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ECOLOGYECOLOGYLECTURE 1LECTURE 1
Professor Ralph KirbyProfessor Ralph KirbyFaculty of Life SciencesFaculty of Life Sciences
Extension 7323Extension 7323Room B322Room B322
What is What is Ecology?Ecology?
Scientific study of the Scientific study of the relationships between relationships between organisms and their organisms and their environmentenvironment
Note Note ALLALL relationships relationships Major Unit is the Major Unit is the
EcosystemEcosystem An ecosystem is made up An ecosystem is made up
of of biotic biotic & & abioticabiotic parts parts BioticBiotic
MicroorganismsMicroorganisms PlantsPlants AnimalsAnimals
AbioticAbiotic AtmosphereAtmosphere Energy sourceEnergy source
• Sunlight Sunlight etc.etc. TemperatureTemperature
• Equator, arctic Equator, arctic etc.etc. SubstrateSubstrate
• Soil, water, air Soil, water, air etc.etc.
In order to study In order to study ecology, a vaste ecology, a vaste range of other areas range of other areas of science are of science are involvedinvolved
Each overlaps in Each overlaps in some way with some way with ecologyecology
Some overlap more Some overlap more than othersthan others
Most important areMost important are GeneticsGenetics BiochemistryBiochemistry Behavior scienceBehavior science PhysiologyPhysiology
The ecosystem is made up of a hierarchy of components
•Above•Biosphere
•Below•Population
•Community
Ecosystem are dynamic Ecosystem are dynamic systemssystems
They change as the They change as the environment in the system environment in the system changeschanges
Natural selection acts to change Natural selection acts to change the biotic (and abiotic to some the biotic (and abiotic to some extent) parts of the ecosystemextent) parts of the ecosystem
Differential success of individuals Differential success of individuals within a population resulting from within a population resulting from their interaction with their their interaction with their environmentenvironment
The major factors affecting the The major factors affecting the organisms’ survival in the organisms’ survival in the system issystem is
FitnessFitness• For each individual, this is its For each individual, this is its
proportionate contribution to the proportionate contribution to the next generationnext generation
• See finches and the effect on a See finches and the effect on a change in seed size on beak sizechange in seed size on beak size
The traits selected for by natural selection need to be inheritable so that the The traits selected for by natural selection need to be inheritable so that the next generation after selection retains the changenext generation after selection retains the change
Three types of selectionThree types of selection DirectionalDirectional
• See finchesSee finches StabilizingStabilizing
• Long necks in giraffesLong necks in giraffes DisruptiveDisruptive
• Sexual dimorphismSexual dimorphism
Note that because natural selection is based on traits affecting fitness being inheritable, the changes that occur in a population due to selection affect the frequency of genes within a population and this in turn affect the phenotype of the individuals carrying the genes
Note however that Note however that environment can affect environment can affect the physiology of an the physiology of an organism without organism without affecting the geneticsaffecting the genetics See plasticity of leavesSee plasticity of leaves See affect of altitude on See affect of altitude on
some plantssome plants
Genetic variation within a population is absolutely Genetic variation within a population is absolutely necessary for natural selection to occurnecessary for natural selection to occur
If all individuals are identical within a population then their If all individuals are identical within a population then their fitness will all be the samefitness will all be the same
Variation is initially introduced by mutationVariation is initially introduced by mutation Asexual reproductionAsexual reproduction
Offspring identical to parent except for mutationOffspring identical to parent except for mutation• Limits population variationLimits population variation
Can involve haploidyCan involve haploidy• All genes are expressed and selected for/againstAll genes are expressed and selected for/against
Lack of variation can be balanced by rapid reproduction such as in Lack of variation can be balanced by rapid reproduction such as in bacteriabacteria
Sexual reproductionSexual reproduction Reassortment of genes provided by two parents in the offspringReassortment of genes provided by two parents in the offspring
• Increases dramatically the variation within a populationIncreases dramatically the variation within a population In most cases requires diploidyIn most cases requires diploidy
• Diploidy protects against deleterious mutationsDiploidy protects against deleterious mutations
What is a speciesWhat is a species Ecology is based on the idea that we can identify different Ecology is based on the idea that we can identify different
groups of organisms within an ecosystemgroups of organisms within an ecosystem These groups are generally called speciesThese groups are generally called species There are three specific means of defining a speciesThere are three specific means of defining a species
Morphological species conceptMorphological species concept• A species is defined as a morphologically consistent group of organisms than A species is defined as a morphologically consistent group of organisms than
can be distinguished from all other speciescan be distinguished from all other species Can fail. So called cryptic speciesCan fail. So called cryptic species
Biological species conceptBiological species concept• A group of populations whose individuals can interbreed and produce fertile A group of populations whose individuals can interbreed and produce fertile
offspring and cannot interbreed with other speciesoffspring and cannot interbreed with other species• Reproductive isolationReproductive isolation
Still fails. If you cannot tell the individuals apart morphologically, how can you tell Still fails. If you cannot tell the individuals apart morphologically, how can you tell if they are interbreeding or notif they are interbreeding or not
Also, some species can interbreed and produce viable offspringAlso, some species can interbreed and produce viable offspring• Bontebok and Blesbok in South AfricaBontebok and Blesbok in South Africa
Genetic species conceptGenetic species concept• A group of populations whose individuals have a distinct genetic makeup and A group of populations whose individuals have a distinct genetic makeup and
who do not interbreed with others groups of populations for some reasonwho do not interbreed with others groups of populations for some reason Bontebok and Blesbok are genetically distinct as well as being morphologically Bontebok and Blesbok are genetically distinct as well as being morphologically
different. Do not naturally overlap in rangedifferent. Do not naturally overlap in range
Allopatric SpeciationAllopatric Speciation Easy to understand.Easy to understand.
