CIE iGCSE Biology-1.3 Features of organisms- Study Notes- New Syllabus
CIE iGCSE Biology-1.3 Features of organisms- Study Notes – New syllabus
CIE iGCSE Biology-1.3 Features of organisms- Study Notes -CIE iGCSE Biology – per latest Syllabus.
Key Concepts:
Core
- State the main features used to place animals and plants into the appropriate kingdoms
- State the main features used to place organisms into groups within the animal kingdom, limited to: (a) the main groups of vertebrates: mammals, birds, reptiles, amphibians, fish (b) the main groups of arthropods: myriapods, insects, arachnids, crustaceans
- Classify organisms using the features identified in 1.3.1 and 1.3.2
Supplement
- State the main features used to place all organisms into one of the five kingdoms: animal, plant, fungus, prokaryote, protoctist
- State the main features used to place organisms into groups within the plant kingdom, limited to ferns and flowering plants (dicotyledons and monocotyledons)
- Classify organisms using the features identified in 1.3.4 and 1.3.5
- State the features of viruses, limited to a protein coat and genetic material
Features Used to Classify Plants and Animals into Kingdoms
Living organisms are classified into kingdoms based on shared structural and functional features, including cell structure, nutrition, reproduction, and movement. At this level, we focus on two key kingdoms: Plantae and Animalia.
🧬 What Is a Kingdom?
A kingdom is one of the broadest taxonomic ranks. It groups organisms that share fundamental body structures and life functions.
🧪 Main Features Used for Classification
| Feature | Plants (Kingdom Plantae) | Animals (Kingdom Animalia) |
|---|---|---|
| Cell type | Eukaryotic (nucleus present) | Eukaryotic |
| Cell wall | Present (cellulose) | Absent |
| Chloroplasts | Present (photosynthesis) | Absent |
| Nutrition | Autotrophic | Heterotrophic |
| Movement | Generally non-motile | Can move actively |
| Nervous system | Absent | Present (in most) |
| Reproduction | Asexual & Sexual | Mostly Sexual |
| Growth pattern | Unlimited (meristems) | Definite growth |
| Multicellular | Yes | Yes |
🧠 Summary of Kingdom Characteristics
🌿 Kingdom Plantae:
- Have chloroplasts for photosynthesis
- Cell walls made of cellulose
- Stationary (do not move)
- Includes trees, grasses, mosses, ferns, flowering plants
🐾 Kingdom Animalia:
- No chloroplasts or photosynthesis
- No cell walls
- Can move freely (most have muscles)
- Complex systems (nervous, circulatory, digestive)
- Includes mammals, birds, insects, amphibians, fish
🔁 How Are These Features Used?
- Scientists examine structural and cellular characteristics
- Organisms with shared features are grouped in the same kingdom
- This system helps in evolutionary study, ecology, and biodiversity tracking
Final Recap
Scientists classify plants and animals into kingdoms by observing how their bodies function, how they gain energy, and what their cells are made of. This helps us organize and understand Earth’s living diversity.
