Transcript Document 93627

Ecology
Environmental Science
Levels of Organization
 Species
 A group of similar organisms that are able to
interbreed
 Population
 All the members of a species living in one area at
one time
 Community
 All the populations of organisms living in one area
at one time
 Ecosystem
 A community and its physical (non-living)
environment
Ecological Interactions
 There are two types of factors within an
ecosystem.
 Abiotic - Non-living factors
 Biotic - Living factors
 Both can control what organisms are
found where.
Ecological Interactions
 The cycling of energy and compounds
link all organisms within an ecosystem.
 Affecting one organism in the web, can
affect organisms above, below, and
beside it in the system.
 DQ - Discuss an example where
changing one thing has effects on
many others.
Energy in Ecosystems
 First Law of Thermodynamics - Energy
cannot by created nor destroyed.
 Second Law of Thermodynamics - With
each energy transfer in a system less
energy is available.
 What does this mean?
 DQ - Where does the energy go?
Energy in Ecosystems
 DQ - Where does energy come
from in eco systems?
 Sun is major source for most but not
all!
 Photosynthesis - Using light to make
energy for the organism
 Chemosynthesis - using chemicals to
make energy for the organism
 DQ - How does energy get through
the rest of the ecosystem?
Energy in Ecosystems
 Energy is transferred by organisms consuming other
organisms
 The food chain
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1 min ACTIVTY - Come up with a food chain
There are several different levels to a food chain
Producers
Primary Consumers
Secondary Consumers
Tertiary Consumers
Quaternary Consumers
Decomposers
Trophic Levels
 Each of the levels is called a trophic level
 The amount of energy available decreases as
you move up each level
 2nd law of thermodynamics
 DQ - Why are there so many more insects
than tigers in the world?
 Law of 10% - only 10% of energy is passed
to next level.
Trophic Levels
 Can be expressed in energy pyramids
 Page 64
Trophic Levels
 Example problem - If the producer
started with 25,000 cal, how many
would the primary consumer obtain?
 2,500 cal
 Tertiary consumer?
 25 cal
 DQ - What does this mean for
humans?
Food Web
 A food chain is useful in determining
trophic levels, but not in showing
interdependence.
 For that we use food web
 This shows us several organisms within an
ecosystem.
 Shows that organisms are not always
the same level in every chain
Food Web
Assignment
 Create an example food web with at
least 10 individual organisms.
 Then explain, if one organism were
removed from the web how would it
effect the rest of the organisms.
Other factors to interactions
 DQ - What other types of interactions
are there within an ecosystem?
 Competition
 Symbiotic Relationships
 Commensalism, Mutualism, Parasitism
 Predator-Prey
 Keystone Species
 Spatial Distribution
 Mating
Activity
 Divide into groups of three
 In your groups you will have one of the
relationships listed on the previous slide
to research and will present to the rest
of the class.
Populations
 Individuals of a species live in populations
 Population – consists of all the individuals of a
species that live together in one place at one
time
 What is the reason for a definition like this?
 So scientists can talk about all sorts of
populations with similar terms
 Examples of populations?
Populations
 Human population has tripled since 1930
 DQ - What could stop a population from
growing?
 Limited resources is #1 reason
 As well as other factors
 Thing to remember: Populations are
constantly changing
 What do we mean by this?
Populations
 Every population has features that help
determine it’s future:
 1. Population size
 2. Population density
 3. Dispersion
 Each one can effect a populations in
different ways.
Populations
 Population size – the number of individuals in a
population
 DQ - How could this determine the future?
 Small populations are affected by disturbances more
than large populations
 Inbreeding is a big problem with a small population
 DQ - Why would this be?
 Inbreeding causes the population to be genetically
identical, meaning one disease can wipe out entire
population
Estimating Population
 Within ecosystems, scientists have to have an idea of the
population of an organism.
 This helps them understand how organisms will interact
 DQ - How do they do that?
 Most popular is the capture-recapture method
 Uses a formula:
Marked organism recaptured
= total marked
Total organisms captured (rnd 2)
pop. size
Activity
 We are going to demonstrate this
method and practice using the formula
 Toothpick estimation lab
 Individual lab
Populations
 Population Density – the number of
individuals that live in a given area
 DQ - How is this different than
population?
 DQ - How would this effect a
population?
 If individuals are very spread out, they may
rarely meet, meaning reproduction is sparse
 DQ - What might happen if too close
together?
Populations
 Dispersion – the way the individuals of the
population are arranged in space
 There are three main patterns of dispersion:
 Clumped
 Random
 Uniform
 DQ - How would this effect the
population?
