Human evolution known to be a process in which species adapt to certain
conditions of life, and in the battle of life and death, they are forced
to become stronger in order to survive in this world. Diseases have
always been present during the evolution, acting themselves as a natural
selectors - the weaker organisms get sick and die. Not just humans, but
all species have to establish a great protecting mechanism in order to
survive. That is how our bodies are built, to be able to withstand and
survive in the conditions we live in, and that is why our immune system
has to be taken care of.
The factor that is most likely to have a density-independent influence on population growth is Extreme weather conditions.
Density-independent factors such as weather and climate, exert their influences on population size regardless of the population's density. Conversely, the effects of density-dependent factors intensify as the population increases in size.
Answer:
Certain fossils, called index fossils, help geologists match rock layers. To be useful as an index fossil, a fossil must be widely distributed and represent a type of organism that existed for a brief time period. Index fossils are useful because they tell the relative ages of the rock layers in which they occur.
