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Essential Lens: Analyzing Photographs Across the Curriculum
Genetics and Bioengineering: The Societal Impacts of Mutations #2003 Comparison of unsprayed conventional cotton crop and Bt GM cotton in Australia
#2003 The color photograph is of a field of cotton. The photograph is divided to depict two different crops, which are distinguishable by color.
Metadata
Date: 2006
Location: Australia
Photographer: unknown
Source: Cotton Australia
Caption
Bacillus thuringiensis (Bt) is a spore-forming bacterium that produces crystal proteins that are toxic to many species of insects. Crops have been modified with short sequences of genes from Bt to express the crystal protein Bt makes. With this method, plants themselves can produce the proteins and protect themselves from insects without any external Bt and/or synthetic pesticide sprays.
Rights
Photos downloaded from the Essential Lens site are cleared for educational use only.
Observe
The photograph of a cotton field is graphically organized into four areas. On the left are plants that have cotton growing on them, and on the right the plants are barren. Along the horizon line at the back of the composition is a line of trees, and above that, the sky.
The line down the center of the photograph draws the viewer’s attention into the back of the image.
The effect of the close cropping of the photograph to this particular section of the field is enhanced by the dramatic differences in color.
On the left, the plants have fluffy tufts of cotton.
On the right, the plants are mostly brown and rough-looking, with darker reddish spots throughout. The different textures also serve to enforce a comparison.
Build on Your Observations
The point of view of the photograph, with the field dramatically receding into the distance, emphasizes the large size of the field.
The graphic composition is visual confirmation of what we read in the caption and metadata, which tells us the photograph was made in Australia. It shows a field sprayed with Bacillus thuringiensis (Bt), a spore-forming bacterium that produces crystals protein (cry proteins), which are toxic to many species of insects, and an unsprayed field. Bt is a naturally occurring bacterial disease of insects. Cotton crops are particularly attractive to such insects as cabbage loopers, and this is one of the insects that can be controlled with Bt.
Make Inferences
The photograph is trying to demonstrate the impact of Bt through a graphic comparison.
By providing a sense of the size of this field, the photograph suggests the scale of impact of the use of Bt versus not using Bt on preserving the cotton crop.
Formulate Further Questions
How does Bt work to control insects?
Are there other naturally occurring spores like Bt that scientists use to control insects?
Is Bt only effective in certain regions, or is it used throughout the world?
