Study of the interactions between organisms and the environment
Study of the physical and biological variables governing the distribution & growth of living things
Population
Individuals of a given species occurring at one place at one time
Population ecology
Study of population growth & interactions
Population Size
(births + immigrants) – (deaths + emmigrants) = Population change
Immigration – movement into a population
Emigration – movement out of a population
Growth Rate
Subtract death rate from birth rate
r = b – d
r is growth rate
b is birth rate
d is death rate
Population growth = rN
N = initial population size
Exponential Growth
Rate of increase remains constant
Population size soon increases greatly
Can only occur under ideal conditions
This type of growth cannot continue forever
Exponential Growth of a Bacteria
Carrying Capacity
Indefinite exponential growth is limited
Shortages of growth factors will limit population growth
Carrying capacity = maximum number that can be supported in a particular environment
Sigmoid Growth Curve
Initial exponential growth and subsequent stabilization at carrying capacity
Boom & Bust Cycle
Sometimes populations do not level off
Exponential growth with a sudden die-off
Population Size & Ability to Survive
Very small populations are less able to survive than large populations
Random events can wipe out small populations
Small populations have less genetic variability
Population Density
Number of organisms per unit area
Density influences survival
Dispersion
Way that individuals are arranged
Three patterns
Uniform
Random
Clumped
Uniform Distribution
Individuals evenly spaced
Often results from territoriality
Also plants with allelopathy
Random Distribution
Lacking definite order
Individuals do not influence others growth
Clumped Distribution
Individuals form clusters
Clumping due to interaction of individuals
Density Dependent Factors
Factors that affect a population only if its density changes
Types of density dependent factors
Competition
Predation
Parasitism
Competition
Interaction among organisms for the same resources
Food
Living space
Regulates population size & is a driving force of evolutionary change
Competition Types
Intraspecific – among the same species
Interspecific – between species
Predation
One species will kill & eat another
Interactions maintain natural populations
More prey results in more predators
Less prey reduces predator numbers
Parasitism
One species living at the expense of another
Regulates populations by weakening or killing
Density-Dependent Factors & Boom & Bust Cycles
Example:
Lemmings have large increases & declines
Lemming populations increase, then predators increase
Then, lemming populations are mostly eliminated causing predator populations to decrease because of lack of food
Then, lemming populations can increase….
Density-Independent Factors
Operates regardless of population density
Includes factors such as weather & physical disruptions
A certain percentage of the population will die due to the event
Survivorship
Age distribution
Proportion of individuals that survive to an age category
Differs greatly from species to species
Mortality vs. Survivorship
Mortality – death rate
Survivorship – proportion of an original population that survives to a certain age
Type I Survivorship
Low infant mortality
Small number of offspring, parental care
Most survive to an old age
Type II Survivorship
Often reproduce asexually
Mortality is constant over lifespan
Type III Survivorship
High infant mortality
Those that survive are likely to live to old age
No parental care, high reproductive rate
Demography
Statistical study of human population
Human population is in exponential growth
Human Population Growth has Different Patterns
Stable population
Remains the same
Same number entering reproductive age as at end of reproductive age
Population pyramid
Graphic representation of population age
Shows patterns in population change
Population Growth in Developed Countries
Population Growth in Developing Countries
World Population distribution
Share of the World Population
Interactions Within Communities
Parasites Lost In The News
Community
Grouping of populations living together in a particular area at a particular time
Abiotic Factors
Nonliving factors within the environment
Air
Water
Rocks
Abiotic factors affect living (biotic) factors
Ecosystem
Biotic & abiotic factors in a certain area
Community along with abiotic factors
Habitat
Space within an area where an organism lives
Each organism plays a certain role
Niche
Two ways of defining
An organism’s role in the environment
Organism’s use of biotic & abiotic resources
Competition
Organisms that live near one another strive to obtain the same limited resource
Competitive exclusion principal
If 2 species are competing with one another for the same limited resource , the species able to use the resource most efficiently will eventually eliminate the other species
