Archive for the ‘G12 SL Biology’ Category

Health issues and diet

Friday, January 22nd, 2010

We are going to use click 4 biology to help us through this section.

You need to be able to:

  • Calculate the body mass index (BMI) of a person.  Know the correct units.
  • Use BMI to distinguish between being underweight, normal weight, overweight and obese.
  • Recognize the limitations in using BMI alone as an indicator of weight.
  • Outline the reasons for increasing rates of clinical obesity in some countries.  There are several.
  • Outline the consequences of anorexia nervosa.

Energy in human diets

Friday, January 15th, 2010
fine crop of rice by shop boy on flickr

fine crop of rice by shop boy on flickr

Did you know that per 100g, carbohydrates and proteins contain similar amounts of energy whereas fats contain more than double that?  Actual figures are: 1760 kJ for carbohydrates, 1720 kJ for protein and 4000 kJ for fats (per 100g).

Differences exist between various ethnic groups in terms of their main dietary source of energy.  Your task will be to research different ethnic groups that use rice, wheat, cassava, maize, fish and meat as their staple energy source, and to compare their diets.


MSG by PunkJr on flickr

MSG by PunkJr on flickr

In addition, we will consider that there are social issues relating to inappropriate diets, especially in the developed world.  There is also highly effective marketing of unhealthy foods by profit-making companies (I saw a TV ad recently espousing the benefits of MSG!).  With this in mind, you must be able to explain the possible health consequences of diets rich in carbohydrates, fats and proteins. [Consequences of an excess of each type of nutrient should be explained separately.]

What makes us stop eating?  We have an appetite control centre in the brain.  Do some research and find out how it works.

Nutritional analysis

Friday, January 15th, 2010
kids understanding food labeling by nutrition education on flickr

kids understanding food labeling by nutrition education on flickr

You have been asked to keep a food diary over the past few days.  In class we will use this database to input everything we ate or drank for a 24 hr period, and find out how healthy our daily diet is… or not!

We’ll then compare our diets to an imaginary fast food diet and see which is more nutritious.  You could also compare your week day to your weekend diet.


Vitamin D, iodine and fibre

Monday, January 11th, 2010
Tikar lady with Goitre by superdove on flickr

Tikar lady with Goitre by superdove on flickr

Three of the nutrients that we need to consume in order to maintain a healthy balanced diet are vitamins, minerals and fibre.  We’ll look at one example of a vitamin (D), one example of a mineral (iodine) and then fibre, and aim to answer the following questions:

  • What are the sources of vitamin D in human diets?
  • What are the risks of vitamin D deficiency from insufficient exposure to sunlight vs the risk of contracting malignant melanoma (skin cancer)?
  • What are the benefits of taking dietary supplements to prevent malnutrition? Use iodine as an example.
  • What is the importance of fibre as a component of a balanced diet?

To get you started, here is a short video clip dealing with vitamin D.  I’ll let you research the others yourselves 🙂

Enjoy and learn!

How much Vitamin C does fruit contain?

Thursday, January 7th, 2010
blood orange by Derek Purdy on flickr

blood orange by Derek Purdy on flickr

For this lab you are going to test a range of fruits (lemon, orange, mango, tomato) and determine their vitamin C content.  Here’s how:

Vitamin C is an antioxidant.  It changes DCPIP (a dye) from blue to colourless. 

  1. Use a pipette to add some of the vitamin C solution, drop by drop to 2cm3 of DCPIP in a test tube.
  2. Shake the tube gently after the addition of each drop.
  3. Continue until the solution is decolourised.
  4. Record the exact volume of vitamin C added.  Repeat and average results.
  5. Calculate the mass of vitamin C required to decolourise 2cm3 of DCPIP, knowing that the vitamin C solution was made to contain 1mg of vitamin C in 1.0cm3 of water.
  6. Using a similar technique, compare the vitamin C contents of several different fruits.
  7. To determine the volume of the fruit, place it in a beaker and cover with water.
  8. Mark the level of the meniscus on the outside of the beaker.
  9. Remove the fruit, make the water up to the mark with water from a measuring cylinder.  The volume of water added is equivalent to the volume of the fruit.

This comes from Practical Advanced Biology by King, Reiss and Roberts.

