IGCSE BIOLOGY DOUBTS HERE !!!!

[nid404]

You need to be able to describe the function of the kidney in removing urea/excess water for Core, and need to be able to outline the structure of the kidney and structure + functioning of the nephron for Supplement, including the role of the renal capsule and the tubule.

Only negative feedback loops for maintenance of temperature in skin (Core) and maintenance of glucose content via insulin/glucagon (Supplement) are needed for IGCSE. At least that's what it says on the 2010 Syllabus.

You don't need the details though. Just the main idea that the product inhibits it's own production when it is in excess or when no more of it is required.

[acash09]

Thanks very much Garfield! (I like garfield too! lol!)

Another question -

State the advantages and disadvantages of asexual reproduction

&

State the advantages and disadvantages of sexual reproduction

acash09

[Amii]

Advantages and diadvantages of asexual reproduction
Advantages-

• The process is quick
• Only one parent is needed
• No gametes are needed
• All the good characteristics of the parent are passed on to the offspring.
• Where there is no dispersal (e.g- in potato tubers),offspring will grow in the same favourable environment as the parent.
• Plants tht reproduce asexually ususally store large amounts of food tht allow rapid growth when conditions are suitable.

Disadvantages-

• Thr is little variation created,so adaptation to a changing environment (evolution) is unlikely.
• If the parent has no resistance to a particular disease,none of the offspring will hv resistance.
• Lack of dispersal(e.g potato tubers) can lead to competition r nutrients,water and light.

Advantages And Disadvantages of Sexual Reproduction-
Advantages-

• Thr is variation in the offspring so adaptation to the changing or new environment  is likely,enabling survival of the species.
• New varieties can be created, which may hv resistance to disease.
• In plants, seeds are produced, which allow dispersal away frm the plant, reducing competition.

Disadavantages-

• Two parents are usually needed(though nt always- some plants can self-pollinate)
• Growth of a new plant to maturity frm a seed is slow.

Hope it helps  
Take care n keep smiling!!      

[Deadly_king]

Thanks very much Garfield! (I like garfield too! lol!)

Another question -

State the advantages and disadvantages of asexual reproduction

&

State the advantages and disadvantages of sexual reproduction

acash09

Advantages and Disadvantages of Asexual Reproduction
Asexual reproduction can be very advantageous to certain animals. Animals that remain in one particular place and are unable to look for mates would need to reproduce asexually. Another advantage of asexual reproduction is that numerous offspring can be produced without "costing" the parent a great amount of energy or time. Environments that are stable and experience very little change are the best places for organisms that reproduce asexually. A disadvantage of this type of reproduction is the lack of genetic variation. All of the organisms are genetically identical and therefore share the same weaknesses. If the stable environment changes, the consequences could be deadly to all of the individuals.

Hmmm Amii was quicker

Good job girl

[acash09]

Thanks guys and gals! Need something else, lol!

The drugs section in the syllabus - if someone has notes, could you post it here please?

I hate the drugs section ( except the good ones - antibiotics ), i never got those notes from my friends.

Much appreciated.

Acash09 - I'll keep smilin'! 

[Ivo]

Thanks guys and gals! Need something else, lol!

The drugs section in the syllabus - if someone has notes, could you post it here please?

I hate the drugs section ( except the good ones - antibiotics ), i never got those notes from my friends.

Much appreciated.

Acash09 - I'll keep smilin'! 

I don't think you'll need to know an awful lot about Drugs at IGCSE.  The syllabus already provides a pretty good summary about what you need to know (in case you haven't looked already):

1) Define a drug as any substance taken into the body that modifies or affects chemical reactions body.

2) Describe the medicinal use of antibiotics for the treatment of bacterial infection.

3) Describe the effects of the abuse of heroin: a powerful depressant, problems of addiction, severe withdrawal symptoms and associated problems such as crime and infection e.g. HIV/AIDS.

4) Describe the effects of excessive consumption of alcohol: reduced self-control, depressant, effect on reaction times, damage to liver and social implications.

5) Describe the effects of tobacco smoke and its major toxic components (tar, nicotine, carbon monoxide, smoke particles) on the gas exchange system.

6) Explain why antibiotics kill bacteria but not viruses.

