IGCSE Biology 2026 Syllabus Characteristics and Classification of Living Organisms
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teacherWhat are the seven characteristics of living organisms represented by the mnemonic MRS GREN?
Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition
What is the definition of movement in the context of living organisms?
An action by an organism or part of an organism causing a change of position or place.
What is respiration in living organisms?
The chemical reactions in cells that break down nutrient molecules and release energy for metabolism.
Define sensitivity in living organisms.
The ability to detect or sense stimuli in the internal or external environment and to make appropriate responses.
What does growth refer to in living organisms?
A permanent increase in size and dry mass.
What is reproduction in the context of living organisms?
The processes that make more of the same kind of organism.
What is excretion in living organisms?
The removal from organisms of waste products of metabolism, toxic materials, and substances in excess of requirements.
Define nutrition as it pertains to living organisms.
The taking in of materials for energy, growth, and development.
What is a species?
A group of organisms that can reproduce to produce fertile offspring.
What are the three rules of the binomial system for naming species?
1. It consists of two parts; genus name first, then species name. 2. Genus name starts with a capital letter; species name starts with a small letter. 3. The name is written in Latin.
How does modern classification reflect evolutionary relationships?
It is based on genetic material (DNA) and proteins, indicating common ancestry among organisms.
What distinguishes vertebrates from invertebrates?
Vertebrates have backbones, while invertebrates do not.
Which groups are included under vertebrates?
Fish, Amphibians, Reptiles, Birds, Mammals.
How do mammals and birds regulate their body temperature?
They can control their body temperature through various processes such as sweating or shivering.
What are the common features of arthropods?
Segmented body, jointed legs, hard external skeleton (exoskeleton), bilateral body symmetry.
What does bilateral symmetry mean in arthropods?
It means that the body can be divided into left and right halves if cut in the middle.
What type of eyes are found in many arthropods?
Compound eyes.
How are ferns classified in the plant kingdom?
Ferns are simple plants with no flowers or seeds that reproduce asexually by spores.
What are the two major groups of flowering plants?
Monocots and dicots.
How many pairs of limbs do insects typically have?
Three pairs.
What are the three body parts of insects?
Head, thorax, and abdomen.
What is the definition of a cephalothorax?
A fused head and thorax found in some arthropods.
How many pairs of antennae do myriapods have?
One pair.
What distinguishes dicotyledons from monocotyledons in terms of cotyledons?
Dicotyledons have two cotyledons, while monocotyledons have one cotyledon.
How are the vascular bundles organized in dicotyledons?
Organized in rings.
What type of roots do monocotyledons typically have?
Fibrous roots.
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Description
Boost your knowledge before diving into past papers. Use these questions to reinforce your understanding of the lessons and supercharge your revision. They'll help you recall key concepts and stay on top of your studies
Questions
Download Questions1. What is the process called where organisms remove waste products of metabolism?
2. What is the term for a permanent increase in size and dry mass in an organism?
3. Which process involves taking in materials for energy, growth, and development?
4. What do organisms that share a more recent ancestor have in common?
5. What does DNA contain instructions for?
6. Which organism is most closely related to Organism 1 based on the DNA base sequences?
7. What is the primary reason Organism 4 is considered the least related to the other organisms?
8. What does the similarity in DNA bases among all organisms suggest?
9. In the binomial system of naming species, which part of the name is written first and starts with a capital letter?
10. Why do Organisms 1, 2, and 3 share a more distant ancestor compared to Organism 4?
11. Which of the following groups of animals are capable of regulating their body temperature?
12. What type of body covering do reptiles have?
13. Which vertebrate group lays jelly-covered eggs?
14. What is a key characteristic of invertebrates?
15. Which group of animals is limited to their habitat due to their inability to adapt to different temperatures?
16. Which group of animals is known for having a streamlined body and using a tail to change direction?
17. What does the 'M' in the mnemonic MRS GREN stand for?
18. Which characteristic of living organisms involves the chemical reactions that break down nutrient molecules and release energy?
19. What is the term for the ability to detect or sense stimuli in the internal or external environment?
20. Which type of organisms are made up of many cells?
21. What is the term for the directional growth of plants towards stimuli?
22. What is the ability to detect or sense stimuli in the internal or external environment called?
23. What is the term for the processes that make more of the same kind of organism?
24. What is the binomial system of naming species based on?
25. Which characteristic of living organisms involves the removal of waste products of metabolism?
26. What does the 'R' in the mnemonic MRS GREN stand for?
27. What is the term for a group of organisms that can reproduce to produce fertile offspring?
28. Which rule is NOT part of the binomial system of naming species?
29. What is the basis of modern classification of organisms?
30. Why is DNA classification considered more accurate?
31. What are the building blocks of proteins?
Study Notes
Overview of Invertebrates and Plant Classification
Arthropods
- Diversity and Characteristics: Arthropods are a vast group of invertebrates, including insects, arachnids, crustaceans, and myriapods. They are defined by segmented bodies, jointed limbs, hard exoskeletons, and bilateral symmetry.
- Body Structure and Adaptations: The body structure varies among arthropod groups; for instance, insects have three body parts (head, thorax, abdomen), while arachnids have a fused cephalothorax and abdomen. They possess compound eyes for enhanced vision, with variations in eye types across groups.
Plant Classification
- Plant Kingdom Overview: The plant kingdom is primarily divided into two main categories: ferns and flowering plants. Flowering plants are further classified into dicots and monocots based on seed structure.
- Ferns: Ferns reproduce asexually through spores and lack vascular systems, making them simpler than flowering plants.
- Flowering Plants:
- Types: Flowering plants are categorized into dicots (two seed leaves) and monocots (one seed leaf).
- Flower Structure: Dicots typically have flowers with four or five parts, while monocots usually have three parts.
- Leaf and Root Characteristics: Dicots have wide leaves with branched veins and non-fibrous root systems, whereas monocots feature narrow leaves with parallel veins and fibrous roots.
Key Takeaways
- Arthropods are characterized by their segmented bodies, jointed limbs, and diverse adaptations that enhance their survival in various environments.
- Flowering plants are classified into dicots and monocots based on seed structure, flower parts, leaf characteristics, and root systems.
- Understanding the distinctions between ferns and flowering plants is crucial for grasping the complexity of plant diversity and reproduction methods.