1. Ecology
Biology 30

2. Ecology Same species Same place Same time Population Community
Study of Ecosystems
Abiotic & Biotic factors interacting
Biotic Factors include populations & communities
Population
Same species
Same place
Same time
Community
Groups of pops
interacting

3. Same species: Same place: Same time!

4. Can you explain the difference between a population and a community?
The definition for a population?
The definition for a community?

5. Biotic and Abiotic Factors?
Abiotic factors are the non-living components of an ecosystem
Biotic factors are the living components of an ecosystem

6. Can you tell me…
The difference between abiotic and biotic factors in an ecosystem?
An example of an abiotic factor?
An example of a biotic factor?

7. Ecosystem Community or Population?
_________________

8. Why is the picture in the previous slide an example of a community and not an example of a population?

9. Populations Variables we will consider: Geographic Range Habitat
Ecological Niche
Population Distribution
Population Size
Population Density
Population Growth Rate and Patterns

10. Geographic Range
area where animal has been seen

11. Geographic range can change over time
Fire Ant Range
Geographic range can change over time
due to abiotic factors.

12. Range Changes in Moose Populations
How has the geographic range of moose
changed since the 1870’s??

13. Habitat area where the population lives
where environmental conditions are best for survival

14. How does an organism’s geographic range differ from its habitat?

15. Each group has a different role to
Ecological Niche
Role of the species in the community
Includes ALL biotic and abiotic factors a species needs to survive
Each group has a different role to
minimize competition

16. Populations co-exist only if each group occupies a different niche

17. Explain the meaning of the term ecological niche.

18. Population Distribution
Uniform
Clumped

19. Population Distribution
Determined largely by habitat preference
Divided into three patterns:
1. Clumped - individuals grouped in patches due to certain environmental factors (e.x. trees clump on south slopes of river valleys b/c less direct sunlight and sturdier soils)
2. Random
- not very common
- biotic and abiotic factors have little effect

20. 3. Uniform
competition among individuals for resources results in regular spacing

21. What is the difference between clumped, random and uniform population distribution?
What factors are responsible for creating clumped, random and uniform population distributions?

22. Population Size
Number of organisms of same type in same place, at same time
There are 2000 students at Centre High during the 2004/5 school year.
Can be determined by exact count or estimation!!

23. Population Density N D = ______ S
Describes number of organisms in a defined area
eg. Snow geese at Beaver Hills =
# of geese per hectare
Density (D) calculated by dividing total number (N) by amount of space occupied (S) by the population D = N S
______

24. What is the difference between population size and population density?

25. Density Example There are 80000 snow geese in
a 50 hectare area in 1995.
D = N/S
D =
80000
_______ 50
= 1600 snow geese per ha

26. If 200 lemmings are living in a 25 hectare (ha) area of tundra, what is the population density of this area?
Use the formula D = N/S

27. Growth Rate N rN = _____ T
After finding the population density, we can find the rate of change over time N
Change in number rN =
_____ T
Change in time
Rate of growth

28. Density Change example
In 1993, the mouse population in my backyard was 50 mice/acre. After three years, various control measures had been in place, and the population dropped to 10 mice/acre. Calculate the rate of density change. rN =
13.3
mice/acre/year =
_______ 3

29. When arriving at their summer cabin, the Smiths discovered 10,000 cockroaches roaming throughout their 1000 m2 cabin. After 1 week, the exterminators were able to control the situation and reduced the cockroach population to 10 per 1000 m2. Calculate the rate of density change.

30. Population Growth Natality Mortality Immigration Emmigration
Determined by four factors:
Natality
Mortality
Immigration
Emmigration

31. Population Growth CGR = (births + immigration) Initial # of organisms
(deaths
+ emmigration)
(births +
immigration)
Initial # of organisms
Also known
as per capita
growth rate N
CGR = N

32. Calculation Deaths Original Pop = 200
Using this table, calculate CGR for Sandhill cranes:
Births
Immigration
Deaths
Emigration 40 55
Original Pop = 200

33. N
CGR = =
-15
200
CGR =
200 =

35. Puffins are small marine birds found off the coast of Atlantic Canada
Puffins are small marine birds found off the coast of Atlantic Canada. Calculate the population growth rate of a puffin colony based on the following population in 1999.
Original population =
Natality =
Mortality =
Immigration =
Emigration =

36. Density Problem
Calculate the population density of shrews per m2, if an average of 7.8 shrews are found in an area 14 m wide by 20 m.