As you can see from the above, that's about as much as you'll need to know, maybe knowing a bit more about antibiotics won't do you any harm!

Hope this helps!

[Deadly_king]

Thanks guys and gals! Need something else, lol!

The drugs section in the syllabus - if someone has notes, could you post it here please?

I hate the drugs section ( except the good ones - antibiotics ), i never got those notes from my friends.

Much appreciated.

Acash09 - I'll keep smilin'! 

I think this might help as well 

http://www.s-cool.co.uk/gcse/biology/drugs.html
Just click on the respective titles to get your required notes

Thanks for the help Ivo

[acash09]

I think we need to rename this thread into "Acash09 -  asking many boilogy doubts!" lol! 

Sorry, i've taken a lot of your time people, but i appreciate your help!

Another doubt - in 7.1.2 transpiration -

"discuss the adaptations of the leaf, stem and root to three contrasting environments, to include pond, garden and desert, with emphasis  on local examples (where appropriate) and the factors described in the core"

&

7.1.3 translocation

"compare the role of transpiration and translocation in the transport of materials from sources to sinks, within plants at different seasons"

I know this is becoming to much but my igcse are getting nearer and nearer and i dont have time to look here and there for answers so please bear with me a few questions more 

thanks again! acash09

[Deadly_king]

I think we need to rename this thread into "Acash09 -  asking many boilogy doubts!" lol! 

Sorry, i've taken a lot of your time people, but i appreciate your help!

Another doubt - in 7.1.2 transpiration -

"discuss the adaptations of the leaf, stem and root to three contrasting environments, to include pond, garden and desert, with emphasis  on local examples (where appropriate) and the factors described in the core"

&

7.1.3 translocation

"compare the role of transpiration and translocation in the transport of materials from sources to sinks, within plants at different seasons"

I know this is becoming to much but my igcse are getting nearer and nearer and i dont have time to look here and there for answers so please bear with me a few questions more 

thanks again! acash09

Sorry........won't be able to help much since am busy with exams as well.

Try this though.......it might be helpful

[Ivo]

Another doubt - in 7.1.2 transpiration -

"discuss the adaptations of the leaf, stem and root to three contrasting environments, to include pond, garden and desert, with emphasis  on local examples (where appropriate) and the factors described in the core"

Xerophytes (Desert plants)

They are plants that are able to exist in conditions where water is scarce.  Cacti are xerophytes that survive in hot, dry (arid) desert regions.  Cacti reduce water loss and conserve water in the following ways:

1) Their leaves are reduced to spines.  This reduces the surface area of the leaf over which water can be lost.

2) A thick waxy cuticle covers the plant's surfaces and reduces transpiration.

3) They have swollen stems containing water-storage tissue.

4) They have a shallow, spreading root system to absorb quickly any water from rain and overnight condensation.

5) Many cacti have a round compact shape which reduces their surface area so there is less surface through which water can be lost.

6) They have shiny surfaces which reflect heat and light.

7) Their stomata are closed during the day to reduce water loss.  They open their stomata at night to absorb the carbon dioxide which they store for use in photosynthesis during the day.  Photosynthesis occurs in the outer layers of cells in their stems.

Hydrophytes (Pond plants)

(eg. Water lilies, Nymphaea sp.)

They are plants that grow submerged or partially submerged in water.  Living in water has both its costs and benefits.

Buoyed up by water and with no need for water transport, floating plants save energy since they produce little or no xylem tissue.

Roots, if present, are for anchorage and since there is no need for the roots to absorb water or mineral ions, there are no root hairs.  The leaves and stems of hydrophytes have little or no cuticle, since there is no need to conserve water.  

The problem for hydrophytes is that carbon dioxide, which is needed for photosynthesis, diffuses through the water much more slowly than it does through air.  The same applies for oxygen, needed for plant respiration, since it is not very soluble in water.  Therefore many hydrophytes have an extensive system of air spaces in their stems and leaves through which gases diffuse quickly.  These air spaces provide buoyancy to keep the plants close to the light and are a resevoir of oxygen and carbon dioxide.

Mesophytes (Garden plants)

(eg. Coleus, Solenostemon spp. - brightly coloured garden plants)

Garden plants are grown for their colourful, scented flowers, for their subtle leaf colours, for shade and to provide an attractive environment.

