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MODULE 021131: ECOLOGY
Learning Objectives: Lecture 1
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Ecology covers a hierarchy of levels of organisation,
from individual to biosphere
There are distinctive (emergent) properties of ecological
systems at each of these scales that can only be
understood by studying them at the appropriate scale: a
strictly reductionist approach is invalid
If an ecological problem is to be successfully resolved, it
must be studied at all appropriate scales
Ecology as a hierarchy
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Molecule
cell
Organism
Population
Community
Ecosystem
Landscape, biome, biosphere
At the level of the individual
organism:
• Phenomena include animal behaviour,
ecophysiology
• Applications are in species
conservation, land management
Large blue
butterfly
Maculinea
arion: unique
life-history
is the key to
its
conservation
Spring gentian
Gentiana verna:
found only in a
few places in
Britain, and
sensitive both to
soil conditions
and grazing
Habitat of G.
verna in Upper
Teesdale,
County Durham.
The fence
controls
grazing and
allows abundant
flowering.
The reservoir in the background
flooded over half the habitat of this
rare species
The lichen
Hypogymnia
physodes:
lichens are
highly
sensitive to
air pollution
and are rare in
urban areas.
Their sensitivity can be used as an
index of pollution intensity
Derelict coalmine waste in
the central
Lancashire
coalfield:
grass growth
is poor and
restricted to
gulleys where
water collects
Derelict land encourages other lowvalue uses of land and depresses the
local economy
Plants
cannot grow
on the
waste, due
to extreme
deficiency
of mineral
nutrients
such as
phosphate
Sown grass seed soon dies of drought
as a result of inadequate growth of
their root systems
Adding ground
limestone
(CaCO3; to
raise the soil
pH) and
fertilisers
allows grass
growth on
otherwise
barren sites
No
limestone
Limestone
added
The individual plots received
different combinations of N, P
and K fertilisers
At the population level
• Phenomena: population dynamics,
extinction, competition, predation
• Applications: invasions, pest control,
biological control, conservation
management
Himalayan balsam Impatiens glandulifera
an introduced species that
has escaped from gardens
and now dominates in
waterside habitats
produces huge numbers
of seeds and can swamp
all competitor species
Touch-me-not
balsam Impatiens
noli-me-tangere is a
closely related
native species that
is now very rare in
Britain.
Why is one species
an invasive weed
and the other rare
and threatened?
Invasive
species can
have large
economic
consequences
Patterson’s curse Echium plantagineum
can take over entire fields in Western
Australia
Australian vegetation is especially prone to invasions:
almost all the species in this scene are introduced
from either South Africa or the Mediterranean
Species that are well
controlled by natural
enemies in their
native range, such as
this prickly pear
Opuntia in South
America, can become
damaging weeds in
another country:
here Australia.
Prickly pear was
eventually controlled
by introducing a moth
Cactoblastis
cactorum whose
caterpillars ate it
Community level:
• Phenomena: biodiversity, succession
• Applications: habitat management,
biodiversity conservation
What is the appropriate way to manage
biodiverse habitats such as chalk grassland?
Species-rich grassland is
maintained by grazing
when grazing is removed,
coarse grasses dominate
Tropical wet
forests are the
most diverse
habitats we know:
why are they able
to support so many
species?
Ecosystem level:
• Phenomena: nutrient and material
cycles, stability, ecosystem services
• Applications: pollutant transport,
eutrophication, acid rain, sustainable
agriculture
A polluted ditch threatens an important
wildlife habitat: Askham Bog, near York
Higher levels: landscape,
biome, biosphere
• Phenomena: dispersal,
• Applications: global change,
sustainability
Soil erosion
can have
catastrophic
consequences
for the
environment:
a dust-storm
in Mexico
Long-distance
transport of
eroded soil
connects
distant
ecosystems
Reductionism
• can one explain higher levels or
organisation by understanding the
lower levels?
• does the study of the natural world
ultimately reduce to physics?
• emergent properties