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Presentation on theme: "Ecology."— Presentation transcript:

1 Ecology

2 What is Ecology? =

3 “The environment” Abiotic –

4 Levels of organization in Nature

5 Subatomic particle protons electrons neutrons tachyons baryons mesons
etc. Subatomic Particles

6 Atom p p n e- e- atoms Subatomic Particles

7 Molecule H2O Cl2 Molecules O2 atoms N2 Subatomic Particles

8 Organelle Sacs or their compartments that separate different activities inside the dell Organelle Molecules atoms Subatomic Particles

9 Cell (smallest living unit) May live independently or part of a multicellular organism Cell Organelle Molecules atoms Subatomic Particles

10 Tissue A group of cells and surrounding substances functioning together in a specialized activity. Tissue Cell Organelle Molecules Atoms Subatomic Particles

11 Organ A group of tissues working together to perform a common task.
Cell Organelle Molecules Atoms Subatomic Particles

12 Organ system Two or more organs interacting to contribute to the survival of the whole organism. Organ System Organ Tissue Cell Organelle Molecules Atoms Subatomic Particles

13 multicellular organism
An individual composed of specialized interdependent cells arrayed in tissues, organs, and often organ systems Multicellular Organism Organ System Organ Tissue Cell Organelle Molecules Atoms Subatomic Particles

14 Multicellular Organism
Population: Subatomic Particles Atoms Molecules Organelle Tissue Organ Organ System Multicellular Organism Cell Population A group of individuals of the…

15 Multicellular Organism
Community Subatomic Particles Atoms Molecules Organelle Tissue Organ Organ System Multicellular Organism Cell Population Community = a group of organisms of different species (i.e. many populations)….

16 Multicellular Organism
Organ System Multicellular Organism Subatomic Particles Atoms Molecules Organelle Tissue Organ Cell Population Community Ecosystem Ecosystem All biotic and abiotic components of a certain area

17 Multicellular Organism
Biome Biome Organ System Multicellular Organism Subatomic Particles Atoms Molecules Organelle Tissue Organ Cell Population Community Ecosystem Major types of ecosystems on earth, occupying large geographic regions

18 Multicellular Organism
Biosphere Organ System Multicellular Organism Subatomic Particles Atoms Molecules Organelle Tissue Organ Cell Population Community Ecosystem Biome Biosphere Those regions of the earth’s waters, crust and atmosphere in which organism can exist.

19 Is Life uniformly distributed?

20 Why isn’t all life everywhere?

21 Factors affecting distribution of organisms (biogeography)
Dispersal limitations Not all areas are accessible – geographic isolation Habitat selection Animals Biotic Factors Abiotic Factors

22 3. Biotic Factors Absence of symbioses Lack of pollinators Competition

23 Competition 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. Competition from introduced species can shrink an organism’s actual range

24 What do plants compete for?

25 4. Abiotic Factors Vary from place to place, season to season.
Each organism has an optimum environment needed for maximum growth.

26 ……Thus scientists predict that global warming may radically alter the distribution of organisms/ecosystems on earth

27 Fig 50.18

28 Effects of climate on biogeography
Solar radiation creates wind currents, ocean currents, and precipitation (from evaporation

29 Fig 50.10

30 Fig 50.10

31 Effects of climate on biogeography, continued
Local climate . S slope drier than N slope (thus different plant communities) Microclimate Under a log Within the litter layer

32 Your ecosystem type: coastal temperate rainforest

33 Terrestrial Biomes

34 Locations of the earth’s biomes due to:
. One biome type may occur in different areas of the world Different plant species but same: Physiognomic structure – Similarities due to convergent evolution – similar phenotypes due to similar selection pressures over time Similar climate, soils, disturbance patterns,…

35 Fig

36 1. Tropical rainforest Very diverse!
Large vertical stratification due to competition for light


38 2. Savanna Rainy & dry season Fire adapted


40 3. Desert CAM plants Unique plants with adaptations to harsh environment


42 4. Chapparal Fire-dependent! – seeds germinated after fire, roots fire-resistant


