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YEAR 12
BIOLOGY
ECOLOGY
Overview
 Organisms
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Components of an ecosystem
Habitat
Niche
Adaptations
Law of Tolerances
Overview
 Populations
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Features
Density and distribution
Regulation
Growth
Patterns
Overview
 Communities
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Food chain and webs
Energy flow
Nutrient cycles
Species interactions
Competition
What is Ecology?
What is Ecology?
 Ecology is a branch of science
concerned with organisms, populations,
communities and ecosystems.
 Definition
 The study of how organisms interact with
each other and with their physical
environment.
Species - Definition
 Organisms belong to the same species if
they normally interbreed and produce
fertile offspring.
 In some cases it is possible to classify
organisms as belonging to the same
species if they have similar characteristic.
Species - Subspecies
 Considerable variety can exist between
members of a species.
 In some cases two or more quite distinct
varieties exist. These different varieties
are called Subspecies.
Subspecies
 The Barssica’s
GENUS
SPECIES
SUBSPECIES
COMMON
NAME
Brassica
oleracea
Capitata
Cabbage
Brassica
oleracea
Cymosa
Broccoli
Brassica
oleracea
acephala
kale
Brassica
oleracea
botrytis
Cauliflower
Brassica
oleracea
gemmifera
Brussel
sprouts
Classification Keys
 Keys are used to identify organisms and
to find the name of individual organisms.
 TASK:
 Using the “Life Science” textbook
complete investigations 3 & 4.
Components of an
Ecosystem
 ENVIRONMENT
 Both physical or non-living (abiotic) and biotic
(living) factors affect the organisms in a
community. These factors influence their
distribution, survival, growth and reproduction.
 Abiotic – the physical factors in an
environment. These are non-living factors.
 Biotic – the living factors within an
environment.
Environmental Factors
Biotic Factors
Predators
Parasites
Food supply
Human
influence
competition
Abiotic Factors
Light intensity
Temperature
Humidity
O2 and CO2
levels
Exposure
Salinity
Water pH
Rainfall
Daylength
Wind
Soil type
Wave action
Soil pH
Habitat and Niche
Habitat and Niche
 Habitat – The place or environment in
which an organism lives is termed its
habitat. It must not just include their
general environment (e.g. forest, ocean)
but include some detail about abiotic
conditions in which these organisms
must live in to survive.
Habitat and Niche
 Niche – You could say that the habitat is an
organism’s address, and that the ecological
niche is its profession. The ecological niche is
a description of;
 the opportunities provided by the habitat;
and
 The adaptations of the organism that enable
it to take advantage of those opportunities.
Habitat and Niche
 The niche, then, is the role that the species
plays in the community of interacting species.
This includes;
 Where it lives
 What it eats
 How it responds to stress, and
 What limits its population growth
 Biozone pg67-68
Ecological niche
investigation
 Collect a worksheet from the front of the class.
 Using your instruction sheet, complete the
investigation looking at the ecological niche of
the ‘window’ and ‘notch’ caterpillar
Law of Tolerance
Copy
 An organism’s ability to survive variation in
environmental conditions is called its
Tolerance.
 The law of tolerance states that: For each
abiotic factor, an organism has a range of
tolerances within which it can survive. Toward
the upper and lower extremes of this tolerance
range, that abiotic factor tends to limit the
organism’s ability to survive.
Law of Tolerance
 The wider the tolerance range of a species, the
more widely dispersed the organism is likely to
be.
 Each species will have an optimum tolerance
range within which the species will be most
abundant. Outside of this optimum range,
organism’s may experience physiological
stress.
 Biozone pg 65
Adaptations
 These are inherited characteristics which enable
an organism to survive and reproduce in a
particular habitat.
 Most organisms are a combination of many
adaptations that allow them to fit into their
environment easily. Adaptations are grouped
into three types;
 Structural
 Behavioural
 Physiological
Structural Adaptations
 Physical structures of organisms which help
ensure success in a habitat.
 These include such things as; shape of the
body, the colour, appendages.
 Example:
 Wide wings of birds that enable flight
 Dense plumage of a Kea that provide insulation
 Widely spaced eyes of a rabbit to increase field of
vision to detect predators
Behavioural Adaptations
 Ways in which members of a species act in
order to increase their chance of survival.
 These include such things as; defence
behaviour, nocturnal or diurnal, hiding, spitting,
stinging.
 Example:
 Bats roosting in colonies. Provides warmth and
protection.
Physiological
Adaptations
 Processes that organisms carry out in order to
survive.