Mesophytes are terrestrial plants that usually have enough water and do not have such extreme adaptations to reduce water loss like those of xerophytes.  Many garden plants are mesophytes, as gardeners can provide them with enough water even in parts of the world that might be dry for much of the year.

[Deadly_king]

Xerophytes (Desert plants)

They are plants that are able to exist in conditions where water is scarce.  Cacti are xerophytes that survive in hot, dry (arid) desert regions.  Cacti reduce water loss and conserve water in the following ways:

1) Their leaves are reduced to spines.  This reduces the surface area of the leaf over which water can be lost.

2) A thick waxy cuticle covers the plant's surfaces and reduces transpiration.

3) They have swollen stems containing water-storage tissue.

4) They have a shallow, spreading root system to absorb quickly any water from rain and overnight condensation.

5) Many cacti have a round compact shape which reduces their surface area so there is less surface through which water can be lost.

6) They have shiny surfaces which reflect heat and light.

7) Their stomata are closed during the day to reduce water loss.  They open their stomata at night to absorb the carbon dioxide which they store for use in photosynthesis during the day.  Photosynthesis occurs in the outer layers of cells in their stems.

Hydrophytes (Pond plants)

(eg. Water lilies, Nymphaea sp.)

They are plants that grow submerged or partially submerged in water.  Living in water has both its costs and benefits.

Buoyed up by water and with no need for water transport, floating plants save energy since they produce little or no xylem tissue.

Roots, if present, are for anchorage and since there is no need for the roots to absorb water or mineral ions, there are no root hairs.  The leaves and stems of hydrophytes have little or no cuticle, since there is no need to conserve water.  

The problem for hydrophytes is that carbon dioxide, which is needed for photosynthesis, diffuses through the water much more slowly than it does through air.  The same applies for oxygen, needed for plant respiration, since it is not very soluble in water.  Therefore many hydrophytes have an extensive system of air spaces in their stems and leaves through which gases diffuse quickly.  These air spaces provide buoyancy to keep the plants close to the light and are a resevoir of oxygen and carbon dioxide.

Mesophytes (Garden plants)

(eg. Coleus, Solenostemon spp. - brightly coloured garden plants)

Garden plants are grown for their colourful, scented flowers, for their subtle leaf colours, for shade and to provide an attractive environment.

Mesophytes are terrestrial plants that usually have enough water and do not have such extreme adaptations to reduce water loss like those of xerophytes,  Many garden plants are mesophytes, as gardeners can provide them with enough water even in parts of the world that might be dry for much of the year.

Nice piece of research buddy

+rep

[acash09]

thanks man! good to have you helping moi!

acash09

[MKL]

Quick question: describe the use of microorganisms in the food industry, with reference to yoghurt and single cell protein.

Thanks in advance

[Deadly_king]

Quick question: describe the use of microorganisms in the food industry, with reference to yoghurt and single cell protein.

Thanks in advance

1.Two species of bacteria Lactobacillus bulgaricus and Lactococcus thermophilus in approximately equal proportions, are used to make yoghurt.

NOTE : You need not know the names of the bacteria. I just mentioned it

Commercial producers pasteurize and homogenize the milk before adding the starter. After stirring, the mixture is then incubated for 3-6 hours at 40-450C. At this temperature the two bacteria have a mutually stimulating effect on one another.
Protolytic enzymes from L. bulgaricus break down milk proteins into peptides. These stimulate the growth of L. thermophilus which, in turn, produce formic acid and carbon dioxide, growth stimulants for L. bulgaricus. As the incubation proceeds, L. bulgaricus converts the lactose to lactic acid and the pH falls to 4.2-4.4 which leads to the coagulation of proteins by lactic acid and the thickening of the yoghurt.

Further processing involves the addition of flavour, colour, fruit pulp and heat treatment to kill off any bacteria.

2.The most common single-celled protein is yeast. It is used in the manufacture of bread and beer.

