The human reproductive system is different in males and females. When a sperm and egg join, the egg is fertilised and a baby starts to develop. Its mother provides all a baby’s needs until it is born.Fertilisation happens when an egg cell meets with a sperm cell and joins with it. The fertilised egg divides to form a ball of cells called an embryo. The embryo attaches to the lining of the uterus. It begins to develop into a fetus and finally into a baby.The mother’s lifestyle can affect the developing fetus. For example, smoking reduces the amount of oxygen in the bloodstream. This can lead to low birth weight and premature birth (when a baby is born too soon). Drinking alcohol during pregnancy can harm the developing baby’s nervous system, especially its brain.
Birth
It takes about 40 weeks for a baby to develop in the uterus. This time is called gestation. After this, the baby is ready to be born. The cervix relaxes and muscles in the wall of the uterus contract. Waves of muscle contraction push the baby out of the mother's body through the vagina.
A mutation is a permanent change in the DNA sequence of a gene. This can be beneficial if the change gives a new function to or improves the function of that gene.
<span>The above is a definition. But one must really define "beneficial". Some regard it as beneficial if it helps the specific individual who has it. Others would think it beneficial if it produced some survival advantage that insured more descendents for that individual. </span>
<span>It is the difference between a mutation that allowed for greater athletic ability, but a decreased desire for offspring, versus a more moderate athletic enhancement, but a greater desire for offspring. </span>
<span>The small percentage of ways to improve an organism, versus the near infinite ways of harming the organism, mean that most mutations are not going to be beneficial. At best, they will be "inconsequential" - such as a new shade of eye color, or a mole on a section of your skin. </span>
The populist notion of "powers" that can come from mutations is wildly inaccurate. Even assuming a minor power like the ability to see infra red radiation would take thousands upon thousands of mutations over vast amounts of time. A mutation for blindness is far more likely.
<span>It should also be noted that the traditional model of evolutionary theory no longer applies to man. We don't allow changes in our environment, and without such changes, there is no need for one trait more than another to predominate. After all, it is irrelevent that a mutation might allow for greater speed in running, when everyone drives a car.</span>
The invading bullfrogs ARE HARMFUL. This is because, they cause decline in the population of the native species.
Decline in the population of the native species will throw the ecosystem into a condition of imbalance which will eventually affect all the living organisms that are living in that ecosystem.
The indispensable chemical element is carbon.
