Archive for the ‘G12 HL Biology’ Category

Digestion and absorption – OPTION H

Friday, April 13th, 2012

H2 – digestion.  We’ve done the basics, and because you ask good questions, we’ve gone further, so much of this you will have some idea about already.  You have the background, now we need to fill in the details.  Click here.

  • State that digestive juices are secreted into the alimentary canal by glands, including salivary glands, gastric glands in the stomach wall, the pancreas and the wall of the small intestine.
  • Explain the structural features of exocrine gland cells.
  • Compare the chemical composition of salivagastric juice and pancreatic juice.
  • Outline the control of digestive juice secretion by nerves and hormones, using the example of secretion by gastric juice.
  • Outline the role of membrane-bound enzymes on the surface of epithelial cells in the small intestine in digestion.
  • Outline the reasons for cellulose not being digested in the alimentary canal.
  • Explain why pepsin and trypsin are initially synthesized as inactive precursors and how they are subsequently activated.
  • Discuss the roles of gastric acid and Helicobacter pylori in the development of stomach ulcers and stomach cancers.
  • Explain the problem of lipid digestion in a hydrophilic medium and the role of bile in overcoming this.

B0008462 Ileum section by wellcome images on flickr

H3 – absorption of digested foods.  This is a short section, much of which we’ve covered before.  Click here. You need to be able to:-

  • Draw and label a diagram showing a transverse section of the ileum as seen under a light microscope.
  • Explain the structural features of an epithelial cell of a villus as seen in electron micrographs, including microvilli, mitochondria, pinocytotic vesicles and tight junctions.
  • Explain the mechanisms used by the ileum to absorb and transport food, including facilitated diffusion, active transport and endocytosis.
  • List the materials that are not absorbed and are egested.

Mock exam answer scheme

Sunday, April 8th, 2012

exam tactics by Sean MacEntee on flickr

Here is the mark scheme for your recently completed mock exam paper.

HL Higher Mock March 2012 – marker

H6 Gas exchange

Wednesday, March 14th, 2012

You need to get your head around this.  Gas Exchange     The effect of exercise on heart and lungs    And here’s a great presentation to help.

  • Define partial pressure.
  • Explain the oxygen dissociation curves of adult hemoglobin, fetal hemoglobin and myoglobin.
  • Describe how carbon dioxide is carried by the blood. [Include action of carbonic anhydrase, chloride shift, and plasma proteins]
  • Explain the role of the Bohr shift in the supply of oxygen to respiring tissues.
  • Explain how and why ventilation rate varies with exercise.
  • Outline the possible causes of asthma and its effects on the gas exchange system.
  • Explain the problem of gas exchange at high altitudes and the way the body acclimatizes.

H5 Transport system

Monday, March 12th, 2012

Cardiac_Cycle_Left_Ventricle from wikimedia

Take another look at your notes on blood, blood vessels and the heart from topic 6.  Re-learn your heart diagram.  There is some new vocab to get your head around in this section.  I have highlighted these terms below.  Use this presentation to help you.

Here are some useful animations for the cardiac cycle.

Phases of the cardiac cycle

The cardiac cycle

  • Explain the events of the cardiac cycle. [Talk about atrial and ventricular systole and diastole, and heart sounds]
  • Analyse data showing pressure and volume changes in the left atrium, left ventricle and aorta during the cardiac cycle.
  • Outline the mechanisms that control heartbeat. [Include role of sinoatrial (SA) node, atrioventricular (AV) node and conducting fibres in the ventricular walls]
  • Outline atherosclerosis and the causes of coronary thrombosis.
  • Discuss factors that affect the incidence of CHD (coronary heart disease).