44 5. Temperate grassland Occasional fire Fertile soils


46 6. Temperate deciduous forest
4 seasons (cold winter – dormant) Open forests


48 7. Coniferous Forest 4 seasons, large amounts of snowfall


50 8. Tundra No trees or tall plants 20% of land area on earth
Low annual precipitation


52 4 types of ecological investigation:
Organismal ecology “plant autecology” organism’s response to environment – ability to exist/adapt Population ecology Population size, distribution Community ecology Community structure, organization Competition Diversity Disturbance Succession

53 4. Ecosystem ecology Energy flow/nutrient cycling
Interactions of biotic & abiotic components

54 Plant Population Ecology

55 Characteristics of Populations
Dispersion – Size – Density - the number of individuals living in a specified area

56 1. Dispersion Patterns of Dispersion: Clumped –
Uniform – evenly spaced due to: Competition for resources Allelopathy – Random – unpredictable; position of one individual cannot be predicted from position of another.

57 Clumped lupine

58 Random trees

59 Uniform dispersal of sagebrush

60 2. Population Size Demography = study of factors that affect the growth & decline of populations Life Histories = events from birth through reproduction to death Trade-offs between investments in reproduction & survival when there are limited resources


62 Controls at every stage of life history
death reproduction Herbivory, disease, competition, drought, flood, freeze mature plant growth seedling Seed rain from mature plants Seeds washed away, eaten, decomposed Dormancy (seed bank)

63 Demography Change in Population size = (B + I) – (D + E)

64 Exponential Growth occurs when resources are abundant or when an important constraint has be removed. Ex.

65 The j-shaped curve Time Number of Individuals

66 Biotic Potential (r) = Intrinsic/ maximum rate of natural increase, given: Habitat is free of predators and pathogens.

67 Limits on Population Growth
Given their biotic potential what keeps organisms from filling up the planet?

68 Limits on Population Growth
Density & competition for resources will cause reproduction rates to decline or stabilize

69 Any essential resource that is in short supply is a limiting factor on population growth.
living space pollution-free environment

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

71 Carrying Capacity (K) =
Is not fixed - K may decrease when a large population damages or depletes its own resource supply.

72 Initial carrying capacity
Logistic growth Time Number of Individuals Initial carrying capacity New carrying capacity

73 3. Density-Dependent Control of Population Size
When population density is low, a population grows rapidly. When density is high, populations may grow slowly, remain stabile (zero growth) or decline – why?. High density puts plants at greater risk of …..

74 Density-Independent Control of Population Size
= events that cause more deaths or fewer births regardless of population density Examples?

75 Plants have developed adaptations to population density
At low density, population is limited only by intrinsic rate of growth (r) At high density, population is limited by carrying capacity (K) R selection and K selection

76 High density Naturalization Pop. Size Colonization Low density introduction Time

77 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:

78 K-selection High density, population size close to K
Not much “new” space – competition for resources Adaptations that are successful for these conditions:

79 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

80 Plant Community Ecology

81 Review: definition of community
Group of organisms of different species living together in a particular habitat

82 Characteristics of communities
Diversity – composed of: Richness – Evenness – Relative abundance = # individuals of species X divided by total # of individuals in the community

83 Which community is more diverse?

84 What factors determine the plant species composition & the relative of abundance of different species in a community? Biotic & abiotic components of the habitat

85 Abiotic components of habitat & their effect on community structure:
Each species has a tolerance range – Climate – temp, moisture Soil – types, pH Latitude & altitude Disturbance

86 Disturbance = decrease or total elimination of the biotic components of the habitat Results: decrease in biomass, diversity Natural events – Human-caused – Frees resources, creating opportunities for new species, different composition All communities have evolved with some type of disturbance, varying in type, frequency, & severity

87 Small-scale, frequent disturbance
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



90 Human - caused disturbance + introduced species = disaster
Ex. 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







97 Biotic components of habitat & their effect on community structure
The plant itself Benefit ex: beech/oak forest creates shade needed for other young beech & oak to grow Detriment ex: pine forest creates shade but pines need lots of light to grow (succession)

98 2. Other plant species 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

99 One will become extinct or evolve to use a slightly different set of resources
Species B Species A Species Abundance A D B C low high Light intensity 

