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 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