Biology - Characteristics of living organisms

Following the Pearson Edexcel International GCSE Biology specification

SUBTOPIC 1

Characteristics of Living Organisms

What are the seven characteristics of living organisms?

Movement, respiration, sensitivity, growth, reproduction, excretion and nutrition (MRS GREN)

How is movement defined in biology?

An action by an organism or part of an organism causing a change in position or place, including intracellular movement

What is respiration and why is it essential?

respiration is the biochemical process by which living organisms convert nutrients into energy. It is essential for maintaining cellular functions and supporting life processes.

What is meant by sensitivity?

The ability to detect stimuli and respond appropriately to environmental changes.

How is growth defined in biological terms?

A permanent increase in size and dry mass due to an increase in cell number and/or cell size

What is reproduction?

The biological process by which organisms produce offspring, ensuring survival of the species

What is excretion and how does it differ from egestion?

Excretion is removal of metabolic waste; egestion is removal of undigested food

What is nutrition?

The intake and assimilation of materials for energy, growth and development

What is metabolism?

The sum of all enzyme-controlled chemical reactions in a cell or organism

SUBTOPIC 2

Variety of Living Organisms

What are the five kingdoms?

Animals, plants, fungi, protoctists and prokaryotes

What are the key characteristics of animals?

Multicellular, no cell walls or chloroplasts, heterotrophic nutrition, nervous coordination and movement

: What are the key characteristics of plants?

Multicellular, cellulose cell walls, chloroplasts present, photosynthesise, store carbohydrates as starch or sucrose

What are the defining features of fungi?

Made of hyphae forming a mycelium, chitin cell walls, no chloroplasts, saprotrophic nutrition via extracellular digestion, store glycogen

What are protoctists and why are they difficult to classify?

Mostly unicellular eukaryotes with varied features; some photosynthesise while others feed heterotrophically

What are the key features of prokaryotes?

Unicellular, no nucleus, no membrane-bound organelles, circular DNA and plasmids may be present

What is a eukaryotic cell?

A cell that contains a nucleus and membrane-bound organelles

Which organisms are eukaryotic?

Animals, plants, fungi and protoctists

What is a prokaryotic cell?

A cell that lacks a nucleus and membrane-bound organelles

Where is genetic material found in eukaryotic cells?

Inside the nucleus

Where is genetic material found in prokaryotic cells?

Free in the cytoplasm as circular DNA

What are membrane-bound organelles?

Structures within cells that are surrounded by membranes and perform specific functions

Give examples of membrane-bound organelles

Nucleus, mitochondria, chloroplasts and vacuole

Why are eukaryotic cells more complex than prokaryotic cells?

They contain membrane-bound organelles that compartmentalise functions and increase efficiency

What is the size difference between eukaryotic and prokaryotic cells?

Eukaryotic cells are larger (10–100 µm), while prokaryotic cells are smaller (approximately 1–5 µm)

Which kingdoms are eukaryotic?

Animals, plants, fungi and protoctists

Which kingdom is prokaryotic?

Prokaryotes (bacteria)

What is a pathogen?

A microorganism that causes infectious disease by invading the host and disrupting normal function

What are the four main types of pathogens?

Bacteria, viruses, fungi and protoctists

BVFP (bacteria, virus, fungi, protoctist)

By reproducing rapidly and producing toxins that damage host cells

What is the structure of a virus?

Genetic material (DNA or RNA) enclosed in a protein coat