Part D Changes in ecosystems can be attributed to natural causes, such as natural disasters, seasonal variations
in climate, currents, and tidal activity. Many of these changes can affect the amount of food resources
available in an ecosystem. Research one natural change that currently affects or could affect the aquatic
ecosystem you chose. Use your food web model to explain how this change can affect the competition of
food resources in your aquatic ecosystem.

Match the following terms describing electrical events with the correct phases of the cardiac cycle. the ventricular muscle cells depolarize at the start of this phase. during this phase, na+ entry through the funny channels causes the pacemaker potential of sa nodal cells to gradually become less negative until it reaches threshold. the ventricular muscle cells repolarize right before this phase. the cytosolic concentration of calcium in the contractile cells of the ventricle is highest during this phase. a. isovolumetric relaxation b. ventricular ejection c. isovolumetric contraction d. ventricular filling

Is there any species that went extinct in recent years due to natural causes (not caused by human interaction). if so, what caused it?

You have just sequenced a new protein found in mice and observe that sulfur-containing cysteine residues occur at regular intervals. what is the significance of this finding? it will be important to include cysteine in the diet of the mice. cysteine residues are required for the formation of α helices and β pleated sheets. cysteine residues are involved in disulfide bridges that form tertiary structure. cysteine causes bends, or angles, to occur in the tertiary structure of proteins.