Download Ecology

ECOLOGY
Honors Biology
What you will learn…

1. Ecology general overview.
 A.
Definition
 B. Levels of Organization
 C. Abiotic vs. Biotic Factors

2. Populations
 A.
Definition
 B. Population Density
 C. Population Structure and Dynamics
 D. Determining Population Growth
 E. Age Structure

Communities and Ecosystems
1 A. Definition

•
Ecology is the study of how organisms interact with
their environment and each other.
This interaction of organisms is a two-way interaction.
Organisms are affected by their environment, but by their
activities they also change the environment.
1 B. Levels of Organization
•
Ecology is studied on several levels:
–
Organism
•
–
Population
•
–
Consists of all the populations of different species that inhabit a particular area.
Ecosystem
•
–
Group of individuals of the same species living in a particular geographic area.
Community
•
–
Ecologists may examine how one kind of organism meets the challenges of its
environment, either through its physiology or behavior.
Includes all forms of life in a certain area and all the nonliving factors as well.
Biosphere
•
•
•
The global ecosystem; the sum of all the planet’s ecosystems.
Most complex level in ecology, including the atmosphere to an altitude of several
kilometers, the land down to and including water-bearing rocks under 3,000 m under
Earth’s surface, lakes and streams, caves, and the oceans to a depth of several
kilometers.
It is self contained, or closed, except that its photosynthesizers derive energy from
sunlight, and it loses heat to space.
1 B. Levels of Organization
1 C. Abiotic vs. Biotic Factors

Abiotic components
 Physical
and chemical factors (abiotic) affecting the
organisms living in a particular ecosystem.

Biotic components
 Organisms
making up the community
1 C. Examples of Biotic Factors
Anything that has the characteristics of life!
Starfish
Even bacteria!
Polar bears
Trees and grass
1 C. Examples of Abiotic Factors:
 Solar
energy
 Water
 Temperature
 Wind
 Soil composition
 Unpredictable disturbances
2 A. What is a population?

Populationa
group of individuals of a single species that occupy
the same general area.
 Rely on the same resources, are influenced by the same
environmental factors, and have a high likelihood of
interacting and breeding with one another.
2 B. Population Density – What is
it?

Population density
 The
number of individuals of a species per unit area or
volume
 For example, the number of oak trees per square
kilometer (km2) in a forest or earthworms per cubic
meter (m3) in forest soil
2B. Population Density- How do we
measure it?


In some cases, it is estimated by indirect indicators, such as
number of bird nests or rodent burrows or even droppings
or tracks.
In rare cases, it is possible to count all individuals within
the boundaries of the population.


For example, it is possible to count the number of sea stars in a tide pool.
Instead in most cases, ecologists use a variety of
sampling techniques to estimate population
densities.

For example, they might base an estimate of the density of alligators in the Florida
Everglades on a count of individuals in a few sample plots of 1 km2 each.

The larger the number and size of sample plots, the more accurate the estimates.
2B. Population Density- How do we
measure it?


To measure population density, ecologists use a
variety of sampling techniques to estimate
population densities. In most cases, it is impractical
or impossible to count all individuals of a
population.
Sampling Techniques:
 Point
Sampling
 Transect Sampling
 Quadrat Sampling
 Mark and recapture (capture-recapture)
2C. Population Structure- Dispersion
Patterns



Within a population’s geographic range, local
densities may vary greatly.
The dispersion pattern of a population refers to the
way individuals are spaced within their area.
These patterns are important characteristics for an
ecologist to study, since they provide insights into the
environmental effects and social interactions in the
population.
 Clumped
 Uniform
 Random
2C. Population Structure- Dispersion
Patterns

Clumped pattern
 Most
common in nature
 Individuals are aggregated in patches
 Often results from an unequal distribution of resources in
the environment.
 For
example, plants or fungi may be clumped in areas where
soil conditions and other factors favor germination and growth.
 Clumping
of animals is often associated with uneven food
distribution or with mating or other social behavior.
 For
example, fish are often clumped in schools, which may
reduce predation risks and increase feeding efficiency.
Mosquitoes often swarm in great numbers, increasing their
chances for mating.
2 C. Population Structure- Dispersion
Patterns

