1.1The Nature and Variety of Living Organisms

Characteristics of living organisms — Edexcel Modular - OL Revision Notes & Topical Questions

10 min read 19 parts Lesson 2 of 3 2 quizzes

📚 Edexcel Modular - OL Hub / Topical Revision

0%read

Lesson summary

Characteristics of living organisms Edexcel O Level Modular Biology notes: understand how living organisms share the following characteristics: - they require nutrition - they respire - they excrete their waste - they respond to their surroundings - they move - they control their…

Characteristics of living organisms Edexcel O Level Modular Biology: what to do next
Respiration
Sensitivity
Reproduction
Give / State / Name
Evaluate / Assess

Section 1 of 19Process & sequence

Living things

Show all 7 processes

Made of cells

Non-living things may show some but not all

Section 2 of 19Keep going

Characteristics of living organisms Edexcel O Level Modular Biology: what to do next

These Characteristics of living organisms Edexcel O Level Modular Biology notes covered the key ideas, worked examples and exam technique for this topic. Check your Characteristics of living organisms Edexcel O Level Modular Biology understanding with the practice questions below, then reread any Characteristics of living organisms Edexcel O Level Modular Biology point you were unsure about before moving on.

Practice: Characteristics of living organisms Edexcel O Level Modular Biology practice questions

Next lesson: 1.2 Variety of living organisms — Notes

Course: Edexcel Modular - OL — all units

Official syllabus: Pearson Edexcel International GCSEs

Section 3 of 19Characteristics in more detail

Characteristics in more detail

Respiration

Respiration energy is released from glucose, aerobically if oxygen is present, anaerobically if not.

Excretion

Excretion removal of metabolic waste. Do not confuse with egestion (faeces from undigested remains).

Sensitivity

Sensitivity detecting and responding to stimuli.

Homeostasis

Homeostasis maintaining a constant internal environment, e.g. body temperature of 37 degrees C.

Nutrition

Nutrition taking in nutrients, either by photosynthesis (autotrophs) or by feeding on other organisms (heterotrophs).

Sunflowers tracking the Sun show movement in response to light; plants can reduce temperature through transpiration.

Section 4 of 19Eukaryotic cells

An animal cell and a plant cell seen under a light microscope are both eukaryotic because each has a distinct nucleus bounded by a membrane. Other organelles include cytoplasm, a cell membrane and mitochondria; plant cells additionally have cell walls of cellulose, a vacuole and chloroplasts. Eukaryotic cells are larger than prokaryotic cells.

Section 5 of 19Prokaryotic cells

Prokaryotes are always single-celled, with no nucleus.

The genetic material is a single circular chromosome of DNA in the cytoplasm, and extra small rings called plasmids may be present.

Bacteria have a cell wall, a cell membrane, cytoplasm, plasmids and circular DNA.

They are substantially smaller than eukaryotic cells.

The prokaryotes are different from the other four groups, which are all eukaryotes.

Component	Bacterial (prokaryotic)	Animal	Plant
Cell wall	Yes	No	Yes (cellulose)
Nucleus	No	Yes	Yes
Plasmids	Yes	No	No
Chloroplasts	No (usually)	No	Yes
Size	Small	Larger	Larger

Section 6 of 19Pathogens and groups

Features that group organismswhether the cells have a nucleus, a cell wall, how they store carbohydrate, and the type of nutrition.

Pathogens and groups

A pathogen is an organism that causes disease in another.

Pathogenic bacteria do not always infect the cells of their host: they can remain in body cavities.

Exam tip: you can be asked to complete a table comparing three of the groups, so know each group's features.

Section 7 of 19Nutrition, respiration and movement across kingdoms

Even though all organisms share the same characteristics, the way they carry them out differs between groups.

Nutrition, respiration and movement across kingdoms

Plants make their own food by photosynthesis and respire all the time; fungi digest food outside their bodies by secreting enzymes and absorbing the soluble products; animals ingest food and digest it internally; bacteria vary, some being saprobionts, some parasites and some photosynthetic.

Growth in animals stops at maturity, while plants grow throughout life.

Movement in animals is locomotion; in plants it is slower growth movement towards light (phototropism) or water.

Section 8 of 19Exam focus: comparing groups in a table

Learn a pattern for each

cell type (eukaryotic or prokaryotic), nucleus, cell wall, chloroplasts, carbohydrate store (glycogen or starch), body organisation and nutrition.
Include at least one specific example of each group.

Why the characteristics are tested together

The seven characteristics are best learned with an example for each: movement (an earthworm contracting), respiration (yeast producing carbon dioxide), sensitivity (a Venus flytrap closing), growth (germinating seed), reproduction (budding yeast), excretion (kidneys removing urea), nutrition (leaf making glucose). A virus fails several tests because it cannot respire or grow outside a host, which is why it is not regarded as a typical living organism.

