1.1-Characteristics of living organisms

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CORE:

Describe the characteristics of living organisms by describing:

  • (a) movement as an action by an organism or part of an organism causing a change of position or place
  • (b) respiration as the chemical reactions in cells that break down nutrient molecules and release energy for metabolism
  • (c) sensitivity as the ability to detect and respond to changes in the internal or external environment
  • (d) growth as a permanent increase in size and dry mass
  • (e) reproduction as the processes that make more of the same kind of organism
  • (f) excretion as the removal of the waste products of metabolism and substances in excess of requirements
  • (g) nutrition as the taking in of materials for energy, growth and development

Revision Notes

IGCSE Biology Revision Notes  Characteristics and classification of living organisms

 

 

 

 

 

 

Characteristics-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.

Characteristics-of-living-organisms

Note:

  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

 

 

 

BINOMIAL SYSTEM OF NAMING ORGANISMS/ RULES for SCIENTIFIC NAMES

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

 

Some IGCSE Past Paper Questions for quick reference:

O/N/2014-P12-Q1 Ans: B

 

O/N/2015-P12-Q1 Ans: D

 

O/N/2011-P12-Q6 Ans: D

O/N/201-P12-Q7C

 NOTE: While learning definitions, strictly learn the definitions given as per your exam syllabus

 

Exam Tips

Paper 2 Exam Tips:

  • Some times there are direct questions on  the characteristics of living organisms. You are asked directly to choose from the four options, A, B, C and D , as to which option identifies the characteristics of the living organisms.
  • Some questions expect you to identify the characteristics of living organisms by looking of the pictures given to you.
  • Then there are some tricky questions that ask you to identify one characteristic of living organisms that is made up of three small characteristics: referrecce : Q6 in this pdf
  • You also need to be able to identify the characteristic from its given definition

On the whole, questions based on identifying the characteristics based on the diagrams are more common

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