Prenatal<span> or antenatal </span>development<span> is the process in which a human </span>embryo<span> and later </span>fetus<span> </span><span> develops during pregnancy, from fertilization until birth.</span><span> It is in between the embryonic state and during the birth. Fetal development begins at the gestational age of eleven weeks. The fetal stage is recognized when an embryo develop to the point where the major body organs is present.
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Nonrenewable resources are used commonly and are quickly running out, and it takes longer for us to form more of these.
The cyanobacteria changed the composition of the earth’s atmosphere by evolving oxygen in what is referred to as the Great Oxygenation Event. This also allowed the ozone to be formed and block off most of the UV rays that are destructive to genetic material. Life was, therefore, also able to exist on land other than in water.
Since all cells in our body contain DNA, there are lots of places for mutations to occur; however, some mutations cannot be passed on to offspring and do not matter for evolution. Somatic mutations<span> occur in non-reproductive cells and won't be passed onto offspring. For example, the golden color on half of this Red Delicious apple was caused by a somatic mutation. Its seeds will not carry the mutation.
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A single germ line mutation can have a range of effects:
<span><span>No change occurs in phenotype.
Some mutations don't have any noticeable effect on the phenotype of an organism. This can happen in many situations: perhaps the mutation occurs in a stretch of DNA with no function, or perhaps the mutation occurs in a protein-coding region, but ends up not affecting the amino acid sequence of the protein.</span><span>Small change occurs in phenotype.
A single mutation caused this cat's ears to curl backwards slightly.</span><span>Big change occurs in phenotype.
Some really important phenotypic changes, like DDT resistance in insects are sometimes caused by single mutations. A single mutation can also have strong negative effects for the organism. Mutations that cause the death of an organism are called lethals — and it doesn't get more negative than that.</span></span>
