Biology SL/HL help

[khalid]

Three questions

1) Discuss the use of hormonones in food production( if its a 6 mark question.. can u give me a model answer)

2) Explain why antibiotics kill bacteria but not

viruses

3)Explain the link between physical activity

and rate and depth of breathing in terms of

changes in the rate at which tissues respire

and therefore of carbon dioxide concentration

and pH in tissues and in the blood

Thanks alot

[Mahuta ♥]

1)I have got no idea, can't think of anything at the moment. I will search that.

2)Antibiotics stop the metabolic pathways that allows bacteria to multiply and divide, basically messing up with the system inside the bacterium. On the other hand, viruses move their DNA into the cell so they basically live inside the cell, you have no metabolic pathways there to stop and you're going to have to kill the cell by stopping its metabolic pathways.

3)During physical activity, the tissues starts respiring faster and so they need more oxygen in less time because they are producing CO2 at a high rate, therefore the concentration of CO2 will increase, which will lower the pH below the normal in the blood. The body detects all this change and sends a signal to the diaphragm and other respiratory muscles to start contracting and relaxing faster, which increases the rate and harder and deeper which increases the depth. This leads to more oxygen reaching the tissues at a faster rate.

[Drake Glau]

Three questions

1) Discuss the use of hormonones in food production( if its a 6 mark question.. can u give me a model answer)

I don't know, however...

Discuss the use and misuse of antibiotics and growth hormones in livestock rearing.

Answers must included arguments for and against antibiotics and growth hormone.

for: [4 max]

increase growth rates / milk production;

antibiotics help control infection;

humans seem not to be affected by eating meat treated / milk containing growth hormones;

eating natural foods containing estrogen compounds has no known adverse effects;

against: [4 max]

increase the rate of antibiotic resistance in bacteria;

cause allergy problems in humans;

food may taste different to humans;

hormones may enter the water supply system;

hormones may alter development of children;

hormones may increase the rate of breast cancer;

hormones may cause developmental changes in aquatic organisms;

animals forced to secrete high levels of milk may suffer;

That might help you?

This is the only question I could find with the words "hormone" and some sort of food source in it...

Edited May 20, 2011 by Drake Glau

[Ilkana]

I'm not sure if help is still being given? but..

I have a topic 9 test on Tuesday (Plant Science).

In regards to the phloem.. I have a question here, worth 5 marks, "Outline the role of the phloem in the active translocation of biochemicals". I'm not sure how to make 5 points about that.

Also. I was writing my notes (alongside my syllabus) and apparently we do not need to know the mechanism of translocation (the pressure flow hypothesis, I assume) or the structure of the phloem.

My teacher has attempted to teach us both of these things, in addition to the general role of the phloem (to actively translocate sugars [sucrose] and amino acids from sources to sinks).

The syllabus says no, no detail about the two things I mentioned earlier is required. But my teacher says "You should learn them just in case. I would talk about these just in case."

It's rather disconcerting! How many more things should I have learnt "just in case"!

Eek!

Thank you for your time

[Guest Soiboist]

Which of the following represents a test cross to determine if phenotype T is homozygous or

heterozygous? (Note: allele T is dominant to allele t.)

A. Phenotype T crossed with another phenotype T

B. Phenotype T crossed with a phenotype T which is homozygous

C. Phenotype T crossed with a phenotype T which is heterozygous

D. Phenotype T crossed with phenotype t

My answer was B but i am wrong, i do not get it

Was this taken from an IB exam and was it correctly quoted? If yes, it is one of the most unclear questions ever posed. Why they would not add "which is homozygous" to alternative D confuses me.

[Hinuku]

Hi,

Do I have to know any life cycles for classification? For example the alternation of generations of bryophyta or gymnosperma?

[suggaplum]

Which of the following represents a test cross to determine if phenotype T is homozygous or

heterozygous? (Note: allele T is dominant to allele t.)

