V.C.E. Biology Unit 2

Area of Study 2Dynamic 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 considerations1. where, when and at what age a species breeds2. Its rate of growth3. The time required for sexual maturity

Read and summarise the example of the Canadian cod (p518)

Sustainability and conservationThe 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 salinitySalinity 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 salinity2. Dryland salinity

• Irrigation salinityResults from excessive irrigation – flooding crop

growing areas.Brings excess salt to the surface soil, killing the

roots of plants.

• Dryland salinityResults 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 riversAlso 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 watercan have serious implications for the plants and animals that live in the waterways.The accumulation of dissolved mineral nutrientsin a body of water is termed eutrophication. Eutrophication can result in many secondaryeffects (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 disposalMuch 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 fireIf 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 fireRead 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 successionDifferent communities become established on land

that has not previously been colonised, e.g. a lava flow

• Secondary successionDifferent 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 blanketThe 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