1. IB Biology
Topic 5 - Ecology

2. 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.

3. 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.

4. Definitions Ecology 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

5. Definitions (continued)
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
Community
Population
Habitat

6. 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

7. Ecosystems

8. Biosphere

9. Energy and Ecosystems

10. 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

11. 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

12. Autotrophs

13. Heterotrophs

14. Definitions continued Decomposers
Detrivore
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

15. Food Chains and Food Webs
Trophic Level 2
Trophic Level 3
Trophic Level 1

16. Food Web

17. Flow of Energy in Food Webs1%
100%
10%

18. Ecological Pyramids
Pyramids of Numbers

19. Ecological Pyramids (cont)
Pyramids of Biomass

20. Ecological Pyramids (cont)
Pyramids of Energy

21. Comparison of Pyramids

22. Populations and Growth

23. Four Factors that influence a Population
Natality - Birth Rate
Mortality – Death Rate
Immigration – Moving in
Emigration – Moving out

24. 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

25. Carrying Capacity (cont)
Build up of waste, such as excrement or excess carbon dioxide
Predation
Disease

26. Population Growth Lag 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 mortality
Little accumulation of waste products

27. 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

28. 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.

29. Population Growth (S) Curve

30. 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

31. 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.

32. 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

33. 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.

34. 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.

35. 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.

36. Populations as Units of Structure and Function - Statistics

37. 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

38. 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

39. 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

40. Using Statistics to Measure Populations
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

41. Using Statistics to Measure Populations
Median
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

42. 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)

43. Using Standard Deviation
Formula

44. 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

45. 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

46. Cycling of Nutrients

47. Human Impact on Ecosystems

48. 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?

49. Greenhouse Gases Carbon dioxide (CO2) Carbon monoxide (CO)
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

50. Greenhouse Gases Nitrogen oxides (NOx) Methane (CH3)
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

51. Is the enhanced greenhouse effect leading to Global Warming or Climate Change?

52. Is the enhanced greenhouse effect leading to Global Warming or Climate Change?

53. 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

54. Evaluating the Precautionary Principle
Pros and Cons of implementation in response to Climate Change

55. Consequences of Climate Change on Arctic Ecosystems
What impacts will climate change have on Arctic Ecosystems?