A LOCAL ECOSYSTEM
Outline
The environment has an impact on all organisms in ways that a Biology student will
learn to recognise and explain. Students are able to draw on existing knowledge of
their own local area and expand on their understanding of biological concepts that can
be identified through careful analysis of the biotic and abiotic factors operating.
While the study of the relationships of organisms with each other and with their
physical environment can be theoretically presented in a classroom setting or by using
simulations of natural populations, communities and even ecosystems, the study of
ecology in the field is essential. Study of this module must include field experience of
a local terrestrial or aquatic ecosystem to observe and measure some of the abiotic
parameters to which the main plant and animal species are adapted and to study some
of the trophic, competitive and symbiotic interactions between organisms in that
ecosystem.
Students should be encouraged to analyse and report on those aspects of the local
environment that have been affected by people and propose realistic solutions to the
problems that exist. The report should include: a statement of purpose; a clear and
detailed description of the area studied; any background material collected on the
area; appropriate presentation of data collected; analysis of data; suggestions of the
relationships that exist in the area; and an assessment of human impact on the area.
This module increases students’ understanding of the nature, practice and applications
of biology.
Compare the abiotic characteristics of aquatic and terrestrial environments
Things to consider:
- What does compare mean?
- What does abiotic mean?
- What do you have to address to answer this question?
AQUATIC
* High viscosity meaning it is harder to
move through. Fish have streamlined
body so that they can move through the
water.
* Buoyancy allows organisms to be
supported within their environment.
* Generally a set temperature which in
turn supports vast amount of life.
* Aquatic environments poorly conduct
heat. Organisms lose heat to the
surrounding environment.
* Low levels of oxygen and carbon
dioxide found in this environment.
* Low amount of diffusion.
* Depending on concentration gradient
TERRESTRIAL
* Low viscosity. Easy for animals to
move around.
* Poor buoyancy. Animals with wings
can use the air to support them only.
* Temperature is constantly changing
with varying conditions from very low
temps to very high temps.
* Heat is not lost rapidly, depending on
the surrounding conditions.
* High amounts of gas for organisms to
function efficiently.
* High diffusion rate.
* Water is quickly lost by organisms on
land through evaporation.
* Ions found in soils, plants use these
there is a high availability of water for
organisms.
* Currents carry ions which aid the
function of aquatic organisms.
* Absorbs less light, light is often
reflected rather than absorbed.
* Pressure increases the deeper you
travel.
ions, plants eaten by other animals and
the cycle continues.
* High abundance of light.
* Pressure varies from environment to
environment.
Identify the factors determining the distribution and abundance of a species in each
environment.
Things to consider:
- What does identify mean?
- Underline key words
- Understand what the dot point is asking before you answer the question
A description of the main factors that affect the distribution and abundance of a
species are:
 The amount of light
 The amount of wind and rainfall
 Temperature daily and seasonal
 Effect of topography, altitude and depth
 Strength of tides, currents and waves
 Water its amount, salinity, pH and availability
 Availability of land and shelter from plants/trees
 Availability of gases in particular oxygen
 Food, suitable amount and availability of plant matter for herbivores and meat for
carnivores
 Number of competitors. Competitors may be from the same species of differing
species. They may require similar resources. Death and birth rate nay be affected here.
 Number of mates available and the rate of reproduction
 Number of predators
 Number of disease causing organisms
Describe the roles of photosynthesis and respiration in ecosystems
Things to consider:
- What does describe mean
- What is photosynthesis and what is respiration?
