Biology: Discussion, Questions & Potential Solutions

[gab.r_se]

Hey guys!

1.What did you guys write for the question asking about structural features of the transitional fossil?

2.What were chemical barriers for a plant? I wrote shedding of infected leaves etc. and the plant producing toxins, but not sure if this is right..

I said that for 2. as well. For the structural features, I said even toed hooves and fins.

[vox nihili]

Hey guys,

We should hopefully have some solutions up for you today!

[RazzMeTazz]

Is a copy of the exam available yet?

[vox nihili]

Is a copy of the exam available yet?

We won't be making a copy available here because VCAA exams are copyrighted.

[LOL_ABC]

Ohh okay, do you know where I could find one? Thanks

Yes next year on the VCAA website

[EllingtonFeint]

OHMIGOSH I’m so scared of looking at this page. I keep reloading the tab and then shutting before reading anything. I’m so afraid 😱

[vox nihili]

OHMIGOSH I’m so scared of looking at this page. I keep reloading the tab and then shutting before reading anything. I’m so afraid 😱

Still no exam in our hands unfortunately

[AnonymooseUser]

Just curious about what people think the A+ cutoff will be for the 2018 exam? Similar to 79% in 2017 (correct me if this is wrong) or closer to mid 80s?

[PhoenixxFire]

Just curious about what people think the A+ cutoff will be for the 2018 exam? Similar to 79% in 2017 (correct me if this is wrong) or closer to mid 80s?

I reckon it’ll be higher than last year given last year was a bit of a surprise. I don’t think it’ll be quite 85% though. Maybe 82-84% or something (but I haven’t actually seen the exam yet, from what I’ve heard though it seems there were only a few questions that everyone struggled with).

[Lear]

We won't be making a copy available here because VCAA exams are copyrighted.

Has VCAA asked AN not to post exams or was this a decision made solely by AN to not post exams this year?

[O2square]

Just curious about what people think the A+ cutoff will be for the 2018 exam? Similar to 79% in 2017 (correct me if this is wrong) or closer to mid 80s?

I found the exam tougher than last years and I've been hearing a lot of others have found it hard as well, I'm not too sure, but considering that quite a few people did find it difficult, I'd say the cutoff might be lower this year.

But then again it is hard to predict!

[gab.r_se]

I found the exam tougher than last years and I've been hearing a lot of others have found it hard as well, I'm not too sure, but considering that quite a few people did find it difficult, I'd say the cutoff might be lower this year.

But then again it is hard to predict!

The short answer was a bit tougher than last years, but the multiple choice was quite easy, so maybe the cutoff will be a tiny bit higher than the 2017 exam.

[jinaede1342]

The short answer was a bit tougher than last years, but the multiple choice was quite easy, so maybe the cutoff will be a tiny bit higher than the 2017 exam.

The multiple choice questions didn't feel too hard but there were definitely a few questions where I was tossing up between two answers/a little hesitant in completing, like the evolutionary timeline where we had to label P,Q,R, the gel electrophoresis diagnosis and the precision and accuracy graphs, where I didn't feel as confident in my answers.

[O2square]

The multiple choice questions didn't feel too hard but there were definitely a few questions where I was tossing up between two answers/a little hesitant in completing, like the evolutionary timeline where we had to label P,Q,R, the gel electrophoresis diagnosis and the precision and accuracy graphs, where I didn't feel as confident in my answers.

Yeah I agree, I didn't feel too confident with my answers for a few of the multiple choice questions either. I felt as if some of them weren't as clear.

Also was very confused with the precision and accuracy questions rip 2(?) marks

I thought the short answer was definitely harder than last years for sure though.

[moonlight2018]

My written attempt at the given questions.

Question 1
a.   Ribosomes attach to the mRNA in the cytoplasm of the cell (1m); an initiator codon on mRNA binds to first anticodon of tRNA (1m); the codon on the mRNA and anticodon on the tRNA that match one another will result in the release of an amino acid to join the growing polypeptide chain(1m).

b.   Rough endoplasmic reticulum- packaged into transport vesicle (1m); golgi body- polypeptide is folded and modified into functional protein (1m); secretory vesicle- release protein into extracellular fluid by exocytosis (1m).

Question 2
a.   Cell shrinks and loses contact with neighbouring cells, leading to the condensation of chromatin and its' degradation (1m); nuclear membrane degrades while the chromatin clumps into chromatin bodies (1m); the cell breaks into apoptotic bodies containing densely packed organelles (1m). - Blebbing is not an acceptable answer; choose two

b.   Regulates cell proliferation (1m); maintaining cellular integrity (1m); plays a central role in the formation of appendages and other bodily structures during embryonic development (1m).- Any two of these answers

c.   Loss of proper growth factor (1m); oxidative damage (1m); irreversible DNA damage (1m).- Any two of these answers

Question 3
a.   The secretion of anti-bacterial or anti-fungal agents, such as resins and tannins (1m); the release of defensins from germinating seeds to prevent the growth of pathogens (1m); the secretion of gum around infected site to disallow pathogens from entering the site (1m)- Any two of these answers

b.   Ciliated membranes (1m); intact skin (1m); mucus secretions (1m).- Any two of these answers

c.   Complement proteins destroy bacterial cell wall and attracts macrophages to the site of infection (1m); NK cells are cytotoxic and can destroy cell that have been invaded by viruses by rupturing the membrane of the infected cell.

