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N4 Biology
Unit 3 Life on Earth
KA 3.1 Biomes and ecosystems
World Biomes
Learning Intention: Identify and describe how ecosystems
are different across the world.
Success Criteria:
• Define the term biome.
• Describe the global distribution of world biomes.
• Describe how temperature and rainfall affect the
distribution of world biomes.
• Present detailed information about one world biome.
What is a biome?
• Biomes are large areas of the Earth which are
dominated by specific types of vegetation and are
home to certain types of ecosystem.
• This is caused by differences in the climate in
different parts of the world.
• Major biomes on Earth include tropical rainforests,
savannah, coral reef, desert, tundra and temperate
forests.
World Biomes
Tropical Rainforest
Arctic
Desert
Temperate forest
Coral reef
Temperate forest
Coral reef
Biome project
Tropical rainforest
• Choose a biome
• Make a word
document or
powerpoint
about it.
Desert
Arctic/Tundra
Starter Activity:
How many different plant species are in this field?
Which is the most common species?
What animals live in or visit this field?
How would you find this out?
Appropriate
Clip art to
topic
Sampling Techniques
Learning Intention:
• Using practical techniques to sample plants and
animals.
Success Criteria:
• Describe ways to measure abundance of plants
in an ecosystem.
• Describe ways to sample animals in an area.
Studying ecosystems
• Ecosystems are smaller areas within the
biomes.
• Examples could be a woodland, a pond or a
river.
• Studying an ecosystem involves:
– Finding out what plants and animals live there.
– Finding out how many of them live there.
– Finding out why they live there.
Abundance
• Abundance is the measure of how
frequently a species of plant or animal
appears in particular area.
• Abundance can be measured using
sampling techniques.
Counting plants
• It would be very difficult to count
every single plant in a field. How could
you resolve this problem?
• We can sample using a quadrat.
• Sampling using a quadrat:
– A quadrat is a square frame with a known area
such as 1m2
– It is used to estimate numbers of plants (or slow
moving animals like slugs or snails).
1m
1m
How to sample using a quadrat
Estimating the number of thistles in a field:
• Quadrat placed at random and number of thistles in
quadrat counted.
• Repeated several times.
• Average number per square metre is calculated.
• Area of whole field measured
• Estimate of total number of thistles in field calculated
Example
Calculate the number of flowers in a field with
a total area of 150m2
12
_______flowers
in 1m2.
12
150
_______
x ________=
flowers
1m
1m
1800
____
in a field of 150m2.
To make the results
of abundance more
reliable, many
samples would be
taken using quadrats
and the results then
averaged before
calculating the
abundance of the
entire area.
Quadrat
1
2
3
4
Average
Number of
flowers
12
10
8
14
11
So for the 150m2 area, Abundance = 11 x 150
= 1650 flowers
Quadrat practical
•
Area 1
Quadrat
1
Quadrat
2
Quadrat
3
Average
Quadrat
1
Quadrat
2
Quadrat
3
Average
Moisture
pH
Light
intensity
Number of
species

Area 2
Moisture
pH
Light
intensity
Number of
species
Sampling Animals
– Animals are difficult to count because they
move around, and they tend to hide from
humans.
– Some are well camouflaged as well.
– The best way to estimate their numbers is by
live traps.
Sampling Animals Using a Pitfall Trap
– A container is placed in a hole in
ground to trap animals that are
active at the soil surface.
– The trap is left overnight and
checked next day.
– Several traps should be set up to
increase reliability of the results.
Pitfall Trap
• Traps can be placed to compare
different areas and see what animals
are more common in each.
Other Methods of Sampling
•
•
•
•
Tullgren funnel
Tree beating
Sweep netting
Pond netting
Using a Tullgren funnel
Water
Most animals will float on surface
Starter Activity
How would you explain to a small child how
to identify the following farm animals?
Appropriate
Clip art to
topic
Classification Keys
Learning Intention:
• Branching keys.
Success Criteria:
• I can use a branching key to identify
organisms
• I can construct a branching key
Classification Keys
• When using sampling methods, it is
important that you are able to identify
the plants or animals you have found.
• One method of identification is to use a
key.
Keys
• Used to identify organisms while
sampling.
• There are two types
– Branching keys
– Paired Statement keys
Branching keys
• A key is a series of
questions. Each
question leads to
another until
eventually the name
of the organism is
found.
Branching keys
A leech has no
shell, no legs, no
fins and a
segmented body.
1. Name the
animal with no
shell and eight legs
which is really
small.
2. Describe
a) a freshwater
shrimp
b) A bullhead fish
Branching keys
Describe the
following
animals using
information in
the key.
1.
2.
3.
Woodlouse
Centipede
Harvestman
Branching keys
Put these
animals into the
correct position
in the key:
Snail
Woodlouse
Spider
Butterfly
Worm
Moth
Paired Statement Key
• In this type of key, instead of asking
questions at branching points on a
diagram, you are asked to choose between
two statements.
• Each pair of statements is numbered and
the instructions send you to the next
relevant pair of statements.
1.
Has green coloured body ......go to 2
Has purple coloured body ..... go to 4
2.
Has 4 legs .....go to 3
Has 8 legs .....................................
3.
Has a tail ............................
Does not have a tail ....................................
4.
Has a pointy hump ......................................
Does not have a pointy hump.....go to 5
5.
Has ears ............
Does not have ears ......
1.
Paired Statement Key
2.
4.
5.
6.
3.
Click on a leaf number 1 to start, then
complete leaves 2-6 in that order
Example 1
Construct a branching key for the
information below:
Invertebrate
Spider
Wasp
Fly
Springtail
Number of
legs
8
6
6
6
Wings Body Stripe
No
Yes
Yes
No
No
Yes
No
No
Example 2
Construct a branching key for the
information below:
Plant
Does it have
chlorophyll?
Does it
have cones?
Does it
have
flowers?
Does it
live in
water?
Grass
Yes
No
Yes
No
Spruce
Yes
Yes
No
No
Yeast
No
No
No
No
Moss
Yes
No
No
No
Seaweed
Yes
No
No
Yes
Example 3
Construct a branching key for the
information below:
Bird
Type of feet
Crest on
head
Beak
shape
Head
colour
Swan
Webbed
Absent
Straight
White
Curlew
Not Webbed
Absent
Curved
Brown
Rook
Not Webbed
Absent
Straight
Black
Puffin
Webbed
Absent
Straight
Black
Skylark
Not Webbed
Present
Straight
Brown
Avocet
Not Webbed
Absent
Curved
Black
What is biodiversity?
Biodiversity is the variety of different species in an
area, or on the planet as a whole.
It is important to maintain biodiversity to ensure that
important species do not become extinct.
What can affect biodiversity?
The following factors can affect levels of biodiversity:
• Abiotic factors- these are non-living factors like
light, temperature, water, pH etc.
• Biotic factors- these are factors to do with other
living things, like predators, food, competition and
disease.
Watch the following Glow video clips
Abiotic Factors
Biotic Factors
Changes in Ecosystems
Here are two similar ecosystems.
Imagine a disease wiped out the mosquito larvae.
Which ecosystem would be most affected?
Why?
What might happen to the number of tadpoles in the
loch if mosquito larvae disappeared? Why?
Changes in Ecosystems
The prawns in this ecosystem are killed by pollution. What would
happen to the numbers of
a) trout
b) carp
c) slugs