Biology question (1 Viewer)

[highkeydropout]

hello everyone, does anyone know what is meant by the following points:
"explain the relationship between the structure and behaviour of chromosomes during meiosis and the inheritance of genes"
"outline the features/process of gel electrophoresis"
"and analyzing gel electrophoresis and reading them"

 

[highkeydropout]

hello everyone, does anyone know what is meant by the following points:
"explain the relationship between the structure and behaviour of chromosomes during meiosis and the inheritance of genes"
"outline the features/process of gel electrophoresis"
"and analyzing gel electrophoresis and reading them"

bump

 

[Eagle Mum]

bump

Hi HKD, I think your questions are too open ended so any response would require someone to actually write short essays to answer each of them properly which might be why you haven’t yet received a response. I note that in other threads, posters have asked others to review their notes - if you don’t receive a response to this original post, you might consider doing the same - ie. attempt these questions and ask for a review. I’d certainly be happy to help if you did this.

PS: As a caveat, I don’t actually know the HSC Biology syllabus requirements, but I certainly know quite a bit about both topics.

 

[highkeydropout]

Hi HKD, I think your questions are too open ended so any response would require someone to actually write short essays to answer each of them properly which might be why you haven’t yet received a response. I note that in other threads, posters have asked others to review their notes - if you don’t receive a response to this original post, you might consider doing the same - ie. attempt these questions and ask for a review. I’d certainly be happy to help if you did this.

PS: As a caveat, I don’t actually know the HSC Biology syllabus requirements, but I certainly know quite a bit about both topics.

THANK YOU!!

 

[Eagle Mum]

"explain the relationship between the structure and behaviour of chromosomes during meiosis and the inheritance of genes"

My suggested short essay response to his question is:

“During meiosis, cells, which have already undergone DNA replication during Interphase, to double their DNA content producing sister chromatids, enter two rounds of division to produce four unique haploid cells, with only half the DNA of the original cell.

The two meiotic divisions are known as meiosis I and meiosis II. In each round of division, cells go through four stages: Prophase, Metaphase, Anaphase and Telophase. In meiosis I, separation of homologous (similar but non identical) pairs of chromosomes occurs, whilst in meiosis II, separation is of homologous pairs of sister chromatids.

Meiosis I
In Prophase I, the chromosomes condense and the pairs align so that genetic material from the paternal and maternal copies of each pair of chromosome are able to cross over. The DNA breaks at the same spots on each homologue (more or less randomly) and reconnect in a criss-cross structure. This link is stabilised by proteins and the structure, called a chiasma, holds the homologues together, so that they can exchange part of their DNA in a process called crossing over, creating new and unique DNA combinations in each chromosome.

After crossing over, in Metaphase I, cytoskeletal structures called spindles form by assembly of microtubules and capture chromosomes to move them towards the center of the cell. Each chromosome attaches to microtubules from only one pole of the spindle and the homologues of each pair of chromosomes bind to opposite poles when they line up at the metaphase plate for separation.

In Anaphase I, homologues separate to opposite ends of the cell, with sister chromatids of each chromosome staying together (but they are no longer identical due to the crossing over in Prophase I). Finally, in Telophase I, the chromosomes arrive at opposite poles of the cell and prepare for another round of division - meiosis II

Cells move on from meiosis I to meiosis II without copying their DNA.
Meiosis II is a similar process to meiosis I, but instead of separating chromosomes, sister chromatids separate to produce haploid cells.

Meiosis II
The cells that enter meiosis II are the ones produced in meiosis I.
In Prophase II, chromosomes condense. They line up at the metaphase plate in Metaphase II, with each chromatid of the sister pair attaching itself to opposite poles of the spindle. In Anaphase II, sister chromatids separate to opposite ends of the cell.
In Telophase II, nuclear membranes form around each newly formed haploid set of chromosomes and the chromosomes decondense. Each chromosome now has just one chromatid.

Since there have been TWO rounds of division, with each round halving DNA content and only ONE round of replication prior to meiosis, each of these four gamete cells contains only half the genetic material of the original cell, and because of the crossing over in Prophase I, each gamete cell is unique. Gamete cells form ovum in females and sperm in males and the combination of two unique gametes produces a zygote which, through this process of genetic inheritance, becomes a unique individual organism which has the same number of chromosomes and same amount of DNA as each of its parents.”

Note:
I’ve described meiosis II for completeness, but depending on time in an exam and the marks allocated to the question, the entire paragraph on meiosis II really could be left out without loss of information as long as the preceding sentence “Meiosis II is a similar process to meiosis I, but instead of separating chromosomes, sister chromatids separate to produce haploid cells” is included.