37. CGR Calculation
Calculate the per capita growth rate of a mouse population if the original population size is 34 and over a period of a week, 5 die, 8 are born, 12 immigrate into and 7 emigrate out of the area. N
CGR =

38. Dynamic Equilibrium Present in mature ecosystems
Characterized by long term balance
Pops remain relatively stable over time
Great biodiversity = stability
Can be compared with homeostasis

39. Define dynamic equilibrium.

40. 2 population types: 1. Open populations:
immigration & emigration occurs
2. Closed populations:
Density changes are result of natality and mortality only
No immigration or emigration
eg. Game preserves

41. What is the difference between open and closed populations?

42. Growth Curve Graph showing changes in a population over time.
X = time (independent or manipulated variable)
Y = density or # of organisms (dependent or responding variable)

43. Exponential Pop Growth

44. Growth Curve for Closed System
4 phases:
1. Lag phase…slow…not enough
reproducing organisms
2. Growth phase….exponential increase
3. Stationary phase….natality= mortality
4. Death phase…decline
Not always present

45. Bacterial Growth Curve
Closed population
4 distinct phases

46. Draw a growth curve for a closed population
Draw a growth curve for a closed population. Label and define the four stages of this curve.

47. Growth Curve for Open Systems
When a limiting factor is introduced to a population, curve results in an “S” shape
Typical of an organism placed in a new environment
As organisms respond to increased nutrients, natality increases.
Equilibrium is established again and curve levels off
New carrying capacity (max. # of individuals environment can support)

48. Define carrying capacity.
When does a population growth curve of an open system show an “S shape”?

49. Population Growth Curves
Click on the link above
Read the instructions and hit the “run applet” button
Set the carrying capacity to 1000
Set the birth rate to 1.5
Hit RUN
View the graph and draw this in your notes
Have you simulated an open or a closed population?
Change the parameters and try it again!

50. Population Curves

51. Human Population Growth

52. Population Curves

53. Population Curves

54. How could you describe the population growth of humans in the past 500 years?
Hint: one word that begins with an ‘e’

55. Population Explosion & Crashes
Bottleneck
What happened?

56. Describe the bottleneck effect.

57. Boom and Bust Cycles

58. What trends do you see in the population curve for Soay Sheep that give its characteristic shape of “boom and bust”?

59. Survivorship Curves

60. Population Curves

61. Population Curves

62. Population Histograms
Wide base…fast growth
Narrow base….decline

63. What information is given in a population histogram?
What shape would a histogram look like if it were representing an declining population? A stabilized population? A young population?

64. More Histograms What are these graphs showing?
Which country demonstrates
a very high reproductive rate?
2. Which country represents a
stabilized population?

65. Show Age Structure
of Pop
Histograms

66. What do each of the histograms on slides 63 to 64 tell you?
What trends do you see in the population curves on slides 63 to 64?

67. Biotic Potential Max. # of offspring produced in ideal conditions
Regulated by four factors:
offspring - max #/birth
survival capacity – chance that offspring will reach reproductive age
procreation - # times/year organism reproduces
maturity - age when reproduction begins

68. Environmental Resistance
All factors that limit pop. growth
Can be biotic or abiotic
Examples include…….
Food, water, space, disease, predation, natural disasters, availability of mates, etc

69. Environmental Resistance
In a
fresh
water
habitat

70. Define biotic potential and environmental resistance
Define biotic potential and environmental resistance. Give an example for environmental resistance.

71. Limiting Factors Affect population size! Law of the minimum
flood, fire, extreme cold, disease, starvation, predation
Law of the minimum
various substances are required for growth.
the one with the lowest concentration will limit growth ( known as limiting factor)

72. Limiting Factors can be:
Density Independent:
affecting pop regardless of # of individuals
flood, fire, extreme cold, other abiotic factors
Density Dependent:
affecting pop & dependent on pop size
disease, starvation, predation

73. State the law of the minimum.
Define limiting factors.
What are some examples of limiting factors?

74. Density Dependent Factor!
Name the
Density Dependent Factor!

75. Pops can also be r or K Selected
r - selected
High
Reproductive
Rate
K - selected
Low
Reproductive
Rate
Almost at
Carrying
Capacity

76. K- selected Populations

77. r- selected Populations

78. Differentiate between r and K-strategies
Differentiate between r and K-strategies. Give 2 examples of the types of organisms that use each of these strategies.