When you write up your lab report, include the data collected and the processing of it, though I will not award this a separate grade (as I have told you how to do it).  State your conclusions and write a detailed evaluation.  I will grade this according to the IB rubric. Conclusion and evaluation rubric

Here are a some questions for consideration:

  • Vitamin C is derived from a 6-carbon sugar.  Suggest why it is so abundant in fruits and what functions it may serve.
  • A typical adult requires about 10mg of vitamin C per day, though governments recommend between 30 and 60 mg.  To what extent can these needs be met by a single piece of fruit?
  • Can you find out what effect storing or cooking has on the vitamin C content of foods?

Due date for this is Tuesday 19th January 🙂 If you would like me to take a look at your draft then get it to me by 7.30am Monday, the day before.

Options, Options

Monday, January 4th, 2010
Guide to a healthy balanced diet by Leo Reynolds on flickr

Guide to a healthy balanced diet by Leo Reynolds on flickr

So, no we begin the last part of the course, that is the option section.  We’ll start with OPTION A – Human nutrition and health.  I think you will find this a relatively easy option, hopefully interesting, and certainly relevant.  To get started, here is a copy of the syllabus guide. Option A – syllabus outline


Sunday, November 22nd, 2009
sperm injection into egg from wikimedia commons

sperm injection into egg from wikimedia commons

We are going to try something a little different to help us learn about the process of IVF, and the ethical considerations that go along with it.  Here’s the situation:

A couple have been trying to conceive for over 3 years.  They have had 2 miscarriages. They are considering IVF as their next step. The man is really keen to go ahead with it, but his wife is skeptical.  They have an appointment with a doctor who is a specialist in the area of fertility and IVF.

What to do:

  • Get into groups of 3.
  • Each person will have their own role to play – decide who is going to be the doctor, who is going to be the woman and who is going to be the husband.
  • The doctor must become knowledgeable about the process of IVF, so that s/he can explain it to the couple and answer any questions they may have.
  • The woman must be ready to listen, but also have a well thought out list of concerns about the negative aspects of this treatment and the ethical considerations she is worried about.
  • The husband must have his arguments ready as to why he thinks the treatment would be a good next step for them, and address any of his wife’s concerns.
  • Spend about 30-40 mins researching your role.
  • Role play the interview between the doctor and the couple.
  • Reflect on the process – what difficulties did you find? Is there a “right” answer to this problem? Include your thoughts in a comment on this post.

Reproductive system

Monday, November 16th, 2009


No – it’s not a picture of a sunflower.  Look closely!

Here is what we will cover.  You will notice that it is not that extensive in terms of content.  HL students do a lot more.

  • Draw and label diagrams of adult male and female reproductive systems.
  • How do hormones control the menstrual cycle? (Link to Endocrine system)
  • Relate hormonal changes to thickening of uterine lining, ovulation and menstruation.
  • What are the roles of testosterone in males?
  • Explain the process of IVF and discuss the ethical issues associated with it.

A good presentation can be found here.  Some great videos on this unit have been produced by NOVA.  Watch in segments or all at once.

Last test of semester 1 – hooray!

Monday, November 16th, 2009
calendar card - January by Joe Lanman on flickr

calendar card - January by Joe Lanman on flickr

Our calendar is jammed, so we can’t be very flexible with dates for this test.




(Caitlin and Synnove – we will make arrangements for you to sit it during your study halls on THURSDAY 3rd due to clash with English Orals)

Topics covered will be Nervous System, Endocrine System, Reproductive System – and for HL students Muscles and Movement as well.  That is Topics 6.5 and 6.6 for SL, and Topics 6.5, 6.6 and 11.2 for HL. Come to tutorials armed with questions if you need to 🙂

How do you make a hormone?

Thursday, November 12th, 2009
Illu_endocrine_system from wikipedia commons

Illu_endocrine_system from wikipedia commons

Ask Mr. Hobbins the answer to that one!

Next up is the Endocrine System, which consists of glands that produce hormones that travel in the bloodstream to various sites of action.  We’ll look at this from the perspective of coordination and control, so will be defining the term homeostasis and looking at examples of this in the body.

Questions we’ll tackle:

  • What is the endocrine system and how does it function?
  • What is homeostasis and how does it work?
  • How is body temperature is regulated?
  • How are blood glucose levels maintained?
  • What’s the difference between type I and type II diabetes?