1. Ecology

2. C. Levels of Organization
I. Introduction
A. Definition
The study of the interactions between organisms & organisms with their environment.
B. Parameters
1. Abiotic – non-living. Like?
2. Biotic
C. Levels of Organization

3. D. Distribution of Life 1. Chemistry 2. Biology 3. Ecology
Subatomic Particles
Atoms
Molecules
Macro - Molecules
2. Biology
Tissues
Organs
Organisms
Organelles
Cells
3. Ecology
Population
Community
Ecosystem
Biome
Biosphere
D. Distribution of Life

4. 1. Dispersal Limitations
a. Not all areas are accessible – geographic isolation
b. Each species has an actual and a potential range
Potential range = area over which a species could
survive if transplanted

5. 2. Behavior and Habitat Selection
a. Animals mainly
3. Biotic Factors
a. Disease
b. Herbivory
c. Absence of symbionts
d. Lack of pollinators
e. Competition

6. 4. Competition a. Factors i. Whenever the quantity of useful matter or
energy falls below the level needed for the
maximal growth of two or more organisms which
must draw on the same supply, a contest begins.
ii. The more similar the needs the greater the
intensity of competition.
iii. Competition from introduced species can
shrink an organism’s actual range

7. b. Reasons?
i. water
ii. nutrients
iii. light
iv. heat
v. carbon dioxide, oxygen
vi. space
vii. pollinators

8. 5. Abiotic Factors a. Limits i. Climate
Varies from place to place, season to season.
Each organism has an optimum environment
needed for maximum growth.

9. Temperature & annual precipitation (climate vs
Temperature & annual precipitation (climate vs. weather) are the most important factors determining the distribution of organisms on a global scale (biomes).
……Thus scientists predict that climate change may radically alter the distribution of organisms/ecosystems on earth.

10. Fig 52.20

11. Effects of climate on biogeography
Climate varies with latitude because of
differences in the angle of sunlight (seasons)
Solar radiation creates wind currents, ocean
currents, and precipitation (from evaporation)

12. Fig 52.10

13. Fig 52.10

14. ii. Weather = Local climate
Proximity to water, mountains
E or W side of land mass
S slope drier than N slope (thus different plant communities)
iii. Precipitation = Microclimate
Forest floor vs. canopy
Under a log
Within the litter layer

15. Your ecosystem type: coastal temperate rainforest
Fig

16. II. Biomes A. General Characteristics
1. Limits Locations of the earth’s biomes due to:
a. Latitude – affects temperature, precipitation
b. Positions of the continents
2. Structure One biome type may occur in different areas
of the world but different plant species but same:
a. Physiognomic structure – size; shape; types of
organisms & their relation to each other & the physical
environment
b. Due to convergent evolution – similar phenotypes
due to similar selection pressures over time. Similar
climate, soils, disturbance patterns,…

17. B. Types
Fig

18. 1. Terrestrial a. Name Tropical rainforest b. Location
Equatorial region
c. Characteristics
High average annual temp and precipitation,
Lush, dense vegetation, Very diverse! Large vertical
stratification due to competition for light

20. a. Name
Savanna
b. Location
rimming Equatorial region
c. Characteristics
Grasslands with scattered trees, Large herbivores
& predators, Rainy & dry season! Fire adapted

22. a. Name
Desert
b. Location
Along Tropic of Cancer and Capricorn
c. Characteristics
< 30 cm of rain per year, High temperatures,
CAM plants! Unique plants with adaptations to harsh
environment

24. a. Name
Chapparal
b. Location
Along rugged hilly salt water coasts
c. Characteristics
Evergreen shrubs, Hot dry summers, mild wet
winters, Fire-dependent! – seeds germinated after
fire, roots fire-resistant

26. a. Name
Temperate Grassland
b. Location
Along 30o N and S parallel inland
c. Characteristics
No trees, Typically 4 seasons, Occasional fire,
Fertile soils

28. a. Name
Temperate deciduous forest
b. Location
Along 30o N and S parallel coastal
c. Characteristics
Deciduous trees, 4 seasons (cold winter –
dormant), Open forests

30. a. Name
Coniferous Forest
b. Location
N hemisphere above 30o
c. Characteristics
Evergreen trees (gymnosperms), Largest biome
on earth, 4 seasons, large amounts of snowfall

32. a. Name
Tundra
b. Location
N hemisphere or high altitude
c. Characteristics
Permafrost – permanently frozen subsoil, Very
cold, high winds, No trees or tall plants, 20% of land
area on earth, Low annual precipitation

34. 2. Aquatic a. Name Fresh relatively still - Lakes b. Location ???
c. Characteristics
Thermocline, tubidity varies, oligotrophic versus
eutrophic

36. a. Name
Fresh moving water - Rivers and Streams
b. Location
???
c. Characteristics
Current, temperature and turbidity varies,
vertical zones

38. a. Name
Wetlands
b. Location
???
c. Characteristics
Temporary to semi-permanent, temperature and
turbidity varies

40. a. Name
Estuaries
b. Location
???
c. Characteristics
Salt fluctuations, temperature, depth, and
turbidity varies

42. a. Name
Oceanic
b. Location
???
c. Characteristics
Salt fluctuations, temperature, depth, and
turbidity varies, vertical zones

44. Plant Population Ecology I. Introduction
A. Characteristics
1. Dispersion
a. Patterns of Dispersion:
i. Clumped – individuals in patches (ex. due to
soil types, seed dispersal by animals)
ii. Uniform – evenly spaced due to:
Competition for resources or Allelopathy – plants secrete
chemicals to inhibit nearby growth
iii. Random – unpredictable; position of one individual
cannot be predicted from position of another.

