? 1. las sustancias puras son compuestos químicos. 2. las sustancias simples son sustancias puras. 3. una disolución es una mezcla heterogénea de dos componentes: el disolvente y el soluto. 4. los coloides son mezclas homogéneas de aspecto heterogéneo.

the nitrogen cycle provides nitrogen to the ecosystem from the atmosphere, ground and oceans. nitrogen is an important component of complex molecules such as amino acids and nucleotides, which lead to the creation of proteins and dna, the building blocks of all life. plants absorb nitrogen in the form of ammonium, nitrate ion and, on rare occasions, as amino acids. animals receive nitrogen necessary for biological processes from feeding on living or dead organic matter.

answer; the male's sperm cells have mitochondria, but because the sperm contributes dna but no cytoplasm, no mitochondria are passed to the egg at ferilization;