Competition in Nature
Sage & grass both need the same soil nutrients
Sage out competes grass by secreting toxic chemicals
Barnacle Competition
Balanus & chthamalus
Both live in the intertidal zone
This intertidal zone is their niche
Fundamental Niche
Chthamalus can live out of water longer than Balanus
Fundamental niche
Everywhere a species can inhabit
Realized Niche
When both species are present
Each actually lives where it competes best
This defines their realized niche
Predation
Predator – kills & eats another species
Prey – eaten by another species
Predator-prey relationships affect each other’s populations
Several outcomes are possible
Predator-Prey Example
Didnium – the predator
Paramecium – the prey
Predator & prey introduced into new environment
Outcome 1
Predator exterminates prey
Predator then dies due to lack of food
Outcome 2
Some prey hide in sediment
Predator eats those in clear fluid
Predator dies because it cannot find more food
Outcome 3
Prey is introduced in successive intervals
Predator-prey follow cyclical pattern
Plant –Herbivore Coevolutioin
Plants develop defenses against being eaten
Natural selection chooses animals able to feed on plants with new defenses
Protective Adaptation
Some animals have adapted to eating plants that are toxic
Some (like monarch butterfly) are able to store toxins from food
Stored toxin protects the animal from predation
Protective Coloration
Some highly poisonous organisms advertise with bright colors
Warning coloration is effective defense
Mimicry
Unprotected species have come to resemble harmful or distasteful species
Batesian mimicry
Example: grasshopper that looks like a tiger beetle
Mimicry
Protective coloration of different animals come to resemble each other
Both posses similar defenses
Mullerian mimicry
Example: Monarch & Viceroy butterflies
Camouflage
Animal blends into its surroundings
Not seen by predators
Example: cabbage butterfly caterpillar
Camouflage
Symbiosis
One organism lives with another
Three types
Commensalism
Mutualism
Parasitism
Termite Gut Symbiosis
Commensalism
One species benefits
The other species neither benefits or is harmed
Examples: barnacles living on whales
Mutualism
Both species benefit from relationship
Example: clownfish & anemones
Mutualism
Red billed oxpeckers & impala
Parasitism
One species benefits
One species is harmed
Example: humans & hookworms
Plant Parasitism
Succession
Change in communities over time
Generally linked to disturbance
Primary Succession
Starts on surfaces not previously supporting organisms
Soil must accumulate
Pioneer community becomes established
Usually plants able to grow under harsh conditions
Primary Succession
Pioneer community paves way for growth & development of native vegetation
Plant community changes through time
Eventually a climax community establishes
Primary Succession Mount St. Hellens
Succession of a Pond
Secondary Succession
Areas with soil have been disturbed
Community does not start from no soil stage
Common due to human activity
Ecosystems
Food of the Sea In The News
Ecosystem
Includes abiotic environment & community
Types of organisms of an ecosystem
Producers
Consumers
Decomposers
Producers
Make their own food
Base of the food chain
Plants & photosynthetic protists
Consumers
Heterotrophs – feed on other organisms
Kill & eat their food
Decomposers
Special group of consumers
Nourishment from dead matter
Recyclers
An Ecosystem
Ecosystem Boundaries
May or may not be distinct
Transfer of Nutrients
Ultimate source of most energy is the sun
Green plants capture energy from the sun
Consumers eat producers & other consumers
Detritivores convert organic materials to nutrients usable by plants
Trophic Levels
Feeding levels & transfer of energy
Producer
Primary consumer – feed on producer
Secondary consumer – eat primary consumer
Tertiary consumer – eat secondary consumer
Food Chain
Food Web
Many species do not strictly feed on one trophic level
Interactions become more complicated
Food web – group of interwoven food chains
Energy Flow Through Ecosystems
Most energy is lost & does not transfer to the next trophic level
Higher trophic levels must have fewer individuals
Next highest trophic level has about 1/10 th the number of individuals, biomass & energy
Flow of Energy
Numbers in Trophic Levels
Biomass in Trophic Levels
Energy in Trophic Levels
Obtaining Substances for Life
Materials cycle through ecosystems
Reservoir –area with most of a material
Examples of ecosystem cycles
Water (hydrologic cycle)
Nitrogen
Phosphorus
Oxygen
Carbon
Water Cycle
Most living things are primarily water
Life’s chemical reactions require water
90% of water that reaches atmosphere comes from plant transpiration
Atmospheric water condenses
Water Cycle
Plants take up about 1000 kg of water to produce 1 kg of biomass
Groundwater provides ¼ of water used by humans in U.S.