The principal dry ingredients used in bread-making are wheat flour, salt, sugar, ascorbic acid, and the yeast Saccharomyces cerevisiae. Water or milk is added to produce a thick, sticky dough which is repeatedly folded or kneaded, to create nuclei for gas production and expansion. The mixed dough is rested, folded, and moulded and in a humid atmosphere at 34-350C, it is left for 10 minutes to ‘prove’.
During the process of ‘proving’, fermentation of sugars in the dough, catalysed by enzymes from the yeast cells, produces carbon dioxide. As this gas cannot escapes from the sticky mass, it fills the gas nuclei and causes the dough to “rise” or increase in volume. This process is sometimes is called ‘leavening’. The overall effects of leavening are to make the dough lighter, more digestible, and of better flavour following from the production of organic acids, alcohols and esters by yeast cells. The role of enzymes in the process are summarized as follows:

maltase
a) Maltose ---------------› glucose
(in flour) (from yeast)

invertase
b) Sucrose-----------------› glucose + fructose
(added) (from yeast)

zymase
c) Glucose + fructose----------------› alcohol + carbon dioxide
(from yeast)

The yeast fermented bread have better flavour and texture as compared to the one prepared by using baking powder therefore in the commercial production of bread, Baker’s yeast is used. The living cells of aerobically grown Saccharomyces cerevisiae are collectively referred to as baker’s yeast.

Baker’s yeast is commercially available either as a dried powder i.e. dry yeast with about 95% dry weight or in the form of cakes (about 25-30% dry weight). In recent years, some workers have reported the development of genetically engineered strains of Saccharomyces cerevisiae with improved fermentation properties.

NOTE : Again you need not know the names of the yeast.

Hope it helps

[MKL]

1.Two species of bacteria Lactobacillus bulgaricus and Lactococcus thermophilus in approximately equal proportions, are used to make yoghurt.

NOTE : You need not know the names of the bacteria. I just mentioned it

Commercial producers pasteurize and homogenize the milk before adding the starter. After stirring, the mixture is then incubated for 3-6 hours at 40-450C. At this temperature the two bacteria have a mutually stimulating effect on one another.
Protolytic enzymes from L. bulgaricus break down milk proteins into peptides. These stimulate the growth of L. thermophilus which, in turn, produce formic acid and carbon dioxide, growth stimulants for L. bulgaricus. As the incubation proceeds, L. bulgaricus converts the lactose to lactic acid and the pH falls to 4.2-4.4 which leads to the coagulation of proteins by lactic acid and the thickening of the yoghurt.

Further processing involves the addition of flavour, colour, fruit pulp and heat treatment to kill off any bacteria.

2.The most common single-celled protein is yeast. It is used in the manufacture of bread and beer.

The principal dry ingredients used in bread-making are wheat flour, salt, sugar, ascorbic acid, and the yeast Saccharomyces cerevisiae. Water or milk is added to produce a thick, sticky dough which is repeatedly folded or kneaded, to create nuclei for gas production and expansion. The mixed dough is rested, folded, and moulded and in a humid atmosphere at 34-350C, it is left for 10 minutes to ‘prove’.
During the process of ‘proving’, fermentation of sugars in the dough, catalysed by enzymes from the yeast cells, produces carbon dioxide. As this gas cannot escapes from the sticky mass, it fills the gas nuclei and causes the dough to “rise” or increase in volume. This process is sometimes is called ‘leavening’. The overall effects of leavening are to make the dough lighter, more digestible, and of better flavour following from the production of organic acids, alcohols and esters by yeast cells. The role of enzymes in the process are summarized as follows:

maltase
a) Maltose ---------------› glucose
(in flour) (from yeast)

invertase
b) Sucrose-----------------› glucose + fructose
(added) (from yeast)

zymase
c) Glucose + fructose----------------› alcohol + carbon dioxide
(from yeast)

The yeast fermented bread have better flavour and texture as compared to the one prepared by using baking powder therefore in the commercial production of bread, Baker’s yeast is used. The living cells of aerobically grown Saccharomyces cerevisiae are collectively referred to as baker’s yeast.

Baker’s yeast is commercially available either as a dried powder i.e. dry yeast with about 95% dry weight or in the form of cakes (about 25-30% dry weight). In recent years, some workers have reported the development of genetically engineered strains of Saccharomyces cerevisiae with improved fermentation properties.

NOTE : Again you need not know the names of the yeast.

Hope it helps

Thanks heaps man!