100 Species A Species B B C D A

101 If this theory is true, then actually very little competition in nature, because each plant occupies a niche. Niche = Includes all aspects of a species’ use of biotic & abiotic resources (microclimate, rooting zone, pollinators, etc)

102 3. Other (non-plant species)
Interactions with animals, insects, fungi, bacteria Mutualism – Ex. Ex. Pollinator gets nectar and plant gets pollen transfer Ex. Animals eat fruit (nutrition) and seeds are dispersed Ex. Acacia trees get defense from herbivores & ants get home, food


104 Commensalism – one species benefits & other is not affected
Competition – Predation – one harmed, other benefits Herbivory pathogens

105 Controls on community structure
Dominant species = species with the highest abundance or biomass in the community Controls occurrence & distribution of other species If eliminated, other species take over Ex. Douglas fir

106 Keystone species Ex. Sea otter – reduction in populations caused boom in sea urchin population, destroying kelp forests (drastic decline in diversity)

107 Succession

108 Succession = Species replacement continues until the composition of species becomes relatively steady under prevailing climatic conditions & disturbance regimes (dynamic equilibrium, not climax).

109 Two major types of succession
Primary Succession Secondary Succession

110 1. Primary succession Sequence: .
As these decay, acids weather the rock & primitive soil forms Pioneer plants establish (r-selected) Pioneers replaced by K-selected species

111 The Nature of Pioneer Species
typically small plants, short life cycles, producing an abundance of small seeds which are quickly dispersed (wind & water) can grow in N-poor soil because of their mutualistic interactions with nitrogen-fixing bacteria.

112 Example of primary succession: glacial retreat

113 Fig 53.23


115 Fig 53.20

116 Mosses, lichens, fireweed
Dryas stage .

117 Alders & cottonwoods dominate

118 Spruce enter forest and replace alders/cottonwoods

119 Hemlock slowly replace Spruce. Hemlock is “climax”

120 What Pioneers Do: Facilitation
accumulation of their wastes and remains adds volume to the soil and enriches it with nutrients that allow other species to take hold.

121 2. Secondary Succession Plant community is destroyed but soil remains/ new soil exposed Examples? Typical progression: small herbs & grasses shrubs trees

122 Pioneer species 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

123 Ecosystem Ecology

124 Ecosystems An ecosystem is an association of organisms and their physical environment,

125 Structure of Ecosystems
Physiognomic structure = Relative abundance of trees, shrubs, herbs, mosses, etc. Phenotypes, physical characteristics Vertical & horizontal stratification


127 2. Temporal Structure Diurnal (Daily) patterns Seasonal changes

128 3. Species composition Determined by soil resources, climate tolerance ranges, stresses (ex. Competitive interactions, herbivory)

129 4. Trophic levels = Feeding levels Autotrophs
First level of all food webs---- primary producers Heterotrophs – consumers - depend directly or indirectly on energy stored in tissues of primary producers.

130 Types of Heterotrophs Herbivores Parasites Detritivores
Carnivores – eat herbivores & other carnivores – secondary consumers Omnivores partake of a variety of edibles Decomposers - extract energy and recycle nutrients from organic matter.

131 Decomposition links all trophic levels
Fig 54.2

132 Some organisms like man extract energy from more than one trophic level so it is hard to assign them to a specific trophic level. Actual feeding relationships in an ecosystem are complex –.


134 Energy Flow Through Ecosystems

135 Primary Production = How much energy actually get stored depends on:
1) how many plants are present and 2) the balance between photosynthesis and aerobic respiration. Ecosystems differ in their PP:

136 Fig 54.4

137 Fig 54.5

138 Other organisms tap into the energy that is conserved in plant tissues, remains, or wastes.
They, too, lose heat to the environment.

139 All of these heat losses represent a one-way flow of energy out of the ecosystem.

140 Secondary Production = Ex. Caterpillar eating a plant:
50% loss to feces (energy transfer to detritus) 34% to respiration (heat loss) 16% to growth


142 Trophic efficiency = Thus 85-90% of available energy at one level is not transferred to the next Instead lost as heat, not consumed, or transferred to detritus

143 Fig 54.11: Energy pyramid

144 Fig Biomass pyramid

145 Fig Pyramid of numbers

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