45. Clumped lupine

46. Uniform dispersal of sagebrush

47. Random trees

48. 2. Population Size a. Demography = study of factors that affect the
growth & decline of populations
i. Increase by reproduction, immigration
ii. Decrease by death, emigration
Change in Population size = (B + I) – (D + E)
If B – D = 0, then zero population growth

49. Fig. 53.9

50. b. Life History = events from birth through
reproduction to death
i. Dormancy, germination, growth, reproduction,
dispersal, death
ii. Trade-offs between investments in reproduction
& survival when there are limited resources

51. Controls at every stage of life history
Dormancy (seed bank)
seedling
growth
mature plant
reproduction
death
Seeds washed away, eaten, decomposed
Seeds rain from mature plants
Herbivory, disease, competition, drought, flood, freeze
New resources available, perfect growing conditions, freedom from disease, competition, drought

52. 3. Growth The j-shaped curve a. Patterns i. Exponential
Occurs when resources are abundant or when an
important constraint has be removed.
Ex. Recolonization after fire
Represents a doubling of the population in a specified
time.
Time
Number of
Individuals
The j-shaped curve

53. Initial carrying capacity
i. Logistical
Steady increase followed by a plateau due to ????.
Time
Number of
Individuals
Initial carrying capacity
New carrying capacity
Logistic growth

54. b. Limits Biotic Potential (r)
i. Intrinsic Factors
Plenty of food, living space, and other resources.
No competition
Habitat is free of predators and pathogens.
Density & competition for resources will cause reproduction rates to decline or stabilize

55. Any essential resource that is in short supply is a limiting factor on population growth.
food
micro-nutrients
refuge from predators
living space
pollution-free environment

56. ii. Environmental resistance affects the number of
individuals of a given species that can be sustained
indefinitely in a particular area. K
Time
Number of
Individuals
Introduction
Colonization
Naturalization

57. iii. Carrying Capacity (K)
The maximum population size a particular area or habitat
can support at a particular time.
Is not fixed - K may decrease when a large population
damages or depletes its own resource supply.

58. 4. Control a. Factors i. Density Independent Control
ii. Density Dependent Control

59. 5. Adaptations a. At low density, population is limited only by
intrinsic rate of growth (r)
b. At high density, population is limited by
carrying capacity (K)
c. r versus K strategy
d. Competitive, Ruderals, and Stress Tolerant

60. i. r - selection
Disturbance creates low-density conditions, frees
resources (fire, flood, volcano)
Biotic potential (r) limits population size
Adaptations that are successful for these conditions:
Produce large # of seeds fast
Wind dispersal of seed
Plants grow & flower quickly (annuals)
Few chemical/mechanical defenses

61. ii. K-selection
High density, population size close to K
Not much “new” space – competition for resources
Adaptations that are successful for these conditions:
Perennial
Fewer, larger seeds
Defenses against herbivores, pathogens
Adaptations to shading, poor soils

62. K & r selected species exist together because small-
scale disturbances create space (exposed soil) for r
species (colonizers)
Ex. Downed tree, badger holes, grazing disturbance

64. Plant Community Ecology
I. Background
A. Definition
1. Groups of organisms of different species (populations)
living and interacting with each other and the habitat

65. B. Hypothesis of Structure
1. Question?
Are plant communities a real entity in nature? Why
are certain species found together?
2. Hypotheses:
a. Individualistic hypothesis - Gleason
i. Species are found together in nature because they
have similar abiotic requirements
ii. No distinct boundaries between communities
iii. Each species distributed along its tolerance range
iv. Thus communities change continuously along a
gradient

66. b. Integrated Hypothesis - Clements
i. Plant communities function as a real, integrated unit.
ii. Plant species found together because of interactions
with each other & the rest of the ecosystem.
iii. Thus species are clustered into discrete communities
with definite distribution boundaries.

67. Fig 53.29
Which is correct?

68. c. So? Individualistic/Continuum “more correct”, but evidence of both – some sharp boundaries due to dramatic environmental changes.

