Thursday, 27 October 2011

2.69 Urinary system

Describe the structure of the urinary system, includin the kidneys, uterus, bladder and urethra.

In the urinary system we have two kidneys the right and the left each with its own blood supply carrying out the process of filtration, osmoregulation, and excretion. From each kidney there is a tube leading to the bladder which is called the ureter. The urine stored in the bladder travels to outside through the urethra and down through the vagina or the penis.

2.68 Excretion

Understand how the kidney carries out its role of excretion and of osmoregulation.

To illustrate this we show the excretion of urea (which contains nitrogen which is toxic to the body): The amino acids are used for growth and excess amino acids are excreted as urea. This re-enters into the blood stream and which then enters both kidneys. The kidneys will filter the urea from the blood and the urea will be added to water to form urine and travel down the ureter to collect in the bladder which is stored there as the form of urine. The filtered blood travels back to the blood stream without any urea.

Osmo (osmosis) regulation (to control), hypertonic (too concentrated), hypotonic (too dilute)

We want to keep the tissue fluid isotonic (the amount of water into is equal to the output) which is achieved by controlling the composition of blood. The kidney is the organ which controls the composition of blood. Blood circulates through our kidney and excess water or salt is removed and excreted through the ureter here by controlling the content of water and salts in the blood, the kidney can keep the blood and therefore the tissue fluid can be maintained as isotonic which maintains the function of the cells.

2.67b Human organs of Excretion

Recall that the lungs, kidney and skin are organs of excretion.

In the thorax we have lungs, and the metabolic waste the lung excrete is carbon dioxide which is a waste from respiration which we need to release from the body.
The second organ of excretion is the kidneys (we have 2), which excretes excess water, urea (nitrogen waste from amino acids) and salts.
The third organ of excretion is skin and our skin is known to excrete water and salt (sweat) but also a bit of urea.

2.67a Excretion in plants

Recall the origin of carbon dioxide and oxygen as waste products of metabolism and their loss from the stomata of the leaves.

Let's start with photosynthesis, which uses light energy to turn CO2+H2O=>C6H12O6+O2 [Excretion]
In respiration in plants with aerobic respiration C6H12O6+O2=enzymes>ATP+CO2[Excretion]+H2O

So in conclusion plants excrete Oxygen and Carbon Dioxide depending upon the process it is doing.

Monday, 10 October 2011

3.10 Menstrual cycle

Understand the roles of oestrogen and progesterone in the menstrual cycle

Oestrogen and progesterone are both hormones, which is produced in the structure called endocrine gland. Hormones will travel through the blood to the target tissue, where the hormone will have effects on.

The ovary is the endocrine gland for (produces) oestrogen that will travel through the blood stream to the lining of the uterus.
The effects of estrogen include:
1. The lining of uterus (wall of endometrium) thickens
2. Flows through the blood stream to out brain and brings the release of sex hormone (LH). It reaches its peak by day 13 of the cycle and causes the ovary to release an egg into the oviduct, where it is possible for fertilization to occur. 

During this first half of menstrual cycle, a circular structure becomes larger and larger. Inside this falloco is the egg. The cells around the fallocal are producing oestogen. It reaches it maximum size by day 13 and causes its wall to rapture and the egg is released. 
LH causes ovulation, the release of the egg.

Now that the fallico is released, the now emptied structure changes its function and develops into the yellow color. This gives us the name corpusinteum that produce progesterone
Progesterone travels through the blood stream to the lining of uterus. 
3. This prevents the lining of uterus from breaking down. This makes it possible that the fertilized egg then can plant into the wall of endometrium and develops into pregnancy. 
4. If no fertilized egg is planted into the wall of endometrium, then it will break down and form what we known as menstrual period/bleeding. 
This mark the end of one menstrual cycle. When the lining is broken down completely, the whole process would repeat

(credits to michelle biology)

3.34 Causes of Mutation

Understand that the incidence of mutations can be increased by exposure to ionizing radiation (for example gamma rays, X-rays and ultraviolet rays) and some chemical mutagens (for example chemicals in tobacco). 

Mutation is the change in base sequence of the genes which creates new alleles. (e.g. ACT => AAT)

Radation - Xrays or sunshine (UVB) in this case of UVB this can cause a mutation which leads to skin cancer
Chemicals - effects of tars and tobacco which causes a change in the base sequence which can also lead to cancer.

Chemicals which cause mutation are called mutagens and those that cause cancers are called carcinogen.

3.33 Antibiotic resistance

Understand how resistance to antibiotics can increase in bacterial Population.