A. Phenotype T crossed with another phenotype T

B. Phenotype T crossed with a phenotype T which is homozygous

C. Phenotype T crossed with a phenotype T which is heterozygous

D. Phenotype T crossed with phenotype t

My answer was B but i am wrong, i do not get it

Was this taken from an IB exam and was it correctly quoted? If yes, it is one of the most unclear questions ever posed. Why they would not add "which is homozygous" to alternative D confuses me.

I don't think this is taken from an IB exam, but I can't be certain. For D, it does not say if its homozygous or not since for phenotype t to be expressed, the genotype has to be tt homozygous therefore it does not have to be explicitly stated.

As for the answer, it is C since it is a test cross and they are crossed with heterozygous individuals

I'm not sure if help is still being given? but..

I have a topic 9 test on Tuesday (Plant Science).

In regards to the phloem.. I have a question here, worth 5 marks, "Outline the role of the phloem in the active translocation of biochemicals". I'm not sure how to make 5 points about that.

Also. I was writing my notes (alongside my syllabus) and apparently we do not need to know the mechanism of translocation (the pressure flow hypothesis, I assume) or the structure of the phloem.

My teacher has attempted to teach us both of these things, in addition to the general role of the phloem (to actively translocate sugars [sucrose] and amino acids from sources to sinks).

The syllabus says no, no detail about the two things I mentioned earlier is required. But my teacher says "You should learn them just in case. I would talk about these just in case."

It's rather disconcerting! How many more things should I have learnt "just in case"!

Eek!

Thank you for your time

For the question, the answer from the markscheme states:

Outline the role of the phloem in the active translocation of biochemicals.

living tissue;

composed of companion cells / sieve tube members;

companion cells involved in ATP production;

sucrose / amino acids / assimilate /

products of photosynthesis transported;

bi-directional transport;

source / leaves to sink / fruits / roots /

storage organs / named storage organ;

pressure flow hypothesis /

movement of water into phloem causes transport;

Well, IB loves throwing in random questions and I personally think some questions are also not required in the syllabus so in my opinion, you should learn both "just in case". However, from the past papers I have, I haven't seen a section B question on this, so you can just roughly understand the idea however not in highly specific details

Hi,

Do I have to know any life cycles for classification? For example the alternation of generations of bryophyta or gymnosperma?

No you don't, all you have to know are the features/characteristics & examples of the different species

Edited May 22, 2011 by suggaplum

[Guest Soiboist]

Which of the following represents a test cross to determine if phenotype T is homozygous or

heterozygous? (Note: allele T is dominant to allele t.)

A. Phenotype T crossed with another phenotype T

B. Phenotype T crossed with a phenotype T which is homozygous

C. Phenotype T crossed with a phenotype T which is heterozygous

D. Phenotype T crossed with phenotype t

My answer was B but i am wrong, i do not get it

Was this taken from an IB exam and was it correctly quoted? If yes, it is one of the most unclear questions ever posed. Why they would not add "which is homozygous" to alternative D confuses me.

I don't think this is taken from an IB exam, but I can't be certain. For D, it does not say if its homozygous or not since for phenotype t to be expressed, the genotype has to be tt homozygous therefore it does not have to be explicitly stated.

As for the answer, it is C since it is a test cross and they are crossed with heterozygous individuals

Ah right, that's true. I didn't notice that it said phenotype.

Anyway your answer is incorrect. A test cross is not carried out between heterozygous individuals, though one of them could be heterozygous. A test cross is carried out in order to discover the presence of a recessive allele in an individual with at least one dominant allele, which is seen since that allele is expressed as phenotype. In order to discover the genotype that individual should mate with an individual that is homozygous for the recessive allele. If then some of the offspring shows the recessive allele as phenotype, one can conclude that the first individual is heterozygous, and if not, homozygous.

So the two possible genotypes of the individuals in a test cross is:

Tt x tt or

TT x tt

Thus the answer must be D.

[Hinuku]

Does anyone know what kind of characteristics do I have to know? Lets say, phylum arthropoda or chordata - there are really millions of different features and I'm sure I don't have to know all of them but just which ones? Please help

[Drake Glau]

Arthropodo you need to know the segmented body and exoskeleton TOGETHER. This came up on the p2 this year

Chordata, vertebrates...they have a spine

[Hinuku]

Also, is there any chance of viewing this year's exams? And how did your's go Drake?

