Gases are constantly consumed and produced by cellular and metabolic reactions in most living things, so an efficient system for gas exchange between, ultimately, the interior of the cell(s) and the external environment is required. Small, particularly unicellular organisms, such as bacteria and protozoa, have a high surface-area to volume ratio.
Polyploid. (genetics) an organism or cell having more than twice the haploid number of chromosomes.Of a cell or organism having more than twice the haploid number of chromosomes; a polyploid cell; a polyploid species .Organisms that possess two sets of each chromosome.
Diploid cells have twice the amount of chromosomes as haploid cells. Ploidy is the number of sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Somatic cells, tissues and individuals can be described according to the number of sets present: monoploid, diploid, triploid, tetraploid, pentaploid, hexaploid, heptaploid or septaploid, etc. The generic term polyploid is used to describe cells with three or more chromosome sets. Humans are diploid organisms, carrying two complete sets of chromosomes: one set