I have nothing to do with HSC exams, but I have marked postgrad exam papers, so my general tip is that questions are worded to elicit responses which show that students understand the topic and aren’t just regurgitating generic notes. Therefore, in an exam situation, don’t waste precious time on details which won’t gain marks.

For this question, don’t waste time explaining differences between mitosis & meiosis, nor on the number of chromosomes in different organisms, nor autosomal recessive and autosomal dominant patterns of gene inheritance. It is highly unlikely that any marks would be awarded for any of these details.

With this particular question, the tricky bit is deciding whether to include the DNA replication process which technically occurs prior to (not during) meiosis. This process prior to meiosis is relevant to inheritance of genes so I would include but would ensure that it is clear (to the examiner) that it was understood what occurs prior to and what occurs during meiosis.
Hope this is useful.

 

[highkeydropout]

My suggested short essay response to his question is:

“During meiosis, cells, which have already undergone DNA replication during Interphase, to double their DNA content producing sister chromatids, enter two rounds of division to produce four unique haploid cells, with only half the DNA of the original cell.

The two meiotic divisions are known as meiosis I and meiosis II. In each round of division, cells go through four stages: Prophase, Metaphase, Anaphase and Telophase. In meiosis I, separation of homologous (similar but non identical) pairs of chromosomes occurs, whilst in meiosis II, separation is of homologous pairs of sister chromatids.

Meiosis I
In Prophase I, the chromosomes condense and the pairs align so that genetic material from the paternal and maternal copies of each pair of chromosome are able to cross over. The DNA breaks at the same spots on each homologue (more or less randomly) and reconnect in a criss-cross structure. This link is stabilised by proteins and the structure, called a chiasma, holds the homologues together, so that they can exchange part of their DNA in a process called crossing over, creating new and unique DNA combinations in each chromosome.

After crossing over, in Metaphase I, cytoskeletal structures called spindles form by assembly of microtubules and capture chromosomes to move them towards the center of the cell. Each chromosome attaches to microtubules from only one pole of the spindle and the homologues of each pair of chromosomes bind to opposite poles when they line up at the metaphase plate for separation.

In Anaphase I, homologues separate to opposite ends of the cell, with sister chromatids of each chromosome staying together (but they are no longer identical due to the crossing over in Prophase I). Finally, in Telophase I, the chromosomes arrive at opposite poles of the cell and prepare for another round of division - meiosis II

Cells move on from meiosis I to meiosis II without copying their DNA.
Meiosis II is a similar process to meiosis I, but instead of separating chromosomes, sister chromatids separate to produce haploid cells.

Meiosis II
The cells that enter meiosis II are the ones produced in meiosis I.
In Prophase II, chromosomes condense. They line up at the metaphase plate in Metaphase II, with each chromatid of the sister pair attaching itself to opposite poles of the spindle. In Anaphase II, sister chromatids separate to opposite ends of the cell.
In Telophase II, nuclear membranes form around each newly formed haploid set of chromosomes and the chromosomes decondense. Each chromosome now has just one chromatid.

Since there have been TWO rounds of division, with each round halving DNA content and only ONE round of replication prior to meiosis, each of these four gamete cells contains only half the genetic material of the original cell, and because of the crossing over in Prophase I, each gamete cell is unique. Gamete cells form ovum in females and sperm in males and the combination of two unique gametes produces a zygote which, through this process of genetic inheritance, becomes a unique individual organism which has the same number of chromosomes and same amount of DNA as each of its parents.”

Note:
I’ve described meiosis II for completeness, but depending on time in an exam and the marks allocated to the question, the entire paragraph on meiosis II really could be left out without loss of information as long as the preceding sentence “Meiosis II is a similar process to meiosis I, but instead of separating chromosomes, sister chromatids separate to produce haploid cells” is included.

I have nothing to do with HSC exams, but I have marked postgrad exam papers, so my general tip is that questions are worded to elicit responses which show that students understand the topic and aren’t just regurgitating generic notes. Therefore, in an exam situation, don’t waste precious time on details which won’t gain marks.

For this question, don’t waste time explaining differences between mitosis & meiosis, nor on the number of chromosomes in different organisms, nor autosomal recessive and autosomal dominant patterns of gene inheritance. It is highly unlikely that any marks would be awarded for any of these details.

