How have humans affected the four spheres?

Human activities are impacting our environment and, in particular, the composition of the atmosphere, water, and plants. However, it is sometimes difficult to distinguish the "natural" signature from the one induced by industrial and urban activities. The latest analytical developments allow the fine and precise measurement of isotopic signatures of elements whose content or isotopic composition may be changed by modern industrial activities, such as the transition metals (Ni, Hg, Se, and Zn), lithium, and helium. This approach opens up original and new avenues of inquiry, including the determination of the sources of aerosols, of the elements carried by rivers, the effects of bioaccumulation, the phytoavailability of metals, and allows the refinement of the determination of anthropogenic fluxes.

1) gene flow

- it is described as the transfer of genes from one population to another population so that frequency of gene is increased.

-a zebra migrates to join a different herd of zebras.

2) natural selection

- a mechanism of evolutionary change in which individuals with advantageous traits survive and reproduce whereas the others ( those that can not adapt) eliminate from the population.

-competition for sunlight leads to taller trees.

3) mutation

- permanent change in the nucleotide sequence of dna ( genetic material) that could have harmful or useful consequences.

-the dna of a snake changes to make its venom stronger.

4) genetic drift - it is a random phenomenon ( that occurs by chance such as fire) that results in change in the gene frequency in a small population.    

-a grassfire randomly sweeps through a population of buffalo and kills most of the animals.

explanation: