Good Science Victorian Curriculum Year 7

BIOLOGICAL SCIENCES
3.4
HOW MICRO-
ORGANISMS
AFFECT
ECOSYSTEMS
LEARNING INTENTION
At the end of this lesson I will be
able to describe examples of
beneficial and harmful effects
that microorganisms can
have on living things and the
environment.
KEY TERMS
pathogen
a microorganism that can
cause disease
unicellular
made of one cell
LITERACY LINK
READING
Find a news article about
harmful or beneficial
microorganisms. Read the article
and carefully summarise it in
one paragraph.
1
Microorganisms are microscopic organisms that are too small
to see with the naked eye. They’re found at all feeding levels of
food webs, in every ecosystem on Earth.
Microorganisms have different roles in ecosystems. Some
of these roles benefit other organisms and the environment,
while others are harmful and can lead to major changes.
Bacteria, fungi and protists are
microorganisms
Microorganisms exist all around you. They live in your intestines and
on your skin, in the soil in your backyard and in the water you drink.
They also live at the bottom of the ocean, in volcanic vents and in the air.
There are three main types of microorganisms: bacteria, protists and
fungi. Most are unicellular organisms.
Bacteria are extremely small unicellular organisms. They usually
exist as large colonies of thousands of organisms. The different sizes
and shapes of bacteria can be used to identify them. Bacteria that live
in water environments often have hair and tail-like structures, called
cilia and flagella, to help them move.
Protists are larger than bacteria and they exist alone, rather than
in colonies. Every type of protist has a unique structure that helps it
survive. Some protists carry out photosynthesis, and act as producers
in ecosystems, while others are consumers and decomposers.
Fungi range in size from unicellular yeasts to multicellular mushrooms.
Although they are often grouped with plants, fungi are not producers
in an ecosystem because they cannot photosynthesise.
What are the three main types of microorganism
in ecosystems?
NUMERACY LINK
CALCULATION
Krill are tiny crustaceans that
weigh about 2 grams each. A
blue whale needs to eat about
3600 kilograms of food each day.
How many krill will a blue whale
eat every day?
Figure 3.7 These bacteria use
their long flagella and short cilia
for movement.
Figure 3.8 Freshwater protists have eyespots
that can detect light. They
use their flagella to move towards
the light to carry out photosynthesis.
42 GOOD SCIENCE VICTORIAN CURRICULUM 7