IB Biology

Topic 5 - Ecology

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.

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.

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

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

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

Ecosystems

Biosphere

Energy and Ecosystems

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

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

Autotrophs

Heterotrophs

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

Food Chains and Food Webs

Trophic Level 1

Trophic Level 2

Trophic Level 3

Food Web

Flow of Energy in Food Webs100%

10% 1%

Ecological PyramidsPyramids 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 PopulationNatality - Birth Rate

Mortality – Death Rate

Immigration – Moving in

Emigration – Moving out

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

Carrying Capacity (cont)Build up of waste, such as excrement or excess

carbon dioxide

Predation

Disease

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

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

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 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

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.

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

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.

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 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.

Populations as Units of Structure and Function - Statistics

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

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

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

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

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

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)

Using Standard DeviationFormula

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

Community InteractionsInteractions within ecosystems can be:

Neutral – neither organism is affectedOne organism is affectedBoth organisms are affected

Examples are: Symbiosis / Mutualism Parasitism Predation Competition

Cycling of Nutrients

Human Impact on Ecosystems

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?

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

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

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 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

Evaluating the Precautionary Principle

Pros and Cons of implementation in response to Climate Change

Consequences of Climate Change on Arctic Ecosystems

What impacts will climate change have on Arctic Ecosystems?