After completing the Unit 5 Lab on Connect (above), apply critical thinking to answer the following:
1. DDE and Eggshell Thickness: In 1980, there was a major spill of DDT (a persistent chlorinated insecticide) into Florida’s Lake Apopka that caused high rates of mortality in much of the wildlife there. A metabolite of DDT called DDE causes eggshell thinning in birds that eat fish. These birds are affected more than others because they at the top of the food chain and therefore accumulate higher levels of persistent chemicals like DDE. DDE affects calcium movement in the eggshell glands of the birds.
Answer the following questions:
• Describe the role of calcium in maintaining human bones and teeth. Based on this, how do you think a lack of calcium may affect the shells of these birds?
• Predict what will happen when parent birds incubate the eggs.
• Look at the graph attached. Describe how eggshell thickness is related to DDE concentration.
2. Effects of DDE on the Endocrine System: The American alligators (Alligator mississippiensis) that survived the initial spill were found to have high concentrations of DDE in their tissues. Decades later, the alligators in the lake still have DDE in their tissues and their populations do not seem to have recovered to pre-spill conditions. Many juvenile male alligators have low levels of testosterone.
Answer the following questions:
• How would low levels of testosterone affect the American alligator population?
• Based on your reading of the materials in this unit, how do environmental factors affect fertility in humans?
Q-1):
In birds, the process of bone remodelling plays a vital role in maintaining bone calcium levels. During this process, a small content of calcium is being replaced by new amount of calcium which is absorbed from the blood.
The bone is made up of outer cortical layer and inner spongy matrix. The functional unit associated with bone remodelling is the OSTEON. It shows presence of tissue into which bone matrix is present. Minerals like calcium gets deposited into this matrix.
There are two types of cells associated with maintaining the bone calcium levels. They are OSTEOBLASTS and OSTEOCLASTS.
New matrix is synthesized by the osteoblasts whereas on the other hand, the osteoclasts are associated with degradation of the bone matrix and this is associated with age.
As age increases, the calcium deposition process becomes less efficient. Osteoblasts play a vital role in calcium deposition.
This mechanism is supported by the hormone called CALCITONIN along with hormone TESTOSTERONE in elevating the levels of deposition of calcium in the bone matrix.
Parathyroid hormone stops calcium deposition and stimulates the osteoclasts to initiate the process of bone resorption.
Imbalance between the process ultimately leads to imbalance in bone calcium levels as age progresses. High levels of body activities are associated with enhanced calcium deposition increasing bone strength. Whereas, a person who is lethargic is more prone to bone resorption.
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