Circulatory system.....circulates blood (a vital delivery system of oxygen) throughout the whole body when tissues need it the most and with a constant supply.
When using the term 'life form' I assume you are speaking of animals, bacteria, etc. Scientists take years to find their desired conclusion because of how the environment tends to change quite frequently (Depending on where the creature lives). The earth is constantly revolving and rotating, which causes changes in the environment. These changes affect the animals behavior, eating habits, and overall chances of survival. A factor that must also be considered is that scientists have to examine these creatures in their natural habitat which can be an issue depending on where they live. For example, if I were to study the behavioral patterns of a Leopard, it would be extremely difficult to do so because the Leopards are specifically keen at camouflaging in their environment. That would make observing its behavioral patterns very frustrating and time consuming. In a way, mother nature is always against us.
(Hope this helps)
Answer:
I think Experimentation :)
Explanation:
apologies if its incorrect.
If an area as a relatively large number of leaves, these leaves can block much-needed sunlight for other organisms, whether they remain on the tree of fall to the ground.
Since fire is a chemical reaction, and oxygen is needed for that reaction, having a fire in a cave is a sure sign of the presence of oxygen.
