nota biodiversiti
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Transcript of nota biodiversiti
Ecosystems
Levels of organization
Individual/Organism
Population
Community
Ecosystem
Biosphere
an Ecosystem consists of all of the organisms
living in a community (or communities) together
with the abiotic factors with which they interact
Rocky Shore community – an example
• the mix of barnacles, algal mats,
herbivorous snails on rocks etc.
• the physical environment (dessication,
temp, wave action) leads to a vertical
zonation pattern
• predation and competition influence
distribution eg. snails grazing algal spores,
predatory snails eating herbivores
• disturbance opens spaces, allows
establishment of new species
• different communities result in different
locations
Rocky Shore
community
Structure of a community is usually the result
of many interactions
results from:
– many competitive interactions
– complex mutualisms
– predators increasing and decreasing
– variety of disturbances through time
– environmental fluctuations and more!
Biomes – ecosystems & communities on a global scale
(Miller Ch 4 Fig 4.8)
• vegetation structure in different parts of the
world is similar in similar environments - even
though species are different
• biomes are communities with similar structure
Biosphere (ecosphere) - the biosphere (i.e. all
ecosystems on earth) is an additional level of
organization
• Existence of life depends upon
– an energy source (the sun)
– oxygen, carbon, nitrogen and other elements, all
of which are part of worldwide geological and
chemical cycles
• All ecosystems on Earth are linked via global
biogeochemical cycles.
• an ecosystem is all of the organisms living in a
community (or communities) together with their abiotic
factors
Ecosystem function
through
Energy flow
Cycling of materials
• A systems approach attempts to understand
– the way energy is passed through the system
– how nutrients are cycled
• Individual organisms or species can be
considered in terms of the function they perform
What does biodiversity actually do ?
biological diversity allows the different ecosystem
functions to be carried out
the primary ecosystem functions are to
• Capture
• Store
• Transfer
Energy
Carbon dioxide
Nutrients
Water
ECOSYSTEMS
ecosystems are a network of
interactions, beginning with
the PRIMARY PRODUCERS
(the PLANTS) and
connecting to herbivores,
carnivores, parasites,
decomposers
...energy, nutrients & water
are cycled through the
network by these different
groups
Miller Ch 4
Fig 4.6
Flow of
energy
and
materials
through an
ecosystem
Systems approach to ecosystem function
Essential characteristics of ecosystems
1. Energy flow
Energy flows in a unidirectional way (it does not
cycle!) fig 4.13 Miller Ch 4
This requires a continuous input of energy into an
ecosystem
Energy source autotrophs heterotrophs
Essential characteristics of ecosystems
1. Energy flow
• Autotrophs
(e.g. plants, algae)
organisms capable of
synthesizing all their
required organic
molecules from simple
organic substances and
an energy source
Essential characteristics of ecosystems
1. Energy flow
• Heterotrophs
(e.g. animals)
organisms that cannot
synthesize complex
organic compounds and
must feed on organic
material formed by other
organisms to obtain
energy and necessary
molecular building blocks
for metabolism and
growth
Essential characteristics of ecosystems
2. Cycling of materials
• Materials (e.g. carbon, nitrogen, phosphorus)
are cycled from the abiotic environment,
through living organisms, and back to the
abiotic environment
• This results from metabolic activities of plants
and animals, and organisms such as bacteria
and fungi that break down organic matter
Energy in ecosystems
• All organisms require energy
– maintenance, growth, reproduction, (and movement)
• The energy driving the biosphere (and all
ecosystems) is solar radiation, captured via
photosynthesis by autotrophs
• about 1% of visible light converted to chemical energy
• about 120 billion tonnes of new organic material
produced each year
• about 99% of all organic matter in the biosphere is
autotrophs (i.e. mostly plants)
Photosynthesis
Photosynthesis
6 CO2 + 12 H2O C6H12O6 + 6 O2 + 6H2O
Respiration
Energy (from photosynthesis) is released and used
by the organism when the complex molecules are
subsequently broken down during metabolism
(+ solar energy)
Productivity in ecosystems
(Refer to David T. Krohne ;Pg 358-366)
Primary productivity - the rate at which solar
radiation is converted into chemical energy
by autotrophs (plants) (amount of material or
energy per unit time,
e.g. g/m2/yr)
Secondary productivity - the rate at which
heterotrophs (animals) convert the chemical
energy of their food into new tissue
Productivity in ecosystems
• However, not all of the energy is converted into
new living tissues
– respiration (metabolism) accounts for a large part
• Gross primary productivity - energy fixed in
photosynthesis per unit time
• Nett primary productivity - energy fixed in
photosynthesis minus energy used in respiration (that is, it
is the amount available for harvest at next level)
Productivity in ecosystems
A measure of nett
primary productivity is
the change in biomass
per unit time (but be aware of what may
have been lost)
Biomass - the weight
of living tissue per unit
area (e.g. kg/ha)
What limits primary productivity?
(The factors that limit rate of photosynthesis limit
production)
• light
• water
• temperature
• nutrients (N, P, trace elements)
• all are essential - the resource in shortest supply
will be the one limiting biomass production
Which are the most productive ecosystems?
Ecosystem Nett primary World primary
production production
(g/m2/yr) (billion t/yr)
Tropical rain forest 2200 37.4
Woodland/shrubland 700 6.0
Temperate grassland 600 5.4
Desert and scrub 90 1.6
Swamp and marsh 2000 4.0
Open ocean 125 41.5
Upwelling ocean zones 500 0.2
Algal beds and reefs 2500 1.6
Productivity through time
• Primary productivity will vary seasonally
depending on environmental conditions
- ‘growing season’ in agriculture
- tropical vs temperate forests
• Productivity may change with the age of an
ecosystem (regenerating vs older)
Young ecosystems - often a greater proportion of young
actively growing tissue