With this particular question, the tricky bit is deciding whether to include the DNA replication process which technically occurs prior to (not during) meiosis. This process prior to meiosis is relevant to inheritance of genes so I would include but would ensure that it is clear (to the examiner) that it was understood what occurs prior to and what occurs during meiosis.
Hope this is useful.

THANK YOU SO SO MUCH!!!

 

[highkeydropout]

My suggested short essay response to his question is:

“During meiosis, cells, which have already undergone DNA replication during Interphase, to double their DNA content producing sister chromatids, enter two rounds of division to produce four unique haploid cells, with only half the DNA of the original cell.

The two meiotic divisions are known as meiosis I and meiosis II. In each round of division, cells go through four stages: Prophase, Metaphase, Anaphase and Telophase. In meiosis I, separation of homologous (similar but non identical) pairs of chromosomes occurs, whilst in meiosis II, separation is of homologous pairs of sister chromatids.

Meiosis I
In Prophase I, the chromosomes condense and the pairs align so that genetic material from the paternal and maternal copies of each pair of chromosome are able to cross over. The DNA breaks at the same spots on each homologue (more or less randomly) and reconnect in a criss-cross structure. This link is stabilised by proteins and the structure, called a chiasma, holds the homologues together, so that they can exchange part of their DNA in a process called crossing over, creating new and unique DNA combinations in each chromosome.

After crossing over, in Metaphase I, cytoskeletal structures called spindles form by assembly of microtubules and capture chromosomes to move them towards the center of the cell. Each chromosome attaches to microtubules from only one pole of the spindle and the homologues of each pair of chromosomes bind to opposite poles when they line up at the metaphase plate for separation.

In Anaphase I, homologues separate to opposite ends of the cell, with sister chromatids of each chromosome staying together (but they are no longer identical due to the crossing over in Prophase I). Finally, in Telophase I, the chromosomes arrive at opposite poles of the cell and prepare for another round of division - meiosis II

Cells move on from meiosis I to meiosis II without copying their DNA.
Meiosis II is a similar process to meiosis I, but instead of separating chromosomes, sister chromatids separate to produce haploid cells.

Meiosis II
The cells that enter meiosis II are the ones produced in meiosis I.
In Prophase II, chromosomes condense. They line up at the metaphase plate in Metaphase II, with each chromatid of the sister pair attaching itself to opposite poles of the spindle. In Anaphase II, sister chromatids separate to opposite ends of the cell.
In Telophase II, nuclear membranes form around each newly formed haploid set of chromosomes and the chromosomes decondense. Each chromosome now has just one chromatid.

Since there have been TWO rounds of division, with each round halving DNA content and only ONE round of replication prior to meiosis, each of these four gamete cells contains only half the genetic material of the original cell, and because of the crossing over in Prophase I, each gamete cell is unique. Gamete cells form ovum in females and sperm in males and the combination of two unique gametes produces a zygote which, through this process of genetic inheritance, becomes a unique individual organism which has the same number of chromosomes and same amount of DNA as each of its parents.”

Note:
I’ve described meiosis II for completeness, but depending on time in an exam and the marks allocated to the question, the entire paragraph on meiosis II really could be left out without loss of information as long as the preceding sentence “Meiosis II is a similar process to meiosis I, but instead of separating chromosomes, sister chromatids separate to produce haploid cells” is included.

I have nothing to do with HSC exams, but I have marked postgrad exam papers, so my general tip is that questions are worded to elicit responses which show that students understand the topic and aren’t just regurgitating generic notes. Therefore, in an exam situation, don’t waste precious time on details which won’t gain marks.

For this question, don’t waste time explaining differences between mitosis & meiosis, nor on the number of chromosomes in different organisms, nor autosomal recessive and autosomal dominant patterns of gene inheritance. It is highly unlikely that any marks would be awarded for any of these details.

With this particular question, the tricky bit is deciding whether to include the DNA replication process which technically occurs prior to (not during) meiosis. This process prior to meiosis is relevant to inheritance of genes so I would include but would ensure that it is clear (to the examiner) that it was understood what occurs prior to and what occurs during meiosis.
Hope this is useful.

if it doesn't cause inconvenience, I was wondering how you would describe the chemical nature of genes and chromosomes? relting it to histones maybe? I'm not too sure. thank you!!

 

[Eagle Mum]

if it doesn't cause inconvenience, I was wondering how you would describe the chemical nature of genes and chromosomes? relting it to histones maybe? I'm not too sure. thank you!!

So that I don’t have to write another essay, do you have any notes that I can just comment on? I’d like to be helpful but I also have the time demands of a professional working parent.