Grouping Organisms Within the Animal Kingdom
Features used to classify animals into major sub-groups
Core Idea:
Organisms in the animal kingdom are classified into groups based on shared body features, including:
Presence of a backbone (vertebrates)
Type of limbs, number of legs, body covering, and breathing system
🐾 (a) Main Groups of Vertebrates
Animals with a backbone
| Group | Body Covering | Temperature Control | Breathing | Reproduction | Unique Feature |
|---|---|---|---|---|---|
| Mammals | Hair or fur | Warm-blooded | Lungs | Give birth to live young + feed milk | Have mammary glands (milk) |
| Birds | Feathers | Warm-blooded | Lungs | Lay eggs with hard shells | Have beaks and wings |
| Reptiles | Dry, scaly skin | Cold-blooded | Lungs | Lay leathery eggs | Mostly live on land |
| Amphibians | Moist, smooth skin | Cold-blooded | Gills (young), Lungs + skin (adult) | Lay jelly-like eggs in water | Live in water and on land |
| Fish | Scales and fins | Cold-blooded | Gills | Lay eggs in water | Live entirely in water |
🔎 Summary: Vertebrates
| Vertebrate Group | Example | Body Covering | Temp Control | Reproduction |
|---|---|---|---|---|
| Mammals | Dog, Human | Fur or hair | Warm-blooded | Live young, milk |
| Birds | Eagle, Sparrow | Feathers | Warm-blooded | Hard-shelled eggs |
| Reptiles | Snake, Lizard | Scales | Cold-blooded | Leathery eggs |
| Amphibians | Frog, Toad | Moist skin | Cold-blooded | Eggs in water |
| Fish | Salmon, Shark | Scales & fins | Cold-blooded | Eggs in water |
🐜 (b) Main Groups of Arthropods
Animals with jointed legs and exoskeletons (no backbone)
Common Features of All Arthropods:
Segmented body
Jointed limbs
Exoskeleton (hard outer covering)
Bilateral symmetry
| Group | Legs | Body Segments | Antennae | Examples | Unique Feature |
|---|---|---|---|---|---|
| Myriapods | Many (10+ pairs) | Head + many similar segments | Yes | Centipede, millipede | Long bodies, many legs |
| Insects | 3 pairs (6 legs) | Head, thorax, abdomen | Yes | Ant, butterfly, bee | Usually have wings; 1 or 2 pairs |
| Arachnids | 4 pairs (8 legs) | Cephalothorax + abdomen | No | Spider, scorpion | No antennae; many spin silk |
| Crustaceans | 5+ pairs | Cephalothorax + abdomen | 2 pairs | Crab, shrimp, lobster | Live mostly in water; hard shells |
🧠 Comparison Chart: Arthropods
| Group | Legs | Antennae | Wings? | Habitat |
|---|---|---|---|---|
| Myriapods | Many | Yes | No | Land |
| Insects | 6 | Yes | Often | Land & air |
| Arachnids | 8 | No | No | Land |
| Crustaceans | 10+ | Yes (2) | No | Mostly water |
Note:
- Fish → Gills, Birds → Feathers, Mammals → Hair + milk
- Cold-blooded = body temp changes with surroundings
- Warm-blooded = can maintain constant body temperature
Final Recap:
Classification inside the animal kingdom is based on features like backbones, limbs, body parts, and how organisms reproduce or breathe.
This helps scientists understand how animals are grouped and how they’ve evolved.
Classifying Organisms Using Key Features
(Based on sections 1.3.1 and 1.3.2)
📘 Core Idea:
Organisms are classified into groups based on observable features – like body covering, breathing system, limbs, and other characteristics.
We use these features to identify and place organisms into the right:
– Kingdom
– Vertebrate group
– Arthropod group
🧠 Based on 1.3.1:
Placing into Plant or Animal Kingdom
| Feature | Plant | Animal |
|---|---|---|
| Cell wall | Present (cellulose) | Absent |
| Chloroplast | Present (photosynthesis) | Absent |
| Nutrition type | Autotrophic | Heterotrophic |
| Movement | Stationary | Usually mobile |
| Nervous system | No | Yes (in most animals) |
🐾 Based on 1.3.2 (a):
Classifying Vertebrates
| Feature | Mammal | Bird | Reptile | Amphibian | Fish |
|---|---|---|---|---|---|
| Skin covering | Hair/fur | Feathers | Scales | Moist skin | Scales |
| Reproduction | Live young | Hard eggs | Leathery eggs | Jelly eggs in water | Soft eggs in water |
| Respiration | Lungs | Lungs | Lungs | Gills (young), Lungs (adult) | Gills |
| Warm/Cold blooded | Warm | Warm | Cold | Cold | Cold |
| Habitat | Land | Air/Land | Land | Land + Water | Water |
🐜 Based on 1.3.2 (b):
Classifying Arthropods
| Feature | Insect | Arachnid | Crustacean | Myriapod |
|---|---|---|---|---|
| No. of legs | 6 | 8 | 10+ | Many (10+ pairs) |
| Antennae | Yes (1) | No | Yes (2) | Yes |
| Body segments | Head, thorax, abdomen | 2 parts | Cephalothorax + abdomen | Head + many segments |
| Wings | Often | No | No | No |
| Habitat | Mostly land | Land | Water | Land |
🌱 How to Classify: Step-by-Step
- Look at major features
- Does it have a backbone?
