Answer and Explanation:
The Cretaceous–Paleogene extinction, which occurred around 66 million years ago, is defined as a mass extinction that wiped out around three-quarters of species on Earth.
Among the organisms that disappeared during this event, we find mammals, birds, fish, sharks, pterosaurs, birds, reptiles, insects, and some plant species.
This event is marked by the presence of a sediment layer known as the K-Ph boundary which showed important levels of iridium, an element that is abundant in craters. Therefore, after its discovery, scientists hypothesize this extinction occurred due to the impact of the giant Chicxulub crater which changed the conditions of the atmosphere.
Answer:
antigens
Explanation:
a vaccine may contain that
2, because a theory is not a law that can not be changed, and new evidence can change a theory.
All known living things are made up of one or more cells<span>.</span>
Phagocytosis and the inflammatory response. Macrophages are a cornerstone of the innate immune system. ... Recent work indicates that Toll-like receptors play a key role in reading a "bar code" on invading microorganisms and in eliciting a specific immune respone.