 

[CM_Tutor]

"explain the relationship between the structure and behaviour of chromosomes during meiosis and the inheritance of genes"

My suggested short essay response to his question is:

“During meiosis, cells, which have already undergone DNA replication during Interphase, to double their DNA content producing sister chromatids, enter two rounds of division to produce four unique haploid cells, with only half the DNA of the original cell.

The two meiotic divisions are known as meiosis I and meiosis II. In each round of division, cells go through four stages: Prophase, Metaphase, Anaphase and Telophase. In meiosis I, separation of homologous (similar but non identical) pairs of chromosomes occurs, whilst in meiosis II, separation is of homologous pairs of sister chromatids.

Meiosis I
In Prophase I, the chromosomes condense and the pairs align so that genetic material from the paternal and maternal copies of each pair of chromosome are able to cross over. The DNA breaks at the same spots on each homologue (more or less randomly) and reconnect in a criss-cross structure. This link is stabilised by proteins and the structure, called a chiasma, holds the homologues together, so that they can exchange part of their DNA in a process called crossing over, creating new and unique DNA combinations in each chromosome.

After crossing over, in Metaphase I, cytoskeletal structures called spindles form by assembly of microtubules and capture chromosomes to move them towards the center of the cell. Each chromosome attaches to microtubules from only one pole of the spindle and the homologues of each pair of chromosomes bind to opposite poles when they line up at the metaphase plate for separation.

In Anaphase I, homologues separate to opposite ends of the cell, with sister chromatids of each chromosome staying together (but they are no longer identical due to the crossing over in Prophase I). Finally, in Telophase I, the chromosomes arrive at opposite poles of the cell and prepare for another round of division - meiosis II

Cells move on from meiosis I to meiosis II without copying their DNA.
Meiosis II is a similar process to meiosis I, but instead of separating chromosomes, sister chromatids separate to produce haploid cells.

Meiosis II
The cells that enter meiosis II are the ones produced in meiosis I.
In Prophase II, chromosomes condense. They line up at the metaphase plate in Metaphase II, with each chromatid of the sister pair attaching itself to opposite poles of the spindle. In Anaphase II, sister chromatids separate to opposite ends of the cell.
In Telophase II, nuclear membranes form around each newly formed haploid set of chromosomes and the chromosomes decondense. Each chromosome now has just one chromatid.

Since there have been TWO rounds of division, with each round halving DNA content and only ONE round of replication prior to meiosis, each of these four gamete cells contains only half the genetic material of the original cell, and because of the crossing over in Prophase I, each gamete cell is unique. Gamete cells form ovum in females and sperm in males and the combination of two unique gametes produces a zygote which, through this process of genetic inheritance, becomes a unique individual organism which has the same number of chromosomes and same amount of DNA as each of its parents.”

Note:
I’ve described meiosis II for completeness, but depending on time in an exam and the marks allocated to the question, the entire paragraph on meiosis II really could be left out without loss of information as long as the preceding sentence “Meiosis II is a similar process to meiosis I, but instead of separating chromosomes, sister chromatids separate to produce haploid cells” is included.

I have nothing to do with HSC exams, but I have marked postgrad exam papers, so my general tip is that questions are worded to elicit responses which show that students understand the topic and aren’t just regurgitating generic notes. Therefore, in an exam situation, don’t waste precious time on details which won’t gain marks.

For this question, don’t waste time explaining differences between mitosis & meiosis, nor on the number of chromosomes in different organisms, nor autosomal recessive and autosomal dominant patterns of gene inheritance. It is highly unlikely that any marks would be awarded for any of these details.

With this particular question, the tricky bit is deciding whether to include the DNA replication process which technically occurs prior to (not during) meiosis. This process prior to meiosis is relevant to inheritance of genes so I would include but would ensure that it is clear (to the examiner) that it was understood what occurs prior to and what occurs during meiosis.
Hope this is useful.

I preface this comment by noting that I am not a biologist and wouldn't presume to any expertise about meiosis. I am a scientist with a lot of experience in HSC chemistry, however. My impression is that this answer would not score particularly well for a reason that is commonly seen in student answers in exams and the HSC, which it does not really focus on the question. It is very possible to write an answer with no factual errors and lots of good information and not meet the criteria for a band 5-6 answer, and so be restricted on possible marks.