Sympatric speciationSympatric speciation More difficultMore difficult
Natural Selection and EvolutionNatural Selection and Evolution
Evolution is reflected in changes in gene Evolution is reflected in changes in gene frequencies and gene phenotypesfrequencies and gene phenotypes
However, changes in gene frequencies However, changes in gene frequencies involve tradeoffsinvolve tradeoffs
Giraffes do not graze well on grass due to Giraffes do not graze well on grass due to their long neckstheir long necks
Snow leopards can hide in snowy Snow leopards can hide in snowy mountainsmountains
Ordinary leopards can hide well in green Ordinary leopards can hide well in green treestrees
Organisms reproduce best in Organisms reproduce best in their optimal environmenttheir optimal environment
This optimal This optimal enviroment is enviroment is commonly called commonly called their niche and their niche and is multi-is multi-dimentional in dimentional in terms of the terms of the parameters that parameters that are involved. It is are involved. It is very difficult to very difficult to completely completely define a nichedefine a niche
Example of a feeding nicheExample of a feeding niche For blue-gray For blue-gray
gnatcatchergnatcatcher Size of preySize of prey
• Size of the insect Size of the insect caughtcaught
Foraging heightForaging height• Height above the Height above the
ground that the insect is ground that the insect is caught atcaught at
Optima are about 3.8mm Optima are about 3.8mm and 3.5mand 3.5m
Limits are about Limits are about 1.75/13mm and 1.75/13mm and 0.5/11.5m0.5/11.5m
More bigger prey are More bigger prey are caught at the optimal caught at the optimal height than at any other height than at any other heightheight
All life requires energy to sustain All life requires energy to sustain itselfitself
With very few exceptions, all life With very few exceptions, all life on earth is dependent on solar on earth is dependent on solar energyenergy
Life on Earth exists because it’s Life on Earth exists because it’s fitness is optimal for the fitness is optimal for the environment created by solar environment created by solar energyenergy
However, the effects of solar However, the effects of solar radiation vary across the surface radiation vary across the surface creating a variety of nichescreating a variety of niches
These niches can vary in space These niches can vary in space and in timeand in time
Both position on Earth and Both position on Earth and seasonality are important factors seasonality are important factors in ecosystemsin ecosystems
Mars is not optimal for a viable Mars is not optimal for a viable biosphere because of lack of biosphere because of lack of atmosphere and radiationatmosphere and radiation
Mars might once have had a Mars might once have had a biosphere of some type, hence biosphere of some type, hence Rovers looking at geology and Rovers looking at geology and Beagle’s attempt to look for lifeBeagle’s attempt to look for life
Variation in solar radiation on Earth is quite large Variation in solar radiation on Earth is quite large and thus has a dramatic effect on ecosystemsand thus has a dramatic effect on ecosystems
Compare a Compare a temperate region temperate region with a tropical with a tropical regionregion
Much greater Much greater variation in variation in temperate regiontemperate region
Poles arenot Poles arenot included but see included but see high altitudehigh altitude
Enviromental variations with Enviromental variations with latitude, longitude and heightlatitude, longitude and height
The reason The reason for the for the variation is variation is the cellular the cellular structure structure for air for air movement movement across the across the globeglobe
Note that Note that the fact the fact that the that the Earth spins Earth spins is one of is one of the major the major reasons for reasons for climate climate variationvariation
Note that ocean currents also affect climate, Note that ocean currents also affect climate, sometimes very dramaticallysometimes very dramatically
Compare the climate of England to that of Novia Compare the climate of England to that of Novia Scotia at same latitudeScotia at same latitude
Compare climate of Korea and Spain, Compare climate of Korea and Spain, particularly in winterparticularly in winter
Warm air holds more water vapor than cold airWarm air holds more water vapor than cold air When cold air meets vapor carrying warm air, rain occursWhen cold air meets vapor carrying warm air, rain occurs Thus climate in terms of temperature, winds and ocean currents Thus climate in terms of temperature, winds and ocean currents
affects the world’s rainfallaffects the world’s rainfall Note limited rainfall in east Australia, Namibia, California and ChileNote limited rainfall in east Australia, Namibia, California and Chile
All have cold ocean currentsAll have cold ocean currents
Intertropical ConvergenceIntertropical Convergence
Weather Weather patterns patterns repeat repeat themselves themselves over timeover time
See TaiwanSee Taiwan
Up to the present we have Up to the present we have talked globallytalked globally
However, the topography of However, the topography of the area can have major the area can have major influences on the climate and influences on the climate and therefore the ecologytherefore the ecology
Multiple ecosystems can Multiple ecosystems can exist within a very small areaexist within a very small area
Most organisms exist in a microclimate that is Most organisms exist in a microclimate that is optimaloptimal
Scale of climate in hundreds of kilometresScale of climate in hundreds of kilometres Scale can vary from metres to kilometres to tens Scale can vary from metres to kilometres to tens
of kilometresof kilometres
ConclusionsConclusions
Ecology is a science that involves many other Ecology is a science that involves many other sciencessciences
When you study ecology you need to define the When you study ecology you need to define the areas that are of interestareas that are of interest
Both Abiotic and Biotic influences are importantBoth Abiotic and Biotic influences are important Genetics and evolution play an important role in Genetics and evolution play an important role in
ecosystemsecosystems Ecosystem change both in time and in spaceEcosystem change both in time and in space