 Includes; anything to do with metabolism, the
ability to tolerate high temps or more salty
waters, secretion of enzymes for digestion,
high reproductive rates
 Example
 Excellent hearing at high frequencies of bats to
locate flying insects ( using echolocation clicks)
 Biozone pg 70,74
Adaptations
Populations
 Populations
 Features
 Density and
distribution
 Regulation
 Growth
 Patterns
Features of Populations
 A population is a group of organisms which all
belong to the same species and live in the
same location
 To define a population you need to know the
type of individual, the time and the place e.g.
all the buttercups on the sports field of our
school in February, 2006.
Population Attributes
 As an individual you are born, you grow
and you die. A population has a birth rate
and a death rate.
 As there is normally a large number of
individuals in a population, you can also
measure population attributes. These
include density, distribution, age
structure, survivorship and life
expectancy.
 Biozone pg 76
Density & Distribution
 Density – is the number of individuals of
a population per unit area of habitat at a
specific time.
 In low density populations, individuals
spaced will apart e.g. Tigers are solitary
animals, found at low densities.
 In high density populations, individuals
are crowded together e.g. Termites form
well organised, high density colonies.
Density & Distribution
 Distribution – Populations tend to spread out
in all directions until they come to a physical
barrier. Within that barrier, they may be
random, clumped or uniform.
Distribution patterns
 a) random distribution
 Spacing between
individuals is
irregular.
 b) uniform distribution
 Individuals are evenly
spaced within an area
 c) clumped
distribution
 Individuals are
grouped in patches
 Biozone pg 77
Population Regulation
 Population size is regulated by factors
that limit population growth.
 Density independent factors –
regardless of population density, these
factors are the same for all individuals.
 Density dependent factors – the effects
of these factors are influenced by
population density.
 Biozone pg 78
Population Growth
 The number of individuals comprising a
population may fluctuate considerably
over time. Populations gain individuals
through births or immigration and lose
individuals through deaths and
emigration.
 Biozone pg 79
 A model – collect and complete the
worksheet demonstrating growth of a
sparrow population.
Population Growth
Curves
 Populations becoming
established in a new
area for the first time are
often termed Colonising
populations.
 These show an
exponential growth
curve.
 If the resources in the
new area were endless
then the population
would continue to
increase at an
exponential rate.
Population Growth
Curves
 However, in a natural population, initially
the growth may be exponential but as the
population grows, its increases will slow
and it will stabilise at a level that can be
supported by the environment.
 This is called the Carrying Capacity or
K.
 In an established population the
population numbers will fluctuate about
K.
r and k Selection
 There are two parameters that govern
population growth
 r and k selection
 r selection refers to the maximum reproductive
potential of an organism and r-selected species
are those with a high intrinsic capacity for
population increase.
 k refers to the carrying capacity of the
environment and k-selected species exist near
this point of equilibrium with the environment
r and k-selection
 R-selected species tend to be opportunists
because they are poor competitors and must
continually invade new areas in order to gain
the advantage of their high reproductive
potential.
 K-selected species are also called competitor
species because they are challenged in
competitive environments to use available
resources more efficiently and thereby
compensate for their lower reproductive
potential.
Life Tables and
Survivorship
 Data collected during a population study
can be presented as a table called a life
table or graphically as a survivorship
curve.
 The shape of a survivorship curve shows
graphically at which life stages the
highest mortality occurs.
Survivorship
 There are three types of survivorship curves
 Type I
 Mortality is very low in the infant and juvenile years, and
throughout most of adult life. Mortality increases rapidly in
old age.
 Type II
 Mortality is relatively constant through all life stages (no
one age is more susceptible than another)
 Type III
 Mortality is very high during early life stages, followed by a
very low death rate for the few individuals reaching
adulthood.
Survivorship
Population Age
Structure
 The age structure of a population refers
to the relative proportion of individuals in
each age group in the population.
 The population is usually divided into
three groups
 Pre-reproductive
 Reproductive
 Post-reproductive
Population Age
Structure
 This is usually shown as a age pyramid.
The shape of the pyramid show different
things
 True pyramid – an expanding population
 Bell shaped – a stable population
 Urn shaped – a diminishing population
An Expanding
Population
A Stable Population
A Diminishing
Population
Patterns in Ecology
 The three patterns we will be looking at
are:
 Succession – the change in species over
time
 Stratification – the vertical layering of
organisms
 Zonation – the horizontal bands of
organisms which form in relation to a
gradient in a major environmental factor.
Ecological
Succession
 After a disaster, new organisms colonise
the land, and each modifies the
environment so that is becomes suitable
for a new species.
 This change in species composition over
time is called ecological succession.
