Transcript VCE Biology Unit 2

V.C.E. Biology
Unit 2
Area of Study 2
Dynamic Ecosystems
Chapter 16 – Changes in ecosystems
Key knowledge
• develop understanding of changes to ecosystems over time
• recognise the scope, intensity and impact of various natural
changes
• extend awareness of impacts of human-induced changes on
ecosystems
• identify techniques for monitoring and maintaining
ecosystems
Changes in ecosystems
We can ask ourselves the following questions about changes in
ecosystems:
1. What was the primary cause of the change?
- Natural event or human intervention
2. What part of the ecosystem is initially changed?
- Biotic component or abiotic component
Frequency of change
Changes in an ecosystem may be due to:
• regular and predictable events, such as tides and seasons
• sporadic (irregular) events, such as floods
• one-off events, planned or unpredictable, such as a massive oil
spill that impacts on a marine habitat
Read pages 504-506 and explain the changes that occur in
different ecosystems.
Changes in ecosystems can be on a small or large scale.
Global monitoring of ecosystems
• Satellite Terra is one of many orbiting satellites that gathers
data about our planet and the ecosystems that it supports.
Predicting effects of change
• Can be very difficult to predict as there are not just primary
effects – direct effects as a result of a change, but also secondary
effects – effects that are as a result of the primary effects, rather
than the change itself.
• Global monitoring, occurring through programs such as the
Earth Observation System, and the data obtained from satellites
is the best way of attempting to predict changes that may be
disastrous.
Answer Quick-check questions 4-6 on page 509
Human impacts
Changes in ecosystems due to human impacts are usually
associated with economic development and with meeting the
needs of the growing human population. These actions may
include:
• flood control measures (damming rivers and irrigation)
• fire prevention measures (controlled burns)
• agricultural activities (land clearing and use of fertilisers)
• mining activities
• industrial activities
• needs of urbanised societies
• introduction of exotic flora and fauna (deliberate or accident)
Human impacts 1
Introduction of an exotic species
• An exotic species is one that is not native to that particular area.
• They possess problems as they are not a natural part of the
relationships that has evolved over a long time.
• Many exotic species become major ecological pests as they have
no natural predators and parasite species.
Impacts of invasive exotic species
Displacement and loss of native species can occur:
1. When introduced species are successful predators of native
species (foxes and feral cats)
2. When introduced species bring a new disease into a community
and the native species are not immune to it (exotic fungus)
3. When introduces species use the same resources as the native
species, such as food or shelter, therefore acting as competition
(redfin perch)
4. When the introduced species change the environment of an
ecosystems so that native plants and animals can no longer
survive (swamp buffalo)
Australian exotic species
•
•
•
•
Case 1 – Rabbits (p511-512)
Case 2 – Cane Toads (p512)
Case 3 – Carp (p513)
Case 4 – Athel pines (p513-514)
Read and summarise the Case studies of the above exotic
Australian species
Responding to exotic invaders
• Australian Quarantine and Inspection Service (AQIS) is
responsible for preventing the entry to Australia of new exotic
organisms through strict control measures.
• Measures to reduce or eliminate populations of exotic pests and
weeds to prevent their spread include:
-
declaring a species to be noxious (what does this mean?)
physical control measures
chemical control measures
biological control measures
Biological control measures
This refers to the use of natural enemies (predators, herbivores,
parasites or disease-causing organisms) to control exotic pests
and weeds after they have invaded a new habitat.
Three different types of biocontrol can be identified:
1. Classical biocontrol (natural enemies as mentioned above)
2. Conservation biocontrol (non-introduced, from that area)
3. Biopesticides (bacteria, fungi or worms)
Biotechnology
• Blocking conception in
rabbits – called
immunocontraception
• Single sex in offspring for
carp – to only produce male
offspring
No functional gene -> no
enzyme -> no females!
As existing females in the
population die, each
successive generation will
have fewer and fewer
females, until only males.
Human impacts 2
1. Over-harvesting of a biological resource
- Sustainable – harvesting a species at a rate that they can
reproduce to replenish the stock that is being lost
- Unsustainable use of a biological resource, which can push
populations to a vulnerable point and result in a ‘crash’.
- K-selected species particularly vulnerable . Why?
- Important considerations
1. where, when and at what age a species breeds
2. Its rate of growth
3. The time required for sexual maturity
Read and summarise the example of the Canadian cod (p518)
Sustainability and conservation
The use of biological resources in a sustainable manner requires a
commitment to conservation.
The goal of conservation is to maintain living things in their
diverse ecological settings and to permit the use of natural
resources in a sustainable manner.
Conservation may be:
• Keeping an area of habitat protected
• Restrictions of industry in vulnerable areas
• Restrictions on waste disposal
• Protecting an individual species from harvesting
Can you think of any others?