Question 4
a.      Correct diagram (1m); correct explanation (1m)

b.   Changing the 3D shape of the polypeptide chains (1m)

c.   During the first botox injection, antigen presenting cells present the foreign epitopes to helper T cell through the MHC II complex. The helper T cell then activates the production of plasma B cells (1m); plasma B cells produce antibodies against the antigens of Clostridium botulinum. Some B cells become memory B cells (1m); during the secondary immune response, the immune system develops an immunological memory of that antigen, so it could respond quicker and stronger when presented with the same antigen for the second time (1m)

Question 5
a.   
i. 1958 (1m)

ii. A higher number of reported measles lead to a higher number of deaths (1m); both graphs demonstrate a similar trend in the fluctuation of the number of reported measles and the number of deaths between 1954 and 1966, followed by a drastic drop in the number of reported measles and the number of deaths between 1966 and 1967 (1m)

b.   Herd immunity occurs when a significant portion of a population is vaccinated, providing some protection for individuals who have not developed immunity (1m); herd immunity makes it difficult for a disease to spread because there are very few susceptible people to the disease (1m).

Question 6
a.   A structural gene is responsible for the production of proteins that affect the structure or function of an organism (1m); a regulatory gene is a gene involved in controlling the expression of one or more genes (1m).
 
b.   The expression of Hox genes Unx and Scr can be turned 'on' or 'off' to control the growth of different appendages. (1m)

c.   BMP 4 gene codes for the production of a protein that stimulates bone growth, which stimulates beak growth in finches or jaw formation in cichlid fish (1m);

Finches with larger beaks have larger amount of BMP4 gene expression (1m); Finches with high beak depth and width are able to crush large and hard seeds (1m)
OR High level of BMP4 gene expression results in thicker jaws (1m); jaw gets shorter and thicker to enable specialized biting in these cichlid species (1m)

Question 7
a.   Natural variation exists because of random mating , random fertilisation, recombination between homologous chromosomes during meiosis (2m- with explanation on how these factors can lead to an increase in natural variation); natural variation is possible because of the presence of different alleles within the population that enable the ability of individuals to survive and reproduce (1m)

b.   Founder effect (1m); allele frequency of the new population is a not a representative of the original population because of a small number of individuals in the small island as compared to a larger number in the large island (1m)

c.   Shorter hind leg is a favourable phenotype (1m); this phenotype will be passed onto subsequent generation because of the ability of these lizards to survive and to produce fertile offspring (1m)

Question 8
a.   Binds to the active site of the enzyme (1m); prevent folic acid from binding to the enzyme (1m)

b.   Prevent DNA replication and transcription (1m); prevent protein  synthesis in translation (1m); interfere with the synthesis phase of interphase during cell replication (1m)

c.   No, antibiotics interfere with bacterial growth by disrupting the key aspects of bacterial metabolism (1m); eukaryotic cells are not affected because of difference in structure and metabolic pathway to bacteria (1m)

Question 9
a.   Pakicetus is extinct (1m)

b.   Ambulocetus fossil has features of ancestral land mammal and present-day cetaceuans (1m); Ability to walk on land to obtain more energy from a large variation of food on land (1m); Have fins to hunt underwater (1m).

c.   
i. Any two of humpback whale, common bottlenose dolphin, burrunan dolphin and killer whale or any two of whale shark, bronze whaler and blacktip reef shark (1m); share a common ancestor but difference in niche leads to difference in average length (1m)

ii. One from phylogenetic tree A and the other from phylogenetic tree B (1m); no common ancestor but similar environmental pressure and similarity in diet leads to similar physical appearance (1m)

d.   DNA hybridisation  with description (1m); comparison of amino acid sequences with description (1m)

e.   Outcome 1: extinction due to very low genetic diversity count and high level of human activity (1m); Outcome 2: become a new species due to a long period of isolate, occurs when these dolphins cannot interbreed with outside population to produce fertile offspring (1m).

Question 10
a.   Yes, they are transgenic because they contain foreign genetic materials (1m); Bt cotton contains genes from Bacillus thuringiensis (1), golden rice contains genes from Erwinia uredovora and Narcissus pseudonarcissus (1m)

b.   Insect resistance, crop yield will increase due to a reduction in insect damage (1m)

c.   Bt cotton (social implication: increased cost of plant Bt cotton; biological implication:  can trigger an allergic reaction) (2m); golden rice (social implication: reduction in Vitamin A deficiency within a large population; biological implication: cross pollination between Golden Rice and non-genetically modified crops) (2m)


Question 11
a.   If photosynthesis occurs, then phenol red indicator will change from yellow to pink.

b.   
1. same number of algae balls in each test tube
2. time given for each experimental set
3. initial amount of dissolved carbon dioxide gas in the solution
4 (choose 3): temperature of algae balls in each test tube

c.   IV: Colour of algae balls; DV: change in the colour of pH indicator

d.   No change in the colour of pH indicator for each test tube (1m); same colour change of the pH indicator for each test tube (1m)

e.   To determine whether phenol red indicator will change colour from yellow to pink without light (1m)

f.   (unsure)- my understanding is that it is asking whether there are other factors that can lead to the change in phenol red indicator colour from yellow to pink
1. Some of the dissolved carbon dioxide gas have been lost to the environment, causing the phenol red indicator to change colour (1m)
2. The change of phenol red indicator from yellow to pink in the test tubes without light is caused by the dissolved carbon dioxide gas, and not because photosynthesis is not present (1m)