The mechanisms of reproductive isolation prevent the reproduction of two individuals from different species. The prezygotic mechanisms disrupt the stages of reproduction before the forming of the zygote or prevent the mating at the start, and the postzygotic mechanisms affect the stages of reproduction after the forming of the zygote.
So, the first and the third example (the urchins and the grasshoppers) show the prezygotic mechanism, as the two individuals are not able to mate or form a zygote.
The second and the fourth example ( zonkey and the death of a zygote) show the working of the postzygotic mechanisms, as the zygote is formed, but it seems to be inviable, and the zonkeys are sterile, preventing the individual to reproduce.
1 kilometer = 6.68 × 
(<<<AU is in scientific notation here)
To convert 300 billion kilometer (3,000,000,000 km) into AU you must multiply the kilometer by the equivalent of 1 km in AU (6.68 × )
3,000,000,000 × (6.68 × ) = 20.04 AU
Hope this helped!
The answer is photosynthesis.
The copepods would most likely decrease because the copepods eat the shrimp
Homozygous means that it has the same alleles and lower case represents a recessive trait therefore the genotype for a homozygous recessive individual is: bb