When I read the answer, my first impression was that it fitted a "Describe" question very well, such as:

Describe the behaviour of chromosomes during meiosis and how this leads to genetic inheritance​

or something like that. There is plenty of description of the process, divided into stages, and the answer brings together genetic inheritance through the unique gametes, etc. However, the question was:

Explain the relationship between the structure and behaviour of chromosomes during meiosis and the inheritance of genes​

The directing word was "explain" rather than "describe", and so the answer needs to focus more on why than what - specifically, on the relationship between the structure of chromosomes and their behaviour during meiosis. How does their structure support the process that chromosomes undergo? How does this then connect to inheritance?

A common problem with such questions is including so much description that there is not space (or time) to offer the required explanation. At the same time, an explanation that provides no description can be vague or difficult to interpret, so you need enough description for the explanation to be clear and unobscured.

I suggest that you also reflect on how the answer required changes as the questions are modified. Consider formulations like:

Assess the importance of the structure of chromosomes in supporting their behaviour during meiosis and promoting genetic variation

Justify how the behaviour of chromosomes during meiosis is relating to their structure

Account for the inheritance of genes through meiosis with reference to the structure and behaviour of chromosomes.​

Maybe these need modifying (non-biologist here, etc) but these sorts of variations are possible in lots of HSC science areas and (in my experience) cause a lot of problems.

 

[Eagle Mum]

I preface this comment by noting that I am not a biologist and wouldn't presume to any expertise about meiosis. I am a scientist with a lot of experience in HSC chemistry, however. My impression is that this answer would not score particularly well for a reason that is commonly seen in student answers in exams and the HSC, which it does not really focus on the question. It is very possible to write an answer with no factual errors and lots of good information and not meet the criteria for a band 5-6 answer, and so be restricted on possible marks.

When I read the answer, my first impression was that it fitted a "Describe" question very well, such as:

Describe the behaviour of chromosomes during meiosis and how this leads to genetic inheritance​

or something like that. There is plenty of description of the process, divided into stages, and the answer brings together genetic inheritance through the unique gametes, etc. However, the question was:

Explain the relationship between the structure and behaviour of chromosomes during meiosis and the inheritance of genes​

The directing word was "explain" rather than "describe", and so the answer needs to focus more on why than what - specifically, on the relationship between the structure of chromosomes and their behaviour during meiosis. How does their structure support the process that chromosomes undergo? How does this then connect to inheritance?

A common problem with such questions is including so much description that there is not space (or time) to offer the required explanation. At the same time, an explanation that provides no description can be vague or difficult to interpret, so you need enough description for the explanation to be clear and unobscured.

I suggest that you also reflect on how the answer required changes as the questions are modified. Consider formulations like:

Assess the importance of the structure of chromosomes in supporting their behaviour during meiosis and promoting genetic variation

Justify how the behaviour of chromosomes during meiosis is relating to their structure

Account for the inheritance of genes through meiosis with reference to the structure and behaviour of chromosomes.​

Maybe these need modifying (non-biologist here, etc) but these sorts of variations are possible in lots of HSC science areas and (in my experience) cause a lot of problems.

I concede there was excessive descriptive content in my response but that was partly because I don't know how much the original poster knew & what she wanted to get from this thread, but there was an emphasis on the explanation of how the quantity and quality of chromosomal content was achieved at each stage of the meiosis process throughout the response, which served as the basis for the conclusions in the last paragraph which encapsulate the fundamental concepts of genetic inheritance in sexually reproducing organisms - the production of unique individuals, with paternal & maternal contributions, without altering the amount of DNA from one generation to the next.

I did state a caveat in my first response that I have no idea what is needed for the HSC, so perhaps it is best that I just contribute with more general remarks (although I have to say, I've always scored well in exams at all levels of study and successfully helped prepare many students for post grad exams).

 

[highkeydropout]

I concede there was excessive descriptive content in my response but that was partly because I don't know how much the original poster knew & what she wanted to get from this thread, but there was an emphasis on the explanation of how the quantity and quality of chromosomal content was achieved at each stage of the meiosis process throughout the response, which served as the basis for the conclusions in the last paragraph which encapsulate the fundamental concepts of genetic inheritance in sexually reproducing organisms - the production of unique individuals, with paternal & maternal contributions, without altering the amount of DNA from one generation to the next.

I did state a caveat in my first response that I have no idea what is needed for the HSC, so perhaps it is best that I just contribute with more general remarks (although I have to say, I've always scored well in exams at all levels of study and successfully helped prepare many students for post grad exams).

Still, extremely helpful!!!

