Skins and synopsisBill Indge

Synopsis

Synopsis

The material in this presentation is designed to encourage students to think

about synopsis. The idea behind synoptic questions is to assess students’

understanding of the general principles on which so much of the subject depends,

which is much more important than simple recall of knowledge.

This presentation supports the article ‘Tales from the museum’ by Henry McGhie

in the April 2014 issue of Biological Sciences Review. The presentation is based

on three different exercises; these may be used independently.

The questions and the accompanying mark schemes are available as a separate

Word document.

Synopsis

Synopsis is about•understanding the principlesTaking diffusion as an example, all specifications consider this topic relatively early in the AS course. An understanding of diffusion is essential to the understanding of a number of topics considered later in the course.

Diffusion

Nerve impulses

Gas exchange

Digestion

Synopsis

Enzymes

?

Synopsis is about•understanding the principlesAnother such topic is enzymes. Students might wish to think about specific enzymes that link to different aspects of physiology.

? ?

Synopsis

Acetylcholinesterase

Carbonic anhydrase

Amylase

Synopsis is about•understanding the principles

Enzymes

Synopsis

What are these principles?

• Diffusion• Enzymes• Polymerisation, condensation and hydrolysis• Osmosis• Active transport• Respiration and ATP• Size and surface-area-to-volume ratio• Natural selection• How science works … ?

Synopsis

Synopsis is like a birthday present.You may not recognise the wrapping paper but you know exactly what is inside.

Synopsis

You may not be familiar with the context but you should know all about the principles on which the question is based.

You may know nothing about snails…but the question may be asking you about selection or respiration.

Synopsis is about•relating the principles to new contexts

Synopsis

You may know nothing about possums…but the question is asking you about ‘how science works’ and surface-area-to-volume ratios

You may not be familiar with the context but you should know all about the principles on which the question is based.

Synopsis is about•relating the principles to new contexts

Synopsis

• Brush-tail possums are mammals that are native to Australia.

• They were introduced to New Zealand mainly in the years 1890 to 1900.

• The total number of possums released was between 200 and 300.

• Possums are now widespread

in New Zealand and, in suitable habitats, reach population densities of up to 30 animals per hectare.

Possums

Synopsis

Location Latitude Total length/mm Tail length/mm

Auckland 36°37’ 786 321

Hawke’s Bay 39°43’ 787 322

Wairurapa 40°54’ 780 297

Orongorongo Valley 41°22’ 789 328

Nelson 41°55’ 831 356

Taramakau River 42°45’ 840 n/a

Lengths of male possums from different parts of New Zealand

Synopsis

1(a) The measurements in the table were obtained from labels attached to museum skins. It would not be reliable to measure the actual skins. Suggest why. (2 marks)The process of preparation is likely to lead to a change in length of the actual skin;

May be stretched/may shrink (as it dries);

Synopsis

1(b) Suggest why all the data were collected from animals of one sex. (2 marks)

Ensures that the data will be comparable;

Because sex is likely to influence size;

Synopsis

2 How would you expect mean annual temperature to vary with latitude? (1 mark)

Mean annual temperature should decrease with latitude;

Synopsis

3 The scientists who collected the data in the table predicted that body size would be positively correlated with latitude.

(a) Suggest why larger body size would be an advantage to a possum further south. (3 marks)

Synopsis

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Synopsis

3 The scientists who collected the data in the table predicted that body size would be positively correlated with latitude.

(a) Suggest why larger body size would be an advantage to a possum further south. (3 marks)

A larger animal would have a smaller surface-area-to-volume ratio;

Would lose less heat;

In colder conditions;

Synopsis

Evaluate means judge the worth of something.•Look for ways in which the data support the prediction.•Now write the word but•And look for ways in which the prediction is not supported by the data.

3 The scientists who collected the data in the table predicted that body size would be positively correlated with latitude.

(b) Use the data in the table to evaluate this prediction. (3 marks)

Synopsis

Location Latitude Total length/mm Tail length/mm

Auckland 36°37’ 786 321

Hawke’s Bay 39°43’ 787 322

Wairurapa 40°54’ 780 297

Orongorongo Valley 41°22’ 789 328

Nelson 41°55’ 831 356

Taramakau River 42°45’ 840 n/a

Lengths of male possums from different parts of New Zealand

Synopsis

There is a positive correlation between total length and latitude/total length increases with latitude;

(but)

If tail length is subtracted from total length;

There is little/no correlation between body length and latitude;

Other factors/factors such as altitude may also affect mean temperature; 3 max

3 (b) Use the data in the table to evaluate this prediction. (3 marks)

Synopsis

You may know nothing about peregrines or sparrowhawks…but the question is asking you about ‘how science works’ and food chains and food webs

You may not be familiar with the context but you should know all about the principles on which the question is based.

