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ECOSYSTEMS
CHAPTER 19
ORGANISATION
E1 Populations are the units of the
community
• E1.1 know that a community is made up of
localised, interacting populations:
• Life is organised into structural levels
• A population- group of individuals of one
species capable of interbreeding and
producing fertile offspring, that exist in a
particular living space/habitat
• Community- ALL living organisms found
together in a particular living space or habitat
ECOSYSTEM:
• THE SUM OF ALL –the organisms living in a
particular area along with the habitat and the
physical components that affect the
organisms- e.g. oxygen levels, carbon dioxide
levels, water, sunlight soil characteristics etc
Ecosystem organisation
• THE ECOSYSTEM
IS MADE UP OF
Communities
POPULATIONS
group of the 1 species
(The living component
Of the ecosystem- made up
of various different
populations )
ORGANISMS
TISSUE
CELLS
MOLECULES
• Populations/communities that inhabit common
environments i.e. savannah woodland or grassy
plains-interact with one another
• The interactions of a populations with each other
(communities) and their interaction with the
physical environment =ecosystem
• A community is often defined by the common
vegetation e.g. River red gum community
– Producers- red gums plus??
– Consumers –feed on others for nutrients
– Decomposers –feed on dead and decaying material
recycling the essential nutrients
Plant communities
• Differ depending on the most dominant plant
type
– Forests & woodlands - trees
– Scrub- shrubs
– Grasslands- usually no trees or shrubs
Interactions between organisms can be between
members of the same species or members of
different species
 Three main areas:
 Competition
 Predation
 symbiosis
COMPETITION
• Organisms compete for same resources-light,
space, oxygen and food
– Most intense between members of the same
species (read this section in text for specific
examples)
– Some organisms exist quite well together and
depending on each species need will mean some
have very little competition between different
populations
PREDATION
• One organism feeding on another or eats it
• Could be Animal on plant or eating other
animals or on occasion plant eating animal
• Predation shapes a community-affects the
populations numbers of a community-the
biodiversity and the evolution of the
organisms involved.
PREDATORS
• Physical characteristics easily observed
–
–
–
•
Fast
Canine teeth
Agile
Most organisms have defence mechanisms to help
them avoid predators.
PLANT DEFENCES:
-Physical- thorns, spikes, hairs, waxy or silica
secretions –all can provide protection against insects
-Chemical-some plants produce chemicals that deter
herbivores, some have poisonous sap…… (see text)
ANIMAL DEFENCES
• Chemical– Again some produce chemicals that deter
predators: some poisonous butterflies, the
cocktails from spiders, bees, wasps, snakes and
other organisms use chemicals to defend
themselves
Colouration- The use of colour is very effective as either a
warning to others- bright colours can mean toxic
-Camouflage- some blend or can hide form
predators
-Mimicary- mimics or copies the appearance of
another species that is known to have protection
SYMBIOSIS
• Relationships whereby organisms exist with
another- three categories:
• Mutualism- Lichen lives with algae and
fungus- algae provides food and oxygen and
fungus the moisture…the relationship
between organisms provides survival for all
three…. “win win” for all
Commensalism
• One species benefits only, but other is unharmed
– E.g. barnacles attached to razor fish- home for the
barnacles and razor fish unharmed
Parasitism:
-Form of symbiosis the prey is harmed or eaten by
something smaller than itself- ticks, fleas, mistletoe and
some fungi
DO FOCUS QUESTIONS
E1.2: Explain that populations in a community
consist of different species and know the
characteristics that define a species.
• Populations in a community are diverse and
interact
• Species- defined as a population or group
where the members have similar
characteristics and the capacity to interbreed
and produce fertile offspring.
• DOES NOT APPLY TO-species that reproduce
via asexual means, i.e. single cell organisms
(see more explanation in text)
SPECIES
• Carl Linnaeus-1753
• Binomial system- Genus and species name
• Classification- Kingdom, phylum, class, order,
family, genus, species
• Review The rosella example in text pg 182 ish
(large book)
E1.3 Give examples of mechanisms that
maintain reproductive isolation of a species in a
community.(review list in text too)
• A mechanism that maintains reproductive
isolation means something that is biological and
prevents gene flow between different species,
even though they may appear similar.
• In other words- what stops them interbreeding
between species
• Barriers that prevent fertilisation:
– Pheromone differences
– Mating calls
– Mating rituals
- Shape of the genitalia/ flower shape prevents
copulation or pollination
Sometimes mating does occur if none of the previous
things prevent it, but then the sperm may not unite with
the ova
-sperm may be destroyed in the reproductive tract
-Fail to be attracted to the ova
-unable to penetrate the egg
If the sperm does penetrate the ova still other issues can
occur
-unequal numbers of chromosomes- foetus does not
develop
-occasional success but offspring infertile- (mule)
reproductive isolation maintained
E2. A community has several trophic
levels
• E2.1 Give examples of producers, consumers
and decomposers in a community
– 2 types of nutrition in a communityautotrophic/heterotrophic
– AUTOTROPHS-convert inorganic materials into
organic molecules-plants-photosynthesis (light
energy to chemical energy)- PRODUCERS
HETEROTROPHS
• -Organisms that must feed on others for
survival
• -involves eating the organic material of other
organisms, digesting the food so that essential
requirements are absorbed for use by cells.
