10 points and brainliest for the first to answer!
word bank:
acid, atomic number, base, buffer, chemical bond, chemical reaction, covalent bond, crystalline, hydrophilic, hydrophobic, ionic bond, isotope, matter, neutron, ph, physical property, polar molecule, proton, radical, radioactive

a(n) substance has a regularly repeating arrangement of atoms.

A crystalline substance has a regularly repeating arrangement of atoms.

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:

he is very short, and he can only reach halfway up on the elevator buttons. but on a rainy day, he has his umbrella with him, and he uses it to poke the button at the top.