Youran+C.

=__**#3 THE SENSES**__= The body contains millions is neurons that react directly to stimuli from the environment, i.e. light, sound, motion, pressure, and change in temperature. These neurons are known as sensory receptors, react to a specific stimulus such as light or sound by sending impulses to other neurons, and eventually to the CNS.

Sensory receptors are located throughout the body but are concentrated in the sense organs including the eyes, the inner ears, the nose, the mouth, and the skin,

There are five general categories of sensory receptors: pain receptors, thermo receptors, mechanoreceptors, chemoreceptors, and photoreceptors. __**(from 122 bio textbook, 35-4)**__

a picture showing the 5 different sense organs.

=video= __ [] __

**Sight**

The eye is the organ of vision. It has a complex structure consisting of a transparent lens that focuses light on the retina. The retina is covered with two basic types of light-sensitive cells-rods and cones. The cone cells are sensitive to color and are located in the part of the retina called the fovea, where the light is focused by the lens. The rod cells are not sensitive to color, but have greater sensitivity to light than the cone cells. These cells are located around the fovea and are responsible for peripheral vision and night vision. The eye is connected to the brain through the optic nerve. The point of this connection is called the "blind spot" because it is insensitive to light. The brain combines the input of our two eyes into a single three-dimensional image. In addition, even though the image on the retina is upside-down because of the focusing action of the lens, the brain compensates and provides the right-side-up perception. The range of perception of the eye is phenomenal. In the dark, a substance produced by the rod cells increases the sensitivity of the eye so that it is possible to detect very dim light. In strong light, the iris contracts reducing the size of the aperture that admits light into the eye and a protective obscure substance reduces the exposure of the light-sensitive cells. __ [] __

__ [] __ = **Hearing ** = The ear is the organ of hearing. The outer ear is shaped like a cup to direct sounds toward the tympanic membrane, which transmits vibrations to the inner ear through a series of small bones in the middle ear called the //malleus//, //incus// and //stapes//. The inner ear, or cochlea, is a spiral-shaped chamber covered internally by nerve fibers that react to the vibrations and transmit impulses to the brain via the auditory nerve. The brain combines the input of our two ears to determine the direction and distance of sounds. The inner ear has a vestibular system formed by three semicircular canals that are approximately at right angles to each other and which are responsible for the sense of balance and spatial orientation. The inner ear has chambers filled with a viscous fluid and small particles (otoliths) containing calcium carbonate. The movement of these particles over small hair cells in the inner ear sends signals to the brain that are interpreted as motion and acceleration.

__ http://pmr-science.wikispaces.com/1.5+The+Sense+of+Hearing __ __ [] __

= Taste = The receptors for taste, called taste buds, are situated in the tongue, but they are also located in the roof of the mouth and near the pharynx. They are able to detect four basic tastes: salty, sweet, bitter, and sour. The tongue also can detect a sensation called "umami" from taste receptors sensitive to amino acids. Generally, the taste buds close to the tip of the tongue are sensitive to sweet tastes, whereas those in the back of the tongue are sensitive to bitter tastes. The taste buds on top and on the side of the tongue are sensitive to salty and sour tastes. At the base of each taste bud there is a nerve that sends the sensations to the brain. The sense of taste functions in coordination with the sense of smell.

__ http://pmr-science.wikispaces.com/1.4+The+Sense+of+Taste __ __ [] __ = Smell = The nose is the organ responsible for the sense of smell. The cavity of the nose is lined with mucous membranes that have smell receptors connected to the olfactory nerve. The smells themselves consist of vapors of various substances. The smell receptors interact with the molecules of these vapors and transmit the sensations to the brain. The nose also has a structure called the vomeronasal organ whose function has not been determined, but which is suspected of being sensitive to pheromones that influence the reproductive cycle. The smell receptors are sensitive to seven types of sensations that can be characterized as camphor, musk, flower, mint, ether, acrid, or putrid. The sense of smell is sometimes temporarily lost when a person has a cold.

__ [] __ __ [] __ = Touch = The sense of touch is distributed throughout the body. Nerve endings in the skin and other parts of the body transmit sensations to the brain. Some parts of the body have a larger number of nerve endings and, therefore, are more sensitive. Four kinds of touch sensations can be identified: cold, heat, contact, and pain. Hairs on the skin magnify the sensitivity and act as an early warning system for the body. The fingertips and the sexual organs have the greatest concentration of nerve endings.

__ [] __

__ [] __

=__**#2 Evolution (Why I don't believe in evolution)**__=

The theory of evolution becomes universal acceptable, but this theory still can’t convince me that the whole universe, this earth all appeared by coincidence. Imagine this, if you leave parts of cars in a garage, give them favorable conditions, and wait for billions of years, will they eventually combine and make a car themselves? As more I learn about biology, I am more convinced that there is a creator who created the universe, the earth, and all the organisms on this earth. Every cell is an amazing factory, there is no way human beings can start a factory like that, and I think it will also be impossible if the first cell came by chance. When I learned protein synthesis in biology class, I thought how rare will a cell appear on the earth and develop into the stage where they become vital to our lives.

