Unit 2 Looking at Living Things

Unit 7 Living Things and Air

Topic

Is yeast a living thing?

Curriculum Link

2 Looking at Living Things (Characteristics of living things)
7 Living Things and Air (How do living things obtain energy and respire)

Estimated Lesson Time

80 minutes

Introduction

There is a wide range of uses of yeasts, such as baking bread and wine fermentation. Since yeasts usually come in powder form, many people do not recognize yeasts as living things. Yeasts in fact are microorganisms and so, like animals and plants, yeasts need respiration to support life. Sugar is a kind of nutrition that yeasts can take in to produce energy for supporting life. During the process of energy production, carbon dioxide is released.


Yeasts in powder form

Key question

Yeasts do not look like either an animal or a plant. Is yeast a living thing?

Learning Objectives

In this activity, the students should be able to

  1. identify some of the characteristics of  living things through observation;
  2. infer that living things obtain their energy from the chemical energy stored in food;
  3. recognize respiration as the process during which the chemical energy in food is released;
  4. infer that carbon dioxide is produced during respiration;
  5. acquire planning and designing skills (SP3) in designing an experiment to observe whether respiration occurs for yeasts;
  6. acquire measuring skills (SP1) and experimenting skills (SP4) to perform an experiment;
  7. acquire interpreting data skills (SP5) in analyzing the data collected;
  8. acquire comparing and classifying skills (SP2) by identifying changes, if any, of respiration of yeasts when different amounts of nutrition is provided.

Teaching Plan

Task (Time) Brief Description Materials Objectives

Engagement
(10 min)

Teacher engages students to think and discuss about

  • some characteristics of living things
  • things that will be taken in and given out by a living thing during the course of supporting its life
   (1), (3) & (5)

Exploration
(50 min + several hours)
  • Students design an experiment to explore whether yeasts respire
  • Students prepare solutions of sugar of different concentration and yeast of different amount in a systematic way
  • Students take relevant measurement at regular intervals during a duration of several hours
  • Yeast, sugar, water and relevant apparatus*
 (2), (5) & (6)

Evaluation
(10 min)

Students analyze the set(s) of data to

  • infer that carbon dioxide is produced during respiration
 (4) & (7)

Elaboration &
Explanation
(10 min)
  • Students predict the results of different amounts/concentrations of sugar solution/yeast used
   (7)

Exploration
(40 min + several hours)
  • If time allows, students repeat the experiment with different concentration of sugar solution and different amount of yeast
  • Students compare and explain the results
   (8)

*Apparatus and materials required:

Yeast (俗稱依士粉) sugar beaker plastic bottle
 
balloon timer spoon