IGCSE Biology Revision Notes


1.The syllabus for IGCSE Biology has many important changes for examinations for 2023/3024 and 2025.

2. Here are the latest revised notes for  Biology 2023 to 2025 examinations

CHAPTER 1: Characteristics and classification of living organisms:


Following are the seven characteristics of living organisms:

1.Movement: It is an action by an organism or part of an organism causing a change of position or place.

2.Respiration: The chemical reactions in the cells that break down nutrient molecules and release energy for metabolism are called as respiration

3.Sensitivity: It is the ability to detect and respond to changes in the internal or external environment.

4.Growth: It is the permanent increase in size  and  dry mass

5. Reproduction: Processes that makes more of the same kind of organism.

6. Excretion: It is the removal of the waste products of metabolism and substances in excess of  requirements.

7. Nutrition: It is the taking in of materials for energy, growth and development.



  1. The above are the exact wordings of definitions for the  curriculum for 2023 to 2025 examinations given in the syllabus by CAIE.
  2. The Now there are no separate definitions for the core and the extended curriculum. Students are advised to strictly learn and write the definitions as per this material inorder to avoid losing marks in their respective exams.

Skin, kidneys and lungs are the three major organs of excretion in humans:

1. Sweat glands in the skin produce sweat. This contains water, urea and salt. Excreting sweat helps keep the body cool in hot conditions.

2. The kidneys remove excess water, salts and urea to prevent a toxic build-up of these substances in the body.

3. The lungs remove excess carbon dioxide (and some water) when breathing out


Classification of organisms

1. Organisms can be classified into groups by the features they share.

2.  Classification system aims to reflect evolutionary relationships.

3. Sequence of bases in DNA are used as a means of classification.

4.Group of organisms that share a more recent ancestor (are more closely related) have base sequences in DNA that are more similar than those that share only a distant ancestor.


Key definitions:

1.Binomial system of naming species: It is an internationally agreed system in which the scientific name of an organism is made up of two parts showing the genus and the species.

2. Species: It is a group of organisms that can reproduce to produce a fertile offspring..

3.Ingestion:  It means to take in food from the mouth.

4.Egestion: Egestion is the discharge or expulsion of undigested material (food) from a cell in case of unicellular organisms, and from the digestive tract via the anus in case of multicellular organisms





1. The entire two-part name must be written in italics (or underlined when handwritten). •

2. The generic name (genus ) is always written first. •

3. The genus name must be capitalized. •

4. The specific epithet ( species name ) is never capitalized. Examples: Common name Scientific ( Generic ) name Modern humans Arabian camel African elephant Albatross Alpaca Asian Elephant Blackbuck Homo sapiens Camelus dromedarius Loxodonta africana Diomedeidae Lama pacos Elephas maximus Antelope cervicapra

Note: All scientific names have been derived from Latin


IGCSE Biology-Revision notes/Study notes/Notes-The following  pdf notes are for the 2022 syllabus for Biology

Biology Highly popular notes-with solved exam question examples designed by Cambridge expert teachers  with regular updates.

This section on biology revision notes  will be developed in a unique way. Not like the way it is normally done. Here We plan to pick random topics that we feel are  tougher  or challenging and then make them easier as much as possible.

Topic13:  Excretion:

13.1-Excretion basics

13.2-Assimilation and deamination

13.3-Functions of liver


13.6-Kidney transplant-advantages-disadvantages

13.7-Structure of kidneys-Ultrafiltration


Application Based Board Exam Questions:

This section is being developed to help you understand the correct way of answering your board exam papers. All answers are written by Cambridge trained and experienced teachers with rich experience in teaching the curriculum  .

 Now here are a few questions taken from past papers[ answers provided below] to check your understanding of the above concepts that you studied from the past papers:

  1. Define excretion [3]
  2. How is urea transported in the blood to the kidney?[1]
  3. What happens to the amino acids in the liver cells?[3]
  4. Label the parts of the kidney tubule from A to D and  state one function of each[8]glomerulus labelled diagram



  1. Excretion is the removal of the waste products of metabolism and toxic  and harmful products and also products in excess of their  requirements.
  2. Urea gets dissolved in the blood and is then transported to the kidneys 
  3. The proteins are synthesised in the liver.Excess of the amino acids are broken down [ deaminated]. During deamination, amino group is removed from ammonia and is changed to urea.Rest of the molecule is respired to provide energy. The amine group can also be transferred via transamination to make new amino acids.
  4. The parts and their functions are as follows: 
  • A-Glomerulus- Function: Filtration of blood
  • B-capsule-Function: To collect the filtrate
  • C-Tubule- Selective reabsorption of water/salts/minerals/ions
  • D-Collecting duct-reabsorbs water or passes urine to pelvis or ureter


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