When students work hard and yet still score low marks in IB Biology Exams.

Wednesday 10 July 2013

I have been troubled for a number of years about those students who write a lot of correct Biology in their exams but only achieve low marks. As an IB examiner I find myself scratching around trying to match parts of these answers to the different marking points in the IB mark scheme.  What are students doing wrong and what can we, as teachers, do to help them?

These frustrating student answers will usually do one of following;

  • ·         give only part of the detail for the marking points in the mark scheme.
  • ·         give general vague ideas rather than specific details.
  • ·         give answers which are not anticipated by the chief examiners.

Here are a some examples:

Question A

Outline the characteristics of three named biomes, including temperature, moisture & vegetation. (3 marks)

Answer A1: (would achieve 0 marks)

Biome

Temperature

Moisture

Vegetation

Desert:

 

Hot and cold:

some fluctuation

 

Dry

 

Cactus

 

Tundra

 

Cold

little fluctuation

 

Wet

 

Grasses

 

Temperate Rain forest

 

Warm

little fluctuation

 

Dry

 

Evergreen

 

 

What’s wrong with this answer?

The first two Biome names are good but the descriptions of the climate are too vague. Three correct points are needed for one mark.  “Hot and Cold”, needs to explain when it’s hot, i.e. “hot in the daytime and cold at night” would be worth 1/3rd of a mark. The fact that Moisture is “Dry” in the desert is not wrong, but again needs qualifying, as it can rain in the desert. “Long dry periods” or, “very little moisture” would be better.  “Cactus” is a type of plant that grows in some desert areas, but this answer is again lacking in detail. “few plants”  or “xerophytes” would be better, “scattered cactus plants” might have been awarded credit.

This table shows details which would improve this answer to achieve 3 marks.

Biome

Temperature

Moisture

Vegetation

Desert:

 

Hot in daytime and cold at night:

some fluctuation

 

Very Dry, long periods without rain

 

Cactus, or other scattered xerophyes

 

Tundra

 

Very long Cold winters

little fluctuation

 

 Dry Very little rain / snow

 

Grasses Lichens/mosses

 

Temperate Rain forest

 

 

Warm  

little fluctuation

 

Wet throughout the year

Evergreen conifers and broadleaved trees

 

 

Question B

Distinguish between biome and biosphere. (1 mark)

Answer B1 (would achieve 0 marks)

A Biome is a certain type of climate and a Biosphere is all the climates in the world

What’s wrong with this answer?

The Biome definition is not quite a definition, although Biomes do each have “a certain type of climate”, and the Biosphere definition is also too vague.

These improvements would achieve the mark

A Biome is a geographical area with a certain type of climate and a Biosphere is all the climates biomes in the world

Question C

Discuss the evolution of altruistic behaviour in animals other than humans.  (6 marks)

Answer C1   ( This answer would achieve just 1 mark out of 6)

Altruistic behaviour is defined as the behaviour of any animals to sacrifice its own benefit for the benefit of another organism or animals.  This is seen in multiple organisms and species in our ecosystems as they interact together to maintain efficiency and to ensure the continuation of the population or community.  An example of altruistic behaviour is that of the female bees in a beehive who sacrifice their own fertility in order to ensure that the queen does not face any competition and is the only on responsible for continuation in the hive.  Evolution has evolved so that right from birth itself one bee is chosen to be queen and is fed royal jelly to ensure that she is fertile.  All other female bees are sterile and conduct other activities such as foraging for food and making honey, so that the queen can focus on reproduction.  Another example of altruistic behaviour is found in bats.  Bats forage for food at night and are therefore not always successful in finding nourishment. Thus when they return to their hives if they could not find any food other bats let the hungry bats feed on themselves in order to ensure their population’s continued survival. Thus sacrificing their flesh for another bat’s nutrition.   Altruistic behaviour has evolved over time to what we see today.

What’s wrong with this answer?

There are some correct points in the answer (the description of altruism in honey bees achieved a mark) but many are not expressed precisely enough to achieve marks.
The structure of the answer is good, starting with a definition, and then giving some examples.  Unfortunately the examples given are not precise species names. “Bats” is not specific enough when “Vampire Bats” is the altruistic bat species described. Evolution is only mentioned in passing.

These improvements in red below would achieve full marks.

Discuss the evolution of altruistic behaviour in animals other than humans.  (6 marks)

Answer C1   ( This answer would achieve 6 marks out of 6)

Altruistic behaviour is defined as the behaviour of any animals which risks harming itself to sacrifice its own benefit for the benefit of another individual organism or animals.(1st  mark)  This is seen in multiple organisms and species in our ecosystems animals with complex social structures as they interact together (2nd mark)   to maintain efficiency and to ensure the increased survival continuation of the population or community. (3rd  mark)  An example of altruistic behaviour is that of the female honey bees in a beehive who sacrifice their own fertility in order to ensure that the queen does not face any competition and is the only on responsible for continuation in the hive. Evolution has evolved so that right from birth itself one bee is chosen to be queen and is fed royal jelly to ensure that she is fertile.  All other female bees are sterile and conduct other activities such as foraging for food and making honey, so that the queen can focus on reproduction. (4th mark)    Another example of altruistic behaviour is found in vampire bats.  Bats forage for food at night and are therefore not always successful in finding nourishment. Thus when they return to their hives if they could not find any food other bats let the hungry bats feed by vomiting food (5th  mark)   on themselves in order to ensure their population’s continued survival. Thus sacrificing their flesh food for another bat’s nutrition.   Altruistic behaviour has evolved over time to what we see today by evolution working at the level of the colony. (6th  mark)

These examples illustrate the sort of answers which students often right. It seems obvious that they have learnt some Biology.  They have only made a part of the journey to a clear understanding of the biology.. What can we get these students to do, to be able to write these improved answers at the first time of trying? 

Here are a few suggestions:

  • a)      Encourage students to be precise in all their answers, spoken and written, at all times.
  • b)      Give students time to correct their answers, and those of their peers, and give credit for this work.
  • c)       While we need to explain the complexities of biological systems so that students have a good overall understanding, students also need clear notes which are simple enough to revise successfully.
  • d)      Students need to be tested and preferably to test themselves on factual parts of the IB guide.
  • e)      We should give students practice expressing their ideas in a progression of increasingly complex ways.

Tags: pedagogy, exams