Question

data in the biotic environment affect the carbon cycle. photosynthesizing and respiring organisms can affect the amount of co₂ in the atmosphere. if the masses of respiring organisms exceed that of photosynthesizing organisms, co₂ will be removed from the atmosphere and the amount of biomass will increase. respiration returns carbon to the atmosphere.
photosynthesis and carbon

• photosynthesis removes carbon from the atmosphere by fixing carbon in co₂ into carbohydrate molecules (e.g. glucose). plants use the glucose to build structures such as wood.
• respiration in living organisms returns some carbon to the atmosphere. if the amount or rate of carbon fixation exceeds that released in respiration then carbon will build up in the biosphere and be depleted in the atmosphere.

respiration and carbon

• cellular respiration breaks down glucose and releases carbon into the atmosphere as carbon dioxide.
• if the rate of carbon release is greater than that fixed by photosynthesis then carbon may accumulate in the atmosphere over time. deforestation and the burning of fossil fuels have increased the amount of carbon in the atmosphere and depleted what was stored in the biosphere.

investigation 1.1: carbon cycling simulation
plants move about 120 gt of carbon from the atmosphere to the biosphere a year. respiration accounts for about 60 gt of carbon a year. in this computer - based investigation, you will reproduce a simulation carried out to study the effect of varying the rates of respiration and photosynthesis on carbon deposition in the biosphere or atmosphere. to keep the simulation simple, only the effects to the atmosphere and biosphere were considered. effects such as ocean deposition and deforestation were not studied. the simulation is also available on biozones resource hub. the results are shown below for each of three simulations.
simulation 1\tsimulation 2\tsimulation 3
rate of photosynthesis equals rate of cellular respiration\trate of photosynthesis increases by 1 gt per year\trate of cellular respiration increases by 1 gt per year
years\tgt carbon in biosphere\tgt carbon in atmosphere\tgt carbon in biosphere\tgt carbon in atmosphere\tgt carbon in biosphere\tgt carbon in atmosphere
0\t610\t600\t610\t600\t610\t600
20\t608\t600\t632\t580\t590\t619
40\t608\t600\t651\t558\t570\t641
60\t609\t598\t671\t538\t548\t664
80\t612\t598\t691\t518\t528\t686
100\t610\t596\t710\t498\t509\t703

1. set up a spreadsheet in microsoft excel®, or similar program. enter the data for the three simulations in columns as above. select the data range including an appropriate header for each column of data.
2. from the menu choose <insert <chart xy scatter <scatter with straight lines and markers. right click on the graph and choose select data. you will have to choose switch row/column. click ok.
3. right click on your plot to format your graph to add a graph title, axis titles, and a legend (key)
4. in your group, study the results of your simulation and discuss the effect of:

(a) increasing the rate of photosynthesis on atmospheric and biospheric carbon
(b) increasing the rate of cellular respiration on atmospheric and biospheric carbon
(c) identify human activities with the same effects as increased respiration.
summarize your discussion and any notes on a separate sheet and attach it to this page

Explanation:

Step1: Analyze effect of increased photosynthesis

When the rate of photosynthesis increases (Simulation 2), more carbon is removed from the atmosphere and fixed into the biosphere. Over 100 years, the amount of carbon in the biosphere increases from 610 Gt to 710 Gt and in the atmosphere decreases from 600 Gt to 498 Gt. This is because photosynthesis takes in CO₂ from the atmosphere and converts it into organic compounds in the biosphere.

Step2: Analyze effect of increased cellular respiration

When the rate of cellular respiration increases (Simulation 3), more carbon is released from the biosphere into the atmosphere. Over 100 years, the amount of carbon in the biosphere decreases from 610 Gt to 509 Gt and in the atmosphere increases from 600 Gt to 703 Gt. This is because cellular respiration breaks down organic compounds and releases CO₂ into the atmosphere.

Step3: Identify human - related activities

Activities like deforestation (cutting down trees which reduces photosynthesis) have the same effect as increased respiration as it decreases the amount of carbon being fixed in the biosphere and can lead to more carbon in the atmosphere. Burning of fossil fuels (coal, oil, gas) also releases large amounts of stored carbon into the atmosphere, similar to increased respiration.

Answer:

(a) Increasing the rate of photosynthesis decreases atmospheric carbon and increases biospheric carbon.
(b) Increasing the rate of cellular respiration increases atmospheric carbon and decreases biospheric carbon.
(c) Human activities such as deforestation and burning of fossil fuels have effects similar to increased respiration.