Functions of the liver

Friday, March 9th, 2012

BIO 120 liver 010 by djneight on flickr

Here are a couple of presentations for you. Functions of the liver  and this one.  You should be able to:

  • Outline the circulation of blood through liver tissue, including the hepatic artery, hepatic portal vein, sinusoids and hepatic vein.
  • Explain the role of the liver in regulating levels of nutrients in the blood.
  • Outline the role of the liver in the storage of nutrients, including carbohydrate, iron, vitamin A and vitamin D.
  • State that the liver synthesizes plasma proteins and cholesterol.
  • State that the liver has role in detoxification.
  • Describe the process of erythrocyte and hemoglobin breakdown in the liver, including phagocytosis, digestion of globin and bile pigment formation.
  • Explain the liver damage caused by excessive alcohol consumption.

Past Paper Practice

Tuesday, March 6th, 2012

Past paper multiple choice practice: Biology HL paper 1   Answers here: Biology HL paper 1

Past paper extended response question practice: May 03 Extended Response Qs        Nov 04 Extended Response Qs

And here are the answers: MAY 2003 Paper 2 SECTION B Marker        NOV 2004 Paper 2 SECTION B Marker

Option H – Hormonal control

Friday, March 2nd, 2012

As we delve into Option H, we’ll be reviewing human biology concepts at the same time.  This first section is about hormonal control.  Hormones are chemical messengers secreted by endocrine glands into the blood and transported to specific target cells.  They can be steroids (eg progesterone, testosterone, estrogen), proteins (eg insulin, ADH, FSH, LH) and tyrosine derivatives (eg thyroxin).

You need to:-

  • Distinguish between the mode of action of steroid and protein hormones.
  • Outline the relationship between the hypothalamus and the pituitary gland.
  • Explain the control of ADH (vasopressin) secretion by negative feedback.

Another fantastic presentation here.  We’ll use this one too. Hormonal Control

E6 – Further studies of behaviour

Wednesday, February 15th, 2012

peacock by ozgurmulazimoglu on flickr

The last section on this option before we find out how much you’ve learned.  REMINDER – test on THURS 1st MARCH on all of OPTION E.

Here’s what we need to cover in this last section of Option E.

  1. Honey bees are social organisms.  Describe the organization of a bee colony – who does what.  Find one other example of such social organization and describe it. Bio E6 Q1 bee pres
  2. What is the role of natural selection in colonies like this? alessandra_bianca_gio_natural selection   How natural selection may act at the level
  3. Give 2 non-human examples of altruistic behaviour and discuss in terms of evolution. E6 altruisitc examples
  4. What is foraging?  Bluegill fish forage for Daphnia.  Find one other example, and explain how this type of behaviour optimizes food intake. Foraging   Behavior- Foraging
  5. Peacocks have pretty fancy tail feathers.  Why have they evolved this way? Explain in terms of mate selection Group 5 Alisa Yurie Pratik.  Q5 Evolution of exagerrated traits
  6. Animals show rhythmical variations in activity.  Outline 2 examples illustrating this.  Eg, seasonal reproductive behaviour in deer. G6 Dan, Anna, Ashild Biology Powerpoint

Here’s a very useful slideshare presentation on this section.

Test review – enzymes, respiration, photosynthesis

Wednesday, February 15th, 2012

Please use some time in class to go over your test papers and make corrections as necessary.  It is not just important to write down the correct answer.  It is more important to understand WHY that is the correct answer and why your response was not correct.  You may use each other for help in this.  Please visit me during tutorials with any issues or misunderstandings. enz resp photo test marker

E3 Innate and learned behaviour

Monday, February 6th, 2012

pavlov cartoon from

Can you distinguish between innate and learned behaviour?

What are some examples of behaviour in living organisms that are innate or learned?

What is taxis and what is kinesis when referring to types of behaviour?

You are then going to do a lab (yay!) where you design an experiment to investigate innate behaviour in invertebrates.  Lab sheet here: Invertebrate behaviour lab

You need to be able to analyse experimental data for these kinds of experiments in terms of the effect of this behaviour on chance of survival and reproduction (it all boils down to this – see Freud or Dawkins!).

Discuss how the process of learning can improve the chance of survival.

Outline Pavlov’s experiments into conditioning of dogs.  [Include conditioned and unconditioned stimuli and response]

Outline the role of inheritance and learning in the development of birdsong in young birds.

Here is a useful resource from Mr Taylor.