43886287 lecture 1 a ecosystem i (1)

8/3/2019 43886287 Lecture 1 a Ecosystem I (1)

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ECOSYSTEMS I

SCE3107

Ecosystems and Biodiversity

Lecture 1

Dr Sabrina Abdullah, IPGKPTupdated 4Jun2010


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ECOSYSTEMS

What are they ?

How do they function?

Dr Sabrina Abdullah, IPGKPT2010updated 4Jun2010


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Ecosystems: What are they?

An Ecosystem consists of all of theorganisms living in a community(or

communities) together with the abioticfactors with which they interact

3Dr Sabrina Abdullah, IPGKPT

2010updated 4Jun2010


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Ecosystems: What are they?

An ecological system

Composed of a biological community &

its physical environment Biotic factors (living components)

Abiotic factors (non-living components)



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Definition: Environment

(1) The circumstances or conditions thatsurround an organism or groups of

organisms (2) the complex of social or cultural

conditions that affect an individual orcommunity

Environner (French): to encircle or surround



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Ecosystems

Levels of organization

Individual/OrganismPopulation

Community

EcosystemBiosphere



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Species

Species:

all organisms of the same kind

Genetically similar enough to breed in natureand produce live, fertile offspring



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Population

Population:

All members of a species living in a given

area at the same time



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Biotic community

Biological community:

All populations of organisms living and

interacting in a particular area



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Biotic Factors

Organisms

their products

(secretions, wastes,remains)

& effects in a given

area



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Abiotic Factors

Climate

Water

Minerals sunlight



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Biosphere

Biosphere (ecosphere) - thebiosphere (i.e. all ecosystems on earth) is

an additional level of organization

12 Dr Sabrina Abdullah, IPGKPT2010updated 4Jun2010


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Ecosystems:How do they function?

System organization and functions:

Organisms interact with each other and with

their environment Roles played by various members of the

community

Ways in which energy and materials areobtained, processed, stored or cycledbetween components of the ecosystem



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Ecosystem Components & Relationships

Ecosystems

BioticAbiotic Communities

Populations

Species

Energy Matter Habitat Niche

Producers

Consumers

Decomposers

Recycled

Heat

Radiated

to space

Dispersed

or

degraded



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Ecosystem-how do they function?

All ecosystems on Earth are linked viaglobal biogeochemical cycles.

Existence of life depends upon an energy source (the sun)

oxygen, carbon, nitrogen and other elements,

all of which are part of worldwide geologicaland chemical cycles



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Ecosystems function through:

Energy flow

Cycling of materials

A systems approach that attempts tounderstand

the way energy is passed through the system

how nutrients are cycled



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Ecosystem Functions

Individual organisms or species can beconsidered in terms of the function they

perform



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Role of Biodiversity in ecosystem:

Biological diversity allows the different

ecosystem functions to be carried

out



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The primary ecosystem functionsare to:

Capture Store

Transfer

Energy

Carbon dioxide

Nutrients

Water

Dr Sabrina Abdullah, IPGKPT201019 updated 4Jun2010


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Dr Sabrina Abdullah, IPGKPT201020

ECOSYSTEMS

ecosystems are a network of

interactions, beginning with

the PRIMARY PRODUCERS

(the PLANTS) and

connecting to herbivores,carnivores, parasites,

decomposers

...energy, nutrients & water

are cycled through the

network by these different

groups

updated 4Jun2010


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Systems approach to ecosystem function

Dr Sabrina Abdullah, IPGKPT201021

Flow ofenergy

andmaterialsthrough anecosystem

Miller Ch.4Fig 4.6

updated 4Jun2010


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Essential characteristics ofecosystems

Energy flow

Cycling of Materials



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1. Energy Flow - essential characteristic of ecosystems

Energy flows in a unidirectionalway (it doesnot cycle!) fig 4.13 Miller Ch 4

This requires a continuous input of energyinto an ecosystem

Energy sourceautotrophs heterotrophs



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Autotrophs

(e.g. plants, algae)organisms capable of

synthesizing all theirrequired organicmolecules fromsimple organic

substances and anenergy source

Heterotrophs

(e.g. animals)

organisms that cannot

synthesize complexorganic compounds andmust feed on organicmaterial formed by otherorganisms to obtain

energy and necessarymolecular building blocksfor metabolism andgrowth

Dr Sabrina Abdullah, IPGKPT201024 updated 4Jun2010


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2. Cycling of Materials -essential characteristic of ecosystems

Materials (e.g. carbon, nitrogen, phosphorus)are cycled from the abiotic environment, through

living organisms, and back to the abioticenvironment

This results from metabolic activities of plants

and animals, and organisms such as bacteriaand fungi that break down organic matter



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Energy in ecosystems All organisms require energy

maintenance, growth, reproduction, (and movement)

The energy driving the biosphere (and all ecosystems) issolar radiation, captured via photosynthesis byautotrophs

about 1% of visible light converted to chemical energy

about 120 billion tonnes of new organic material produced eachyear

about 99% of all organic matter in the biosphere are autotrophs(i.e. mostly plants)

updated 4Jun201026 Dr Sabrina Abdullah, IPGKPT2010


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Sunlightthe source of energy for the biosphere

Photosynthesis:

6 CO2 + 12 H2O C6H12O6 + 6 O2 +6H2O

Respiration:Energy (from photosynthesis) is released and used bythe organism when the complex molecules aresubsequently broken down during metabolism

+ solar energy

Miller Ch 4 Fig 4.14



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Productivity in ecosystems(David T. Krohne ;Pg 358-366)

Primary productivity - the rate at which solarradiation is converted into chemical energyby autotrophs (plants) (amount of material or

energy per unit time,e.g. g/m2/yr)

Secondary productivity - the rate at whichheterotrophs (animals) convert the chemicalenergy of their food into new tissue



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Productivity in ecosystems

However, not all of the energy is convertedinto new living tissues

respiration (metabolism) accounts for a large

part

Gross primary productivity - energy fixed inphotosynthesis per unit time

Nett primary productivity - energy fixed inphotosynthesis minus energy used in respiration (that is, itis the amount available for harvest at next level)



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Productivity in ecosystems

A measure of nett primary productivity is thechange in biomass per unit time(but be aware of what may have been lost)

Biomass - the weight of living tissue per unitarea (e.g. kg/ha)



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What limits primary productivity?

The factors that limit rate of photosynthesislimit production:

light water

temperature

nutrients (N, P, trace elements) all are essential - the resource in shortest

supply will be the one limiting biomassproduction



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Productivity through time

Primary productivity will vary seasonallydepending on environmental conditions

- growing season in agriculture- tropical vs temperate forests

Productivity may change with the age of an

ecosystem (regenerating vs older)

Young ecosystems - often a greater proportion of youngactively growing tissue



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Which are the most productive

ecosystems on Earth?



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THANK YOU



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Next Lecture

Lecture 2: Ecosystems II

Types of ecosystems Locations

Biodiversity, complexity and stability

Dr Sabrina Abdullah IPGKPT

43886287 lecture 1 a ecosystem i (1)

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