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Chapter 1: Cells – the Basic
Building Blocks of Life
Lesson 5: Understanding Unicellular Organisms
 Recognise different types of unicellular organisms.
 Describe differences in unicellular organisms.
 Compare and contrast features of unicellular
organisms.
Lesson 5: Unicellular Organisms
 Unicellular organisms are made up of just one cell.
 They carry out all the life processes needed to exist independently
 They differ from each other in their structure, how they feed and how
they move.
 Algae are plant-like unicellular containing chloroplasts and make their
own food.
 Fungus-like unicellular organisms are called yeasts. They have a cell
wall but cannot make their own food.
Lesson 5: Prokaryotes
 Unicellular organisms can be classified into two
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main groups – prokaryotes and eukaryotes.
Prokaryote means ‘before life’ – prokaryotes are
thought to be the first organisms to live on Earth.
They do not have a nucleus, and can be up to 200
times smaller than eukaryotes.
Bacteria are examples of prokaryotes.
They come in different shapes and sizes, live in
different environments and have a range of food
sources.
Lesson 5:Eukaryotes
 Eukaryotes contain a nucleus, surrounded by a nuclear membrane.
 They also contain many organelles (which prokaryotes do not),
including mitochondria, chloroplasts and vacuoles.
 Examples of eukaryotes are euglena (a type of algae containing
chloroplasts), yeast, amoeba, and paramecium – the last two are types
of protozoa.
 the euglena has a flagellum, or tail, to enable it to move.
Lesson 5: Key Vocabulary and Notes
Key Vocabulary: yeast, prokaryote, eukaryote, bacterium,
protozoa
Key Notes:
 Unicellular organisms are made from one cell
 The two main types are called: prokaryote and eukaryote
 Prokaryotes do not have nucleus or organelles, and come
in different sizes and shapes. Bacteria is an example of a
prokaryote
 Eukaryotes have a nucleus and organelles such as
mitochondria, chloroplasts, vacuoles
Lesson 5: Questions and Answers
1. List three ways unicellular organisms differ from each
other.
Ans. structure, how they feed, how they move!
2. What is one main difference between prokaryotes and
eukaryotes?
Ans. Nucleus
3. Name the two other difference between prokaryotes and
eukaryotes? (hint: size and structures)
Ans. Eukaryotes are 200 times bigger, they have
organelles