Protein synthesis
During protein synthesis, there are two process—transcription and translation. A complementary strand of mRNA is made by unzipping the DNA molecule by RNA polymerase. Transcription doesn`t happen just anywhere, it only happen on specific regions of DNA – promoter regions, a similar region known as terminator would cause the transcription process to stop. Transcription is not just converting DNA into mRNA, but there are RNA splicing and capping involved. Some regions of DNA do not code for any proteins known as introns, they have to be spliced out. Those DNA that joins all the coding region called exons will remain. After splicing, on one end of mRNA, there will be modified guanine put on, and at the other end, a pile of adenine will be added. How does the cell know the DNA must be transcript into mRNA in order to get out of nucleus, how does the cell know which part will be introns, which part will be exons? Cells are intelligent, will these functions just come by chance? http://en.wikipedia.org/wiki/Transcription_(genetics)

In the cytoplasm of the cell, the mRNA will be read and decoded. mRNA will be read in triplets known as codons. Translation begins when the mRNA binds to the rRNA on a ribosome, and the mRNA will move along the sequence until an AUG(start) codon is found. tRNA will come to attach and drops off the appropriate amino acid by matching up the codon and anticodon. This process continues until a stop codon is found. Sequential amino acids are linked by peptide bonds. Polypeptide goes through up to four stages of folding to become a mature protein. https://biolabs.wikispaces.com/Protein+Synthesis

I found this process very amazing, the cells always put regions that signal the beginning and ending of the process. Every part in the cell have a mission, they are very sufficient, so I just can not imagine how these just appeared and evolve. (Most information is from Mr.Smith’s notes.) See more about protein synthesis [] []

video about proteins [] Another reason I don’t really like the idea of evolution is because the white blood cell.

Leukocytes(white blood cells)
White blood cells (WBCs), or **leukocytes**, are a part of the immune system and help our bodies fight infection. Leukocytes circulate in the blood so that they can be transported to an area where an infection has developed. In a normal adult body there are 4,000 to 10,000 (average 7,000) WBCs per microliter of blood. http://www.urmc.rochester.edu/Encyclopedia/Content.aspx?ContentTypeID=160&ContentID=35 Here are the six main types of WBCs and the average percentage of each type in the blood: Neutrophils - 58 percent Eosinophils - 2 percent Basophils - 1 percent Bands - 3 percent Monocytes - 4 percent Lymphocytes - 4 percent most leukocytes are found in bone marrow.[]
 * Neutrophils** are the one of the body's main defenses against bacteria. They kill bacteria by actually ingesting them --called phagocytosis. Neutrophils can phagocytize five to 20 bacteria in their lifetime.
 * Eosinophils** kill parasites and have a role in allergic reactions.
 * Basophils** are not well understood, but they function in allergic reactions.
 * Monocytes** enter the tissue, where they become larger and turn into macrophages. There they can phagocytize bacteria (up to 100 in their lifetime) throughout the body. These cells also destroy old, damaged and dead cells in the body.

Learn more [] []

There are many other reasons which make me not a fan of evolution, like the water cycle of the earth, complicated structures of many organisms, I believe one day, all the questions will be solved.

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =__**#1 Genetics -- How Twins are Conceived**__=

==== How does it feel to have a twin sister or brother—having someone truly understands you, having someone who can sense your emotional change. I always wished I could have a twin to live with. How are twins conceived? Let’s take a look. ====

==== Twin is defined as “either of two offspring born together; either of two people or animals born to the same mother at the same time” in Bing Dictionary. We all know that in order to get pregnant, an egg must meet a sperm and they fertilize, and then the fertilized egg will develop and gradually grow into a baby. How can twins be formed? ====

==== **Identical twins(monozygotic)** are created when the fertilized egg divides sometime early on in the pregnancy, while **fraternal twins(dizygotic)** are conceived when two eggs are released during ovulation and then fertilized.( 1) ====

[]
[]

This picture shows how identical and fraternal twins are developed when cell divide.

**__ Fraternal twins (dizygotic __**)

Fraternal twins occur when two separate eggs are fertilized by two separate sperm. Fraternal twins can be the same sex and/or blood type or different sex. They always have separate placentas, but their placentas may fuse together during the course of pregnancy and appear as one at birth. Fraternal twins will never share the same amnion* and chorion#. Fraternal twins may be due to hereditary influences(family history can affect the rate of conceiving twins).Fraternal twins are the most common type of twinning.( 2)

In rare circumstances, if a woman releases the two eggs several weeks apart and they are fertilized at different times, the two births can occur weeks apart as well. The twins can have different birthdays; this type of twinning is called superfetation.(4)

*amnion is a membrane that when first formed, closely covers the embryo. It fills with fluid, the amniotic fluid which causes the amnion to expand and become the amniotic sac which serves to provide a protective environment for the developing embryo.(3)


 * 1) chorion is one of the membranes that exist during pregnancy between the developing fetus and mother.

Further reading: []

Talk more about fraternal twins in details

[[image:fraternal twins.jpg]] fraternal twins of different genders
[]

fraternal twins with different skin color

[]


 * __ Identical Twins (monozygotic) __**

Identical twins (monozygotic) occur when a single egg, fertilized by a single sperm, splits into two identical halves. Two separate babies with identical DNA are formed. Identical twins are always the same sex and blood type. They almost always share the same placenta but may also have two separate placentas. Depending on when the egg splits, it usually determines if identical twins will share the same placenta, and/or chorions and amnions. Twins are always identical when they share the same amnion and chorion. The split will most often take place within the first few days.(2)

Further reading : []

Interesting facts about identical twins, i.e. cause.

identical twins

[]

= __**Conjoined Twins**__ = When the egg splits in the first two days after it has been fertilized, the resulting identical twins will likely have separate placentas, chorions, and amnions. Most often the egg will split after two days, which then results in twins sharing a placenta but maintaining separate sacs. Rarely, when the split occurs late enough, the result is twins sharing every element, including the same sac (A very high risk pregnancy due to umbilical cord entanglement - known as a mono-mono twin pregnancy). And even rarer still, a particularly late split will likely result in conjoined twins.(2)

Further reading on conjoined twins: []

Talks about the cause, different types, the separation…

Conjoined twin

[]

media type="youtube" key="sOBvRhXIJN4" width="560" height="315"

Sources I used:
 * 1) []
 * 2) []
 * 3) []
 * 4) []