Topic 5 - Ecology
Introduction
 In our first unit, we will look at making sense of the
millions of organisms that live on this Earth, and their
interactions.
 There are approximately 1.5 million different species
that have been identified by scientists, of which over
half are insects.
 Estimates are that there are over 10 million or more,
that have not been identified.
Introduction continued
 We need to understand organisms, not just identify
them.
 We need to determine what it eats, how it reproduces,
its habitat, interaction with other organisms and its
environment.
 We also need to know our impact on these organisms
as well.
Definitions
 Ecology
 The study of the relationships
between living things and their
environment
 Ecosystem
 A settled unit of nature consisting of
a community of organisms,
interacting with each other and the
abiotic (non-biological) environment
Definitions (continued)
 Community
 Population
 All the living organisms in a habitat or
ecosystem, which is the total of all the
populations
 All the living organisms of the same
species in a habitat, at any one time
 Habitat
 The locality of physical area in which
individuals of a certain species can be
found. If the area is extremely small,
we call it a microhabitat
Definitions (continued)
 Species
 A group of individuals of common
ancestry that closely resemble each
other and are capable of interbreeding
and producing fertile offspring
 Biomass
 Biodiversity
 The total mass or organic matter
 The variety of life in an ecosystem
Ecosystems
Biosphere
Energy and Ecosystems
Definitions
 Autotrophs
(self feeding)
 Organisms that synthesize its organic
molecules from simple organic
substances
 Also called producers
 Green plants are an example, as they
produce their food (glucose) through
photosynthesis
Definitions continued
 Heterotrophs  Organisms that obtain organic
molecules from other organisms
 Most of the organisms use only
existing nutrients, which they obtain
by digestion and then absorb into
their cells and tissues for use
 Also called consumers
Autotrophs
Heterotrophs
Definitions continued
Decomposers
 Detrivore
 Organisms that ingest dead organic
matter, like scavengers and earthworms
 Saprotroph  (putrid feeding)
 Organisms that live in or on, non-living
organic matter, secreting digestive
enzymes into it, and absorbing the
products of digestion
Food Chains and Food Webs
Trophic Level 2
Trophic Level 1
Trophic Level 3
Food Web
Flow of Energy in Food Webs
100%
10%
1%
Ecological Pyramids
 Pyramids of Numbers
Ecological Pyramids (cont)
 Pyramids of Biomass
Ecological Pyramids (cont)
 Pyramids of Energy
Comparison of Pyramids
Populations and Growth
Four Factors that influence a
Population
 Natality - Birth Rate
 Mortality – Death Rate
 Immigration – Moving in
 Emigration – Moving out
Carrying Capacity
 Populations cannot grow forever, and there comes a
time when the growth of a population stabilizes in
terms of its numbers
 The number, or the maximum number of individuals
that a particular habitat can support is call the
Carrying Capacity (K)
 Limiting factors, which define the carrying capacity of
a habitat include:
 Availability of resources, such as water, food, sunlight,
shelter, space, or gases, such as oxygen in aquatic
habitats
Carrying Capacity (cont)
 Build up of waste, such as excrement or excess carbon
dioxide
 Predation
 Disease
Population Growth
 Lag Phase
 Organisms are adapting to the new
conditions, and very little
reproduction occurring (low natality)
 Exponential
 Organisms numbers increase rapidly,
as
there
is
an
abundance
of
nutrients
Growth Phase
/ resources, with little competition
 High natality and low mortality
 Little accumulation of waste
products
Population Growth (cont)
 Linear Growth  Growth slows due to decrease in
Phase
natality, but still high, and an
increasing mortality rate
 Checks on growth are due to more
competition, less nutrients and
more waste
 Starting to approach carrying
capacity
 Start to see environmental resistance
Population Growth (cont)
 Plateau Phase
 There is no new growth, due to the
environmental resistance and
the population reaching carrying
capacity.
 Natality and mortality are equal as
there is a limit to the amount of
resources supplied by the
environment, maximizing how
many individuals can be supported.
Population Growth (S) Curve
Causes of Population Growth
 Causes of the Exponential Phase
 Plentiful resource such as food, space or light
 Little or no competition from other inhabitants
 Favourable abiotic factors, such as temperature or
dissolved oxygen levels
 Little or no predation or disease
Causes of Population Growth
(cont)
 Causes of the Transitional or Linear Growth Phase
 With an increase in individuals in the population, there
is increasing competition for resources
 Predators, attracted by a growing food supply, start to
move in to the area
 Large numbers of individuals living together in a limited
space, opportunities for diseases to spread within the
population increase.
