If you use more than one independent variable at a time, and will observe a change, you will not know which variable contributed to a changed result.
In the broadest sense of the term, we have modified the genes of almost everything. We used selective breeding to breed the most resistant form of crops, the largest sized chickens, and others. In recent years we have even modified them through gene splicing and other methods. Nearly everything we eat, including including "organic" foods have been changed from their original DNA structure, in fact we do not even know anything's original genetic structure because of this. Genetic modification could also include mutations. Some crops have mutated due to pollution, disease, or other effects such as climate change. Without genetic modification our world would differ from what it looks like today.
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(VEE-nuh KAY-vuh) A large vein that carries blood to the heart from other areas of the body. The vena cava has two parts: the superior vena cava and the inferior vena cava. The superior vena cava carries blood from the head, neck, arms, and chest.
Limiting factors, or things in the environment that can lower the population growth rate, include low food supply and lack of space. When organisms face limiting factors, they show logistic type of growth (S-curve).
