Answer to Question 1
Cancer starts with the abnormal growth of one cell, which can then multiply into billions of cancerous cells. A critical turning point in the development of cancer is when a tumor reaches about a million cells. At this stage, it is referred to as carcinoma in situ. The undetected tumor may go for months or years without significant growth. While it remains encapsulated, it does not pose a serious threat to human health.
In time, a few of the cancer cells start producing chemicals that signal the body to start angiogenesis, or the growth of a new network of capillaries (blood vessels) that penetrate the tumor and help it grow by delivering oxygen and nutrients and carrying away waste products. During normal healthy processes, angiogenesis is limited to a few infrequent functions such as healing wounds or development during pregnancy.
During cancer, angiogenesis is the precursor of metastasis. Through the new blood vessels formed by angiogenesis, cancerous cells now can break away from a malignant tumor and migrate to other parts of the body, where they can cause new cancer.
Answer to Question 2
Answers may include any six of the following.
Everyone should become familiar with the following warning signals for cancer and bring those present to a physician's attention:
Change in bowel or bladder habits
Sore that does not heal
Unusual bleeding or discharge
Thickening or lump in the breast or elsewhere
Indigestion or difficulty in swallowing
Obvious change in wart or mole
Nagging cough or hoarseness
Unexplained weight loss
Ongoing pain or fatigue
The growth in demand for energy use is met by burning fossil fuels
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Early growth of corn (Zea mays), a typical monocot.
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The normal cell cycle and each of its growth phases