Yahoo answers giv the most understandable things....

So this is my last info post. tomorrow i will have to warp everything up. mastery review is just next week and i wont hav time to post any mor posts. so on this second last post, i would like to share with u my "best answers" from yahoo answers.

For the difference between the cow's digestive system and the human's digestive system:
Actually cows do NOT have four stomachs. They have a four compartmented digestive system but have one true abomasum ..which like our stomach has pepsin and HCl. The rumen and reticulum are predigestive bacterial vats where carbohydrates and other food constituents are metabolized by bacteria under anaerobic conditions ( fermented ). This means that the dietary protein is altered in composition to more favor bacterial protein ( lower bilogical value than sayy soy or alfalfa ) and dietary carbohydrates are entirely converted to acetic , propionic and butyric ( plus a few other ) volatile fatty acids. The cow must make all her glucose from propionate at the tissue level. The bacteria and protozoa in the rumen and the reticulum ( a somewhat smaller vat on the downside of the rumen ) can digest materials we cannot like cardboard , whole cottonseed, etc etc . Another compartment called the omasum ( many plies ) absorbs a large amount of water coming from the rumen/reticulum with the bacterially digested mass before that mass enters the true stomach or abomasum..where partial digestion of the bacterially altered proteins and fats begins. Afte the abomasum the mass enters the small intestine and functions much like our system does .

And for how twins are formed:
Twins can be monozygotic (identical) where one sperm fertilises an egg wheich then splits and develops separately. They are identical because they inherited the same genes from the same sperm and egg.
Alternatively, fraternal (non-identical) twins occurs when two eggs are released and are fertilised by different sperms. They can be of opposite sexes since the sperm carries the X or Y chromosome determining if the fotus will be male or female. Fraternal twins are no more likely to be alike than other siblings, it is simply two pregnacies occuring at the same time.

Less frequently three or more eggs may be fertilised leading to triplets or other multiple births.

IVF (In Vitro Fertilisation) treatment for couples having trouble conceiving leads to multiple births.
1. The female is given hormonal treatment to bring about multiple ovulation (release of eggs from the ovary).
2. The eggs are collected using a fine tube.
3. Eggs are added to sperm from the partner or donor in a nutrient medium and allowed to incubate at 37oC for several days.
4. The pertri dish is examined under the microscope to look for presence of embryos (a tiny ball of cells formed by division of fertilised eggs)
5. Several embryos are implanted in the womb of the female at the time of the month when her womb is most developed for a potential pregnancy.
6. Unused embryos are frozen for use if the first attempt at IVF is unsuccessful.

If two or more of the implanted embryos successfully implant in the female's womb then it will lead to multiple births.

so a big ty for those who helped me answer my questions. tomorrow would then really be the last post. (wont have much to say in it though)

23/7/08
Wednesday