Biomorph Challenge #4

Marine Biology: Animals and Ocean

1. The Biomorphs reassure you: "Our technology will add only 0.0001 moles/liter of hydrogen ions to your ocean. This tiny amount will have no effect on the ecosystem."

What do you say?

Facts about Oceans

The oceans cover 71% of the Earth's surface and contain 97% of the Earth's water.

Less than 1% of Earth's water is fresh water, and 2-3% is contained in glaciers and ice caps.

The pH of the ocean, like that of human blood, depends on the ratio of bicarbonate to carbon dioxide. Most of the carbon dioxide (CO₂) converts to carbonic acid (H₂CO₃), which dissociates to bicarbonate (HCO₃^-) and hydrogen ion (H⁺). The hydrogen ions lower the pH (negative log₁₀(H⁺)).

In 1850, the ocean was at pH 8.16. Today, it is pH 8.11. By the year 2100, it is predicted to be pH 7.85.

Coral reefs and other marine phototrophs have shells of calcium carbonate (CaCO₃). The shells dissolve as pH decreases.

At the deepest point in the ocean the pressure is more than 8 tons per square inch, or the equivalent of one person trying to support 50 jumbo jets.

At 39 degrees Fahrenheit, the temperature of almost all of the deep ocean is only a few degrees above freezing.

If the ocean's total salt content were dried, it would cover the continents to a depth of 5 feet.

2. The evolution of cephaglobinids of Shora is measured by a "molecular clock" gene whose sequence varies by mutation at 0.8% change per million years. The following table shows the percent relatedness of all pairs of species. Based on this table, draw a phylogenetic tree showing the relative divergence over time (time shown on the x axis).

Label	Creature	% Relatedness to	A	B	C	D	E	F	G
A	Small blue-striped rocket squid		100	42	72	72	72	63	92
B	Legfish		42	100	42	42	42	42	42
C	Starworm		72	42	100	96	87	63	72
D	Fleshborer		72	42	96	100	87	63	72
E	Shockwraith		72	42	87	87	100	63	72
F	Seaswallower		63	42	63	63	63	100	63
G	Large brown-spotted rocket squid		92	42	72	72	72	63	100

3. The pH of Shora’s ocean is 8.35.

(a) Calculate the concentration of H⁺ in the water.

(b) Is this pH good for the "raft corals"? Explain why or why not.

4. As CO₂ dissolves in water, some of it converts to carbonic acid, which releases hydrogen ions. Write the chemical equation for these processes.

5. In human blood, if the bicarbonate/CO₂ ratio is 30, what is the blood pH? What medical problems does this cause?

6. In seawater, the acid dissociation constant (K_a) for carbonic acid is 9.3 x 10^-7M (moles per liter).

(a) Estimate the percent ionization (dissociation) of solutions with the following concentrations (moles/liter) of carbonic acid. Assume that only a tiny amount of carbonic acid is dissociated, and that no other acids contribute hydrogen ions:
0.0001 M
0.001 M
0.01 M

(b) Calculate the pH at each concentration. Comment on the trend you see in your results. What does it imply for the effect of increasing Earth's atmospheric CO₂ on marine life?

7. The biology of cooperation: Examples from Shora, and from real life.

(a) Microbes cooperate with other organisms: Explain an example from Shora, and an example from real life. Explain why the cooperation is favored by natural selection.

(b) Large animals and/or plants cooperate with each other: Explain an example from Shora, and an example from real life. Explain why the cooperation is favored by natural selection.