ECOLOGY LECTURE 1

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ECOLOGYLECTURE 1

• Professor Ralph Kirby
• Faculty of Life Sciences
• Extension 7323
• Room B322

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What is Ecology?

• Scientific study of the relationships between
  organisms and their environment
• Note ALL relationships
• Major Unit is the Ecosystem
• An ecosystem is made up of biotic abiotic parts
• Biotic
• Microorganisms
• Plants
• Animals
• Abiotic
• Atmosphere
• Energy source
• Sunlight etc.
• Temperature
• Equator, arctic etc.
• Substrate
• Soil, water, air etc.

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• In order to study ecology, a vaste range of other
  areas of science are involved
• Each overlaps in some way with ecology
• Some overlap more than others
• Most important are
• Genetics
• Biochemistry
• Behavior science
• Physiology

• The ecosystem is made up of a hierarchy of
  components
• Above
• Biosphere
• Below
• Population
• Community

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• Ecosystem are dynamic systems
• They change as the environment in the system
  changes
• Natural selection acts to change the biotic (and
  abiotic to some extent) parts of the ecosystem
• Differential success of individuals within a
  population resulting from their interaction with
  their environment
• The major factors affecting the organisms
  survival in the system is
• Fitness
• For each individual, this is its proportionate
  contribution to the next generation
• See finches and the effect on a change in seed
  size on beak size

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• The traits selected for by natural selection need
  to be inheritable so that the next generation
  after selection retains the change
• Three types of selection
• Directional
• See finches
• Stabilizing
• Long necks in giraffes
• Disruptive
• Sexual dimorphism

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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 environment can affect the
  physiology of an organism without affecting the
  genetics
• See plasticity of leaves
• See affect of altitude on some plants

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Genetic variation within a population is
absolutely necessary for natural selection to
occur

• If all individuals are identical within a
  population then their fitness will all be the
  same
• Variation is initially introduced by mutation
• Asexual reproduction
• Offspring identical to parent except for mutation
• Limits population variation
• Can involve haploidy
• All genes are expressed and selected for/against
• Lack of variation can be balanced by rapid
  reproduction such as in bacteria
• Sexual reproduction
• Reassortment of genes provided by two parents in
  the offspring
• Increases dramatically the variation within a
  population
• In most cases requires diploidy
• Diploidy protects against deleterious mutations

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What is a species

• Ecology is based on the idea that we can identify
  different groups of organisms within an ecosystem
• These groups are generally called species
• There are three specific means of defining a
  species
• Morphological species concept
• A species is defined as a morphologically
  consistent group of organisms than can be
  distinguished from all other species
• Can fail. So called cryptic species
• Biological species concept
• A group of populations whose individuals can
  interbreed and produce fertile offspring and
  cannot interbreed with other species
• Reproductive isolation
• Still fails. If you cannot tell the individuals
  apart morphologically, how can you tell if they
  are interbreeding or not
• Also, some species can interbreed and produce
  viable offspring
• Bontebok and Blesbok in South Africa
• Genetic species concept
• A group of populations whose individuals have a
  distinct genetic makeup and who do not interbreed
  with others groups of populations for some reason
• Bontebok and Blesbok are genetically distinct as
  well as being morphologically different. Do not
  naturally overlap in range

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• Allopatric Speciation
• Easy to understand.
• Sympatric speciation
• More difficult

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Natural Selection and Evolution

• Evolution is reflected in changes in gene
  frequencies and gene phenotypes
• However, changes in gene frequencies involve
  tradeoffs
• Giraffes do not graze well on grass due to their
  long necks
• Snow leopards can hide in snowy mountains
• Ordinary leopards can hide well in green trees

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Organisms reproduce best in their optimal
environment

• This optimal enviroment is commonly called their
  niche and is multi-dimentional in terms of the
  parameters that are involved. It is very
  difficult to completely define a niche

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Example of a feeding niche

• For blue-gray gnatcatcher
• Size of prey
• Size of the insect caught
• Foraging height
• Height above the ground that the insect is caught
  at
• Optima are about 3.8mm and 3.5m
• Limits are about 1.75/13mm and 0.5/11.5m
• More bigger prey are caught at the optimal height
  than at any other height

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• All life requires energy to sustain itself
• With very few exceptions, all life on earth is
  dependent on solar energy
• Life on Earth exists because its fitness is
  optimal for the environment created by solar
  energy
• However, the effects of solar radiation vary
  across the surface creating a variety of niches
• These niches can vary in space and in time
• Both position on Earth and seasonality are
  important factors in ecosystems
• Mars is not optimal for a viable biosphere
  because of lack of atmosphere and radiation
• Mars might once have had a biosphere of some
  type, hence Rovers looking at geology and
  Beagles attempt to look for life

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Variation in solar radiation on Earth is quite
large and thus has a dramatic effect on ecosystems

• Compare a temperate region with a tropical region
• Much greater variation in temperate region
• Poles arenot included but see high altitude

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Enviromental variations with latitude, longitude
and height
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• The reason for the variation is the cellular
  structure for air movement across the globe
• Note that the fact that the Earth spins is one of
  the major reasons for climate variation

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• Note that ocean currents also affect climate,
  sometimes very dramatically
• Compare the climate of England to that of Novia
  Scotia at same latitude
• Compare climate of Korea and Spain, particularly
  in winter

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• Warm air holds more water vapor than cold air
• When cold air meets vapor carrying warm air, rain
  occurs
• Thus climate in terms of temperature, winds and
  ocean currents affects the worlds rainfall
• Note limited rainfall in east Australia, Namibia,
  California and Chile
• All have cold ocean currents

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Intertropical Convergence

• Weather patterns repeat themselves over time
• See Taiwan

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• Up to the present we have talked globally
• However, the topography of the area can have
  major influences on the climate and therefore the
  ecology
• Multiple ecosystems can exist within a very small
  area

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• Most organisms exist in a microclimate that is
  optimal
• Scale of climate in hundreds of kilometres
• Scale can vary from metres to kilometres to tens
  of kilometres

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Conclusions

• Ecology is a science that involves many other
  sciences
• When you study ecology you need to define the
  areas that are of interest
• Both Abiotic and Biotic influences are important
• Genetics and evolution play an important role in
  ecosystems
• Ecosystem change both in time and in space