Biology Marathon 2006 (2 Viewers)

[Petinga]

The Xylem vessels are involved in moving water and inorganic minerals ions from root to leaves. The xylem consist of long hollow vessels extending from root to leaves thickneded with lignin and are dead. The current theory for the ascent of xylem sap in plants is the CAT Mechanism (cohesion-adhesion-transpiration). The ascent of xylem sap is mainly due to the transpirational pull of the sun rather than root pressure. Cohesion allows water molecules to stick together forming a long continous stream from roots to leaves. Adhesion allows water molecules to stick to cellulose in the xylem walls, preventing the water from falling when transpirational pull is weak such as at night. As a water molecule is lost through the leaves by tranpiration, another moves up to take its place hence pulling the entire stream of water molecules up towards the leaves. This is a form of passive transport.

The Phloem vessels are involved in moving photosyntheic materials (i.e. sugars) from leaves to rest of the plant. The phloem are living and have a perforated sieve plate at each end of the tube with companion cells. The current theory for the movment of sugars is the Pressure-Flow mechanism (i.e sink - source). Sugars are actively loaded into the phloem tube at the leaf source. Water follows by osmosis increasing the pressure at the source end of the end. At the sink were sugars aree removed to be stored or used, sugars move out of the phloem tube. Water follows by osmosis resulting in a decrease in pressure at this end of the tube. Thus this increase and decrease in pressure allows the flow of water and hence sugars dissolved in the water.

Question: Why do transplantations of tissues/organs trigger or stimulate an immune response?

 

[ugly14]

Question: Why do transplantations of tissues/organs trigger or stimulate an immune response?

Organs from another organism are recognised as foreign by the human immune system. The surfaces of the new organ contain antigens. These trigger an immune response and the body attacks the new organ as if it were a pathogen.

ways in which to reduce rejection of organs: immune-suppressors

i dont have a question now...i'll post one later though

 

[Cattle]

OK i have a question

Describe the work done by Sutton and Boveri

 

[Petinga]

In 1902, Boveri and Sutton showed the importance of chromosones.
Boveri worked with sea urchins and showed that not all chromosones are identical and a definite number of chromosones is required for normal growth and deveolpment of organism.
Sutton worked with Grasshopper testes and showed chromosones are carriers of hereditary units, later known as genes.
The work of sutton and boveri became known as the chromosonal theory of inheritance.


Question: Evaluate the effectiveness of quarantine in preventing the spread of plant and animal disease into Australia or across regions of Australia

 

[UzurOger]

Answer: Evaluate the effectiveness of quarantine in preventing the spread of plant and animal disease into Australia or across regions of Australia


EFFECTIVENESS OF QUARANTINE
In some instances the quarantine system may fail. This may occur from illegal boats landing on the coast which have insects or fungi. These ‘passengers’ are not currently found in Australia but may pose a threat to agriculture or native species.

Two examples of organisms that have found their way into Australia illegally and slipped through quarantine include grape Phylloxera (an aphid microorganism) and the fire ant. Others that have been eradicated or prevented from entering Australia include citrus canker and the giant African snail
.
Fire ants – thought to have entered Australia through potted plants from South America. The potential threat is being compared to the cane toad. The ant builds large nest-mounds when mature, which is approx 1m in diameter and 1m high. This disturbs agricultural farming and cattle.

Grape phylloxera – would devastate the wine industry in SA and WA. They are native to North America. In the 1870s it nearly destroyed French wine industries. The American grapes are resistant to these aphids, however the French are not. Therefore there are very few pure French grape vines existing (in SA and WA).
Other potential problems include fruit flies and black sigatoka fungus. If you are traveling in certain fruit growing areas in Australia, bines are provided for you to leave fruit in, so that you do not accidentally introduce a pest into an area. Australia and the states have very strict quarantine laws that can even cause tensions with our trading partners.

Question: Distinguish between the terms allele and gene, using examples

 

[Vicsta]

Ok i dont noe how to do the whole spoiler thing but herez ur answer...

An allele is an alternative for a particular inheritable characteristic. E.g. tall (T) and short (t) are two alleles for the characteristic of height in some plants. Humans, straight (s) and widow’s peak (s) are two alleles for hairline. Development of modern genetics, we now identify these factors as genes. A gene is a section of DNA coding for proteins that expresses itself as the phenotype of an organism. Alleles are alternative forms of a gene. you will find the terms allele and gene used to mean the same thing... [/FONT]

Heres my question: what is the general use of hormone replacement therapy in people who cannot secrete aldosterone?[/FONT]

 

[Dr_Doom]

Answer:

For people affected by Addison's disease.

