Fetal Development

Fetal development all starts with the development of organized gastrula cells, which is called differentiation. Differentiation goes on for thirty eight weeks that are separated into three trimesters. In each trimester essential development takes place. Complications can occur during development, leading to birth defects and miscarriages. 

In the first trimester, after four weeks the brain and spinal cord start to form. Eight weeks into the first trimester, fingers and toes become visible along with the development of the kidneys, ears, lungs, liver, and muscles. Sexual distinction is almost complete by twelve weeks.

Sixteen to eighteen weeks into the second trimester, the mother will be able to feel the fetus move. At twenty four weeks the fetus will be able to survive prematurely outside of the mother with the help of specialized care.The fetus' eyelids also open at this stage.

In the third and final trimester, the fetus continues to grow and accumulates a lot of fat causing a significant weight gain. This last trimester also gives the lungs and other important parts of the fetus to finish up their development. 

During fetal development, birth defects can occur causing the organ systems to have problems developing, or growth restrictions. Birth defects are caused by teratogens which are substances or factors in the mother that are harmful such as diseases, infections, or chemicals. Most commonly, birth defects happen when the major organ systems are developing. Common birth defects include: spina bifida,brain abnormalities, heart defects, clubfoot, Down syndrome, and fetal alcohol syndrome.

Scientists use comparative embryology to see what similarities and differences there are between different species during fetal development. Through this research, we can see that at the first stage of development all embryos look very similar and that throughout development, more differences start to appear between the compared species. In the last stage of embryonic development you are able to clearly tell what species has been developing. When comparing the embryos, you can see that some have more similarities than others. For example, a human embryo doesn't look like a fish as much as an embryo of an ape would. When embryos look quite similar even in later stages compared to others, it means they are more closely related. 

http://blog.lib.umn.edu/chamb169/myblog/2011/11/fetal-development-barriers.html

Sexual and Asexual Reproduction

There are two types of reproduction that organisms use to produce offspring; asexual reproduction and sexual reproduction. Asexual reproduction results in genetically identical offspring and only requires one parent, whereas sexual reproduction requires two parents and the offspring produced will always be genetically different from the siblings, parents, and other members of its species. There are many advantages and disadvantages to both types of reproduction. 

The advantages to asexual reproduction are: A large number of offspring is produced promptly from only one parent when conditions are preferable,and the large amount can get together to outcompete other organisms for nutrients and water. With a large number, that species may live longer when the environment and the amount of predators change. Also, no energy is needed to find a mate. Along with the advantages come disadvantages: because the offspring produced are all genetically identical, a negative mutation can make them prone to diseases which wipes out a considerable amount of offspring. In some methods, the offspring are produced quite close together causing them to fight for nutrients and space, also,  if conditions are not preferable (ex. extreme temperatures) significant amounts of offspring will perish.

In sexual reproduction there are two types of fertilization; internal and external. Internal is when sperm cells are deposited inside the females body, where they will meet an egg cell to fertilize. Most animals that live on land such as humans and mountain goats, and some animals living in water such as orcas use internal fertilization. External fertilization is when the sperm and egg cell meet outside of the bodies of the parents. This method is most often used by organisms that live in water such as salmon and sea urchins. Plants like ferns and mosses also use external fertilization.There are disadvantages and advantages to sexual reproduction involving both internal and external fertilization. The advantages to sexual reproduction are: not much energy is needed to find a mate (external fertilization),  and larger amounts of offspring can repopulate after a setback in their environment (external fertilization). A greater amount of security is given to the embryo and offspring receive more parental care(internal fertilization), and offspring are genetically different from their parent, so they have a greater chance of surviving new diseases or other hazards in their environment. The disadvantages of sexual reproduction are: a greater amount of energy is needed to find a mate (internal fertilization),  and a smaller amount of offspring is created, so if the number of predators expands a population will decrease (internal fertilization). Also, through external fertilization gametes, embryos, and offspring are exposed to predators.

Since the offspring created through sexual reproduction is genetically different from any other organism in its species, we get much more diversity compared to the result of asexual reproduction. This is where an advantage comes in for sexually reproduced organisms. Being different from others means you are less likely to inherit genetic diseases and you have a chance of surviving new diseases or other hazards in their environment.If an asexually reproduced organism gets a disease, a very large amount of the offspring will also be affected because they are genetically identical.

External Fertilization (BC Science 9 textbook) 

Internal Fertilization (BC Science 9 textbook)

Genetic Diseases

A genetic disease is caused by the occurrence of a negative genetic mutation. A mutation is the change in the bases of the A,T,G,C in DNA. A base can be added, deleted, or substituted. Mutations are cause by mutagens, which are factors in the environment such as: cigarette smoke, radiation, and pesticides.Negative mutations are those that affect your well being in a harmful way. A few genetic diseases are: Down Syndrome, Hemophilia, and Cystic Fibrosis. Each of these diseases occur in a different way and some are inherited.

Down Syndrome is a chromosome mutation which ninety five percent of the time is caused by an additional twenty first chromosome. People living with Down syndrome appear differently than others in which they are shorter and their facial features are distinctive. Also, with this disease you are more likely to develop heart defects and diseases such as leukaemia and Alzheimer's. Because of these diseases and heart defects being likely,people living with Down syndrome will have a shorter lifespan. Along with diseases, they also have mental delays causing them to need come extra help through care givers. Down syndrome is not inherited. 