- Be succinct in your answer
- It may be easier to answer it in a table or under two different headings such as
photosynthesis and respiration
Photosynthesis is carried out by plants. It is the process by which the plant converts
some of the suns light energy, trapped by the chloroplasts, reacts with carbon dioxide
and water to produce glucose and oxygen. These products (oxygen + glucose) are
either converted into other carbohydrates or are the driving force behind cellular
respiration. Respiration is the process whereby glucose and oxygen react to produce
water, carbon dioxide and energy. This energy is required by the plant for cell
processes. Photosynthesis and respiration play a pivotal role in an ecosystem, as they
are the main food source for herbivores and to some extent omnivores. When a
herbivore eats a plant the complex carbohydrates that make up the plant are broken
down by the herbivore into glucose and are converted to other substances or glucose
becomes the major reactant of cellular respiration, which in turn provides energy for
the herbivores cell processes. Therefore it is evident that photosynthesis and
respiration play an important role in an ecosystem in the cycling of important
nutrients.
Identify uses of energy by organisms.
Things to consider:
- What does identify mean?
- Underline key words
- Be succinct in your answer
Energy is used by a variety of organisms in a variety of ways. For example organisms
use energy for movement, making sound, carrying out chemical reactions which
include cellular respiration, producing heat and producing light. Organisms which
produce light include glow worms, flash light fish and fireflies. They produce light
through the use of chemicals.
Identify the general equation for aerobic cellular respiration and outline this as a
summary of a chain of biochemical reactions
Things to consider:
- What does outline and identify mean?
- Underline key words
- Understand what the question is before you answer it
The general word equation for aerobic cellular respiration is:
Glucose + Oxygen
water + carbon dioxide + energy
Bio meaning living and chemical meaning involving chemicals illustrates that this
reaction occurs in a living organism. Glucose and oxygen are the reactants which
means that they react together to produce a product. Glucose is accessed from the
organism’s diet and is the product of the breaking down of complex carbohydrates.
Oxygen is usually accessed from the organism’s blood. These two chemicals react
together to produce water which is used to maintain hydration, carbon dioxide which
is eventually exhaled from the body and energy which comes in the form of ATP
which enables the organism to move, make sound and to perform necessary cellular
metabolism.
Process and analyse information obtained from a variety of sampling studies to justify
the use of different sampling techniques to make population estimates when total
counts cannot be performed (Refer to experiment handout)
Things to consider:
- What do the following words mean process, analyse and justify
- Underline key words
- Understand what the question is asking
TRANSECTS/QUADRATS/CAPTURE RECAPTURE
A transect is a strip that crosses a certain area between two points. You only work
within the transect, recording your observations found. On your transect you mark the
position of the organisms within the area. Transects can be a aerial view (plan) or a
side view (profile.)
When organisms cover a large area or are scattered it is quicker and easier to study the
area using a quadrat. A quadrat is an area usually between 1 and 50 metres squared.
Within this area numbers or estimates of the chosen organism are recorded. This
result can then be related to the total area and a total estimate can be made.
Capture recapture method is used when the organism being studied is constantly on
the move. The following equation is used.
ANSWER THE FOLLOWING QUESTIONS:
1. Bob went out on the field one day and captured 5 lizards. He tagged these
lizards and released them. The next day Bob went to the same location and
caught 10 lizards. Of the 10, 4 of the lizards already had tags.
a.) What is the total population estimate for this area? (Show working)
b.) How many of the original lizards were caught in the recapture?
2.
a.)
b.)
c.)
d.)
Calculate the abundance of a species from the following data. (Show working)
25 captured, 15 recaptured, 5 of them marked
300 captured, 350 recaptured, 300 of them marked
33 captured, 29 recaptured, 20 of them marked
50 captured, 66 recaptured, 27 of them marked
Examine trends in population estimates for some plant and animal species within an
ecosystem.
Things to consider:
- What does examine mean?
- Underline key words
- Work out what you are going to write before you write your answer
Population levels of an organism rarely are exactly the same from year to year. Many
factors may affect their numbers, for example availability of food, predation,
availability of water and reproduction. When the same species is found in the same
ecosystem in approximately the same number this population is said to be stable or in
balance. In some other cases populations may increase dramatically, this is known as
population explosion. Disease, predation, competition from other species and human
activity are all contributing factors to population decline.
ACTIVITY:
1. The pictures above are of the crown-of-thorns starfish (Acanthaster
planci) this organism is currently undergoing a population explosion.