Can you think of some examples of conservation in any form?
2. Land degradation producing salinity
Salinity refers to the salt content of water or soil at a level where
the salt content damages the soil and degrades the water
quality.
Excess salt in the soil or water places many native species at risk of
extinction, and also causes significant agricultural losses
Two kinds of salinity exist in Australia:
1. Irrigation salinity
2. Dryland salinity
• Irrigation salinity
Results from excessive irrigation – flooding crop growing areas.
Brings excess salt to the surface soil, killing the roots of plants.
• Dryland salinity
Results from the clearing of deep rooted native tree species.
Removing these trees means that more water enters the soil,
causing the watertable to rise, dissolving salt in the soil and
bringing it to the surface.
Human impacts 3
Involve changes in the abiotic part of the ecosystem.
1. Damming of rivers and diversion of water from rivers
Also called ‘river regulation’ as we are changing the natural flow of
the rivers.
This is done so that the flow of water is constant over the year.
Read and summarise
- The Barmah-Millewa ecosytems and the Snowy river (p523-524)
2. Nutrient overload of waterways and waste disposal
• Nutrient overload
Changing the level of nutrients in the water
can have serious implications for the plants and
animals that live in the waterways.
The accumulation of dissolved mineral nutrients
in a body of water is termed eutrophication.
Eutrophication can result in many secondary
effects (as shown in the table on the right),
including blooming of cyanobacteria and
widespread death of aquatic plants.
Read and summarise
- Blooming cyanobacteria (p525)
- Death of the seagrasses (p526)
• Waste disposal
Much of the waste produces today is recycled, however, large
volumes of non recycle waste must still be disposed of.
Procedures for waste disposal include:
• Disposal in landfills
• Incineration
• Disposal of effluent into waterways and into the sea
These procedures all have a negative impact on the environment
and the various surrounding ecosystems.
Think about several implications for each of the procedures
mentioned above.
Questions
Answer Quick-check questions 7-11 p517
Answer Quick-check questions 12-15 p521
Answer Quick-check questions 16-20 p527
Natural change agents: Fire
Due to the fact that fire has been a natural agent for change of the
Australian environment for millions of years, many native
species of flora have adapted to need fire for one reason or
another.
Adaptations include:
• Vegetative reproducers (VR) – re-grow after fire through means
of buds located under the bark or in underground stems.
• Obligate seeders (OS) – plants do not survive the fire, but the
seeds to. In fact, the seeds need the heat produced by natural fires
to initiate germination
E.g. Acacia, Banksia, Casurina, Hakea and some Eucalyptus sp.
• Frequency of fire
If fires are too infrequent, the plants will not be able
to regenerate through VR or OS, and will therefore
not produce successive generations.
If fires are too frequent, the germinated seeds from
OS plants will not have time to produce seeds of
their own, and when the fires come through the
plants will die.
• Absence of fire
Read and summarise
- Fire for the parrots (p531)
- Fire for forest giants (p531)
- Human interventions (p532)
Natural succession in ecosystems
Changes are continually occurring within ecosystems without any
human intervention.
The natural replacement over time of one community by another
community with different dominant species is termed natural
succession.
There are two kinds of succession:
• Primary succession
Different communities become established on land that has not
previously been colonised, e.g. a lava flow
• Secondary succession
Different communities become established in an area that was
previously colonised, but was disturbed e.g. an abandoned
paddock
Restoring the balance
There are things humans can do to reduce the negative impact that
we, as a species are having on the environment.
•
•
•
•
Personal level
Local council level
State government level
Federal government level
Choose two dot points from each sub heading above on p534-535 to
write for each of the above four headings
The global ecosystem: the biosphere
The biosphere is the life-support system of planet Earth and its
source of energy in the radiant energy of the sun.
The biosphere contains all the ecosystems of the planet Earth and
the continued existance of living things depends on a
functioning biosphere.
Ozone layer: a protective blanket
The ozone layer protects the Earth from the lethal effects of
shortwave ultraviolet (UV) radiation.
The long term use of certain chemicals, chloroflurocarbons (CFC’s),
in many aerosols and propellants have caused the ozone layer to
thin and break down.
The long term impacts include:
- Global warming (and the secondary effects associated with GW)
- Widespread crop damage
- Increase of incidence of skin cancers
Total Ozone Mapping Spectrometer (TOMS)
is used to monitor the state of the ozone layer
Questions
Answer Quick-check questions 21-22 on page 533
Answer Quick-check questions 23-24 on p 534
Answer Quick-check questions 25-26 on p 538
Answer Chapter Review questions:
2, 3, 4, 5, 6 and 7