Uniform, or even, pattern
 Pattern
of dispersion often results from interactions
between the individuals of a population.
 For
example, some plants secrete chemicals that inhibit the
germination and growth of nearby plants that could compete
for resources.
 Animals
may exhibit uniform dispersion as a result of
territorial behavior.
 For
example, penguins and humans
2 C. Population Structure- Dispersion Patterns

Random dispersion
 Individuals
in a population are spaced in a patternless,
unpredictable way.
 For
example, clams living in a coastal mudflat might be
randomly dispersed at times of the year when they are not
breeding and when resources are plentiful and do not
affect their distribution.
 Varying
habitat conditions and social interactions make
random dispersion rare.
2 C. Population Structure

Life Tables
 Used
to determine the average lifespan of various
plants and animal species to study the dynamics of
population growth.
 http://www.ssa.gov/OACT/STATS/table4c6.html
2 C. Population Structure

Survivorship curves
 Graphs
generated from life tables to make the data
easier to comprehend.
 Plot the proportion of individuals alive at each age.
•
•
•
Type 1- produce few offspring, take care of their young,
many survive into maturity.
Type 2- intermediate, more constant mortality over the
entire life span.
Type 3- high death rates for the very young, mature
individuals survive longer, usually involves very large # of
offspring with little or no parent care
2 C. Population Structure
Three types of survivorship curves
2 D. Determining Population Growth

Population Growth
 The
number of individuals comprising a population may
fluctuate over time. These changes make populations
dynamic.
 A population in equilibrium has no net change in its
abundance.
 Population Growth = B – D + I – E
• Factors that influence the number of individuals in a
population:
–
–
–
–
Birth (B) also known as natality
Death (D) also known as mortality
Immigration (I)
Emigration (E)
2 D. Determining Population
Growth
 The




Exponential Growth Model
The rate of population increase under ideal conditions. (High Birth
Rate, Low Death Rate)
Gives an idealized picture of unregulated population growth; no
population can grow exponentially indefinitely.
The whole population multiplies by a constant factor during each
time interval.
http://www.pbs.org/wgbh/nova/earth/global-populationgrowth.html
2 D. Determining Population Growth

Logistic Growth Model (Carrying Capacity)


A description of idealized population growth that is slowed by limiting factors as
the population size increases.

Limiting factors are environmental factors that restrict population growth.

carrying capacity is the maximum population size that a particular
environment can support or “carry”
S-shape curve
 1. Exponential Growth Phase-When the population first starts growing,
population growth is close to exponential growth
 2. Transitional Phase- The population growth starts to slow
 3. Plateau Phase- Carrying capacity is reached and the population is as big
as it can theoretically get in its environment
2 D. Determining Population Growth
Logistic Growth Curves
2 D. Determining Population
Growth
2 D. Determing Population Growth

Factors that appear to regulate growth in natural populations:
 1. Density-dependent factors:
 Competition among members of a growing population for limited
resources, like food or territory.
 Health of organisms
 Predation
 Physiological factors (reproduction, growth, hormone changes)
 2. Density independent factors
• Regardless of population density, these factors affect individuals to the
same extent.
– Weather conditions
– Acidity
– Salinity
– Fires
– Catastrophies
2 D. Determing Population Growth
Factors that appear to regulate growth in natural
populations (continued):
 3.
Boom-and-bust cycles –

the number of individuals within the population seems to show a
cyclic change.
 Predator/prey relationships
 Changing food supply
2 E. Birth and Death Rates and Age
Structure, OH MY! 

Human population can also be described by age
structure diagrams. These diagrams are frequently
dependent on the economy and social state of the
country that they are measured in.
3. Communities


A few terms you should know…
Species –
A
group of organisms which can interbreed with each
other and able to produce a fertile offspring.

Habitat –
 the
environment in which a species normally lives or the
location of a living organism.
3. Communities


A biological community is an assemblage of all the
populations of organisms living close enough
together for potential interaction.
Key characteristics of a community:
 a.Species
diversity
 b.Dominant species
 c.Response to disturbances
 d.Trophic structure
 e. Community interactions
3a. Species Diversity

How would you define diversity?
 What
makes a group diverse?
 What should be present? Any specific quantity?
 What do you think should be considered when considering
a community’s diversity?
3a. Species Diversity

The variety of different kinds of organisms that make it up,

Has two components:
 1. species richness
 The total number of different species in the community.
 The more species present in a sample, the 'richer' the sample.
 2. species abundance (sometimes referred to as “evenness”)
 a measure of the relative abundance of the different species making up
the richness of an area.
3a. Species Diversity

To give an example: we might have sampled two different fields for wildflowers.



