Question

use the following information for question 14. a table gives characteristics of organisms living in 3×10^12 cubic meters of water in a small marine bay ecosystem. the average density of the main producers in the ecosystem, phytoplankton, is 1×10^6 per cubic meter. the apex predator is a single shark and clams are the primary consumers. organism average mass (g) number in community blue crab 60 6×10^4 clam 50 5×10^4 phytoplankton 7.7×10^(-13) 4×10^17 shark 80,000 1 scale, proportion, and quantity construct a biomass pyramid for this ecosystem; report biomass in grams per cubic meter and describe potential reasons for the pyramid shape.

Explanation:

Step1: Calculate total biomass of each organism

Blue - crab: Multiply average mass by number. Total mass = $60\times6\times10^{4}=3.6\times10^{6}$ g. Biomass per cubic meter = $\frac{3.6\times10^{6}}{3\times10^{12}} = 1.2\times10^{-6}$ g/m³.
Clam: Total mass = $50\times5\times10^{4}=2.5\times10^{6}$ g. Biomass per cubic meter = $\frac{2.5\times10^{6}}{3\times10^{12}}=\frac{25}{3}\times10^{-7}\approx8.33\times10^{-7}$ g/m³.
Phytoplankton: Total mass = $7.7\times10^{-13}\times4\times10^{17}=3.08\times10^{5}$ g. Biomass per cubic meter = $\frac{3.08\times10^{5}}{3\times10^{12}}\approx1.03\times10^{-7}$ g/m³.
Shark: Total mass = $80000\times1 = 80000$ g. Biomass per cubic meter = $\frac{80000}{3\times10^{12}}\approx2.67\times10^{-8}$ g/m³.

Step2: Arrange in biomass - pyramid order

The biomass per cubic meter in descending order is: Blue - crab ($1.2\times10^{-6}$ g/m³), Clam ($8.33\times10^{-7}$ g/m³), Phytoplankton ($1.03\times10^{-7}$ g/m³), Shark ($2.67\times10^{-8}$ g/m³).

Step3: Explain pyramid shape

The pyramid has a traditional shape with primary consumers (clams and blue - crabs) having more biomass per cubic meter than the apex predator (shark) because there is more energy available at lower trophic levels. Phytoplankton, despite being numerous, have a very low individual mass, resulting in a relatively lower biomass per cubic meter compared to some primary consumers in this case.

Answer:

Biomass per cubic meter: Blue - crab: $1.2\times10^{-6}$ g/m³; Clam: $8.33\times10^{-7}$ g/m³; Phytoplankton: $1.03\times10^{-7}$ g/m³; Shark: $2.67\times10^{-8}$ g/m³. The pyramid has a traditional shape with more biomass at lower trophic levels (primary consumers more than apex predator) and phytoplankton having low individual - mass resulting in relatively lower biomass per cubic meter compared to some primary consumers.