- How many legs?
- What’s the skin covering?
- What body parts can you observe?
- Decide on the Kingdom
- Is it a plant or an animal?
- If Animal: Vertebrate or Invertebrate?
- Has a backbone → Vertebrate
- No backbone, jointed legs → Arthropod
- Use charts to identify the exact group
🔍 Example 1: Classify an unknown animal
- Features: Has feathers, lays eggs, flies
- Feathers → Bird
- Lays hard-shelled eggs → Bird
- Classified as: Bird (Vertebrate)
🔍 Example 2:
- Features: Has 6 legs, 2 wings, antennae
- 6 legs → Arthropod
- Has wings + antennae → Insect
- Classified as: Insect (Arthropod)
The Five Kingdoms of Living Organisms
Core Idea:
All living organisms can be grouped into five kingdoms based on their cell structure, nutrition, and body organisation.
These kingdoms are:
- Animalia (Animals)
- Plantae (Plants)
- Fungi
- Prokaryotae (Bacteria)
Protoctista (Protists)
🧪 Main Features Used for Classification:
| Feature | Helps Determine… |
|---|---|
| Cell type | Prokaryotic or eukaryotic |
| Number of cells | Unicellular or multicellular |
| Cell wall | Present or absent; made of what? |
| Nutrition method | Autotrophic (makes own food) or heterotrophic |
| Mode of reproduction | Asexual, sexual, or both |
| Movement | Mobile or stationary |
🌿 The Five Kingdoms: Features Summary
| Kingdom | Cell Type | Cell Wall? | Nutrition | No. of Cells | Examples |
|---|---|---|---|---|---|
| Animalia | Eukaryotic | No | Heterotrophic | Multicellular | Humans, birds, insects |
| Plantae | Eukaryotic | Yes (cellulose) | Autotrophic (photosynthesis) | Multicellular | Trees, mosses, grasses |
| Fungi | Eukaryotic | Yes (chitin) | Heterotrophic (saprophytic) | Mostly multicellular | Mushrooms, yeast, moulds |
| Prokaryotae | Prokaryotic | Yes (not cellulose) | Some autotrophic, mostly heterotrophic | Unicellular | Bacteria, cyanobacteria |
| Protoctista | Eukaryotic | Some have walls | Mixed (auto + hetero) | Mostly unicellular | Amoeba, algae, paramecium |
🧠 Key Terms Explained:
- Eukaryotic: Cells with a nucleus and organelles
- Prokaryotic: Cells without a nucleus (simpler structure)
- Autotrophic: Makes its own food (e.g. plants)
- Heterotrophic: Gets food by consuming others (e.g. animals, fungi)
Classifying Plants: Ferns and Flowering Plants
Key Idea:
Within the plant kingdom, organisms are classified based on reproductive structures, leaf patterns, and seed characteristics.
This topic focuses on two major groups:
Ferns
Flowering plants, further divided into:
• Monocotyledons (monocots)
• Dicotyledons (dicots)
🌱 1. Ferns
| Feature | Ferns |
|---|---|
| Vascular tissue | Present (xylem & phloem) |
| Reproduction method | Produce spores (no flowers or seeds) |
| Leaves | Large, divided leaves called fronds |
| Habitat | Moist, shaded areas (spores need water) |
| Roots | True roots present |
| Example | Bracken, Maidenhair fern |
Note: Ferns reproduce using spores, not seeds – this is a major difference from flowering plants.
