ECOSYSTEMS

CHAPTER 19ORGANISATION

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(The living componentOf the ecosystem- made up of various different populations )

POPULATIONSgroup of the 1 species

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 shrubsInteractions 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 eggIf 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

community-autotrophic/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 decomposersBreak down matter To inorganic substances To be taken up by plantsAnd recycled

Carbon Cycle- pg 190• http://www.youtube.com/watch?v=9b_

95wj3wyg• http://

www.youtube.com/watch?v=A98S-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