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V.C.E. 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 ... – PowerPoint PPT presentation

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Title: V.C.E. 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
  • - Biotic component or abiotic component

Frequency of change
  • Changes in an ecosystem may be due to
  • regular and predictable events, such as tides and
  • sporadic (irregular) events, such as floods
  • one-off events, planned or unpredictable, such as
    a massive oil spill that impacts on a marine
  • Read pages 504-506 and explain the changes that
    occur in different ecosystems.
  • Changes in ecosystems can be on a small or large

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
  • 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
  • fire prevention measures (controlled burns)
  • agricultural activities (land clearing and use of
  • 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

Impacts of invasive exotic species
  • Displacement and loss of native species can
  • When introduced species are successful predators
    of native species (foxes and feral cats)
  • When introduced species bring a new disease into
    a community and the native species are not immune
    to it (exotic fungus)
  • When introduces species use the same resources as
    the native species, such as food or shelter,
    therefore acting as competition (redfin perch)
  • When the introduced species change the
    environment of an ecosystems so that native
    plants and animals can no longer survive (swamp

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
  • declaring a species to be noxious (what does this
  • 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
  • Three different types of biocontrol can be
  • Classical biocontrol (natural enemies as
    mentioned above)
  • Conservation biocontrol (non-introduced, from
    that area)
  • Biopesticides (bacteria, fungi or worms)

  • Blocking conception in rabbits called
  • Single sex in offspring for carp to only
    produce male offspring
  • No functional gene -gt no enzyme -gt 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
  • where, when and at what age a species breeds
  • Its rate of growth
  • 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
  • Irrigation salinity
  • 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
  • 1. Damming of rivers and diversion of water from
  • 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
  • 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
  • These procedures all have a negative impact on
    the environment and the various surrounding
  • Think about several implications for each of the
    procedures mentioned above.

  • 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
  • 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
  • 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
  • not produce successive generations.
  • If fires are too frequent, the germinated seeds
  • 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

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)
  • The long term use of certain chemicals,
    chloroflurocarbons (CFCs), 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

  • 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
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