Ecology
AP Biology

Ecology
• Scientific study of the interactions between organisms and their environment

Levels of Study
• Organism
– Individual
– 1 turtle

Levels of Study
• Population
• Individuals of the same species living in the same area
• All the turtles of the same species

Levels of Study
• Community
• All the organisms living in an area
• All the turtles, plants, insects, algae, bacteria

Levels of Study
• Ecosystem
• All the organisms and all the abiotic factors
• All the organisms
& the soil, water, gases, minerals

Levels of Study
• Biosphere
• All the organisms & all the abiotic factors on
Earth
• Earth

Abiotic Factors
• Nonliving
• Temperature
• Climate
• Soil type
• Rainfall
• Gases
• Minerals

Biotic Factors
• Living
• Predators
• Parasites
• Herbivores
• Carnivores
• Decomposers

Biomes
• Tropical rainforest
• Tall trees
• High temperature
• Heavy rainfall

Biomes
• Savannas
• Tropical
• Grasslands
• Scattered trees
• High temperature
• Less rainfall than tropical rain forest

Biomes
• Temperate grasslands
• Grasses
• Seasonal droughts
• Occasional fires
• Lower temperature & less rainfall than savannas

Biomes
• Deciduous forests
• Deciduous trees
• Oak, maple
• Warm summers
• Cold winters
• Moderate rainfall

Biomes
• Taiga
• Coniferous forests
• Pines & firs
• Cold winters
• Heavy snowfall

Biomes
• Tundra
• Grasses & sedges
• Very cold winters
• Permafrost
• High winds
• Little rain

Population Ecology
• Refer to written notes as you go through the slides

Population
• Definition:
– Group of individuals:
• Of same species
• Living in same area
• Using the same resources
• Responding to same stimuli

Population Characteristics
• Density
• Number of individuals per unit area or volume

Population Characteristics
• Dispersal Patterns
• Spacing between individuals
• Clumped
• Uniform
• Random

Population Characteristics
• Dispersal Patterns
• Clumped

Population Characteristics
• Dispersal Patterns
• Uniform

Population Characteristics
• Dispersal Patterns
• Random (ferns)

Population Characteristics
• Demographics
• Study of vital statistics
• Age structure
– Groupings by age
– Graphed
• Sex ratio
– % of females compared to males

Analyze the following graphs
• Determine what is causing the various demographic trends in each country

Population Characteristics

Survivorship Curves
• Graph of # of survivors vs. relative age

Survivorship Curves
• Type I
• Most survive to middle age
• Humans

Survivorship Curves
• Type II
• Likelihood of death same at any age
• Squirrel

Survivorship Curves
• Type III
• Most die young
• Oyster

Limiting Factors – add to notes at bottom of page 2
• Prevent population from reaching biotic potential
• Types
– Density dependent
– Density independent

Limiting Factors
• Density dependent
• Effect becomes more intense with increased density
• Examples
– Parasites & diseases
– Competition for resources
– Toxic effect of waste products
– Predation

Limiting Factors
• Density independent
• Occur independently of density
• Examples:
– Natural disasters
– Climate extremes

Population Growth Models
• Exponential Growth
• Change in # of individuals (  N) over time (  t) is equal to the growth rate (r) times the number of individuals (N)

N
 t
 rN

Population Growth Models
• Exponential Growth
• J-shaped curve

Population Growth Models
• Logistic Growth
• When limiting factors restrict size of population to carrying capacity
• Carrying capacity (K) = max. # of individuals of a population that can be sustained by the habitat

N
 t
 rN
K
N

Population Growth Models
• Logistic Growth
• Sigmoid (S) shaped curve

Life-History Strategies
• r-selected species
• Exhibit rapid growth (J-curve)
• Examples – grasses, insects
• Characterized by opportunistic species
– Quickly invade habitat
– Quickly reproduce
– Then die
• Produce many offspring that are small, mature quickly, require little parental care

Life-History Strategies
• k-selected species
• Population size remains relatively constant
• Example - humans
• Produce small number of relatively large offspring that require extensive parental care
• Reproduction occurs repeatedly during lifetime

Community Ecology
• Defintion
– An assemblage of populations interacting with one another within the same environment
– Use the following slides as reference for question 2

Community Interactions
• Interspecific Competition
• Competition between different species
• When 2 species compete for same resources one will be more successful
• To survive, the less successful species
– Must use slightly different resources
– Must use resources during different time of day

Community Interactions
• Predation
• Any animal that totally or partly consumes a plant or animal
• True predator kills and eats another animal
• Parasite lives in and off a host
• Herbivore is an animal that eats plants

Community Interactions
• Symbiosis
• Two species that live together in close contact
• Types
– Mutualism
– Commensalism
– Parasitism

Community Interactions
• Mutualism
• Both species benefit from relationship
• Examples
– Bacteria in root nodules
– Lichens – algae & fungus living together

Community Interactions
• Commensalism
• One species benefits while the other is neither harmed nor helped
• Examples
– Birds building nests in trees
– Egrets that eat insects around cattle

Community Interactions
• Parasitism
• One species benefits while the other is harmed
• Examples
– Tapeworm inside animal
– Ticks on dog

Ecological Succession
• Def- species replacements in a community following a disturbance
• Primary – occurs in areas where there is no soil formation (volcanic eruption, glacial retreat)
• Secondary – area where soil is present (after a fire, farmland)

