Where Exams Make Sense
Premium academic resources for international exam students
www.examslogic.com
Ordinary Level Revision Notes
Leaving Cert Ordinary Level Biology
Chapter 2: Characteristics of Life
Study Leaving Cert Ordinary Level Biology Characteristics of Life with ExamsLogic revision notes, diagrams, summaries, and exam-focused practice.
Subtopics Covered
- Chapter Overview
- Learning Outcomes
- Concept of Life
- Continuity of Life
- The Five Characteristics of Life
- Organisation
What This Pack Includes
- Structured chapter notes formatted for ExamsLogic website reading
- Exam-focused diagrams, definitions, and worked examples
- Interactive practice sections carried over from the source notes
- Independent study guidance based on the official curriculum
- Print-friendly layout for future PDF export when needed
This publication is an independent educational resource developed by ExamsLogic and compiled by experienced educators. It is based on publicly available official curricula, including Cambridge, Pearson Edexcel, IB, and the Irish Leaving Certificate. This product is not endorsed by, affiliated with, or sponsored by any examination board or governing authority. All registered trademarks remain the property of their respective owners.
1. Chapter Overview
This chapter explains how biologists decide whether something is living. Living organisms share key characteristics such as organisation, nutrition, excretion, response and reproduction. These life processes allow organisms to survive, grow and continue life from one generation to the next.
ExamsLogic Big Idea: A living organism is not defined by one feature only. It is recognised by a combination of life processes working together.
2. Learning Outcomes
- I can define metabolism.
- I can explain the continuity of life.
- I can identify the five characteristics of living organisms.
- I can explain organisation, nutrition, excretion, response and reproduction.
- I can distinguish between sexual and asexual reproduction.
- I can distinguish between excretion and egestion.
- I can apply the characteristics of life to unfamiliar examples.
3. Concept of Life
Living organisms carry out life processes. These processes allow organisms to obtain materials, release energy, remove waste, respond to changes and produce offspring.
Metabolism
Metabolism is the sum of all chemical reactions occurring in an organism.
| Type of metabolic reaction | Meaning | Example |
|---|---|---|
| Anabolism | Building larger molecules from smaller molecules. | Making proteins from amino acids. |
| Catabolism | Breaking larger molecules into smaller molecules. | Breaking glucose down during respiration. |
Examiner Tip: Do not define metabolism as “digestion” only. Metabolism means all chemical reactions in an organism.
4. Continuity of Life
Continuity of life means that life continues from one generation to the next. This happens through reproduction, where organisms produce offspring and pass on genetic information.
Best OL wording: Continuity of life is the continuation of life from generation to generation through reproduction.
| Why continuity of life is important | Explanation |
|---|---|
| Species survival | Reproduction prevents a species from dying out. |
| Inheritance | Genetic information is passed from parents to offspring. |
| Variation | Sexual reproduction can produce variation among offspring. |
5. The Five Characteristics of Life
| Characteristic | Meaning | Example |
|---|---|---|
| Organisation | Living things are made of cells and have organised structures. | Cells form tissues, organs and systems. |
| Nutrition | Obtaining or making food for energy, growth and repair. | Plants photosynthesise; animals eat food. |
| Excretion | Removal of metabolic waste products. | Carbon dioxide, urea and excess water are removed. |
| Response / Sensitivity | Detecting and responding to stimuli. | Plants grow towards light; humans pull away from heat. |
| Reproduction | Production of offspring. | Humans reproduce sexually; bacteria reproduce asexually. |
6. Organisation
All living organisms are made of cells. Some organisms are unicellular, meaning they consist of one cell. Others are multicellular and have cells organised into tissues, organs and organ systems.
| Level | Meaning | Example |
|---|---|---|
| Cell | Basic unit of life. | Muscle cell. |
| Tissue | Group of similar cells working together. | Muscle tissue. |
| Organ | Different tissues working together. | Heart. |
| Organ system | Organs working together. | Circulatory system. |
| Organism | A complete living individual. | Human, plant, bacterium. |
7. Nutrition
Nutrition is the way organisms obtain or make food for energy, growth and repair.
| Type of nutrition | Meaning | Example |
|---|---|---|
| Autotrophic nutrition | Organism makes its own food. | Green plants make glucose by photosynthesis. |
| Heterotrophic nutrition | Organism obtains food by consuming other organisms or organic matter. | Animals eat plants or other animals. |
Examiner Tip: If asked about plant nutrition, mention photosynthesis and glucose production.
8. Excretion
Excretion is the removal of metabolic waste products from the body.
| Waste product | Where it comes from | How it is removed |
|---|---|---|
| Carbon dioxide | Respiration. | Exhaled by lungs in humans. |
| Urea | Breakdown of excess amino acids. | Removed in urine by kidneys. |
| Excess water and salts | Body regulation. | Urine and sweat. |
Examiner Trap: Faeces are not classed as excretory waste because they are mainly undigested food, not metabolic waste.
| Term | Meaning |
|---|---|
| Excretion | Removal of metabolic waste. |
| Egestion | Removal of undigested food from the digestive system. |
9. Response / Sensitivity
Response or sensitivity is the ability of an organism to detect and respond to stimuli in its environment.
| Stimulus | Response |
|---|---|
| Heat | Human pulls hand away from hot object. |
| Light | Plant shoot grows towards light. |
| Gravity | Plant roots grow downwards. |
| Touch | Some plants close leaves when touched. |
Student Common Mistake:
❌ Plants do not respond because they do not move around.
✅ Plants respond to stimuli such as light, gravity and touch.
❌ Plants do not respond because they do not move around.