Why might this be?
2. An increase in the number of plants in an area is usually followed by a
rise in the numbers of one or more animal species. Can you think why
this might be?
Outline factors that affect numbers in predator and prey populations in the area
studied
Things to consider:
- What does outline mean?
- Underline key words
- Be succinct
- Understand what you are going to write before you write your answer
This is a relationship between one animal, the predator, which obtains its nutrients
from other animals by eating them, the prey. This relationship increases the predator’s
chances of survival as well as the predators abundance increasing. Predator-prey
relationships tend to fluctuate, for example the greater the number of prey, the more
likely the abundance of the predator is going to increase.
The main factors that affect the predator-prey populations in a local ecosystem are:
The size of the ecosystem will determine how many organisms can inhabit the area,
fewer predators than prey, the supply of food for the prey, the greater the food supply
the more likely the increase in prey numbers, the reproductive cycles of predator and
prey determines the number of predator and prey numbers, competition for the same
prey, disease can affect both prey and predator and migration patterns of predator or
prey may affect the distribution and abundance of the predator or prey.
Identify examples of allelopathy, parasitism, mutualism and commensalism in an
ecosystem and the role of organisms in each type of relationship
Things to consider:
- What does identify mean?
- Underline key words
- Understand what you need to write before writing your answer
Allelopathy is a relationship where one organism directly obstructs or hinders another
organism’s growth and main functions by releasing toxins. For example lantana is an
introduced plant species, currently undergoing population explosion due to the perfect
conditions in Australia. Not only does lantana compete for sunlight, water and soil
nutrients from native plant species, lantana also releases a toxin into the soil which
inhibits the growth of some native plant species.
Parasitism is the relationship in which one organism uses the other organism’s
nutrients for their benefit. The organism in which the parasite lives is called the host.
Disease causing parasites are more commonly known as pathogens. The role of the
parasite in an ecosystem is to invade the host and lodge in a specific area in the host
so that the parasite can obtain necessary nutrients. For example many tapeworms
lodge in the digestive system of an organism and absorb digested food from the host.
Mutualism is the relationship between two organisms where both organisms benefit
from the relationship. An example of mutualism is the symbiotic relationship between
a herbivore such as a kangaroo and the bacteria/protozoa which breaks down the
cellulose in plant material. This is an example of mutualism because the
bacteria/protozoa break down the cellulose for the kangaroo to digest and in return the
bacteria/protozoa have a stable environment as well as an ample food supply.
Commensalism is the relationship between two organisms in which one organism
benefits from the relationship and the other is unaffected by the relationship. An
example of commensalism is the sea anemone and a clown fish. The clown fish is the
only benefactor from this relationship as the anemone provides protection for the fish
from predators, while it is apparent that the anemone does not receive anything in
return.
Describe the role of decomposers in ecosystems
Things to consider:
- What does describe mean?
- Underline key words
- Be succinct in your answer
- Use scientific terminology
Decomposers have an important role to play in local ecosystems. They absorb
nutrients from dead organisms or waste materials and return organic matter to the soil.
Detritus is the organic material that is derived from organisms once they die. Snails,
worms, termites, millipedes, mites and other organisms such as bacteria and fungi are
all known as detrivores. Detrivores play an important role in the ecosystem as the
break down large organic molecules into smaller molecules that are finally
decomposed by bacteria and fungi. This bacteria and fungi secrete digestive enzymes
that break down the organic molecules further into simpler molecules such as sugars,
and eventually into inorganic molecules such as carbon dioxide and nitrogen.
(Decomposers usually found at ground level in soil)
Explain trophic interactions between organisms in an ecosystem using food chains,
food webs and pyramids of biomass and energy.
Things to consider:
- What does explain mean?
- Underline key words and understand what they mean, E.G. trophic.
