A cancer cell affect the near by cell or tissue. They break down the basal lamina and establish secondary growth areas through out the body.
Proteases secreted by metastatic tumors degrade the surrounding extracellular matrix and interferes with the normal cell reproduction and division.
Their replication process is unstoppable and so a cancer cell never die. Normal cells affected by cancerous cell also posses the similar characteristics.
A decrease in dissolved oxygen. This is because oxygen is a byproduct of photosynthesis. If the plants are in water, some of the oxygen they produce will become dissolved in it. Without those plants, you have less dissolved oxygen.
The cell theory of course had an important impact on later scientific discoveries as many different hypothesis and scientific discoveries were derived and concluded with the help of basics from this theory.