-Hormone replacement therapy produces hormones which assist in the metabolism of fats and protein to increase blood sugars and liver glycogen.
-Also has a role in producing sex hormones which assist in the development of sexual characteristics.

Question:

Describe TWO roles of macrophages and explain how they differenciate between 'self' and 'non-self' substances.

 

[aileenli]

Gegor Mendel showed his thoughts on DNA, he was successful cause he was a scientist

hahahahahahaha

this guy is funny!!!!!

 

[Petinga]

Macrophages are involved in Phagocytosis and cell death to seal off a pathogen.
Phagocytosis is the process by which some white blood cells(i.e Macrophages and neutrophils) actively move from blood into tissues were they engulf and destroy any foreign particles such as pathogens by secreting enzymes such as lysosymes.
Cell death to seal off a pathogen involves macrophages and lymphocytes completely surrounding the foregin particle in a cyst, effectivelty isolating it and preventing it to spread to other tissues.

Macrophages differentiate from self and non self substances by receptors on the surface of the macrophages which identify self or non self substances. If it is a self substance the macrophages will not attack the substance but if it is not a self substance a immune response will be triggered destroying the substance. Not a very good explanation but i think its beyond the syllabus for the HSC.



Question: Define mutation and Discuss the mutagenic nature of radiation.

 

[Dr_Doom]

Mutation is an alteration in the DNA sequence. There are chromosomal mutations which include chromosome rearrangements such as deletion, inversion, translocation and duplication. There are also gene mutations such as base substitution and frameshift mutation.

Radiation such as (ultraviolet radiation) produces ultraviolet light which is absorbed by the DNA. Cytocine and thymine are vulnerable to this form of radiation and hence change base properties. UV light can also cause thymine pairs to pair up with each other!

Question: Name barriers in the first line of defense and describe their roles.

 

[ugly14]

Question: Name barriers in the first line of defense and describe their roles.

1. Skin : When skin is unbroken, it prevents the entry of pathogens. Pores in the skin also secrete substances that kill bacteria.

2. Chemical barriers: Stomach acid destroys pathogens. Alkali in small intestines destroys acid resistant pathogens. Lysozyme in tears dissolves the cell membranes of bacteria.

3. Mucous membranes: Cells lining the respiratory tract and openings of the urinary and reproductive systems that secrete a protective layer of mucus, this Mucus is sticky and traps pathogens and other particles so that they dont entre the body.

4. Other body secretions: such as secretions from sweat glands and oily secretions from glands in hair follicles. these contain chemicals that destroy bacteria and fungi.

my question: distinguish between the functions of B-cells and T-cells

 

[Petinga]

The B cells are the bodys 3rd line of defence which are produced and matured in the bone marrow. In the prescence of an antigen, the B cells are stimulated to produce memory B cells and plasma cells. The plasma cells secrete one type of antibody that is specific to the antigen that trigered the response. The B memory cells remain in circulation for long periods of time and confer long term immunological memory against the particular antigen that triggerd the immune response.

The T cells are the bodys fourth line of defence that are produced within the bone marrow and matured in the thymus gland. The role of T cells is to directly destroy antigens by secreting substance (i.e cytotoxins). Also produce B memory cells that remain in circulation for long time and confer celluar immunity against particular pathogens.

Question 1: Expain why cleanliness in food, water and personal hygiene are importnat in the control of the spread of infectious diseases.

Question 2: Identify an example of an Australian hybrid and explain the purpose of the hybrid

 

[UzurOger]

Expain why cleanliness in food, water and personal hygiene are importnat in the control of the spread of infectious diseases.

Hygienic practices reduce the number of pathogens that we are exposed to in our environment. Not all micro-organisms are pathogenic. Microorganisms are everywhere and are a potential source of infection. Hygienic practices reduce disease.

In order to control disease we much consider: The origin of outbreak (natural reservoir), mode of transmission, methods that can be employed to contain it
The best method of control is prevention.
The four main methods of control are: Behavioral control, modifying the environment, treatment and immunisation

Sewage treatment and the treatment of drinking water has virtually eliminated dangerous waterborne disease from developing countries. These disrupt the normal infection cycle of pathogens.

