BIOS 3010: Ecology
Lecture 2: Habitat: Resources
•  Lecture summary:
– Resources:
•  Definition
•  Abiotic
•  Biotic
•  Space
•  Classification
– The niche
Albrecht Dürer: A Young Hare 1502, The Large Turf 1503 (GSA, Vienna)
Dr. S. Malcolm
BIOS 3010: Ecology
Lecture 2: slide 1
2. Resources and global security:
•  The UN predicts that by 2025, two-thirds
of us will experience water shortages, with
severe lack of water blighting the lives and
livelihoods of 1.8 billion. According to the
UN World Water Assessment Programme,
by 2050, 7 billion people in 60 countries
may have to cope with water scarcity.
–  Chenoweth, J. 2008. Water, water everywhere.
New Scientist 23 August 2008: 28-32.
Dr. S. Malcolm
BIOS 3010: Ecology
Lecture 2: slide 2
3. What is a resource?:
•  All things consumed by an organism (Tilman, 1982)
–  But, space is also a resource - therefore:
•  Resources are quantities that can be reduced by the
activity of an organism
–  Or, in the glossary to Begon et al. (1996) a resource is defined as:
•
that which may be consumed by an organism and, as a
result, becomes unavailable to another
–  e.g. food, water, nesting sites, etc.
–  Thus CO2, O2, and light can be either resources or conditions - and
are more likely to be resources at high population densities and small
scales.
–  Note: like conditions, resources can also act as constraints and
cues.
Dr. S. Malcolm
BIOS 3010: Ecology
Lecture 2: slide 3
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4. Contrast with conditions:
•  A condition is an abiotic environmental
factor which varies in space and time.
Conditions are not consumed or used up
by organisms or made less available to
others.
–  e.g. temperature, moisture or humidity, light,
chemistry (e.g. O2, pH, salinity), gravity, pressure,
sound, fire, wind, stream or current flow velocity,
pollutants.
Dr. S. Malcolm
BIOS 3010: Ecology
Lecture 2: slide 4
5. Abiotic Resources:
•  Solar radiation is a resource and not a condition when the
supply can be influenced by other organisms
•  Resource supply can vary:
–  Systematically
–  Unsystematically
•  Systematic Variation - e.g. globally, seasonally or diurnally
when solar radiation operates more like a condition.
–  Fig. 3.1, solar radiation with latitude
–  Fig. 3.3, annual and diurnal variation in solar radiation with latitude
–  Figs. 3.6 & 3.8 of strategic responses (rigid responses with little
tactical maneuverability) to predictable variation in the
Photosynthetically Active Radiation spectrum (PAR of 380-710 nm) for
plants that vary strategically in abilities to photosynthesize under
different light regimes.
Dr. S. Malcolm
BIOS 3010: Ecology
Lecture 2: slide 5
6. Abiotic Resources:
•  Unsystematic Variation - e.g. local, plastic or tactical
responses resulting in resource depletion zones (RDZ):
–  e.g. the leaves in a forest (Fig. 3.2) or plant roots
responding tactically to resource concentration with more
root hairs:
•  e.g. wheat grown in sand + clay - more roots respond to available
water and minerals in clay, see Figs. 3.20 & 3.21.
–  Resource depletion zones vary according to physical
characteristics, e.g. nitrates are soluble but phosphates
are not - hence mycorrhizae are used by all plants to aid
in foraging.
•  Note: read the text (Begon et al. chapter 3) for accounts of CO2, water,
mineral nutrients and O2 as resources
Dr. S. Malcolm
BIOS 3010: Ecology
Lecture 2: slide 6
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7. Biotic Resources:
•  The product of autotrophic fixation of energy by
plants and used by heterotrophs as consumers.
•  Produces decomposers, parasites, predators and
grazers/herbivores.
•  Nutritional content of these resources varies:
–  Fig. 3.23 - nutritional composition of plants versus animals
nutritional variation among and within plants:
•  plants have much higher C:N ratios than animals.
–  Fig. 3.17 - the complex of herbivores on raspberry plant
partition resources in space and time:
•  considered later under competition.
Dr. S. Malcolm
BIOS 3010: Ecology
Lecture 2: slide 7
8. Space as a resource:
•  e.g. lizards basking on a rock compete for microsite space to bask.
•  or monarch butterflies overwintering on trees require space to avoid
freezing mortality or mouse predation on the ground.
•  or testosterone-manipulated red grouse territories in Fig. 3.23 (3rd ed.).
Dr. S. Malcolm
BIOS 3010: Ecology
Lecture 2: slide 8
9. Tilman s Classification of
resources:
•  after Tilman 1982.