2% of U.S. groundwater is polluted
Industry
Pesticides
Carbon Cycle
CO 2 found in atmosphere & oceans
Producers & some consumers incorporate carbon into organic molecules
Animals & combustion return carbon to atmosphere
Oxygen Cycling
Plants use CO 2 , release O 2
Consumers use O 2 , release CO 2
Some CO 2 is liberated by decomposition
Nitrogen Cycle
Important plant nutrient
Atmosphere is reservoir
Nitrogen fixing bacteria convert N 2 to ammonia
Phosphorus Cycle
Required plant nutrient
Soil has only small amounts
Animals obtain phosphorus by eating plants
End chapter 40
Biomes & Life Zones
Food for Thought In The News
Biomes
Large ecosystems occurring over wide areas of land within specific climatic regions
Support communities of characteristic organisms
Patterns that Determine Biomes
Amount of solar radiation
Global atmospheric circulation
Features of the earth (topography)
Solar Energy
Some parts of earth receive more energy
Greater latitude, colder climate
Circulation Patterns
Differential heating creates six coils of rising & falling air
Rotation of earth deflects winds
Trade winds of equator
Westerlies of middle latitudes
Precipitation
Warm air rises & is cooled
Cool air holds less moisture
Warm air absorbs available moisture
Shadow Effect
Air traveling up a mountain is cooled
Precipitation forms
Windward side is moist
Leeward side is arid
Ocean Circulation
Ocean moves in great spiral patterns
These surface currents affect climate
Redistribute heat
Climatic Regions Classify Biomes
Tropical rain forest
Savannas
Deserts
Temperate grasslands
Temperate deciduous forests
Taiga
Tundra
Elevation & Biomes
Tropical Rain forests
High temperature & rainfall
200 – 450cm/yr (80 – 175 in/yr)
Average 25 º C (77º F)
Found on both sides of the equator
Rain Forests
Extensive canopy of plants
2% of light reaches forest floor
Plants do not grow well on forest floor
Epiphytes grow on trees
Giant diversity of life
Poor soils, do not support agriculture
Savannas
Areas near the equator
High temperature, moderate rainfall
90 – 150 cm/yr (35 – 60 in/yr)
Savannas
Open grasslands, scattered shrubs & trees
Supports large number of grazing herbivores
Large number of plant eating invertebrates
Termite Mounds of Australia
Deserts
Low precipitation
25 cm/yr (10 in/yr) or less
20 to 30 degrees north & south of equator
Deserts
Organisms with adaptations
High diversity, small populations
Many nocturnal animals
Temperate Deciduous Forests
Distinct seasons
Trees are deciduous
Precipitation moderate
75 – 150 cm/yr (30 – 60 in/yr)
Temperate Deciduous Forests
Upper canopy of dominant trees
Animal life abundant in trees & forest floor
Includes many human population centers
Temperate Grasslands
Includes prairies & steppes
25 – 75 cm/yr (10 – 30 in/yr) of precipitation
Temperate Grasslands
Large quantities of perennial grass
No trees
Grazing animals & burrowing rodents
Rich soils
Many areas converted to agriculture
Taiga
Long cold winters
Little precipitation
Most is in summer
Plants go through life cycle in short amount of time
Taiga
Cone bearing trees common
Many large mammals
Tundra
Found at the top of the world
Permanent ice
Low precipitation like deserts
Tundra
Life is apparent in short summer
Grasses & sedges
Fresh-water Ecosystems
Intertwined with terrestrial ecosystems
Includes only 2% of earth
Ponds & lakes, rivers & Streams
Different water depths have different communities
Life Zones of a Lake
Rivers & Streams
Characterized as an open ecosystem
Nutrients washed into water
Feeds heterotrophs
Autotrophs rare
Estuaries
Freshwater meets saltwater
Producers are mostly algae & phytoplankton
Nutrients abundant
High diversity of organisms
Oceans
Covers nearly ¾ of Earth
Variety of habitats
Intertidal zone
Neritic zone
Open sea zone
Intertidal Zone
Harsh environment for life
Tide rolls in & out
Abundant light for photosynthesis
Variety of producers
Different habitats based on substrate
Rocky shore
Sandy shore