Populations
 Scientist use models to predict how
populations will grow
 Three types of growth rate
 1. Stage I model
 Rate of growth = birthrate – death rate
 2. Exponential growth curve
 Also called the stage II model
 Complicated equation
 Set interval of reproduction
 (example – bacteria)
Populations
 The third type of Growth Rate:
 3. Logistic Growth
 Also called Stage III model
 Another complicated equation
 Takes into account the limited
amount of resources
 Best one for nature
 Can cause frequency of changes within
population
 Carrying Capacity – population size that
the environment can sustain.
Populations
 Real populations exhibit a range of
growth patterns
 DQ - Why might this be?
 Many times organisms overshoot then
die off
 DQ - What would this look like on
a graph?
Populations
 Population pyramids:
Population Changes
 Populations have factors that help
determine life expectancy and
survivorship.
 Life expectancy - the probable
number of years of survival for an
individual
 Survivorship - % of a population that
survives to a certain age.
 Environmental resistance environmental factors that cause the
carrying capacity
DQ - What are some of these
factors?
 Factors that influence populations:
 Predation
 Amount of resources
 Human interaction
 Gene flow
 Disease
 Natural disasters
 Others
Survivorship curves
 4 main types of survivorship
 Each curve represents different types
death rates.
 Each curve has several animals that can
be used for examples
 No fancy names just Type 1,2,3, and 4
 Easier to identify with the animals that
follow the curve.
 Pg. 123 in book
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Survivorship Curves
 Type 1 - What is going on?
 Most organisms survive to old age, then die
off quickly
 Example organisms?
 Humans, most top consumers in an
ecosystem
 Type 2 - What is going on?
 Organisms die off at a pretty steady rate
 Death not as related to age
 Examples?
 Many birds, including seagulls and hawks
Survivorship curves
 Type 3 - What is going on?
 High young mortality rate but if they survive,
live very long lives
 Examples?
 Fish, trees, most animals at the bottom of the
food chain
 Type 4 - What is going on?
 High mortality before maturity and after
reproductive age
 Examples?
 Humans (developing), deer, rabbits
Population Changes
 Populations have trait frequencies
 These frequencies will stay the same as
long as outside factors do not influence
the population
 What is wrong with this?
 There are always outside factors that
influence populations!!!!
 What are some of these factors?
Population Changes
 Another factor that can effect how a
population changes:
 Natural selection
 The organism that is best fit for its
environment will eventually dominate the
population frequencies
 Survival of the fittest
 Occurs when there is variation in a population
Population Changes
 Types of Selection:
 Directional selection – the form of
selection that causes the frequency of a
particular trait to move in one direction
 Causes the trait to become
more or less common
 Examples?
Population Changes
 Types of Selection:
 Stabilizing selection – distribution
of traits becomes narrower
 Eliminates the extremes
of the trait
 Examples?
 More common in nature
Assignment
 Pg 129
PQ - 2,6,9 CT - 2, 4
 Bring a tube of M&M minis
 Quiz tomorrow
Activity
 Hunting M&Ms on Fabric
Ecosystem Health
 Several ways to judge how healthy an
ecosystem is.
 DQ - What do you think those are?
 Productivity
 Biodiversity
 Cycling of materials
 DQ - How do each of these affect
how healthy the ecosystem is?
Biodiversity
 What is it?
 the number of different species living
within an eco-system
 High Biodiversity = ??
 Better health
 Plays a HUGE role in determining the
complexity and resiliency of a system
 What are these?
Biodiversity
 Complexity - # of species at each
trophic level
 High complexity = Better health
 DQ - Why?
 Resiliency - Resistance to Disturbances
 There are always disturbances so
systems need a high resiliency.
Productivity
 What is it?
 The rate of biomass production
 Why would this be a big deal?
 DQ - Relates directly to the amount of
energy available to the system.
 More productivity means more of the suns energy
is being converted.
 DQ - Examples of consistently
productive ecosystems?
 Forests, coral reefs, estuaries, agricultural
land.
Cycling of materials
 There is a cycle of materials within an
ecosystem
 The four most important ones:
carbon, nitrogen, phosphorus and water
 If something throws off the cycle, the
eco-system loses materials, and
becomes weaker
Eco-systems
 Water cycle:
Eco-systems
Carbon Cycle:
Eco-systems
 Nitrogen cycle
Changing Ecosystems
 Sometimes the disturbances can
destroy an ecosystem or part of it.
 Sometimes this is beneficial to many
species
 Forest Fires, Volcanoes, floods
 How can it be beneficial?
 Brings nutrients to the system, and
breaks up the dominant species
 Cause the community to change
Communities changing
 As communities changes new types of
species can take over
 This is called succession
 Two Types:
 Primary succession - land that is bare of
soil. (nothing lived there before)
 Secondary succession - existing community
is disturbed and a new one develops.
Succession
 As time goes on, the system becomes
more complicated.
 Pioneer species - first colonists
 Can survive on few resources
 Lichens, mosses, microbes
 They create organic material and
nutrients for later species
 Ends with Climax Community that lasts
until the next large disturbance