• Feed on producers- herbivore
• Feed on both producers and other
heterotrophs-Omnivores
• Feed on just other heterotrophs- Carnivore
• Review food chains from text-draw a simple
one- (consumers/producers etc. 1st-3rd orders)
decomposers
• - vital in any ecosystem
• Bacteria, fungi and earthworms
• They obtain their nutrients form dead material
at all the trophic levels, includes animal
wastes, plant material and dead organisms
• The recyclers of the community
• Break down organic material and return
essential nutrients to the environment
Chapter 20
• E3 Characteristics of communities are
determined by environmental conditions
• E3.1 Describe how environmental factors may
determine the type of the community
• Each ecosystem has its own
producers/consumers/decomposers-the composition
of the community is determined by the
environmental conditions of the habitat
• Different continents and similar conditions will have
similar plant communities
• Australia- diverse plant communities/large arid
areas/variable water levels- subject to fire and high
salinity levels
Scelerophyll plants
• Leaves rigid
• Thick and waxy cuticles
(ADAPTATIONS)
• Acacias and Eucalypts contain these
adaptations
• Adaptations are needed to enable
species to survive the bushfires etc
Survival of a species is determined by
various factors:
• Interactions between other organisms- same species or
different
• Availability of resources
• The climate
• Impact of human activities
• Each species has evolved features/characteristics that enable
its survival in its particular habitat
• Various environmental factors shape evolutionary history of
species: SUNLIGHT; WATER; TEMPERATURE;NUTRIENTS;
WIND; SALINITY; WAVE ACTION….
• WRITE YOUR OWN NOTES ON THESE FACTORS IT IS QUITE
OBVIOUS- TABLE PAGE 186 OFFERS A GOOD SUMMARY OF
PLANTS AFTER YOUR NOTES ON THE FACTORS
E4 Resources are largely recycled in
undisturbed communities
• E4.1 Understand that the level of available
resources will determine the productivity of
the community
• Resources are classified” biotic or Abiotic
• Abiotic for producers includes:- light, rainfall,
soil, temperature and nutrient levels
• How effective a community is at converting
the suns energy is called its productivity-
PRODUCTIVITY
• of the total amount of energy
available/trapped by the producers only
a small amount is available to the next
trophic level
• The producers uses some energy to
maintain its own life processes-growth,
cell division, uptake nutrients and
synthesise molecules
Nett primary productivity
• Proportion of energy trapped in plant tissue
available to consumers
• Measured in dry weight- or grams/metre
squared/ per year
• BIOMASS- refers to total weight of living
matter in a community
• Productivity obviously various between
communities depending on conditions
favourable for plant growth: i.e desert vs
forest
Constraints to productivity
• Energy available
• Amount and quality or resources
• **** humans often use fertilizers and
irrigation to boost productivity but can be
detrimental to environment
• Trace elements in the soil are instrumental in
the survival of crops etc
E4.2 Explain why decomposers are
essential in returning resources to the
community
•
•
•
•
•
•
•
•
We know all organisms need energy to build tissue
The main elements being
Carbon
Oxygen
Nitrogen
Sulphur
Phosphorus
Potassium and calcium
There are about 40 essential nutrients
needed by large animals to sustain life.
• Matter is neither created or destroyed
(remember !)
• Therefore we must have ecosystems that can recycle
matter
• Recycling is done by decomposers
• These decomposers
Break down matter
To inorganic substances
To be taken up by plants
And recycled
Carbon Cycle- pg 190
• http://www.youtube.com/watch?v=9b_
95wj3wyg
• http://www.youtube.com/watch?v=A98
S-BqP4Po
Phosphorus Cycle
• So we have looked at recycling and Nitrogen
and carbon cycle
• There is also a phosphorus Cycle
– Organisms require much less of this compared to
other elements (RARE ELEMENT)
– Still essential for existence- Found in Phosphorous
Rock
– Critical component of what?
• Nucleic Acids
• RNA and DNA
• AS well as part of ATP
Phosphorous
• As Rocks are weathered/eroded by rainfall
• Phosphate released into soil
• Taken up by plants
• Some have Mycorrhiza that enables
them to grow in poor phosphate soils
• Animals obtain phosphate by eating plants/other
organisms
• When animals die- decomposers return the
phosphate to the ecosystem
• Excess phosphate (fertilisers etc) enters water
ways disturbs the natural delicate balance
Phosphorous Cycle