Edited May 22, 2011 by Hinuku

[Drake Glau]

This years? Yes, ask your bio teacher, they might have them already

Check the bio exam discussion for the 2nd question

[Robertito]

Other Chordata features are that they usually have a relatively complex central nervous system and most of them have tails

[Hinuku]

This years? Yes, ask your bio teacher, they might have them already

Check the bio exam discussion for the 2nd question

o,O Nice What books did you use for studying?

Does anyone know what is the bloody difference between a thallus and a prothallus?

[Mahuta ♥]

I have got no idea where you need the difference in, as in what chapter. But I googled it and it gave me this:

Thallus:

1. When the plant body is not differentiated into root, stem and leaves, it is called thallus. It is found in algae.

2. It is a gametophyte but reproduces both asexually and sexually.

3. Specialised sex organs, such as antheridium and archegonium are not formed.

4. Gametes are mostly biflagelleted.

5. It may be unicellular or multicellular.

Prothallus:

1. It is a small, thallus-like green, flat and heart-shaped structure found in ferns.

2. It is a gametophyte and reproduces only sexually.

3. Prothallus contains antheridium and archegonium.

4. Gametes are multiflagllated.

5. It is multicellular.

[Hinuku]

is there any difference between a saprotroph and a detritivore? I found this on Yahoo anwers and it made me confused since the IB diploma clearly requires a difference:

there is no difference they are the same thing

Earthworms are a good example of soil-dwelling deposit feedersDetritivores, also known as detritus feeders or saprophages, are heterotrophs that obtain nutrients by consuming detritus (decomposing organic matter).[1] By doing so, they contribute to decomposition and the nutrient cycles.

Detritivores are an important aspect of many ecosystems. They can live on any soil with an organic component, and even live in marine ecosystems where they are termed interchangeably with bottom feeders.

Typical detritivorous animals include millipedes, woodlice, dung flies, many terrestrial worms, burying beetles, some sedentary polychaetes such as amphitrite, terebellids and fiddler crabs.

Many species of bacteria, fungi and protists, unable to ingest discrete lumps of matter, instead live by absorbing and metabolising on a molecular scale. Scavengers are typically not thought to be detritivores, as they generally consume larger quantities of organic matter. Coprovores are also usually treated separately as they exhibit a slightly different feeding behaviour. The eating of wood, whether live or dead, is known as xylophagy.

Thanks

[Mahuta ♥]

Haha it took me an hour to understand the difference, glad I still remember it. They both seem the same I agree, but the difference I always kept in mind is that detritivors ingest the organic material the decompose it inside whereas saprotrophs decompose the organic material before ingesting it by secreting enzymes onto it, breaking it down and absorbing it in. To make sure you don't forget it, detritivors are like certain bugs, they have 'mouths', whereas saprotophs only absorb the product of decomposition, so no mouth..therefore its things like bacteria.

[Hinuku]

Ive got this dilemma of choosing the right carbon cycle. Which one is suitable for the IB diploma, each of my 3 books state different ones, one has more information on something whereas another lacks something. I'm really confused.

Thanks

[Mahuta ♥]

Carbon Cycle, any version that includes what the syllabus says:

"The details of the carbon cycle should include the interaction of living organisms and the biosphere through the processes of photosynthesis, cell respiration, fossilization and combustion"

Nothing else is needed. I always go with Oxford study guide's version on most things.

[Drake Glau]

This years? Yes, ask your bio teacher, they might have them already

Check the bio exam discussion for the 2nd question

o,O Nice What books did you use for studying?

Does anyone know what is the bloody difference between a thallus and a prothallus?

I had the 7th edition Campbell AP Bio book.

Some Biozone book...

And another book with a tiger on it O.o I turned them all on already sorry =/

This last book was AWESOME, it was by something specifically for IB. Might have been the oxford one...it was AMAZING though.

Our teacher also gave us "magic books". These books had all the objectives, listed out and answered exactly as the IB wants them. It was awesome but I forgot the names

Edited May 23, 2011 by Drake Glau