Problem 8 - Campbell Biology

Question

SCIENTIFIC INOUIRY : INTERPRET THE DATA The nitrogen-fixing bacterium Rhizobium infects the roots of some plant species, forming a mutualism in which the bacterium provides nitrogen, and the plant provides carbohydrates. Scientists measured the 12 -week growth of one such plant species (Acacia irorata) when infected by six different Rhizobium strains. (a) Graph the data. (b) Interpret your graph. $$\begin{array}{|c|c|c|c|c|c|c|}\hline \text { Rhizobium strain } & {1} & {2} & {3} & {4} & {5} & {6} \\ \hline \text { Plant mass (g) } & {0.91} & {0.06} & {1.56} & {1.72} & {0.14} & {1.03} \\ \hline\end{array}$$

Step-by-Step Solution

Answer

Strains 3 and 4 are most effective, providing higher plant masses, while strains 2 and 5 are least effective.

Step 1 - Organize the Data

Extract the information from the table: Rhizobium strains are 1, 2, 3, 4, 5, and 6. Plant masses in grams for these strains are 0.91, 0.06, 1.56, 1.72, 0.14, and 1.03 grams respectively.

Step 2 - Set Up the Graph

Draw a horizontal axis (x-axis) for Rhizobium strains and a vertical axis (y-axis) for plant mass (in grams). Label the x-axis with strains 1 through 6, and the y-axis with appropriate mass values.

Step 3 - Plot the Data Points

For each Rhizobium strain, plot a point corresponding to the plant mass observed:- Strain 1: mass 0.91- Strain 2: mass 0.06- Strain 3: mass 1.56- Strain 4: mass 1.72- Strain 5: mass 0.14- Strain 6: mass 1.03

Step 4 - Draw the Graph

Connect the points with straight lines to visualize the trends or variations in plant mass across different Rhizobium strains.

Step 5 - Interpret the Graph

Analyze the graph to interpret the data. Observe which Rhizobium strains lead to higher plant masses. Strains 3 and 4 result in higher plant masses, indicating they are more effective in the mutualism with Acacia irorata. Strains 2 and 5 lead to significantly lower plant masses, indicating they are less effective.

Key Concepts

Nitrogen-fixing bacteria

Nitrogen-fixing bacteria are essential microorganisms that convert atmospheric nitrogen into a form usable by plants.
This process is called nitrogen fixation and is crucial for plant growth because nitrogen is a core component of amino acids, proteins, and nucleic acids.
Some common nitrogen-fixing bacteria include _Rhizobium_, _Azotobacter_, and _Frankia_.
These bacteria form symbiotic relationships with host plants, usually legumes, enabling the plants to thrive in nitrogen-poor soils. By converting inert atmospheric nitrogen into ammonia, they enrich the soil and support plant growth.

Rhizobium

_Rhizobium_ is a genus of bacteria known for its nitrogen-fixing capabilities.
These bacteria infect the root nodules of leguminous plants, including _Acacia irorata_, forming a symbiotic relationship.
The bacteria convert atmospheric nitrogen into ammonia, a form that the plant can readily use for its nutritional needs.
In return, the plant provides carbohydrates and a protective environment for the bacteria.
This partnership is crucial for natural ecosystems and agricultural practices, as it reduces the need for chemical fertilizers and enhances soil fertility.

Mutualism

Mutualism is a type of symbiotic relationship where both organisms involved benefit.
In the case of _Rhizobium_ and _Acacia irorata_, mutualism occurs as the bacteria get carbohydrates and a habitat within the plant's root nodules, while the plant receives a readily usable form of nitrogen.
This relationship enhances the growth and health of the plant, which in turn supports the bacteria's proliferation. Such interactions are vital in ecosystems as they support biodiversity and stability.
Mutualistic relationships illustrate the interdependence of species and the complex web of life.

Data Interpretation

Data interpretation involves analyzing and drawing conclusions from data.
In this exercise, we have measurements of plant mass based on different _Rhizobium_ strains.
The goal is to determine which strains are most beneficial for the plant's growth.
Interpreting the data involves observing trends and variations, identifying the strains that lead to higher plant masses (e.g., Strains 3 and 4), and those that result in lower masses (e.g., Strains 2 and 5).
This analysis helps in understanding the effectiveness of different _Rhizobium_ strains in enhancing plant growth.

Graphing Data

Graphing data is a crucial skill in scientific inquiry as it helps visualize relationships and trends.
In this example, we graph the mass of plants (y-axis) against different _Rhizobium_ strains (x-axis).
Steps to graph the data include:

• Setting up the horizontal axis (Rhizobium strains 1-6) and vertical axis (plant mass).
• Plotting data points for each strain: 1 (0.91 g), 2 (0.06 g), 3 (1.56 g), 4 (1.72 g), 5 (0.14 g), 6 (1.03 g).
• Connecting the points to visualize trends.

From the graph, one can easily compare which strains are more or less effective, aiding in data interpretation and drawing scientific conclusions.