Hemophilia, unlike Down syndrome, is commonly hereditary. It is caused by a defect in the gene that decides how your body will produce blood clotting factor. Because of this defect, you will have little to no clotting factor. This makes your blood unable to clot,  causing you to bleed very easily. People living with hemophilia have to be careful to not get injured because this could cause them to bleed. Also, regular trips to the doctor are necessary to receive transfusions of clotting factors. People living with hemophilia will have a shorter lifespan as well. 

Cystic Fibrosis is disease that is caused by more that thirteen hundred mutations in one gene. The mutations cause a protein that is supposed to carry chloride ions into and out of cells to be made incorrectly, causing the level of chloride ions to be flawed. Because the levels are incorrect, mucus inside of the lungs is too thick making breathing a challenge. This mucus buildup also blocks pancreatic juice from flowing to the small intestine, making the body unable to break down food.  People living with cystic fibrosis are required to take medication daily and go to physical therapy to avoid lung infection.

Example of a genetic mutation involving substitution (http://mrsgsbiologyclass.edublogs.org/files/2013/03/DNA-Mutation-148mrie.gif)

Mitosis Flipbook

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Mitosis

This slide displays the early prophase. Cell A is in interphase. You can see that in cell B the chromosomes have gotten more thick and shorter. This shows the beginning of mitosis.

This slide displays the prophase. You are now able to see that the chromosomes in the larger spot have gotten more short and thick. 

This slide displays the metaphase. You can now see that the chromosomes have moved to the middle of the cell and now appear as short, thick rods.

 This slide displays the early anaphase. Cell D shows that the chromosomes have doubled and that those two parts are starting to separate from each other. At the lower part of the cell, spindle fibers are slightly visible.(marked by S)

 This slide displays the anaphase. Now in cell E, every chromosome has finished separating. Now the cell will be able to produce two identical sets of chromosomes.

 This slide displays the late anaphase. The two sets of chromosomes are now spreading further apart and will soon start to get situated into two whole nuclei.

 This slide displays the telophase. You can now see that the sets of chromosomes have formed into what will soon be a nucleus. There are no longer single chromosomes. In between the sets, you can see spindle fibers.

This slide displays the late telophase. The H cells are now showing the last stage of mitosis. You can see the walls of these cell have not fully developed yet. Cell A has completed mitosis and is now in interphase.

Mutations

A mutation is the change of the DNA in a cell. Various factors in the environment contribute to the cause of a mutation. These are called mutagens.  Various poisonous chemicals such as cigarette smoke and pesticides are examples of mutagens. As well as poisonous chemicals, radiation is also a nutagen. A mutation can be positive, negative, or neutral. A positive mutation would be when you are benefited by it. For example, some people have a mutation that protects them from getting HIV. A neutral mutation would be when the mutation does not affect your well being. An example of a neutral mutation would be  your eye color, it doesn't give you any advantages or disadvantages. A negative mutation would be a mutation that affects your well being in a harmful way. A disease such as Down's Syndrome would be an example of a negative mutation. When DNA mutates, the pairs that bases are suposed to go into get switched around. Meaning a base could be added, taken away, or a base could be put in place of another. This changing of bases is what causes the mutation.

Detergent Lab

Science 9- Block C                                                                                                 September 10th, 2013

Do expensive detergents clean better than cheaper varieties?

Purpose: To find out if expensive detergents clean better than cheaper varieties.

Hypothesis: I predict that Tide will clean the stain better than the rest of the detergents.

Apparatus and Materials: cloth, ketchup, Tide, Woolite, Western Family detergent, Sunlight, eye dropper, beaker, water

Procedure:

1. Cut cloth into 5 strips and stain cloth with ketchup, let it sit over night

2. Measure out 10 drops of each detergent in 200ml of water and mix with room temperature water

3. Wash cloth for 3 minutes

4. Let cloth dry completely

5. Record your results with pictures

Observations and Results:

(in order from cleanest to dirtiest)

Tide: Cleaned the cloth very well, it left only the slightest sign that the stain was there. Tide cleaned the ketchup stain better than the rest of the detergents.

Sunlight: Sunlight also cleaned the cloth very well, but there are a few more traces of ketchup left compared to the one cleaned with Tide.

Western Family: The Western Family detergent did not clean nearly as well as Tide and Sunlight. It is obvious the stain is still there, but it is faded.

Woolite: This detergent did not clean out the stain easily, making it the worst detergent out of the four. It did clean the stain a little bit, but it is more noticeably stained than the rest.

Water: Surprisingly, water cleaned just about as well as the Woolite. It took out a some of the stain, but it is still not very clean.

Before

  

After
Water, Tide, Western Family, Sunlight, Woolite

Conclusions: To conclude, my hypothesis was supported. Tide cleaned the best out of the four detergents, it left very little evidence that there was a ketchup stain on the cloth. Tide is more expensive than some other brands, but it cleaned the best. Although Woolite was the most expensive out of all the brands we used, it cleaned the least well out of the four. Which makes it not true that more expensive detergents clean better than cheaper varieties.

Why Do We Get Bored?