Answer:
1. Earth's ozone layer is responsible for absorbing infrared and ultraviolet rays from the sun.
2. Changes in the composition of the atmosphere have caused gradual changes in earth's climate, causing changes in plant and animal life that contributed to mass extinctions.
3. Chemical chlorofluorocarbons (CFCs) have been banned and replaced with hydrochlorofluorocarbons (HCFCs).
4. Naturally occurring volcanic eruptions can produce large amounts of gases which contain sulfur. These gases accumulate in the atmosphere in the same way as man-made sulphuroxides.
Sorry, but after that I don't know.
Explanation:
" This is the most stupidest answer / question ever!"
Answer:
The F1 progeny is completely heterozygous for the <em>loci</em> of interest since they were obtained by mating between two pure-breeding plant lines. In the next generation, the backcross progeny will have homo-zygous individuals and therefore they will be more variable, resulting from meiosis in F1 hybrids
Explanation:
An F1 resulting from the cross between two pure-breeding plant lines will produce all hybrid individuals, all of them genetically (and phenotypically) identical. Meiosis in F1 hybrids is well known to produce homo-zygous genotypes and thus increases genetic diversity in progeny. For instance, for a single <em>locus</em>, the expected ratio of genotypes obtained from crossing two heterozygous parents is 1:2:1, i.e., one homo-zigous dominant individual, two heterozygous individuals (genetically identical to the parents) and one homo-zygous recessive individual; while the expected phenotypic ratio is 3:1 (i.e., 3 dominant expressing: 1 recessive expressing).
