Ecology
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Transcript of Ecology
Ecology
Chapter 18 Intro to Ecology
Ecology• Study of interactions between
organisms and the living and nonliving components of their environment
• All organisms interact with part of their environment
• Their survival depends on this Interdependence
Factors• Environmental factors separated into
2 categories1. Biotic factors: living components2. Abiotic factors: nonliving
components
BIOTIC or ABIOTIC?
Levels of organization• Environments and interactions can be
studied at many levelsOrganism- one member of a speciesPopulation- many members of the same species in the same are
Community- populations of different species living in the same area
Ecosytem- communities+ nonliving components
Biosphere- thin volume of Earth and atmosphere that support life (skin on an apple)
NICHE• Species do not occupy all
parts of their environment• Niche: specific role, or way of
life, of a species in its environment• Includes range of tolerances and Resources used
Generalists: broad niche (opossums)
Specialists: narrow niches (koalas)
ENERGY TRANSFER• Autotrophs make their own
food• They must capture energy
& use it to make organic molecules• They are producers
Most PHOTOSYNTHETICSome CHEMOSYNTHETIC:
energy stored in inorganic molecules to produce carbs
PRODUCTIVITY• GROSS PRIMARY PRODUCTIVITY:
rate at which producers capture light energy by making organic molecules
• Some organic molecules used for respiration• BIOMASS: organic material produced • NET PRIMARY PRODUCTIVITY:
rate at which biomass accumulates
CONSUMERS• Heterotrophs depend upon
autotrophs • CONSUMERS: Energy obtained
by eating organic molecules from other organisms•HERBIVORES: eat producers•CARNIVORES: eat other consumers•OMNIVORES: eat producers & consumers
DETRIVORES• Consumers that feed on
‘garbage’ (known as detritus)
• Detritus: waste, recently dead organisms, fallen leaves, etc.
• Decomposers: cause decay by breaking down complex molecules into simpler ones
ENERGY FLOW• When one organism eats another,
molecules are metabolized, & energy is transferred
• ENERGY flows from producers consumers
• Trophic levels: indicate an organism’s position in energy transfer sequence
FOOD WEBS AND CHAINS• Food chains: simple, linear feeding
relationships• Food webs: many interrelated food chains
ENERGY TRANSFER• Energy is lost as it moves through
ecosystems• heat
• ~10% of energy is available to next trophic level
• b/c energy transfers are limited, there are not many trophic levels in an ecosystem
• Also, # of individuals decreases at each trophic level
• Higher trophic levels contain less energy, so they support less individuals
Crash course: Ecology• https://www.youtube.com/watch?v=izRvPaAWgyw
Consider This…• Amount of U.S. grain fed to farm animals: 70%
• Pounds of corn and soy required to produce just one pound of pork: nearly 7
• Water needed to produce a pound of wheat: 14 gallons
• Water needed to produce a pound of meat: 441 gallons
• Of all water used for all purposes in the United States, more than half goes to: livestock production
Crash course: Water & Carbon cycles• https://www.youtube.com/watch?v=2D7hZpIYlCA
Water cycle
• Transpiration: water loss by plants through leaves• Evaporation: liquid water vapor
• EVAPOTRANSPIRATION = evaporation + transpiration
• Condensation: water vapor liquid
Crash Course: Nitrogen & Phosphorus Cycles• https://www.youtube.com/watch?v=leHy-Y_8nRs
Carbon cycle
photosynthesis
CO2
combustion
Respiration
Death and decay
Nitrogen cycle• Nitrogen in atmosphere is unusable (N2)• Plants can use nitrate (NO3)• Nitrogen fixation:
conversion of nitrogen gas into nitrateDone by nitrogen-fixing bacteria
• Bacteria live in roots of plantsPlants supply carbs, bacteria supply nitrogen
• Ammonification: formation of ammonia in soil by action of bacteria on decaying matter
• Nitrification: nitrites and nitrates produced by bacteria in soil
• Denitrification: returning of nitrogen to atmosphere
Phosphorous cycle• Plants get it from soil• Animals get it from plants• Phosphorous stored in mineral deposits• No atmospheric component
Ch 19 Populations
Crash Course: Populations• https://www.youtube.com/watch?v=RBOsqmBQBQ
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Population characteristics• Population size•# of individuals
• Population density•# of individuals per unit area
• Dispersion • Clumped: individuals clustered together• Uniform: individuals separated by consistent distance• Random: each location independent of others
Population growth• Growth rate: amount by which a population
changes over a given time• Affected by 4 factors:
1. Immigration2. Emigration3. Birth rate4. Death rate
2 Types of Growth Curves1. Exponential Growth• Ideal Conditions• No Limiting Factors• Constant Growth Rate• “J” Shaped Curve
2. Logistic Growth• Limiting Factors Present• Falling Growth rate• “S” Shaped Curve• Resources become less available
Exponential Growth
Exponential Growth
Let’s examine bacteria…If a species of bacteria can reproduce once
every 20 minutes. • How many bacteria will there be after one
day?• How is this unrealistic?
Growth Curves Continued• Under ideal conditions•Growth continues
• However there are limiting factors•1. nutrients•2. space•3. competition
Logistic Growth
Logistic Growth
• Population growth slows or stops•Resources become less available
Carrying Capacity• Largest number of individuals (species)
that a given environment can supportNu
mbe
r of Y
east
Cel
ls
Time (hours)
Carrying capacity
Limiting Factors• Any factor that causes population
growth to decrease
Example:•Competition•Predation•Parasitism and disease•Drought and climate extremes•Human disturbances
Density-Dependent factors• Limiting factor that depends on
population size.
Example•Competition•Predation•Parasitism•Disease
Density-Independent Factors• Affects all populations in similar ways• Regardless of population size
Examples• Unusual weather• Natural disasters• Seasonal cycles• Human activities (damming rivers / clear-
cutting forests)
Resurrecting the Past (2:09 mins)
• http://www.cbsnews.com/videos/the-fast-draw-resurrecting-the-past/
Ch 20 Community Ecology
COMMUNITY ECOLOGY• Species interactions govern communities• Five main interactions1. Predation2. Competition3. Parasitism4. Mutualism5. Commensalism
Predation• When a predator eats an individual from another
species• Relationship between predator and prey
influences size of each population• Predator adaptations• Fangs• Venom• Speed• Specific teeth
Prey adaptations• Main strategy is avoidance• Speed or camoflauge• Batesian mimicry: harmless species mimics a
harful one• Mullerian mimicry: two or more harmful species
look similar
Competition • Occurs when niches overlap• Interspecific: competition between two or more
species• Intraspecific: between members of the same
species• One species usually gets pushed out or removed
from a community• Competitive exclusion
Symbiosis • Symbiosis: close, long-
term relationship between 2 organisms
• Parasitism: one individual is harmed; other benefits• Parasites live on or in a host
• Mutualism: both individuals benefit
• Commensalism: one benefits, other is unaffected
Species richness• Number of species in
a community• Varies with latitude• Greatest in tropical
rain forests because they are very stable
Successional changes• Ecological succession: gradual, sequential
growth or regrowth of a community• Follows disturbances• Primary succession: development of a
community where one has not previously existed• glacial retreat, volcanoes
• Secondary succession: sequential replacement of species following a disturbance• Fires, floods, • Climax community: stable end point following
succession