✅ Plants respond to stimuli such as light, gravity and touch.
10. Reproduction
Reproduction is the production of new individuals of the same species. It ensures the continuity of life.
| Feature | Sexual Reproduction | Asexual Reproduction |
|---|---|---|
| Number of parents | Usually two. | One. |
| Gametes involved? | Yes. | No. |
| Genetic variation | Produces variation. | Offspring are genetically identical to parent. |
| Speed | Usually slower. | Usually faster. |
| Examples | Humans, flowering plants. | Bacteria, yeast budding, runners in plants. |
Examiner Tip: The key advantage of sexual reproduction is variation. The key advantage of asexual reproduction is rapid reproduction.
11. Common Student Mistakes
- Defining metabolism as digestion only.
- Forgetting that metabolism includes all chemical reactions in the organism.
- Confusing excretion with egestion.
- Saying faeces are metabolic waste.
- Thinking plants do not respond to stimuli.
- Forgetting that asexual reproduction produces genetically identical offspring.
- Writing “movement” as the only proof of life.
- Not linking reproduction to continuity of life.
12. Examiner Traps
Trap 1: Metabolism is not only digestion; it is all chemical reactions in the organism.
Trap 2: Excretion removes metabolic waste; egestion removes undigested food.
Trap 3: Plants respond to stimuli even though they do not move from place to place.
Trap 4: Asexual reproduction does not involve gametes.
Trap 5: Sexual reproduction usually creates genetic variation.
13. Examiner Secrets
Secret 1: Use the phrase “metabolic waste” when defining excretion.
Secret 2: Link reproduction to continuity of life.
Secret 3: In reproduction comparisons, mention gametes and variation.
Secret 4: Organisation always links back to cells.
14. Section A: Multiple Choice Practice
- Which term means the sum of all chemical reactions in an organism?
A. Nutrition B. Metabolism C. Excretion D. Reproduction - Which process removes metabolic waste?
A. Egestion B. Nutrition C. Excretion D. Growth - Which structure is the basic unit of life?
A. Tissue B. Organ C. Cell D. Organ system - Which type of reproduction produces genetically identical offspring?
A. Sexual B. Asexual C. Fertilisation D. Pollination - Which is an example of response in plants?
A. Respiration B. Photosynthesis C. Shoot growing towards light D. Seed production only
15. Section B: Structured Practice Questions
- Define metabolism. [2 marks]
- Explain the term continuity of life. [3 marks]
- Name five characteristics of life. [5 marks]
- Distinguish between excretion and egestion. [4 marks]
- Give two examples of response in living organisms. [4 marks]
- Compare sexual and asexual reproduction. [6 marks]
- Explain why organisation is a characteristic of living organisms. [3 marks]
16. Mark Scheme Answers
Section A:
1. B 2. C 3. C 4. B 5. C
Section B:
Q1. Sum of all chemical reactions [1] occurring in an organism/cell [1].
Q2. Life continues from one generation to next [1]; through reproduction [1]; genetic information/species survival maintained [1].
Q3. Organisation, nutrition, excretion, response/sensitivity, reproduction [5].
Q4. Excretion removes metabolic waste [2]; egestion removes undigested food/faeces [2].
Q5. Any two valid examples with stimulus and response: plant shoot grows towards light, roots grow downwards, human pulls hand from heat, animal moves away from predator [4].
Q6. Sexual: usually two parents/gametes/variation/slower [any 3]; asexual: one parent/no gametes/identical offspring/faster [any 3].
Q7. Living organisms are made of cells [1]; cells may form tissues/organs/systems [1]; these structures work together in the organism [1].
1. B 2. C 3. C 4. B 5. C
Section B:
Q1. Sum of all chemical reactions [1] occurring in an organism/cell [1].
Q2. Life continues from one generation to next [1]; through reproduction [1]; genetic information/species survival maintained [1].
Q3. Organisation, nutrition, excretion, response/sensitivity, reproduction [5].
Q4. Excretion removes metabolic waste [2]; egestion removes undigested food/faeces [2].
Q5. Any two valid examples with stimulus and response: plant shoot grows towards light, roots grow downwards, human pulls hand from heat, animal moves away from predator [4].
Q6. Sexual: usually two parents/gametes/variation/slower [any 3]; asexual: one parent/no gametes/identical offspring/faster [any 3].
Q7. Living organisms are made of cells [1]; cells may form tissues/organs/systems [1]; these structures work together in the organism [1].
17. Quick Revision Card
- Metabolism: Sum of all chemical reactions in an organism.
- Continuity of life: Life continues through reproduction.
- Characteristics of life: Organisation, nutrition, excretion, response, reproduction.
- Organisation: Cells → tissues → organs → systems → organism.
- Nutrition: Getting or making food for energy, growth and repair.
- Excretion: Removal of metabolic waste.
- Response: Reaction to a stimulus.
- Sexual reproduction: Gametes and variation.
- Asexual reproduction: One parent and identical offspring.
18. Interactive Simulator: Is It a Life Process?
Choose the Characteristic
Scenario: A plant shoot bends towards light.
Examiner Feedback
Ready
Choose the characteristic shown in the scenario.
Score: 0/0
19. Mastery Checklist
- I can define metabolism.
- I can explain continuity of life.
- I can identify the five characteristics of life.
- I can explain organisation, nutrition, excretion, response and reproduction.
- I can distinguish between excretion and egestion.
- I can compare sexual and asexual reproduction.
- I can apply the characteristics of life to unfamiliar examples.
- I can answer Ordinary Level exam questions on characteristics of life.