- Be succinct, use scientific terminology
Firstly trophic interactions refer to the level occupied by a consumer. If we look at the
trophic interactions in a food chain there are many different levels. For example in a
simple food chain between grass, a wallaby and a kangaroo there are two trophic
interactions. The grass is a producer, the wallaby eats the grass and is a first order
consumer which means it occupies the first trophic level, the dingo then eats the
wallaby making it a second order consumer or second trophic level. Trophic
interactions are also used in food webs. Food webs are generally constructed by
placing the producers on the bottom, and then the consumers are generally grouped
according to their trophic level and are placed in order from lowest to highest. For
example according to fig 1.9.2 the hawk can be classified on the second and third
trophic levels according to what is eats in relation to other interactions in the
environment. Trophic interactions can also be seen in biomass pyramids. Biomass
pyramids is the total amount of mass in a given community. Matter is lost at each
trophic level; therefore producers are greater then that of first or consumers and so on.
Biomass pyramids also show the biomass at each trophic level. In an ecosystem a
stable biomass would include a large amount of producers a relatively small first
trophic level of organisms and a very small amount of second trophic level organisms.
(Refer to fig 1.9.3 pg 27) Trophic interactions are also expressed through energy
pyramids. Energy pyramids show the amount of energy at each trophic level. The
lower the organism on a food chain the more energy it has available to it. From this it
can be deduced that if you are for example on the third trophic level of an ecosystem
you have less energy available to you according to the energy pyramid system.
Define the term adaptation and discuss the problems associated with inferring
characteristics of organisms as adaptations for living in a particular habitat.
Things to consider:
- What does define and discuss mean?
- Underline key words
- Be succinct, use scientific terminology
Adaptation refers to the characteristics that enable organisms to survive in an
environment. An adaptation may be structural, meaning relating to the structure of the
body, physiological, meaning how the organism functions or behaviour referring to
the behaviour of the organism. There are many problems associated with inferring
characteristics of organisms as adaptations for a particular habitat. To understand
whether or not it is an adaptation we need to know as much as possible about where
the animal lives, the conditions in which it lives, what are the abiotic factors such as
the weather patterns, does it have any natural predators, how does it move about and
what does it eat to name a few. Knowing this information may help scientists explain
any key features of the organism that may be considered an adaptation according to
the organism’s environment. Without this information scientists would merely be
guessing whether or not it was an adaptation or not. Therefore it is important that we
have a sound knowledge of the environment in order to determine if the organism has
adapted to the environment.
Identify some adaptations of living things to factors in their environment
Things to consider:
- What does identify mean?
- Underline key words
- Be succinct
The main food source of spiders is insects. Due to the nature that all insects are not
the same, spiders have adapted accordingly to their food source. The following is a
list of spider names and their adaptation. Orb spinner spider spins webs to catch
mainly flying insects. Huntsman lies flat on the bark of trees in wait of prey. The net
casting spider spins a web and casts its net over its prey to catch them. The
magnificent spider releases a chemical to attract male moths. These adaptations
enable the spiders to survive in such a diverse ecosystem.
Identify and describe in detail adaptations of a plant and an animal from the local
ecosystem
Things to consider:
- What does identify and describe mean?
- Underline key words
- Be succinct, use scientific terminology
MANGROVES
SUPPORT AND MOVEMENT: Woody plants that are anchored by a complex
network of roots which enable it to withstand the shifting sand/mud flats.
GASEOUS EXCHANGE: Gas exchange is through the stromata in the leaves
through the process known as transpiration. Mangroves of the genus Avicennia have
aerial roots known as pneumatophores which have lenticels which enables gaseous
exchange.
CONTROL OF WATER BALANCE: Mangroves are halophytes which means they
can tolerate high amounts of salt. They do this in three ways, accumulation, secretion
and exclusion.
CONTROL OF INTERNAL TEMPERATURE: Thick cuticle of leaves helps
control water loss. In dense populations shade helps lower layers stay at a lower
temperature.
OBTAINING LIGHT: Dominant plant in ecosystem. Leaves place at specific angles
to maximise photosynthesis.
