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