🌸 2. Flowering Plants (Angiosperms)
Divided into two key groups:
🌾 A. Monocotyledons (Monocots)
| Feature | Description |
|---|---|
| Number of seed leaves | One cotyledon |
| Leaf venation | Parallel veins |
| Flower parts | In multiples of 3 (e.g., 3, 6 petals) |
| Root type | Fibrous roots (no main taproot) |
| Stem structure | Vascular bundles scattered |
| Examples | Grass, maize, lilies, orchids |
🌿 B. Dicotyledons (Dicots)
| Feature | Description |
|---|---|
| Number of seed leaves | Two cotyledons |
| Leaf venation | Net-like (branched) veins |
| Flower parts | In multiples of 4 or 5 (e.g., 4, 5, 10 petals) |
| Root type | Taproot system (main central root) |
| Stem structure | Vascular bundles in a ring |
| Examples | Beans, sunflower, rose, pea |
🔁 Comparison Table:
| Feature | Ferns | Monocots | Dicots |
|---|---|---|---|
| Reproduction | Spores | Flowers & seeds | Flowers & seeds |
| Seed leaves (cotyledons) | None | One | Two |
| Leaf veins | Divided fronds | Parallel | Net-like |
| Roots | True roots | Fibrous | Taproot |
| Flower parts | No flowers | Multiples of 3 | Multiples of 4/5 |
Final Recap:
Inside the plant kingdom, ferns are spore-producing non-flowering plants, while flowering plants make seeds and are split into monocots and dicots based on seed leaves, veins, and flower parts.
Classifying Organisms Using Key Features
(Based on sections 1.3.1 and 1.3.2)
📘 Core Objective:
Classify organisms within the plant kingdom using key features such as:
- Reproductive method (spores or seeds)
- Seed structure (cotyledon count)
- Leaf venation
- Root type
- Flower structure
This applies specifically to:
- Ferns
- Monocotyledons
- Dicotyledons
🧪 How to Classify Step-by-Step:
Step 1: Reproduction Method
If it produces spores → Ferns
If it produces seeds in flowers → Go to Step 2
Step 2: Number of Seed Leaves (Cotyledons)
One cotyledon → Monocot
Two cotyledons → Dicot
Step 3: Leaf Venation
Parallel veins → Monocot
Net-like/branched veins → Dicot
Step 4: Flower Parts
In 3s or multiples of 3 → Monocot
In 4s or 5s or multiples → Dicot
Step 5: Root Type (if visible)
Fibrous root system → Monocot
Main taproot → Dicot
Example Classifications:
Example 1:
Features: Reproduces using spores, has large fronds
Classification: Fern
Example 2:
Features: One seed leaf, long narrow leaves with parallel veins, flower with 3 petals
Classification: Monocot
Example 3:
Features: Two seed leaves, net-like leaf veins, flower with 5 petals
Classification: Dicot
Features of Viruses
📘 What Is a Virus?
A virus is a tiny infectious particle that is not made of cells.
It is considered non-living because it cannot grow, move, respire, or reproduce without entering a host cell.
🧬 Two Main Features of a Virus:
1️⃣ Genetic Material (DNA or RNA)
- Found inside the virus, in the center.
- Can be either DNA or RNA, never both.
- Carries the instructions (genes) to make new copies of the virus.
- This material is inactive outside a host – but once inside, it takes over the host cell’s machinery.
Types of viruses:
- DNA viruses – e.g., Herpes virus
- RNA viruses – e.g., Influenza virus, HIV
2️⃣ Protein Coat (Capsid)
- Surrounds and protects the genetic material.
- Made up of protein subunits called capsomeres.
- Helps the virus attach to specific receptors on the surface of a host cell – like a key fitting into a lock.
- Different viruses have different shapes of capsids: helical, icosahedral, or complex.
Optional Structures in Some Viruses (Not Required but Helpful):
| Structure | Present in Some Viruses | Purpose |
|---|---|---|
| Lipid Envelope | Yes (e.g., HIV, flu) | Extra outer layer from host cell membrane. Helps the virus merge with host cells. |
| Spikes (Glycoproteins) | Yes | Help viruses recognize and enter host cells. |
🔁 How Viruses Work (Basic Idea):
Virus attaches to a host cell using proteins on its coat.
It injects or enters its genetic material.
The host cell is reprogrammed to make new viruses.
New viruses burst out, killing the cell and spreading.
Summary Table:
| Feature | Description |
|---|---|
| Genetic Material | Either DNA or RNA, holds the virus’s instructions. |
| Protein Coat | Protective shell around the genetic material, helps attach to host cells. |
📌Note:
- Viruses are not classified in any kingdom – they are acellular (not made of cells).
- They can only reproduce inside living cells, which is why they’re called obligate parasites.
- Examples of viruses: HIV, Influenza, Measles, COVID-19 (Coronavirus)