The sample from the first field consists of 300 daisies, 335 dandelions and
365 buttercups.
The sample from the second field comprises 20 daisies, 49 dandelions and
931 buttercups (see the table below).
What would you say regarding the diversity (richness and abundance) of
this community?
3a. Species Diversity




Both samples have the same richness (3 species) and the same total
number of individuals (1000).
However, the first sample has more abundance, or evenness, than the
second. This is because the total number of individuals in the sample is quite
evenly distributed between the three species.
In the second sample, most of the individuals are buttercups, with only a
few daisies and dandelions present.
Sample 2 is therefore considered to be less diverse than sample
3b. Dominant Species


In general, a small number of species exert strong control
over a community’s composition and diversity.
Keystone species is a species that exerts strong control on
community structure because of its ecological role, or niche.


Example: sea otters are a keystone predator in the North Pacific.
Sea otters feed on sea urchins, and sea urchins feed mainly on kelp, a
large seaweed.


In areas where sea otters are abundant, sea urchins are rare and
kelp forests are well developed.
Where sea otters are rare, sea urchins are common and kelp is
almost absent.
3b. Dominant Species

Human overfishing is a problem in Alaska. As a
consequence, seal and sea lions have lost their food
source and have declined in population. Killer
whales, therefore have also lost their food source,
and now started eating sea otters. Predict what will
happen as a result.
3b. Dominant Species

The loss of this keystone species has allowed sea urchin
populations to increase, resulting in the destruction of
kelp forests.
3c. Response to Disturbances
Communities change drastically following a
severe disturbance that strips away vegetation
and even soil.
 The disturbed area may be colonized by a
variety of species, which are gradually
replaced by a succession of other species, in a
process called ecological succession.

3c. Response to Disturbances

Primary succession
 When ecological succession begins in a virtually lifeless area with no
soil.
 Usually takes hundreds or thousands of years.
 For example, new volcanic islands or rubble left by a retreating
glacier. Often the only life-forms initially present are autotrophic
bacteria. Lichens and mosses are commonly the first large
photosynthesizers to colonize the area. Soil develops gradually as
rocks weather and organic matter accumulates from the decomposed
remains of the early colonizers. Lichens and mosses are gradually
overgrown by grasses and shrubs that sprout from seeds blow in from
nearby areas or carried in by animals. Eventually, the area is
colonized by plants that become the community’s prevalent form of
vegetations.
3c. Response to Distrurbances
 Secondary
 Occurs
succession
when a disturbance has destroyed an existing
community but left the soil intact.
 For example, forested areas that are cleared for farming,
areas impacted by fire or floods.
3c. Response to Disturbances

Primary Succession


Example: autotrophic prokaryoteslichens,
mossesgrassesshrubstreesclimax communty
Secondary Succession

Example: herbaceous plants woody shrubs trees climax
community
3c. Response to Disturbances
 Early
successional communities are characterized by a
low species diversity, simple structure and broad niches
 The succession proceeds in stages until the formation of
a climax community.
 The
most stable community in the given environment until
some disturbance occurs.
3c. Response to Distrurbances

Are disturbances always a bad thing? When can
they be beneficial?
3c. Response to Disturbances

Small-scale disturbance often have positive effects. 

For example, when a large tree falls in a windstorm, it disturbs the immediate surroundings,
but it also creates new habitats.

For instance, more light may now reach the forest floor, giving small seedlings the opportunity
to grow; or the depression left by its roots may fill with water and be used as egg-laying
sites by frogs, salamanders, and numerous insects.

