Surely they have sperm and eggs, but what exactly is it that makes a mule , etc. sterile? Are there ever exceptions to this?
2007-02-09 14:59:24 · 2 answers · asked by rebecca h 2 in Science & Mathematics ➔ Zoology
Hybridization between two different species is a rare occurrence. Usually there are prezygomatic (before fertilization) barriers which prevent this type of breeding from being successful. However, in those rare cases, postzygomatic (after fertilization) barriers will present themselves in one form or another.
If the hybrid is viable enough to grow and thrive (in other words, the hybrid can survive on its own or with little assistance needed biologically), then the only remaining barrier to prevent a new biological species from propogating is Natural Sterilization. In this, the hybrid is unable to produce any gametes needed for reproduction. Since neither egg nor sperm can be produced to create an offspring, that hybrid becomes the last in its line.
2007-02-09 18:00:53 · answer #1 · answered by icehoundxx 6 · 0⤊ 0⤋
A key factor in evolution is speciation. By definition, species are populations that cannot interbreed. The DNA of the two species are not sufficiently compatible to produce viable offspring: different numbers of chromosomes, different assortment of genes on the chromosomes etc.
If two animals can mate and produce viable offspring, they are by definition of the same species.
2007-02-09 16:49:30 · answer #2 · answered by mister science 2 · 2⤊ 1⤋