69. II. Characteristics of communities
A. Diversity – composed of:
1. Richness – the total number of species in
the community
2. Evenness – the relative abundance of
species in the community (some dominant, some rare)
a. Relative abundance = # individuals of
species X divided by total # of individuals in the
community

70. Which community is more diverse??
Fig 54.9
Which community is more diverse??

71. Fig. 54.9

72. B. Factors 1. Abiotic a. Each species has a tolerance range – range
of conditions under which it can survive & reproduce
b. Climate – temp, moisture
c. Soil – types, pH
d. Latitude & altitude

73. e. Disturbance
i. Decrease or total elimination of the biotic
components of the habitat
ii. Results: decrease in biomass, diversity
iii. Natural events – fire, flood, volcano, avalanche
iv. Human-caused – herbicides, roads, development,
logging, grazing, farming, mining
v. Opens resources, creating opportunities for new
species, different composition
vi. All communities have evolved with some type of
disturbance, varying in type, frequency, & severity

74. vii. Small-scale, frequent disturbance
Creates patches within the ecosystem
Thus increase in diversity
Ex. Trees downed in wind storm
Can prevent large-scale disturbance – fire!
Ex. Yellowstone fire of 1988
Fire suppression in fire-dependent ecosystem
caused massive, stand-replacing fire

77. viii. Human Caused
Example Cheatgrass – wildfire cycle
Overgrazing in ecosystem that did not evolve with
large herbivores
Cheatgrass introduction
Decrease in fire frequency (100 yr to 5 year cycle)
Conversion of ecosystem with tremendous loss of
Diversity
These types of problems creating mass extinction
worldwide.

84. 2. Biotic a. The plant itself i. Can modify the environment
ii. Modifications can be +, -, or neutral to the plant
iii. Benefit ex: beech/oak forest creates shade
needed for other young beech & oak to grow
iv. Detriment ex: pine forest creates shade but
pines need lots of light to grow (succession)

85. b. Other plant species i. Theory of competitive exclusion: When two
species compete for the same limiting resource
(occupy the same niche), the species that is less
adapted will be excluded from the community by the
superior competitor.
If this theory is true, then actually very little competition in
nature, because each plant occupies a niche.

86. low
high
Light intensity 
Species Abundance
Species A
Species B A B C D

87. Resource partitioning creates nichesB C D
Species A
Species B

88. ii. Niche
A set of conditions exploited best by only one species
Includes all aspects of a species’ use of biotic & abiotic
resources (microclimate, rooting zone, pollinators, etc)
A species’ role in the ecosystem.

89. c. Other (non-plant species)
i. Mutualism – both organisms benefit
Examples:
Mycorrhizal fungi, N-fixing bacteria in root nodules
Pollinator gets nectar and plant gets pollen transfer
Animals eat fruit (nutrition) and seeds are dispersed
Acacia trees get defense from herbivores & ants get
home, food

91. ii. Commensalism – one species benefits & other is
not affected
Bird nests in trees, seeds stuck on animal fur
iii. Competition – both harmed
iv. Predation – one harmed, other benefits
Herbivory
Pathogens

92. Predation or the need to keep your wits about you?

93. C. Controls on community structure
a. Dominant species = species with the highest
abundance or biomass in the community
i. Best species among all species in the
community at exploiting the limiting resource
ii. Controls occurrence & distribution of other
species
iii. If eliminated, other species take over Example: Douglas fir

94. b. Keystone species
i. Control community structure by their ecological role
ii. If eliminated, drastic change in community structure
or composition Example Sea otter – reduction in
populations caused boom in sea urchin population,
destroying kelp forests (drastic decline in diversity)

95. III. Succession A. Definition 1. Changes in community structure &
composition over time following a disturbance
2. Species thriving on a site are gradually
replaced by other species.
3. Species replacement continues until the
composition of species becomes relatively steady
under prevailing climatic conditions & disturbance
regimes (dynamic equilibrium, not climax).

96. B. Types 1. Primary Succession a. Characteristics
i. New area of mineral rock – no soil yet (volcano, glacier
retreat)

97. b. Sequence:
i. Lichens & mosses colonize bare rock
ii. As these decay, acids weather the rock & primitive soil
forms
iii. Pioneer plants establish (r-selected or Stress tolerant)
iv. Pioneers replaced by K-selected (Ruderal and
Competitive)

98. c. The Nature of Pioneer Species
i. Adapted to growing in habitats that cannot support
most species: intense sunlight, wide swings in
temperature, moisture deficits.
ii. Typically small plants, short life cycles, producing
an abundance of small seeds which are quickly
dispersed (wind & water)
iii. Can grow in N-poor soil because of their
mutualistic interactions with nitrogen-fixing bacteria.

99. Example of primary succession: glacial retreat

103. Alders & cottonwoods dominate

104. Spruce enter forest and replace alders/cottonwoods

105. Hemlock slowly replace Spruce. Hemlock is “climax”

106. iv. Facilitation
Improve the living conditions for other species, setting the
stage for their own replacement.
Accumulation of their wastes and remains adds volume to
the soil and enriches it with nutrients that allow other
species to take hold.

107. 2. Secondary Succession a. Characteristics
i. Plant community is destroyed but soil remains
while new soil exposed
ii. Examples?
abandoned farm fields, clear cuts, wind storms, fire.
iii. Typical progression: small herbs & grasses
shrubs trees

108. b. Pioneer species
i. r-selected (stress tolerant) (species move in first when
competition is low (low density).
ii. Sometimes these opportunistic species (especially
invasive weeds!) inhibit the growth of the native climax
species changing the structure and type of climax
community forever. Ex. cheatgrass

109. It has been a journey worth taking.