Small-scale disturbances may enhance environmental patchiness, which can contribute to
species diversity in a community.
3d. Trophic Structure
 The
feeding relationships among the various species
making up the community.
 A community’s trophic structure determines the passage
of energy and nutrients from plants and other
photosynthetic organisms to herbivores and then to
carnivores.
3d. Trophic Structure
 The
sequence of food transfer up the trophic levels is
known as a food chain
 Trophic
levels are arranged vertically, and the names of the
levels appear in colored boxes.
 The arrows connecting the organisms point from the food to
consumer. This transfer of food moves chemical nutrients and
energy from the producers up though the trophic levels in a
community.
3d. Trophic Structure
 At
the bottom, the trophic level that supports all others
consists of autotrophs, called producers.
 Photosynthetic
producers use light energy to power the
synthesis of organic compounds.
 Plants are the main producers on land.
 In water, the producers are mainly photosynthetic protists
and cyanobacteria, collectively called phytoplankton.
Multicellular algae and aquatic plants are also important
producers in shallow waters.
3d. Trophic Structure

All organisms in trophic levels about the producers
are heterotrophs, or consumers, and all consumers
are directly or indirectly dependent on the output
of producers
3d. Trophic Structure

Trophic Levels:

Primary producers




Primary consumers

Herbivores, which eat plants, algae, or phytoplankton.

On land include grasshoppers and many insects, snails, and certain vertebrates like grazing
mammals and birds that eat seeds and fruits

aquatic environments include a variety of zooplankton (mainly protists and microscopic animals such
as small shrimp) that eat phytoplankton.
Secondary consumers

Include many small mammals, such as a mouse, a great variety of small birds, frogs, and spiders, as
well as lions and other large carnivores that eat grazers.

In aquatic ecosystems, mainly small fishes that eat zooplankton
Tertiary consumers


Mostly photosynthetic plants or algae
Snakes that eat mice and other secondary consumers.
Quaternary consumers

Include hawks in terrestrial environments and killer whales in marine environment.
3d. Trophic Structure

Another trophic level of consumers are called detritivores which derive
their energy from detritus, the dead material produced at all the trophic
levels.
 Detritus includes animal wastes, plant litter, and all sorts of dead
organisms.
 Most organic matter eventually becomes detritus and is consumed
by detritivores.
 A great variety of animals, often called scavengers, eat detritus.
For instance, earthworms, many rodents, and insects eat fallen
leaves and other detritus. Other scavengers include crayfish,
catfish, crows, and vultures.
3d. Trophic Structure

A community’s main detritivores are the prokaryotes and fungi, also
called decomposers, or saprotrophs, which secrete enzymes that
digest organic material and then absorb the breakdown products.
 Enormous numbers of microscopic fungi and prokaryotes in the
soil and in mud at the bottom of lakes and oceans convert
(recycle) most of the community’s organic materials to inorganic
compounds that plants or phytoplankton can use.
 The breakdown of organic materials to inorganic ones is called
decomposition.
3d. Trophic Structure
3d. Trophic Structure
A
more realistic view of the trophic structure of a community
is a food web, a network of interconnecting food chains.
 Food webs, like food chains, do not typically show
detrivores, which consume dead organic material from all
trophic levels.
3e. Community Interactions

Consider this…
 You’ve
planted a garden in your backyard. You see
that a squirrel population and a chipmunk population
has begun to inhabit the area. There reproductive
patterns are similar, they eat the same food, and have
similar sleeping patterns.
 What do you expect to happen?
 Is it possible for them to cohabit the area?
3e. Community Interactions
 Interspecific
competition:
 If
two different species are competing for the same
resource.
 Causes the growth of one or both populations may be
inhibited.
 May play a major role in structuring a community.
 Examples:


Weeds growing in a garden compete with garden plants for
nutrients and water.
Lynx and foxes compete for prey such as snowshoe hares in
northern forests.
3e. Community Interactions

Intraspecific Competition:
 Intense
competition that exists within individuals of the
same population because they compete for the exact
same habitat and resources
3e. Community Interactions

Competitive Exclusion Principle idea:
 In
1934, Russian ecologist Gause studied the effects of
interspecific competition in laboratory experiments with
two closely related species of Paramecium.
3e. Community Interactions
Competitive Exclusion Principle Experiment:
 Gause cultured these protists under stable conditions with a
constant amount of food added every day.
 When he grew the two species in separate cultures, each
population grew rapidly and then leveled off at what was
apparently carrying capacity of the culture.
 But when Gause cultured the two species together, one
species was driven to extinction.
3e. Community Interactions

Competitive Exclusion Principle Conclusion:



Gause concluded that two species so similar that they compete
the same limited resources cannot coexist in the same place.
One will use the resources more efficiently and thus reproduce
more rapidly than the other.
Even a slight reproductive advantage will eventually lead to
local elimination of the inferior competitor.
3e. Community Interactions
 The
competitive exclusion principle applies to what is
called a species’ niche.
 In
ecology, a niche is a species’ role in its community, or the
sum total of its use of the biotic and abiotic resources of its
habitat.
3e. Community Interactions

A niche is the functional position of an organism in
its environment, comprising its habitat, resources and
the periods of time during which it is active. The
following are included in a niche:
 Physical
conditions – Ex. Humidity, sunlight,
temperature, salinity, pH, exposure, depth
 Resources offered by the habitat – Ex. Food sources,
shelter, mating sites, nesting sites, predator avoidance.
 Adaptations for – locomotion, biorhythms, tolerance of
physical conditions, defence, predator avoidance,
reproduction, feeding.
3e. Community Interactions
 There
are two possible outcomes of competition
between species having identical niches: Either the less
competitive species will be driven to local extinction, or
one of the species may evolve enough through natural
selection to use a different set of resources.
 This
differentiation of niches that enables similar species to
coexist in a community is called resource partioning.
3e. Community Interactions
Resource


Partioning:
It is a way in which different species can use the same resource, such as
food, without occupying the same physical location at the same point in
time.
For example, different warblers eat the same caterpillar, but they occupy
different positions in the tree. Two primarily occupy the area near the
trunk, with the others share the edges of the branches, but at different
heights. The result is the warblers do not overtly compete for food in the
same space.
3e. Community Interactions
 Predation
is an interaction between species in which
one species, the predator, kills and eats another, the
prey.
 Because eating and avoiding being eaten are
prerequisites to reproductive success, the adaptations
of both predators and prey tend to be refined through
natural selection.
3e. Community Interactions

What are some ways predators can catch prey?
 What
tools can they use?
 What are some essential characteristics?
3e. Community Interactions
 Examples
 Most
of prey capturing strategies:
predators have acute senses enable them to locate
prey.
 In addition, adaptations such as claws, teeth, fangs, stingers,
or poisons help catch and subdue prey.
 Predators are generally fast and agile, whereas those that
lie in ambush are often camouflaged in their environments.
 Predators may also use mimicry; some snapping turtles have
a tongue that resembles a wriggling worm, thus luring small
fish.
Camouflage
Chemical Defense
3e. Community Interactions

What are some ways prey can avoid predators?
 What
tools can they use?
 What are some essential characteristics?
3e. Community Interactions
 Predator
defenses:
 Mechanical
defenses: such as the porcupine’s sharp quills or the
hard shells of clams and oysters.
 Chemical defenses: animals are often bright colored, a warning
to predators; like a poison arrow-frog or a skunk.
 Batesian mimicry: a palatable or harmless species mimics an
unpalatable or harmful one; like the king snake mimics the
poisonous coral snake
 Mullerian mimicry: two unpalatable species that inhabit the same
community mimic each other; like bees and wasps
Batesian Mimicry
Mullerian Mimicry
3e. Community Interactions

Herbivory
 Animals that eat plants or algae
 Aquatic herbivores include sea urchins, snails, and some fishes.
 Terrestrial herbivores include cattle, sheep, and deer, and small insects.
 Herbivorous insects may locate food by using chemical sensors on their feet,
and their mouthparts are adapted for shredding tough vegetation or sucking
plant juices.
 Herbivorous vertebrates may have specialized teeth or digestive systems
adapted for processing vegetation. They may also use their sense of smell to
identify food plants.
 Because plants cannot run away from herbivores, chemical toxins, often in
combination with various kinds of anti-predator spines and thorns, are their
main weapons against being eaten.
3e. Community Interactions

Herbivory
 Some herbivore-plant interactions illustrate the concept of coevolution, a
series of reciprocal evolutionary adaptations in two species.
 Coevolution
occurs when a change in one species acts as a
new selective force on another species, and
counteradaptation of the second species in turn affects
the selection of individuals in the first species.
3e. Community Interactions

Herbivory Coevolution Example:
 an herbivorous insect (the caterpillar of the
butterfly Heliconius, top left) and a plant (the
passionflower Passiflora, a tropical vine).
3e. Community Interactions