Ecological
Succession
 The community passes through a sequence of
stages (seres) until eventually a stable climax
community is formed.
Primary Succession
 Primary succession refers to the
colonisation of regions where there is no
preexisting community.
 Examples include
 New volcanic islands
 New coral atolls
 Islands with communities that have been
extinguished by a volcanic eruption.
Primary Succession
Secondary
Succession
 This occurs when an existing community
has been cleared by some disturbance
that leaves the soil intact.
 In this case the area often eventually
returns to its original state.
 Secondary succession can be broken
down into two types: Catastrophe cycle
and Gap regeneration.
Secondary
Succession
 Gap regeneration
 Smaller scale e.g. large tree fall
 Catastrophe Cycle
 Usually large scale e.g. fire, cyclone
damage, slips
 The degree of destruction varies
Zonation
 Bands of organisms may form in relation to a
gradient in a major environmental factor. This
is Zonation.
 The plants and animals in the various zones
have different adaptations that fit the slightly
different environments.
 Some species may overlap onto more than one
zone, however, here they often have reached
their limit of tolerance and cannot compete with
the other occupiers of that zone.
Zonation
 Factors that lead to zones on a rocky shore:
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Exposure to air
Exposure to extremes in temperature
Fluctuations in Salinity
Lack of food while the tide is out
Respiration, gas exchange problems
Light
Wave action
Toxic wastes
Predators
Space
Stratification
 Stratification – vertical layering, usually of
plants.
 The forest is usually divided into 5 distinct
layers, each with its own microclimate.
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Canopy
Subcanopy
Tree fern layer
Shrub layer
Ground layer
Stratification
 Each successive layer in a forest creates
different microclimates below it.
 Such environmental factors as sunlight,
wind, temperature and humidity all differ
at each level and determine the types of
plants able to survive there.
Food Chains
Food Webs
Energy Flow in an
ecosystem
 The two main energy flows in an
ecosystem are:
 The grazing relationship. Plants are eaten
by herbivores. In turn, herbivores are eaten
by carnivores.
 The organic detritus relationship. All the
dead parts and wastes of organisms are
broken down by bacteria and fungi.
Energy flow in an
ecosystem
 Both of these systems have food chains,
or food webs. Each link in the chain or
web is called a trophic level, and at each
link energy is lost.
 Only about 10% of the energy is passed
on, which is why most food chains are
only about 4 links long – the energy runs
out.
Energy Pyramids
 Trophic levels of any ecosystem can be
arranged in a pyramid shape. The first
trophic level is placed at the bottom and
subsequent trophic levels are stacked on
top in their feeding sequence.
 There are three types of pyramids:
 Numbers, Biomass, and Energy.
Nutrient Cycling
The Carbon cycle
 Life is based on the carbon cycle. It is the key
compound in carbohydrates, fats and proteins.
 Key points
 Most carbon is as limestone in the oceans, rocks
and the soil. It is not readily available unless there
is an upwelling of ocean sediments.
 Atmospheric carbon dioxide is only about 0.03% of
air. It is used for photosynthesis for all plants on
land.
 Carbon compounds are dissolved in water.
 Fossil fuels such as coal and oil and natural gas all
contain carbon.
How humans affect
the cycle.
 We burn down forests. This removes
CO2 absorptions by photosynthesis and
increases CO2 given out by combustion
 We burn fossils fuels such as coal and
also wood.
 We burn petrol; and diesel and oil
machines and factories.
The carbon cycle
Nutrient cycling
The Nitrogen cycle
 Key points
 The air is 78% nitrogen ( however, only a few
organisms can use this)
 The main entry point into the living world is as a
nitrate ion (NO3-). This gets dissolved in soil water
and is absorbed by plant roots
 These are absorped by the plant roots and turned
into proteins.
 Animals then eat these proteins and each other.
The nitrogen cycle
cont..
 At each step of the food chain, wastes such as dead
leaves and bodies, urine and faeces are acted on by
decay fungi and bacteria. Eventually ammonia is
formed.
 The ammonia is turned into Nitrite (NO2-) by nitrifying
bacteria. It is called nitrification.
 Then the nitrite is turned into nitrate by different
nitrifying bacteria.
 The nitrate is now available for plants to absorb again.
 Nitrogen in the air can be fixed by lightning or certain
nitrogen-fixing bacteria. This process is called nitrogen
fixation.
The Nitrogen cycle
cont..
 Some nitrogen is lost to the system.
There are denitrifying bacteria which can
break down nitrates to nitrogen which
moves to the reservoir in the air. This is
known as denitrification.
The nitrogen cycle
Species Interactions