• Detroit

Climax Community
• F.E. Clements – succession in a particular area will always yield the same type of community – this community is called the Climax
Community

Pioneer species – the first species to begin secondary succession (plants)

Trophic Levels
• Primary producers
• Plants
• Photosynthetic bacteria
• Algae

Trophic Levels
• Primary consumers
• Herbivores
• Eat producers

Trophic Levels
• Secondary consumers
• Carnivores
• Eat primary consumers
(herbivores)

Trophic Levels
• Tertiary consumers
• Secondary carnivores
• Eat secondary consumers

Pyramids
• Pyramid of numbers
• Most = producers
• Least = top level consumers

Pyramids
• Pyramid of energy
• Most = producers
• Least = top level consumers

Pyramids
• 10% rule
• Only 10% of energy available at each trophic level is converted into new biomass at the next level

Food Chain

Food Web

Nitrogen Cycle

Water Cycle

Carbon Cycle

Human Impact
• Greenhouse effect
• Ozone depletion
• Acid rain
• Deforestation
• Pollution
• Species extinction

Chapter 48

Outline
64
• The Nature of Ecosystems
– Biotic Components
– Autotrophs
– Heterotrophs
• Energy Flow
– Ecological Pyramids
• Global Biogeochemical Cycles
– Hydrologic Cycle
– Carbon Cycle
– Nitrogen Cycle

65
Nature of Ecosystems
• Biosphere is the organism-containing part of the
– Atmosphere
– Hydrosphere, and
– Lithosphere
• An ecosystem is a place where organisms interact with the physical environment
– Ecosystems characterized by:
• Cyclical flow of materials from abiotic environment through biotic community and back
• One-way flow of energy

66
Ecosyste ms

67
Biotic Components:
Autotrophs
• Producers are autotrophs
– Require only inorganic nutrients and an outside energy source to produce organic nutrients
– Photoautotrophs
– Chemoautrophs

Biotic Components:
Heterotrophs
• Consumers are heterotrophs
• Require a source of preformed organic nutrients
– Herbivores - Feed on plants
– Carnivores - Feed on other animals
– Omnivores - Feed on plants and animals
68
• Decomposers are also heterotrophs
– Bacteria and fungi

69
Biotic
Components

Energy Flow and
Chemical Cycling
• Nutrients pass one-way through food chain from one level to another
– Each level retains some energy
– The rest is converted to heat, which dissipates into the environment
• Chemicals cycle as organic nutrients
70
• Once used, they are returned back to the producers by
– Excretion
– Death

71
Nature of an
Ecosystem

72
Energy
Balances

73
Grazing & Detrital
Food Webs

74
Ecological Pyramids
• A trophic level
• Composed of all the organisms that feed at the same level in a food chain
• Only about 10% of the energy of one trophic level is useable to the next trophic level
– Explains why few top carnivores can be supported in a food web

75
Ecological
Pyramid

76
Global
Biogeochemical Cycles
• Chemical cycling may involve:
– Reservoir - Source normally unavailable to producers
• Fossil Fuels
• Minerals
• Sediments
– Exchange Pool - Source from which organisms generally take chemicals
• Atmosphere
• Soil
• Water
– Biotic Community - Chemicals remain in food chains, perhaps never

77
Model for Chemical
Cycling

78
Hydrologic Cycle
• Fresh water evaporates from bodies of water
• Precipitation on land enters the ground, surface waters, or aquifers
• Water eventually returns to the oceans

79
The Hydrologic
(Water) Cycle

80
Carbon Cycle
• Atmosphere is an exchange pool for carbon dioxide
– The total amount of carbon dioxide in the atmosphere has been increasing every year
– Thought to be due to fossil fuel combustion
• Transfer Rate

81
The Carbon
Cycle

82
Greenhouse Effect
• Greenhouse gases
– Carbon dioxide, nitrous oxide, methane
– Allow sunlight to pass through atmosphere
– Reflect infrared back to earth
– Trap heat in atmosphere
• If Earth’s temperature rises
– More water will evaporate
– More clouds will form, and
– Setting up a potential positive feedback loop

83
Earth’s Radiation
Balances

84
Nitrogen Cycle
• Atmospheric nitrogen is fixed by bacteria
– Make it available to plants
– Nodules on legume roots
• Nitrification - Production of nitrates
• Denitrification - Conversion of nitrate to nitrous oxide and nitrogen gas
– Balances nitrogen fixation

85
The Nitrogen
Cycle

86
Nitrogen and Air Pollution
• Acid Deposition
– Nitrogen oxides and sulfur dioxide are converted to acids when they combine with water vapor
– Acid rain dramatically reduces pH of surface waters in some areas
– Causes heavy metals to leach out of rocks, poisoning aquatic organisms
– Kills plants and causes fish to be unfit for human consumption
• Smog

87
Acid
Deposition

88
Thermal
Inversion

89
Phosphorus Cycle
• Phosphorus does not enter the atmosphere
– Sedimentary cycle
• Phosphate taken up by producers incorporated into a variety of organic molecules
– Can lead to water eutrophication
• Biomagnification

90
The Phosphorus
Cycle

91
Sources of Water
Pollution

Review
92
• The Nature of Ecosystems
– Biotic Components
– Autotrophs
– Heterotrophs
• Energy Flow
– Ecological Pyramids
• Global Biogeochemical Cycles
– Hydrologic Cycle
– Carbon Cycle
– Nitrogen Cycle

Ending Slide Chapter 48