Transmitting of diseases can be prevented or significantly reduced by adopting safe behaviours e.g. use of condoms, quarantine, and personal hygiene.

Identify an example of an Australian hybrid and explain the purpose of the hybrid

William Farrer pioneered Australian wheat research with the creation of the "Federation" cross pollination. This resulted in:

-Earlier ripening to suit the shorter growing season in the Australian wheat-growing areas; early ripening is recessive to late ripening
- Improved baking quality
-Improved yield (grains per head)
-Resistance to the fungal disease known as bunt

Q: Outline the Role of the nervous system in detecting and responding to environmental temperature change.
3 Marks

 

[prettyinpink06]

what are cells?

 

[UzurOger]

cell
n.

1. A narrow confining room, as in a prison or convent.
2. A small enclosed cavity or space, such as a compartment in a honeycomb or within a plant ovary or an area bordered by veins in an insect's wing.
3. Biology. The smallest structural unit of an organism that is capable of independent functioning, consisting of one or more nuclei, cytoplasm, and various organelles, all surrounded by a semipermeable cell membrane.
4. Architecture. See web.
5. The smallest organizational unit of a centralized group or movement, especially of a political party of Leninist structure.
6. Electricity.
   1. <LI type=a>A single unit for electrolysis or conversion of chemical into electric energy, usually consisting of a container with electrodes and an electrolyte; a battery. Also called electrochemical cell.
   2. A single unit that converts radiant energy into electric energy: a solar cell.
7. A fuel cell.
8. Computer Science. A basic unit of storage in a computer memory that can hold one unit of information, such as a character or word.
9. A geographic area or zone surrounding a transmitter in a cellular telephone system.
10. A storm cell.
11. A small humble abode, such as a hermit's cave or hut.
12. A small religious house dependent on a larger one, such as a priory within an abbey.
13. A box or other unit on a spreadsheet or similar array at the intersection of a column and a row.

Choose one your bound to understand one

 

[Dr_Doom]

The nervous system detects changes in the bodies temperature by the use of receptors, for example the mechanoreceptors in the skin are used to sense a change in temperature. The message of the new stimulus is sent through the sensory neurons to the brain (central nervous system), where the hypothalumus sends messages to the effectors via motor neurons.

In hot environment the blood vessels will dilate (vasodilation) to allow blood to run more closely to the surface to cool. The hairs on your skin will flatten when the tendons relax.

In cold temperatures the blood vessels will constrict (vasoconstriction) which conserves heat. Also the hairs will stand up "goosebumps" to insulate a layer of air and hence conserve more heat.

Differenciate between haemodialysis and peritoneal dialysis.

 

[UzurOger]

Differenciate between haemodialysis and peritoneal dialysis.

Hemodialysis is the artificial kidney which uses a counter current system. Anti-clotting agents are also required to ensure that the blood flow is smooth throughout the procedure. Need to be done 4-6 times a day.

Automated Peritoneal Dialysis, uses a machine to perform the fluid exchanges. Takes 8-10 hours, done while sleeping.

Q:Outline the Work of the geneticists Sutton and Boveri in identifying the importance of chromosomes in the cell biology
3 Marks

 

[Dr_Doom]

Sutton: Experimented on grasshoppers, recoreded results in similarities between the behaviour of genes and chromosomes during segregation and recombination. Also showed that:
-Chromosomes contain many units of inheritance
-Chromosomes occur in homologous pairs
-The distribution of each homologous pair is independent of each other pair
-During cell division the chromosomes keep their individuality
-As a result of meiosis every gamete recieves one chromosome of each pair

Boveri: Experiemented on sea urchins and proved that normal development of an organism requires a complete set of chromosomes.

Question: Outline the role of phagocytosis in active transport (not immune defence)

 

[simplistic]

Differenciate between haemodialysis and peritoneal dialysis.

Hemodialysis is the artificial kidney which uses a counter current system. Anti-clotting agents are also required to ensure that the blood flow is smooth throughout the procedure. Need to be done 4-6 times a day.

Automated Peritoneal Dialysis, uses a machine to perform the fluid exchanges. Takes 8-10 hours, done while sleeping.
ummm :mad1: were does renal dialysis come in then

 

[Dr_Doom]

ummm :mad1: were does renal dialysis come in then

Haemodialysis and Peritoneol Dialysis are forms of renal dialysis (renal means kidney).