The Earth's freshwater is even rarer. For humanity to thrive, or even exist, we need to sprinkle that teeny bit of fresh water in the right places, at the right times and in just the right amounts, Gallo said. Here's how Earth's freshwater is spread around the globe: 1  70 percent of freshwater is locked in ice caps.
Believe it or not these are not the first lines of terrible jokes, but real scientific questions with real living answers. Hybrid animals are the offspring produced when two animals of closely related â but different â species breed.The young produced will usually not be fertile, and so hybrid species are not normally seen in the wild. In order for more of these hybrid animals to exist the original two species must be cross-bred again.elieve it or not these are not the first lines of terrible jokes, but real scientific questions with real living answers. Hybrid animals are the offspring produced when two animals of closely related â but different â species breed.
Animal and plant breeding. From the point of view of animal and plant breeders, there are several kinds of hybrid formed from crosses within a species, such as between different breeds. Single cross hybrids result from the cross between two true-breeding organisms which produces an F1 hybrid (first filial generation). The cross between two different homozygous lines produces an F1 hybrid that is heterozygous; having two alleles, one contributed by each parent and typically one is dominant and the other recessive. Typically, the F1 generation is also phenotypically homogeneous, producing offspring that are all similar to each other. Double cross hybrids result from the cross between two different F1 hybrids (i.e., there are four unrelated grandparents). Three-way cross hybrids result from the cross between an F1 hybrid and an inbred line. Triple cross hybrids result from the crossing of two different three-way cross hybrids. Top cross (or topcross) hybrids result from the crossing of a top quality or pure-bred male and a lower quality female, intended to improve the quality of the offspring, on average. Population hybrids result from the crossing of plants or animals in one population with those of another population.