Section 9 of 19Compare

The seven life processes
Process	Meaning	In animals	In plants	Organ/structure	Non-living comparison
Movement	Moving all or part of the body	Walking, swimming	Leaves turn to light	Muscles / stems	Car moves but is not alive
Respiration	Releasing energy from glucose	In all cells	In all cells	Mitochondria	Fire uses oxygen but is not alive
Sensitivity	Responding to stimuli	Eyes, ears, skin	Roots grow down, shoots to light	Senses / tips	Thermostat responds
Growth	Getting bigger permanently	Child to adult	Seed to tree	Cell division	Crystals grow
Reproduction	Making offspring	Babies, eggs	Seeds, runners	Reproductive organs	—
Excretion	Removing cell waste	Urine, CO₂	O₂ and CO₂ from leaves	Kidneys, lungs, leaves	—
Nutrition	Getting food	Eating	Photosynthesis	Gut / leaves	Car uses fuel

Section 10 of 19Worked examples

Explain why a bacterium is a prokaryote. [2]2 marks
Compare an animal cell and a bacterium (two differences). [2]2 marks
State what happens during excretion. [1]1 mark

Section 11 of 19Pathogens and disease

A pathogen is an infectious agent that causes disease in a host. Pathogens include certain bacteria, fungi and protoctists, as well as viruses. Most members of these groups are not necessarily disease-causing; the term pathogen applies to those that cause disease.

Examples:

Examples Pneumococcus is a bacterium associated with pneumonia; some fungi cause plant diseases; the protoctist Plasmodium causes malaria and is transmitted by mosquitoes. Match each named disease to its pathogen group rather than assuming all infections are bacterial.

Section 12 of 19Why viruses are different

Why viruses are different

Viruses are much smaller than bacteria and are not cells. A virus contains genetic material (DNA or RNA) enclosed in a protein coat. It cannot carry out the full set of life processes independently and can reproduce only after entering a living host cell.

Antibiotics target bacterial structures or processes. They do not kill viruses, so identifying the type of pathogen matters when discussing treatment and control.

Section 13 of 19Tobacco mosaic virus

Tobacco mosaic virus

Tobacco mosaic virus (TMV) infects plants, including some crop species. Infected leaves develop a patchy mosaic pattern because chloroplast function is disrupted. With less effective photosynthesis, growth and crop yield can fall.

TMV spreads through contact with infected plants or contaminated material and can persist in the growing environment. Good field hygiene and resistant crop varieties help limit spread; there is no simple cure for an infected plant.

Section 14 of 19HIV and influenza

HIV and influenza

HIV infects cells of the immune system.

An early flu-like illness may be followed by a long period with few obvious symptoms.
If the immune system becomes severely damaged, the late stage is called AIDS and the person becomes vulnerable to other infections.
HIV can pass through sexual contact, contaminated blood or shared needles, and from mother to child.
Antiretroviral treatment can control viral replication and greatly slow progression.

Influenza virus infects cells lining the airways and causes a contagious respiratory illness. Typical symptoms include fever, body aches and fatigue. In an exam answer, describe both the affected tissue and the resulting symptoms, rather than simply naming the virus.

Section 15 of 19Check your understanding

Question:

Question Why can TMV lower a crop's yield? Answer: Damaged chloroplast function reduces photosynthesis, so the plant makes less glucose for growth and produces a smaller yield.

Question:

Question Why would an antibiotic not cure influenza? Answer: Influenza is caused by a virus, while antibiotics act on bacterial targets.

Section 16 of 19Key terms

Term	Meaning
Prokaryote	Organism with cells lacking a nucleus.
Eukaryote	Organism with cells with a membrane-bound nucleus.
Plasmid	A small ring of DNA in a bacterium.
Autotroph	An organism that makes its own food.
Heterotroph	An organism that takes in ready-made food.

Section 17 of 19Syllabus checklist

understand how living organisms share the following characteristics: - they require nutrition - they respire - they excrete their waste - they respond to their surroundings - they move - they control their internal conditions - they reproduce - they grow and develop.

Section 18 of 19Command terms

Command terms

Give / State / Name

Recall a fact; one idea per mark.

Define

Give the exact meaning using the specification keywords.

Describe

Give an account of what happens / the pattern in data, quoting values; no reasons needed.

Explain

Give reasons with linked statements (cause → effect). Each linked step is usually a separate marking point.

Suggest

Use knowledge in a new context; more than one answer may be accepted.

Compare

Similarities and differences; each point must refer to both items.

Calculate

Show working; include units; check significant figures. Method marks are given even if the final answer is wrong.

Discuss

Explore the issue from different angles and link the points.

Evaluate / Assess

Weigh strengths and weaknesses and reach a supported judgement.

Deduce

Draw a conclusion from the information given.

Justify

Support a statement/choice with evidence.

Section 19 of 19Exam technique

Saying bacteria have no DNA.

Saying plant cells have no cell membrane.

Confusing egestion and excretion.

Saying all cells have a nucleus.

Last updated: 11 October 2026