Transcript Ecology - mrsdrysdalescience

Ecology
Year 12
What is ecology?
• the scientific study of the
distribution and abundance of living
organisms and the interactions among
and between the organisms and their
environment
http://en.wikipedia.org/wiki/Ecology
Ecosystem
• natural unit consisting of all plants,
animals and micro-organisms in an
area functioning together with all the
non-living physical factors of the
environment
http://en.wikipedia.org/wiki/Ecosystem
Components of an
Ecosystem
• All systems are made up of both biotic
(living) and abiotic (non-living) components
• In any ecosystem many factors exert an
influence on living organisms and their
environment. These factors can be
broadly classified integrating or limiting
Habitat
• The particular place an organism lives is called its
habitat.
• Each habitat is likely to be the home for several
species.
• Usually these species will not be able to survive in
other habitats where conditions can be quite
different but some organisms can tolerate a
range of conditions and can therefore live in a
variety of habitats, eg flax.
Niche
• Within a habitat each species will have a
special role or way of living. Generally this
is related to how the species obtain food,
eg as a producer, predator etc.
• The role of a species in a habitat is called
its ecological niche.
• The area which the organism can occupy is
called its fundamental niche.
• Sometimes however due to competition
the niche becomes smaller, this is the
realised niche.
Factors that affect
organisms in their habitat
Biotic
Abiotic
Predators
Parasites
Food supply
Human influence
Competition
Light intensity
Salinity
Tidal Exposure
Day Length
Rainfall
Humidity
Temperature
Wind
pH levels
Wave action
Carbon dioxide
Tolerance & Limiting
Factors
• The environmental factors that can affect an
organism do not remain constant
• For a species to be able to survive in its habitat it
must be able to tolerate variation in these factors
• If it cannot, members will either die or migrate to
a more suitable habitat
• A species is usually adapted to tolerate a range of
variation in most environmental factors
• The range in which it thrives is called the
optimum range for that factor
• When an environmental factor exceeds the
tolerance limits of an organism, the organism
suffers stress
Tolerance & Limiting
Factors cont…
Tolerance & Limiting
Factors cont…
• Organisms can adjust their tolerance
limits. This is called acclimation. It can be
either:
– Temporary – such as developing a suntan to
prevent harmful UV rays affecting skin cells
– Seasonal – such as the thick coat that domestic
animals such as cats develop in autumn to
withstand winter conditions.
Liebig’s Law of the
Minimum
• The functioning of an organism is
limited or controlled by whatever
essential environmental factor/s is
present in the least favourable
amount
Gause’s Competitive
Exclusion Principle
• “No two species can occupy the same
ecological niche in the same habitat
for an indefinite period”
Gause’s Principle
• This shows that although both
species appear similar, they do not
have the same Niche requirements
• Competition between species within
habitats that overlap may be reduced
by character displacement
Biological Relationships
• The relationships between the organisms
making up a community are sometimes
based on cooperation, but more often on
competition or exploitation. If a
relationship is between members of the
same species it is described as intraspecific. Relationships between members
of different species are inter-specific.
Group Co-operation
• Some animals rely on intra-specific
co-operation.
• Members work together to ensure
mutual survival
• Many groups have developed complex
social behaviour eg: hunting in packs,
shared rearing of young
Inter-specific
Competition
• Competition between different
species in a community
• Often over resources
• More specifically there are feeding
relationships
Adaptations
• All organisms inherit characteristics that
increase their chances of survival.
• These are commonly divided into three
categories:
– Behavioural – how the organism behaves
– Structural – the shape and size of an organism
– Physiological – the working of an organisms
body
Population Attributes
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Natality: birth rate
Mortality: death rate
Net Migration Rate
Density
Age Structure
Distribution
Survivorship Curves
Population Growth Curves
Population Counting
• Can be difficult as they often cover a
large area
• Measuring methods should be chosen in
accordance to what is being measured
• Sampling methods include:
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Quadrats
Counting
Line transects
Belt transects
Mark and recapture
Food and Energy
• The main interaction between
organisms involve food
• Green plants produce their own food
via photosynthesis (producers)
• Animals eat other plants and animals
(consumers)
• Food chain and food webs show the
interactions
• Energy flows along the food chains
Food Chains
PRODUCERS
Producer
Photosynthetic plant
CONSUMERS
Primary
Secondary
Tertiary
Herbivore
Browses or
grazes plants
10 Carnivore
Eats
herbivore
2o Carnivore
Eats 1o
carnivore
Food Webs
• Groups of food chains joined together
• Represent entire feeding relationships
in community
• Show that individual organisms can
exist in more than one trophic level
Energy and Food
• Ecosystems rely on a regular supply of energy,
this comes mainly from the sun
• Radiant energy arrives as heat and light and is
converted into chemical energy in food molecules
by plants in photosynthesis
• Only 1-5% is used this way
• The energy is then passed along the food as one
organism eats another, flows in one direction
• About 10% of the stored energy in a trophic
level gets stored in the tissue of the next
• Decomposers release the remaining energy as
heat
Nutrient Cycling
• Nutrients cycle through an
ecosystem
• Carried out mainly by decomposers
and detritivores
• The chemical elements needed in
significant amounts are:
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–
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Carbon
Hydrogen
Oxygen
Nitrogen
Community Patterns
• Variations in habitat conditions can
cause changes in communities
• The three main patterns of change
are:
– Succession
– Stratification
– Zonation