Unit 3 Topic 1
Ecology
• Topic 1:Describing Biodiversity
• Topic 2: Ecosystem Dynamics
What is
biodiversity?
• The range of organisms and the
environments
• Includes diversity of:
• Species
• Ecosystems
• Genes
Determining
species
diversity
• Species richness
• Evenness
• Percentage cover
• Percentage frequency
• Simpson’s diversity index
Species Richness
• A measure of the total
number of species in a
community
Evenness
• How close the number
individuals of each species
are in an ecosystem
Percentage cover
• The amount of coverage of a
given cover.
• Can be:
• Type of ground
• Vegetation
• canopy
Percentage frequency
• The number of individuals as a
percentage of a whole
• % freq.
=
𝑀𝑒𝑎𝑛 𝑶𝑹 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑜𝑛𝑒 𝑠𝑝𝑒𝑐𝑖𝑒𝑠
𝑇𝑜𝑡𝑎𝑙 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑖𝑛𝑑𝑖𝑣𝑖𝑑𝑢𝑎𝑙𝑠 𝑜𝑓 𝑎𝑙𝑙 𝑠𝑝𝑒𝑐𝑖𝑒𝑠
• Is a probability that two individuals will be
different
Simpson’s
Diversity
index (SDI)
• Rating between 0-1
• A score closer to 1 means there is a
higher probability the individuals will be
different from each other, therefore
greater diversity.
• 𝑆𝐷𝐼 = 1 −
𝑛(𝑛−1)
𝑁(𝑁−1)
• Where:
• N = total number of all species
• n = number of organisms of one
species
• Observe the number of species present
• Observe the numbers of each species
Species diversity indices =
compounds many different
species numbers to find
diversity e.g. Simpson’s
Diversity Index
How to
Compare
ecosystems
Index (multiple =
indices) = a
compound
measure of
multiple
indicators
Species interactions – how many can you
remember?
Abiotic factors – what
would these include?
What abiotic
factors would you
compare in a
desert and
rainforest?
Large scale patterns of biodiversity: abundance v
distribution
• 10,000,000 km2
• Population roughly 3.8–6.7 million individuals.
Cattle egret abundance vs distribution
Koala’s Distribution
vs abundance
1.77 koalas per ha= kangaroo island (SA)
Bilby distribution vs abundance
400- 600 animals left in the wild
Golden Lancehead
abundance vs distribution
• Endemic to Snake Island
• 2000-4000 individuals
Limiting Factors
Each organism also has a
range of environmental
factors that it can live in =
tolerance range
If a condition which approaches or
exceeds the limits of tolerance for an
organism it is said to be a limiting factor
for that organism.
Relating this to
individuals
• Explains distribution of organisms
within an ecosystem
• Explains abundance of organisms in an
ecosystem
WHAT? – what did
you learn about?
SO WHAT? – why
does it matter?
NOW WHAT? –
where will we take
this? What else do
you need to know
to understand?
What else could be
interesting?
Rate of photosynthesis in plants. Explain the link
between each of these and limiting factors.
In summary limiting factors limit the abundance and distribution of species in an ecosystem
What are 7
main biomes?
(need at least
2 aquatic)
•
•
•
•
•
•
•
Marine
Freshwater
Desert
Grassland
Rainforest
Temperate forest
Tundra
For each of these
biomes think of
the limiting factors
that might be
present for plants
and/or animals.
To determine biodiversity you
need to be able to classify
organisms into species
Write down as much as you know about classification