Causes of Population Growth
(cont)
 Causes of the Plateau Phase
 Space available for growth, such as plants, or shelter is
occupied to the maximum
 Limited food supply, means less available nutrients and
organisms tend to have smaller numbers of offspring
 Increases in predators and disease increase mortality
 Therefore, birth rate plus immigration is balanced with
the number of deaths and number of emigrations
 Carrying Capacity has been reached
 Environmental Resistance is observed
Limiting Factors on Population
Growth
 Density-Independent
 A sudden, rapid change in one or more of the physical or
chemical components of the environment may occur.
 This affects the population regardless of size, and affect
the overall size of the population or reducing the birth
and death rates.
 Examples are death due to weather, earthquakes,
drought.
Limiting Factors on Population
Growth (cont)
 Density Dependent
 Effect of other members of the population, and of
members of other populations, as the density (numbers
of organisms in a given area) increases.
 Examples are predation, disease or intra-species
competition. The effects of these factors increase with
increasing population numbers.
Limiting Factors on Population
Growth (cont)
 There are several mechanisms that work with the
limiting factors
 Extrinsic Regulatory Mechanisms – originate outside
the population and include biotic as well as physical
factors. For example food supplies, natural enemies,
disease, weather.
 Intrinsic Regulatory Mechanisms – originate in the
anatomy, physiology and behaviour. Competition is the
main regulating mechanism for large groups.
Populations as Units of Structure
and Function - Statistics
Populations as Units of Structure
and Function - Statistics
 Random Sample
 A method to ensure that every individual in a
population has an equal chance of being selected
Group Measuring Techniques
 Capture – Mark – Release – Recapture (Lincoln Index)
 Allows for random sample
 Approximate count of organisms in an area
 Assumes there is no natality, mortality, immigration and
emmigration


Banding of birds
Tagging of larger organisms
Group Measuring Techniques
(cont)
 Quadrat Sampling Method
 Allows for a simple way to measure population size
 Allows for a random sample
 In areas of differing slope or variation (ie. From
terrestrial to aquatic), a line transect can be used
Using Statistics to Measure
Populations
 Statistics
 The mathematics of collection,
organization, and interpretation of
numerical data, especially the analysis of
population characteristics by inference
from sampling
 Mean
 The average value obtained by dividing
the total of a set of values by the number
of values
Using Statistics to Measure
Populations
 Median
 The middle value that separates the higher
half of a data set from the lower half of the
data
 Mode
 The most frequently occurring data
observation
Using Statistics to Measure
Populations
 Standard Deviation
 Mathematical concept used
to summarize the spread of
variables around a mean.
 68% of the values of a
normal distribution fall
within one standard
deviation of the mean (+/-1)
Using Standard Deviation
 Formula
Using Standard Deviation
 Steps
 Find the mean
 Subtract the mean from all values, and square each
difference
 Add up all answers from the above step
 Put answer from above into the equation and calculate
the SD
 State the variance by calculating SD +/- mean
Community Interactions
 Interactions within ecosystems can be:
 Neutral – neither organism is affected
 One organism is affected
 Both organisms are affected
 Examples are:




Symbiosis / Mutualism
Parasitism
Predation
Competition
Cycling of Nutrients
Human Impact on Ecosystems
Greenhouse Effect
 What is the greenhouse effect?
 Do we need the greenhouse effect?
 What is the difference between the greenhouse effect
and the enhanced greenhouse effect?
Greenhouse Gases
 Carbon dioxide (CO2)
 Cellular respiration
 Combustion
 Decalcification
 Carbon monoxide (CO)
 Incomplete combustion
 Water vapour (H2O)
 Occurs naturally, through the water cycle, but product
of cellular respiration and combustion
Greenhouse Gases
 Nitrogen oxides (NOx)
 Combustion of fossil fuels, refining process of ores
 Methane (CH3)
 Naturally occurring, breakdown of organic waste
 Incomplete combustion
 Chlorofluorocarbons (CFC’s)
 Refrigeration / cooling products
 Breaks down ozone
Is the enhanced greenhouse effect leading
to Global Warming or Climate Change?
Is the enhanced greenhouse effect leading
to Global Warming or Climate Change?
Precautionary Principle
 When an activity raises threats of harm, measures
should be taken, even if a cause and effect
relationship has not been established
scientifically.
 Examples
 Smoking in Bars
 Seatbelts
Pros and Cons of implementation in response to
Climate Change
What impacts will climate change have on Arctic
Ecosystems?