even with the membrane some water will move both sides. MORE water will move up the concentration gradient, thus there is a net flow up the gradient.
Explanation:
Answer:
There is only enough food for a few top level consumers
Explanation:
The organisms that eat the producers are the primary consumers. They tend to be small in size and there are many of them. The primary consumers are herbivores (vegetarians). The organisms that eat the primary consumers are meat eaters (carnivores) and are called the secondary consumers. The secondary consumers tend to be larger and fewer in number. This continues on, all the way up to the top of the food chain. About 50% of the energy (possibly as much as 90%) in food is lost at each trophic level when an organism is eaten, so it is less efficient to be a higher order consumer than a primary consumer. Therefore, the energy transfer from one trophic level to the next, up the food chain, is like a pyramid; wider at the base and narrower at the top. Because of this inefficiency, there is only enough food for a few top level consumers, but there is lots of food for herbivores lower down on the food chain. There are fewer consumers than producers.
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.