Rocky Shore
Sandy Shore
Neritic Zone
On continental shelf
Abundant plant & animal life
Includes coral reefs
Open-sea Zone
Beyond continental shelf
Many diverse forms of life
Regions of Open-sea
Photic
Light penetrates
Supports phytoplankton
Mesopelagic
No photosynthetic organisms
Water pressure increases
Regions of Open-sea
Abyssal
Deep water
Benthos
Sea floor bottom
The Biosphere
Shark Test In The News Click here to view video
The Biosphere
The global ecosystem
Includes all life on Earth
Nonrenewable Resources
Formed at a rate more slowly than they are consumed
Examples:
Coal
Oil
Copper
Iron
Fuel Resources
Fossil fuels (nonrenewable)
Coal
Oil
Natural gas
Currently 77% of worlds energy supply
Coal 20%
Oil 36%
Natural gas 21%
Nuclear Power
Nonrenewable, but large supplies
2.2 lbs. produces as much electricity as 2200 tons of coal
Problems
Cost of building power plants
Disposal of radioactive waste
Mineral Resources
Inorganic
Occur naturally
Present in fixed amounts
Supplies will eventually be used
Municipal Solid Waste
Many things thrown away
Paper
Food waste
Plastics
Metals
Rubber
Leather
Textiles
Glass
Wood
Municipal Solid Waste
Strategies to Conserve
Reduce consumption
Reuse some items
Recycling
Buying recycled goods
Renewable Resources
Replace themselves over time
Renewable energy sources
Solar power
Water power
Wind power
Geothermal energy
Bioenergy
Solar Power
Use of sun for heating or to produce electricity
Solar cells convert energy into electricity
May be major source of energy by 2030
Water Power
Falling water drives turbines to produce electricity
Wave power uses energy in sea waves
Tidal power
Problems: high cost & unsteady rate
Wind Power
Wind to generate electricity
U.S. may generate 10-20% of energy by 2030
Geothermal Energy
Hot water or steam from within Earth
Uses
Directly for heating
Converted to electricity
Bioenergy
Using living plants to produce energy
Types of bioenergy
Burning of wood
Decomposition of animal waste
Produce methane-rich gas
Produce electricity
Ethanol production from plants
Pollution
Threatens the biosphere
Substances that physically or chemically change water
Types of contaminants
Infections agents
Runoff, drainage & hazardous waste dumps
Toxic substances
Thermal pollution
Solid waste
Dumping Pollutants into Water
Point source – where they enter water
Non-point source – enter in various places
Sediments in runoff
Often from agriculture
Mine drainings
Poisons leaching from hazardous dumps
Pesticides, herbicides, & fertilizers
Toxic Dump Threatening Groundwater
Toxic Substances
Come from many sources
Most do not degrade
Biological concentration
Toxins accumulate in fatty tissues
Biological magnification
Amounts increase in food chain
Biological Magnification of DDT
Pollution from Organic Nutrients
Common sources
Sewage treatment plants
Paper mills
Meat packing plants
Food for bacteria that grow in water
Decreases oxygen in waters
Pollution from Inorganics
Common sources
Croplands
Laundry detergents
Can lead to eutrophication
Heavy plant growth
Plants die
Bacteria decompose plants, use oxygen
Mismanagement of Solid Waste
Sanitary landfills help, but problems still exist
Space is running out
Groundwater contamination is possible
Air Pollution Sources
Burning Fossil Fuels
Major source of air pollution
Causes smog or grey air
Secondary Pollutants
Sun causes reactions with chemicals in air
New pollutants are created
Ozone is principal secondary pollutant
Irritating to eyes & respiratory system
Ground Level Ozone in U.S. Cities
Acid Rain
Caused by precipitation in polluted air
pH of waters are lowered
Acid Rain Effects
Acidifies lakes
Kills aquatic life
Leaching of metals
Eats away stone
Kills plants
Acid Rain Effects
Damage to Ozone Level
Ozone in stratosphere shields UV rays
Main source of damage is chlorofluorocarbons
Deforestation
2% of Earth (rainforests) has 50% of plants & animals
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