An example of this:
Staphlococcus aureus can lead to skin and lung infections.
People with this bacteria can be treated with Methecilline Antibiotics which can kill Staphlococcus aureus.  The Staphlococcus aureus that can be killed by this antibiotic is called the susceptible form. MSSA (Methecilline susceptible Staphlococcus aureus).
What happened was there was a random mutation to the geno of Staphlococcus aureus and when the antibiotics Methecilline is applied it doesn't die and this is called the resistant form. (Methecelline Resistant Staphlococcus aureus)
The mutation has created genes that allowed the bacteria to break down the antibiotics, resisting it so it  can survive. As antibiotics are used across time this type of bacteria increasingly surivives and becomes more common. In time this has become a serious problem in hospitals.

3.32 Types of mutation

Understand that many mutations are harmful but some are neutral and few are beneficial.

Gene=====mutation=======>new alleles

New alleles can be: beneficial, neutral or harmful.
Example of a beneficial mutation might be to improve an efficiency of an enzyme. Example of a harmful mutation might be a production of an enzyme that does not work. If the mutation has no particular effect, we call it a neutral mutation. Although the neutrality may change due to environmental change which can lead to harmful or beneficial mutations.

3.31 Evolution

Describe the process of evolution by means of natural selection.

Evolution can be a change in the form of organisms
Evolution can be a change in the frequency (how many) of alleles.

Natural selections is the mechanism of evolution and was first proposed by Charles Darwin.

A bacteria staphlococcus aureus which can lead to skin and lung infection is introduced.
The original form of such bacteria is sustained to be kill by methecilline, which is a type of antibiotic. (They are susceptible to the antibiotic.) 
What happens is that a random mutation to the genome of the bacteria allowed us a characteristic of 'breaking down methecilline.' This means that it is no longer killed by the antibiotic. This new form is called the Resistant form, MRSA.
[Refer to definition number 1 of evolution]
Because the MRSA is resistant to the antibiotic, they became increasingly common (increase in frequency of the allele) 
[Refer to definition number 2 of evolution]

Two features of natural selection (process not a thing):
1. Random mutation - produce MRSA form 
2. Non-random selection - due to anti-biotic which is selecting the MRSA to survive and MSSA to be selected and killed

3.30 Mutation

Recall that mutation is a rare, random change in genetic material that can be inherited.

In every DNA there is a base sequence (A,C,T,G,A,A,C,C) which is what constitutes the gene. The form of the gene is called an allele. Certain processes can result in a change of the base sequence which is what we call a mutation. For instance, the base sequence of ACT into AAT. This creates a new version of the allele and it is possible that this process will result in an entirely different protein and therefore creating an entirely different phenotype. The reasons why dominant alleles and recessive alleles exist is because of this process.

3.29 Species Variation

Understand that variation within a species can be genetic, environmental, or a combination of both

Variation = differences in the phenotype
It is often possible to count or to measure these differences and show them in bracket form. Every individual has a phenotype and the appearance for an individual for any of the characteristics is because of their genotype which is be variant to various degrees accordingly to the environment. (Individual Phenotype = Genotype + Environment)
Variation in the population is due to the variation of the genotype and the variation of the environment they occupy and develop in.

Examples of this:

In the first example it shows variation that depends entirely on the genotype with no role of the environment. For example the blood groups.
In the second example it shows where the variation depends on the environment. With one example such as height, one might have been inherited the genotype to be short, however, a good diet may affect his height.
In the third example, it shows a variation in population which depends entirely on the environment. Genes have no roles to play here, for example, languages.

Sunday, 2 October 2011

3.20 Pedigree Diagrams

Understand how to interpret family pedigrees.
If you have inherited a condition, then the square will be filled in if you were male and the circle would be filled in if you were female. Often these are diseases but not necessarily. The circles and squares represent phenotype (characteristics that can be observed)

Pedigree diagrams can also be used to determine whether an affected condition is a dominant allele or a recessive allele:

3.21 Genetic Probabilities

Predict probabilities of outcomes from monohybrid crosses.
Here we are calculating the chances or probability of offspring from monohybrid cross (crosses involving just the one gene):
[this had already been covered in detail in 3.19]

Parents(phenotype)-        Red Petals          x           White Petals
           (genotype)-               RR                 x             rr                                  R(dominant)>r(recessive)

The next stage involves meiosis in plants, its where they produce the pollen grains.

This shows us:
So there is a 100% chance that the offspring will have red petals (phenotype).

 Lets breed two heterozygous flowers with red petals together.
   Rr            x               Rr
the genotype of the random fertilisation is 25% RR, 25% rr, 50% Rr
the phenotype of the outcome is 25% white petals and 75% red petals.