2
CHAPTER
All living things are dependent on each other and the environment around them Relationships between organisms may be beneficial or detrimental
R
LY
2.6
Energy enters the ecosystem through photosynthesis Energy flows through an ecosystem
Matter is recycled in ecosystems
D
R AF
T
2.7
O N
2.5
Introducing a new species may disrupt the balance in an ecosystem
-N
2.4
ECOSYSTEMS
FO
2.3
Population size depends on abiotic and biotic factors
T
2.2
O
2.1
2.9
2.8
SA LE
How do we balance our needs with those of the environment?
Natural events can disrupt an ecosystem
Human activity can disrupt an ecosystem
What if?
Yeast cultures What you need: Spatula, dried yeast, warm water, sugar, test tube, ruler, thermometer, timer What to do: 1 Add 1 spatula of dried yeast to warm water in the test tube and leave for 10–15 minutes before adding 1 spatula of sugar. 2 Measure the temperature of the water at the point of adding the sugar. 3 Measure the height of the yeast culture (an indication of the number of yeast cells) from the base of the test tube. This is the measurement at t = 0 minutes. 4 Measure the height of the culture every minute for 15 minutes. 5 Draw a graph of your results. What if? » What if hot water was added to the culture? (Would the number of yeast cells increase faster?) » What if ice-cold water was added to the culture? » What if twice as much sugar was added?
Science as a human endeavour: • What if no sugar was added? 2.10 Human management of ecosystems continues to change No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means.