 

[highkeydropout]

I concede there was excessive descriptive content in my response but that was partly because I don't know how much the original poster knew & what she wanted to get from this thread, but there was an emphasis on the explanation of how the quantity and quality of chromosomal content was achieved at each stage of the meiosis process throughout the response, which served as the basis for the conclusions in the last paragraph which encapsulate the fundamental concepts of genetic inheritance in sexually reproducing organisms - the production of unique individuals, with paternal & maternal contributions, without altering the amount of DNA from one generation to the next.

I did state a caveat in my first response that I have no idea what is needed for the HSC, so perhaps it is best that I just contribute with more general remarks (although I have to say, I've always scored well in exams at all levels of study and successfully helped prepare many students for post grad exams).

sent as pm, these were the notes on chemical nature of genes and chromosomes
hey! for the chemical nature of genes and chromosomes i thought it was referring to the structure such that:
so for the chemical nature of genes i related it to DNA structure:
DNA structure/ chemical nature of genes

DNA is the structure that carries all the genetic information that encodes for proteins to enable cells undergo growth, repair and function. DNA stores the genetic information that controls the cell and thereby the whole organism DNA is the main chemical making up chromatin in the nucleus, although small amounts of DNA are also found in mitochondria and chloroplasts DNA is responsible for transmitting inherited information from one cell to another during cell division and from one generation to the next during reproduction

• It is composed of a double stranded molecule twisted into a helix found in the nucleus. It is a bipolymer made of repeating subunits (nucleotides) connected to a complementary strand by pairing the basis
• Sugar- deoxyribose
• Phosphate
• Nitrogenous base → AT/CG
• The outside of the DNA strand consists of sugar and phosphate molecules (forming a sugar-phosphate backbone) that run in opposite directions
• The sugar and phosphate are joined together to form the helix backbone→ sugar and phosphate connected by covalent bonds
• The DNA is labelled 5’ to 3’ and are anti parallel - different directions
• DNA strands are held together by weak hydrogen bonds between bases for stability, when adenine bonds to thymine, a double hydrogen bond forms, and when guanine and cytosine, a triple hydrogen bond forms.

and for the chemical nature of chromosomes

Chromosomes form due to proteins (histones) that coil the DNA.

• Refers to DNA and histones
• composed of deoxyribonucleic acid (DNA) and have genes closely related to a compound called ribonucleic acid (RNA).
• Composed of chromatin with 40% DNA and 60% protein

I didn't really know about the second one haha
thank you so very much

 

[Eagle Mum]

I’ve replied briefly to your PM. The topic is very broad and the question is open ended, so again will take some time to write up.

 

[jimmysmith560]

View attachment 31005

Just wondering, have you had a look at the sample answer for this question?

 

[Eagle Mum]

I think the question is poorly worded because the two models aren’t ‘different’. The old model still applies - it’s incorporated into a more complex new model which takes into account that there are many, many crossovers, so co-inheritance or separation of traits are based on linkage disequilibrium. This site explains the recombinations of two independent traits which might help conceptualisation of the array of genotypes which can be produced by crossover at multiple sites of each chromosome. http://www.old-ib.bioninja.com.au/higher-level/topic-10-genetics/102-dihybrid-crosses-and.html

 

[jimmysmith560]

I believe it's because the predator (birds) acts as a selection pressure, which reduces the number of dark beetles over time.

Genetic drift is a mechanism of evolution in which allele frequencies of a population change over generations due to chance (sampling error). This definition therefore suggests that genetic drift would not be something that applies to this question, making D the correct answer.

 

[jimmysmith560]

But isn’t the bird causing a change in allele frequencies over generations? So can’t it be classified as genetic drift

This is an example of a scenario that is similar to the question:



As you can see, selection pressure here occurs in a very similar manner to the question (less dark beetles compared to less tan mice).

Genetic drift occurs due to chance (sampling error). It also occurs in all populations of non-infinite size, but its effects are strongest in small populations. The bird is causing selection pressure which I believe is because it is specifically targeting dark beetles instead of the light ones, giving light beetles an increased chance of surviving over others.

 

[Eagle Mum]

Jimmysmith560 is absolutely correct.
A change in allele frequency is an effect of both genetic drift and/or selection pressure, but the two causes are completely different. Genetic drift occurs even in isolated populations irrespective of external factors. Selection pressure is from external factors.

In scientific study, as much as possible, try to work out cause, effect & correlation in system(s).

 

[[Blank]]

Did you end up finding eagle mum's link helpful? Also, can you re-explain it as I can only assume that you understand it now?

 

[[Blank]]

You guys have been in touch since then?