Arrange the following steps of muscle fiber contraction in the correct sequence. 1. The muscle impulse reaches the sarcoplasmic reticulum and calcium is released. 2. Thin filaments are pulled over the thick filaments. 3. Calcium floods the sarcoplasm and binds to troponin molecules leaving active sites. 4. The impulse arrives at the synapse and travels through the transverse tubules. 5. The muscle fiber shortens and contracts. 6. Myosin heads bind to exposed active sites on actin, forming cross-bridges.

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.

if the hares very faster than they are now, and thus the lynx's hunting success rate drops because it will be harder to catch them, the rate that will change will be the pray-rate. the pray-rate will change because more hares will be able to survive, thus more individuals for reproduction, so the end result will be increasing population of hares.

the predator-rate will remain pretty much the same because there will be more than enough pray, but the hunting success rate is stagnant.

the answer is d. embryo