Synopsis is about•relating the principles to new contexts

Eggs and pesticides

Synopsis

Egg shell thickness

index

1900 1920 1940 1960 1980Date

 

2.0  

1.6  1.2  0.8

Peregrine

Sparrowhawk

1 2 3

Synopsis

The eggs are museum specimens/valuable/cannot be replaced;

The index does not involve breaking them/measuring the thickness involves breaking them;

1 The egg shell thickness index was calculated from the formula: 

thickness index = mass of egg shell (mg) length × breadth of egg (mm)  (a) Suggest why this index was used rather than measuring the actual thickness of the egg shell. (2 marks)

Synopsis

1 The egg shell thickness index was calculated from the formula: 

thickness index = mass of egg shell (mg) length × breadth of egg (mm)

 (b) The mass of the egg shell was divided by its length × breadth. Explain why it was necessary to divide by the length × breadth. (1 mark)

The mass of the egg shell will depend on the size of the egg/length × breadth gives a measure of the egg size;

Synopsis

2 Both the peregrine and the sparrowhawk feed on birds. Use your knowledge of food chains and food webs to explain:

(a) how organochlorine insecticides used to treat seeds enter the tissues of a sparrowhawk (1 mark)

(b) why the concentration of organochlorine insecticide in the tissues of a peregrine falcon is much higher than the concentration on the seeds (2 marks)

Synopsis

The food chains involved in this question

Seeds Wood pigeon Peregrine falcon

Seeds Chaffinch Sparrowhawk

Synopsis

(Transfer through the food chain) via an intermediate seed-eating bird/appropriate example;

2 Both the peregrine and the sparrowhawk feed on birds. Use your knowledge of food chains and food webs to explain:

(a) how organochlorine insecticides used to treat seeds enter the tissues of a sparrowhawk (1 mark)

Synopsis

Insecticide taken up by primary consumer/example from part (a) and accumulates/not broken down in tissues;

Primary consumer eats many seeds so higher concentration in its tissues;

Process repeated in secondary consumer; max 2

2 Both the peregrine and the sparrowhawk feed on birds. Use your knowledge of food chains and food webs to explain:

(b) why the concentration of organochlorine insecticide in the tissues of a peregrine falcon is much higher than the concentration on the seeds (2 marks)

Synopsis

3 In a scientific paper published in 1977, the biologist R. K. Murton pointed out that many biologists assumed egg shell thinning was harmful. They considered that if a population lays eggs with thin shells and at the same time is declining, there must be a causal relationship.

(a) Suggest how egg shell thinning may lead to lower breeding success. (1 mark)

Eggs with thinner shells are more likely to be broken (during incubation).

Synopsis

(b) Explain why a decline in number of birds may not necessarily be caused by egg shell thinning. (2 marks)

Another factor may be involved;

Which might be linked to both decline in birds and egg-shell thinning;

Synopsis

You may know nothing about tigers…but the question is asking you about selection, mitochondria and DNA.

You may not be familiar with the context but you should know all about the principles on which the question is based.

Synopsis is about•relating the principles to new contexts

Tigers

Synopsis

1 Preservation of genetic variability in rare or endangered species may help them to survive. Use your knowledge of natural selection to explain why. (2 marks)

Some forms may be at an advantage/be better adapted;

If there is a change in the environment of the organism;

Synopsis

2 In order to assess tiger genetic variation, it was important that samples were taken from tigers that originally came from different geographical areas.

Explain why it was important that these tigers did not come from the same geographical area. (2 marks)

If they came from the same area they would be more likely to be genetically similar;

Because they might be related/might be adapted to similar conditions/might have had the same ancestors;We need to know about all tigers; max 2

Synopsis

3 The mutation rate in mtDNA is faster than that in nuclear DNA because of differences in the DNA repair systems. Suggest how these differences could result in a slower mutation rate in nuclear DNA. (2 marks)

Mutations in nuclear DNA may be removed/repaired (by the repair system);

System only found in nucleus/not found in mitochondria;

Synopsis

4 If a tiger was born in a zoo, it may be useful to know the origin of the female parent if its mtDNA is to be studied. Explain why. (2 marks)

Synopsis

Male gamete

Zygote

Female gamete

Chromosomes and cytoplasm

Chromosomes

Synopsis

This will tell you the geographical origin of its mtDNA;

Because it is inherited from its mother;

4 If a tiger was born in a zoo, it may be useful to know the origin of the female parent if its mtDNA is to be studied. Explain why. (2 marks)

Synopsis

5 Suppose there were five sites on an mtDNA molecule where it could be cut by the restriction enzyme. How many pieces of DNA would result? Explain your answer. (2 marks)

Five;

Because mtDNA is circular;

Synopsis

6 A polymorphic site is a site on a DNA molecule where the sequence of bases is different in different animals.

(a) A particular restriction enzyme may cut the DNA from one leopard but not from another at a particular site. Explain why. (3 marks)

Sequence of bases is different;

Only a specific sequence fits/binds;

With active site of a particular enzyme;

Synopsis

50

40

30

20  10

0 

 

 

(b) Explain how the graph supports the suggestion that the tigers that are alive today have descended from very few animals. (3 marks)

Synopsis

50

40

30

20  10

0 

 

 

(b) Alleles/different forms of gene may be lost from population as it gets smaller;

Tigers descended from this population will have little genetic diversity;

Graph shows no polymorphic sites;

10 000 years is a short time so few mutations producing differences in DNA; max 3