nexttttt (3 Viewers)

[Takuto]

i call it the source-path-sink

in the hsc its the source-sink =P

 

[tau281290]

can someone explain the process of meiosis for me please?

1. single strands of chromosomes double to form homologous pairs of chromosomes.
2. first meiotic division, the homologous pairs separate, but the double strands of the chromosomes are still joined.
3. 2nd division, the chromatids separate to form 4 gamates/daughter cells

Youtube explains it better than I do:
http://au.youtube.com/watch?v=D1_-mQS_FZ0

 

[Bobbles22]

i call it the source-path-sink

in the hsc its the source-sink =P

Thats what i always call it, to me mass flow only refers to how the water moves the sucrose

 

[tau281290]

How is translocation related to the movement of materials in the phloem? (is that what the theory is called?)

It is called the Source to Sink theory, it is just a theory, so it is not confirmed true yet. But this is how it goes:

Active transport of sugars from leaf tissue (the source)into phloem, passive movement of water by osmosis following sugars. This increased pressure causes the sugar solution to move towards the places where the sugars are needed (the sink). this is active transport of sugars by ATP.

 

[Bobbles22]

It is called the Source to Sink theory, it is just a theory, so it is not confirmed true yet. But this is how it goes:

Active transport of sugars from leaf tissue (the source)into phloem, passive movement of water by osmosis following sugars. This increased pressure causes the sugar solution to move towards the places where the sugars are needed (the sink). this is active transport of sugars by ATP.

Not all the water moves in via osmosis, eventually the concentration gradients are leveled and the nucleus of the companion cells provides energy to move more water into the sieve cell via active transport

 

[Kujah]

You've also got how the sugar loads into the source in the first place - apoplastic and symplastic loading. But thats just way too detailed :S

 

[Takuto]

Can someone give a simple answer on that theory that will get full marks in the exam? so confusing

 

[tau281290]

You've also got how the sugar loads into the source in the first place - apoplastic and symplastic loading. But thats just way too detailed :S

LoL, i just need to know enough to get through the HSC course. Not planning to further my biology anymore after HSC =).

 

[Kujah]

Someones already done xylem a few questions above so i cbf doing it again

Phloem - The current theory is known as the mass flow theory (or bulk flow theory) Sucrose in solution moves in the phloem by translocation either up or down the plant. At a sugar source (photosynthetic cell), sucrose in solution moves into the seive tube cell. This increases sugar concentration in this cells, so water moves from the xylem adjacent to this cell by osmosis. This increases the pressure at the source. At a sugar sink (where sugar will either be used in respiration or stored) suger moves out of the sieve tube cell. This decreases sugar concentration in the phloem, so water moves out of the phloem to the xylem by osmosis. This decreases pressure at the sink. As a result, sucrose in solution will always move from source to sink (which may either be up or down the plant).

Great answer.

 

[WantToDoBetter]

How is translocation related to the movement of materials in the phloem? (is that what the theory is called?)

Remember that there are currently two theories as to the movement of phloem-translocation.

1. Involves cytoplasmic streaming (basically the movement of the cytoplasm in eurkaryotic cells).

2. The movement of organic substances through turgor pressure. This occurs due to the diffusion of water into the phloem cells from the xylem cells due to osmosis.

NOTE: This invovles active transport as sugars are actively loaded into the phloem cells to allow water to enter.

Outline the role of the nervous system in detecting and responding to environmental changes.

 

[WantToDoBetter]

Lol someone beat me to it!

 

[dolbinau]

The nervous system consists of the PHS and the CNS. The Peripheral Nervous system consisting of receptors detect stimuli (environmental changes e.g increase temperature by thermoreceptors) and transfer this via nerves to the Central Nervous System (up Spinal Chord to Brain) where it stimulates effectors via nerves to respond to the environmental change (e.g vasodilation of blood vessels) in the PNS. (Is this enough?)

 

[2S1D3]

Outline the roles of Sutton ans Boveri in identifying the importance of chromosomes.

 

[WantToDoBetter]

Outline the roles of Sutton ans Boveri in identifying the importance of chromosomes.

Try page 3.

 

[imqt]

Discuss Problems Relating To Antibiotic Resistance (case Study)

 

[pooja_107]

guys, how much are we meant to study for "preventing the spread and occurence of once common diseases including-smallpox, diphtheria and polio"...how detail do we go??? what if we get it as an extended response?

 

[danz90]

Discuss Problems Relating To Antibiotic Resistance (case Study)

Some bacteria have natural genetic variation, through which they are resistant to the many antibiotics they are exposed to. As a result of natural selection, they pass on these favourable resistant characteristics to their offspring, thus producing a largely resistant strain. The overuse of antibiotics, as well as failure to complete antiobiotics courses, has led to resistant bacterial strains such as Staphylococcous Aurea - Golden Staph. This has become a major concern in Australian hospitals. This strain has developed resistance to ALL antibiotics, and thus poses grave health risks for any patient in the hospital that may be exposed to the dangerous pathogen.

Explain how advances in scientific understanding brought about by Mendel's discoveries provide evidence for the Darwin-Wallace theory of evolution by natural selection?

 

[pooja_107]

for the case study of antibiotics...i have memorised a antibiotic resistance bacteria called staphyloccus (golden staph)...the antiobiotic vancomycin was very effective initially but over time (due to natural selection) it became less effective...so i think giving an example and them expliaining would be a good idea...but firstly start with an outline as to what are antibiotics and how they work...and at the end i think we should also DISCUSS and propose some solutions as to how we can deal with these problems...for eg not using uneccesary antibiotic containing cleaning agents in the household, in agriculture and not asking for antibiotics from the doctor when you have only a viral infections...another solution may also be to use effecitve vaccination programs...eliminating the need to use antiobiotics...hope thats good enough!

 

[homijoe]

Discuss Problems Relating To Antibiotic Resistance (case Study)

Antibiotics are substances that destroy bacteria (bactericidal) or inhibit their growth (bacteriastatic) and hence are used to treat bacterial diseases. In recent time there has been the misuse of antibiotics such as not carrying out the full course. By not carrying out the full course acts as a selecting agent in selecting those bacetria which have a natural resistant strain to the drug. as a result the bacteria survies, reproduce and passes this resistant strain to its offsprings. Hence leading to the evolution of a colony of bacertia that are resistant to a certain antibiotic. Golden Staph is an example of an antibiotic resistant bacetria, it is resistant to methicilian. As result individuals who are infected by the Staphlycoccus Aureus pathogen are difficult to treat as it is resistant to its complementary antibiotic, methicillin. This has and continues to have a negative impact on society as it is becoming difficult to treat this bacetria, many people are dying from this disease as a result of by infected by the mulitresistant bacteria. Overall, antibiotic resistance is highly detrimental to society as bacetrial diseases are harder to treat and individuals are suffering from these multiresistant bacteria severly. Antibiotics should be carefully used and not discriminantly used to prevent the arise of more antibiotic resistant bacteria.

 

[2S1D3]

Discuss Problems Relating To Antibiotic Resistance (case Study)

-Antibiotics were first effective in controlling bacterial populations.
-But antibiotic resistant bactieria were present, by having favourable characteristics, they could pass this on to the next generations.
-Over time large populations of drug resistant bacteria were present and antibiotics weren't as effective.
-E.g. when penicillin was first introduced it was effective in controlling pathogens, but due to natural selection, the bacteria cannot be destroyed by the antibiotic.


Analyse and present information from secondary sources to report on the progress in the production of artificial blood and use available evidence to propose reasons why such research is needed.