Evidence for evolution, in other words evidence of common descent, include fossils, which have shown a (fairly) steady change in morphology over time for some species. An example would be horse hooves: we have fossils that show when they were still three toed, then two toed, then one toe in our present day horses. Another piece of evidence is vestigial organs. An example of vestigial organs is wings in some flightless birds, such as the kiwi. Their ancestors used it in order to fly across the marine barrier into New Zealand, but natural selection and random genetic drift made them quickly lose the ability to fly. Nonetheless, they still have their wings, however small. It can be assumed that eventually, their wings would be reduced to small stubs fused to other nearby bones, as has been observed in their cousins.
Humans obtain nitrogen by eating other organisms.
<span>When a body's host defenses are overwhelmed by contaminate, we start seeing biological responses to the invading bacteria. We may notice redness, swelling, oozing, pus, foul odor or warmth at the site of the wound. The host may also have an systemic fever, delirium or other responses when overwhelmed with bacteria.</span>