REPRODUCTION: Seeds develop and drop off the plant into the water. They are
buoyant and once anchored in mud/sand they begin to germinate.
KANGAROOS:
SUPPORT AND MOVEMENT: Main adaptations are the tail for balance and
structure as well as the large hind legs which enable less energy to be expelled using
four legs.
GASEOUS EXCHANGE: Lungs
CONTROL OF WATER BALANCE: In arid conditions kangaroos obtain water
from green plant material. They minimise water loss by only sweating during
exercise.
CONTROL OF INTERNAL TEMPERATURE: Kangaroos eat at dawn and early
morning. They control internal temperature by lying in shady areas during the day and
by licking their forelimbs to cool them down.
OBTAINING LIGHT: They have binocular vision, and are mainly nocturnal
animals.
REPRODUCTION: Kangaroos have a small gestation period. Kangaroo numbers
can increase rapidly if the conditions are suitable. If conditions are poor kangaroos
stop reproducing. Another adaptation for kangaroo reproduction is that if the
conditions are suitable a female kangaroo will almost be continuously pregnant.
Describe and explain the short term and long term consequences on the ecosystem of
species competing for resources
Things to consider:
- What does describe and explain mean?
- Underline key words
- Be succinct, use scientific terminology
Competition is the process by which two or more organisms compete for the one
resource. For example their has been a decline in the number of local predators due to
the introduction of feral cats and foxes. Competition can have short term and long
term consequences within an ecosystem. The short term consequence for the
competition of resources is that the abundance of one species will begin to decline.
For example experiments performed on the grain beetle Calandra and the
Rhizopeatha, has shown a decrease in the Rhizopeatha numbers due to the
competition of the same resource. This illustrates the short term consequences of
competition. The long term consequences of competition can be dramatic. One of the
species can be eliminated from that ecosystem or in other cases that organism may
become extinct. The organism may be eliminated or become extinct due to the fact
that they are competing directly for the exact resource or they are unable to adapt to
their ecosystem in order to survive.
Identify the impact of humans in the ecosystem studied
Things to consider:
- What does identify mean?
- What does impact mean?
- Be succinct
Humans always inevitably have an impact on the local ecosystem. We live in many
different ecosystems however we all deliberately change our ecosystem to suit our
needs. This has a substantial effect on the ecosystem and its inhabitants. The main
impacts humans have on an ecosystem are land clearing, introduction of new species,
pollution and the eventual extinction of local species.
Since the arrival of Europeans in Australia we have managed to clear fifty percent of
eucalypt forests and seventy five percent of rainforests. This has a detrimental impact
on the ecosystem as it destroys habitats for local organisms, leads to erosion and
eventually land degradation. In some circumstances due to land clearing, soil type has
changed and water salinity levels fluctuate.
Introduced species have a direct impact on local ecosystems. In some cases these
species have led to the extinction of a native species or their population explodes. For
example the cane toad, European carp and lantana. These introduced species also
compete for resources.
Pollution has a direct impact on the local ecosystem in many ways. Air and water
pollution and the dumping of wastes ruin local ecosystems enough to cause disease
within a population. Pollution not only impacts upon local organisms it impacts
society.
The consequence of land clearing, introduced species and pollution is the extinction
of native species. By destroying habitats, hunting and carelessness we have in some
cases caused a native organism to become extinct. Conserving our environment is a
necessity if native organisms are going to survive within their ecosystem.
Gather information from first hand and secondary sources to construct food webs and
food chains to illustrate the relationship between member species within an
ecosystem.
Things to consider:
- What resources are we going to need to perform a first hand investigation?
- What resources are we going to need to perform a second hand investigation?
- What does illustrate mean?
- What are food webs and food chains?
http://www.gould.edu.au/foodwebs/kids_web.htm
http://www.ecokids.ca/pub/eco_info/topics/frogs/chain_reaction/assets/flash/chain_re
action.swf
http://www.harcourtschool.com/activity/food/food_menu.html