topic 5 - ecology. introduction in our first unit, we will look at making sense of the millions of...
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IB Biology
Topic 5 - Ecology
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IntroductionIn 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.
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Introduction continuedWe 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.
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DefinitionsEcology
Ecosystem
The study of the relationships between living things and their environment
A settled unit of nature consisting of a community of organisms, interacting with each other and the abiotic (non-biological) environment
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Definitions (continued)
Community
Population
Habitat
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
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
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Definitions (continued)Species
Biomass
Biodiversity
A group of individuals of common ancestry that closely resemble each other and are capable of interbreeding and producing fertile offspring
The total mass or organic matter
The variety of life in an ecosystem
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Ecosystems
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Biosphere
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Energy and Ecosystems
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DefinitionsAutotrophs
(self feeding)
Organisms that synthesize its organic molecules from simple organic substances
Also called producersGreen plants are an example,
as they produce their food (glucose) through photosynthesis
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Definitions continuedHeterotrop
hsOrganisms 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
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Autotrophs
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Heterotrophs
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Definitions continuedDecomposersDetrivore
Saprotroph
Organisms that ingest dead organic matter, like scavengers and earthworms
(putrid feeding)Organisms that live in or on,
non-living organic matter, secreting digestive enzymes into it, and absorbing the products of digestion
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Food Chains and Food Webs
Trophic Level 1
Trophic Level 2
Trophic Level 3
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Food Web
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Flow of Energy in Food Webs100%
10% 1%
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Ecological PyramidsPyramids of Numbers
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Ecological Pyramids (cont)Pyramids of Biomass
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Ecological Pyramids (cont)Pyramids of Energy
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Comparison of Pyramids
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Populations and Growth
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Four Factors that influence a PopulationNatality - Birth Rate
Mortality – Death Rate
Immigration – Moving in
Emigration – Moving out
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Carrying CapacityPopulations 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
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Carrying Capacity (cont)Build up of waste, such as excrement or excess
carbon dioxide
Predation
Disease
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Population GrowthLag Phase
Exponential Growth Phase
Organisms are adapting to the new conditions, and very little reproduction occurring (low natality)
Organisms numbers increase rapidly, as there is an abundance of nutrients / resources, with little competition
High natality and low mortalityLittle accumulation of waste
products
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Population Growth (cont)Linear
Growth Phase
Growth slows due to decrease in 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
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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.
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Population Growth (S) Curve
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Causes of Population GrowthCauses of the Exponential Phase
Plentiful resource such as food, space or lightLittle or no competition from other inhabitantsFavourable abiotic factors, such as
temperature or dissolved oxygen levelsLittle or no predation or disease
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Causes of Population Growth (cont)Causes of the Transitional or Linear Growth
PhaseWith 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.
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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 reachedEnvironmental Resistance is observed
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Limiting Factors on Population GrowthDensity-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.
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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.
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Limiting Factors on Population Growth (cont)There are several mechanisms that work with
the limiting factorsExtrinsic 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.
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Populations as Units of Structure and Function - Statistics
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Populations as Units of Structure and Function - StatisticsRandom Sample
A method to ensure that every individual in a population has an equal chance of being selected
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Group Measuring TechniquesCapture – Mark – Release – Recapture
(Lincoln Index)
Allows for random sampleApproximate count of organisms in an areaAssumes there is no natality, mortality,
immigration and emmigration Banding of birds Tagging of larger organisms
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Group Measuring Techniques (cont)Quadrat Sampling Method
Allows for a simple way to measure population size
Allows for a random sampleIn areas of differing slope or variation (ie.
From terrestrial to aquatic), a line transect can be used
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Using Statistics to Measure PopulationsStatistic
s
Mean
The mathematics of collection, organization, and interpretation of numerical data, especially the analysis of population characteristics by inference from sampling
The average value obtained by dividing the total of a set of values by the number of values
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Using Statistics to Measure PopulationsMedian
Mode
The middle value that separates the higher half of a data set from the lower half of the data
The most frequently occurring data observation
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Using Statistics to Measure PopulationsStandard
DeviationMathematical 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)
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Using Standard DeviationFormula
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Using Standard DeviationSteps
Find the meanSubtract the mean from all values, and square
each differenceAdd up all answers from the above stepPut answer from above into the equation and
calculate the SDState the variance by calculating SD +/- mean
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Community InteractionsInteractions within ecosystems can be:
Neutral – neither organism is affectedOne organism is affectedBoth organisms are affected
Examples are: Symbiosis / Mutualism Parasitism Predation Competition
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Cycling of Nutrients
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Human Impact on Ecosystems
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Greenhouse EffectWhat is the greenhouse effect?
Do we need the greenhouse effect?
What is the difference between the greenhouse effect and the enhanced greenhouse effect?
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Greenhouse GasesCarbon dioxide (CO2)
Cellular respirationCombustionDecalcification
Carbon monoxide (CO)Incomplete combustion
Water vapour (H2O)Occurs naturally, through the water cycle, but
product of cellular respiration and combustion
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Greenhouse GasesNitrogen oxides (NOx)
Combustion of fossil fuels, refining process of ores
Methane (CH3)Naturally occurring, breakdown of organic
wasteIncomplete combustion
Chlorofluorocarbons (CFC’s)Refrigeration / cooling productsBreaks down ozone
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Is the enhanced greenhouse effect leading to Global Warming or Climate Change?
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Is the enhanced greenhouse effect leading to Global Warming or Climate Change?
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Precautionary PrincipleWhen an activity raises threats of harm,
measures should be taken, even if a cause and effect relationship has not been established scientifically.
ExamplesSmoking in Bars Seatbelts
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Evaluating the Precautionary Principle
Pros and Cons of implementation in response to Climate Change
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Consequences of Climate Change on Arctic Ecosystems
What impacts will climate change have on Arctic Ecosystems?