•  Distinction between essential and substitutable resources to give the 5
sets of performance (growth) isoclines between 2 resources in Fig. 3.27
–
–
–
–
–
Essential
Perfectly substitutable
Complementary
Antagonistic
Inhibitory
Dr. S. Malcolm
BIOS 3010: Ecology
Lecture 2: slide 9
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10. The ecological niche:
•  G. Evelyn Hutchinson (1957) defined the niche as
an:
–  “n-dimensional hypervolume”
•  Ecologically the niche is an abstract concept and not
a fixed position in space
–  (a “neesh” and not a “nitch!” …… Dr. Seuss.)
•  n-dimensions define the limits within which a species
can survive and reproduce, for n environmental
“factors” that will include both conditions and
resources.
Dr. S. Malcolm
BIOS 3010: Ecology
Lecture 2: slide 10
11. Fundamental & Realized niche:
•  Fundamental niche:
–  So the zero growth isoclines of Fig. 3.27 define niche boundaries in 2
dimensions and this can be done for both lower and upper limits of either
conditions or resources to define the fundamental niche of a species:
•  the space that it could occupy - its overall potential.
–  These niche boundaries can be easily drawn in 1, 2 or 3-dimensions as in
Fig. 2.26, for dimensions such as those shown in Fig. 2.2, or dimensions that
include resources and ecological processes. But it is difficult to visualize the
niche in more dimensions and so the “n-dimensional hypervolume” is the
best simple description of niche space.
•  Realized niche:
–  The realized niche represents the actual niche dimensions of a species after
various ecological processes such as movement, competition and natural
enemy attack have reduced the fundamental niche dimensions.
Dr. S. Malcolm
BIOS 3010: Ecology
Lecture 2: slide 11
Fig. 3.1
Global solar radiation absorbed annually (J·cm-2·min-1)
Dr. S. Malcolm
BIOS 3010: Ecology
Lecture 2: slide 12
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Fig. 3.3
Annual &
diurnal
variation
in solar
radiation
with latitude
Dr. S. Malcolm
BIOS 3010: Ecology
Lecture 2: slide 13
BIOS 3010: Ecology
Lecture 2: slide 14
Fig. 3.6
Photosynthetic
CO2 uptake in
response to
radiation
intensity
Dr. S. Malcolm
Fig. 3.8
•  Annual variation in (a) PAR (☐) and leaf photosynthesis (●)
and (b) CO2 exchange in the day (¢) and at night (●)
Dr. S. Malcolm
BIOS 3010: Ecology
Lecture 2: slide 15
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Fig. 3.2
•  Reflection (R)
and attenuation
of solar
radiation in:
•  (a) mixed
boreal forest,
(b) pine forest,
(c) sunflowers,
(d) corn field
Dr. S. Malcolm
BIOS 3010: Ecology
Lecture 2: slide 16
Fig. 3.20
•
(a) shortgrass prairie plant roots; (b) wheat roots in sand and clay layers
Dr. S. Malcolm
BIOS 3010: Ecology
Lecture 2: slide 17
BIOS 3010: Ecology
Lecture 2: slide 18
Fig. 3.21
•  Radioautographs
of mustard
seedlings to
show depletion
of 32PO4- in soil
Dr. S. Malcolm
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Fig. 3.23
•  Composition
of different
plant and
animal
resources
Dr. S. Malcolm
BIOS 3010: Ecology
Lecture 2: slide 19
BIOS 3010: Ecology
Lecture 2: slide 20
Fig. 3.17 (3rd ed)
•  Life cycle and
phenology of
raspberry plant
(Rubus idaeus)
parts as
resources for
animal
consumers
Dr. S. Malcolm
Fig. 2.26 (3rd ed. - see Fig 2.2)
•  Ecological niche in 1 (a), 2 (b) & 3 (c) dimensions
Dr. S. Malcolm
BIOS 3010: Ecology
Lecture 2: slide 21
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Fig. 2.2
•  Various niches in (a) 1 dimension and (b) 2 dimensions
Dr. S. Malcolm
BIOS 3010: Ecology
Lecture 2: slide 22
Niche theory according to
Dr. Seuss
•  And NUH is the letter I use to spell Nutches,
Who live in small caves, known as Nitches, for hutches.
These Nutches have troubles, the biggest of which is
The fact there are many more Nutches than Nitches.
Each Nutch in a Nitch knows that some other Nutch
Would like to move into his Nitch very much.
So each Nutch in a Nitch has to watch that small Nitch
Or Nutches who haven t got Nitches will snitch.
–  Geisel, T.S. ( Dr. Seuss ) 1955. On beyond Zebra. Random House
Publishing, New York.
–  http://shade.grove.iup.edu/~rgendron/Seuss.htmlx
Dr. S. Malcolm
BIOS 3010: Ecology
Lecture 2: slide 23
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