Herbivory Coevolution Explanation:
Passiflora produces toxic chemicals that protect its leaves from
most insects, but Heliconius caterpillars have digestive enzymes
that break down the toxins. As a result, Heliconius gains access to
a food source that few other insects can eat.
The Passiflora plants have evolved defenses against the
Heliconius insect. The leaves of the plant produce yellow sugar
deposits that look like Heliconius eggs. Therefore, female
butterflies avoid laying their eggs on the leaves to ensure that
only a few caterpillars will hatch and feed on any one leaf.
Because of this, the Passiflora species with the yellow deposits
are less likely to be eaten.
3e. Community Interactions
 Symbiotic
Relationships are interactions between two
or more species that live together in direct contact.
 Three
main types:
 Parasitism
 Commensalism
 Mutualism
 *Parasitism and mutualism can be key factors in
community structure.
3e. Community Interactions
 Parasitism
A
parasite lives on or in its host and obtains its nourishment from
the host.


For example: A tapeworm is an internal parasite that lives inside the
intestines of a larger animal and absorbs nutrients from its hosts.
Another example: Ticks, which suck blood from animals, and aphids,
which tap into the sap of plants, are examples of external parasites.
 Natural
selection favors the parasites that are best able to find
and feed on hosts, and also favors the evolution of host
defenses.
Tapeworm in Small Intestine
Tick on a dog
3e. Community Interactions

Commensalism



One partner benefits without significantly affecting the other.
Few cases of absolute commensalism have been documented, because it is
unlikely that one partner will be completely unaffected.
For example: algae that grow on the shells of sea turtles, barnacles that
attach to whales, and birds that feed on insects flushed out of the grass by
grazing cattle.
Algae on Sea Turtle
Barnacles on Whale
3e. Community Interactions
 Mutualism
 Benefits
both partners in the relationship.
 For example: the association of legume plants and nitrogenfixing bacteria.

Bacteria turn nitrogen in the air to nitrates that the plants can use
 Another
example: Acacia trees and the predaceous ants they
attract.


Tree provides room and board for ants
Ants benefit the tree by attacking virtually anything that touches it.
Acacia Trees and Ants
4. Ecosystems
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An ecosystem consists of all the organisms in a community as well as the
abiotic environment with which the organisms interact.
Ecosystems can range from a microcosm such as a terrarium to a large area
such as a forest.
4a. Ecosystems- Energy Flow
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Regardless of an ecosystem’s size, its dynamics involve two processesenergy flow and chemical cycling.
Energy flow: the passage of energy through the components of the
ecosystem.
 For most ecosystems, the sun is the energy source, but exceptions include
several unusual kinds of ecosystems powered by chemical energy
obtained from inorganic compounds.
4a. Ecosystems- Energy Flow
4a. Ecosystems- Energy Flow
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For example, an a terrarium, energy enters in the form of sunlight.
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Plants (producers) convert the light energy to chemical energy.
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Animals (consumers) take in some of this chemical energy in the form of organic
compounds when they eat the plants.
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Detrivores, such as bacteria and fungi in the soil, obtain chemical energy when they
decompose the dead remains of plants and animals.
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Every use of chemical energy by organisms involves a loss of some energy to the
surroundings in the form of heat.
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Eventually, therefore, the ecosystem would run out of energy if it were not powered by
a continuous inflow of energy from an outside source.
4a. Ecosystems- Energy Flow
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Biomass is the term ecologist use to refer to the amount, or mass, of living organic
material in an ecosystem.
Primary production is the amount of solar energy converted to chemical energy
(organic compounds) by an ecosystem’s producers for a given area and during a
give time period.
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It can be expressed in units of energy or of mass.
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The primary production of the entire biosphere is 170 billion tons of biomass
per year.
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Different ecosystems vary considerably in their primary production as well as in
their contribution to the total production of the biosphere.
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Net primary production refers to the amount of biomass produced minus the
amount used by producers as fuel for their own cellular respiration.
 Gross production- respiration = net production (GP-R=NP)
4a. Ecosystems- Energy Flow
•Tropical rainforests are
among the most
productive terrestrial
ecosystems and
contribute a large portion
of the planet’s overall
production of biomass.
•Coral reefs also have
very high production, but
their contribution to global
production is small
because they cover such
a small area.
•Even though the open
ocean has very low
production, it
contributes the most to
Earth’s total net primary
production because of
its huge size- it covers
65% of Earth’s surface
4a. Ecosystems- Energy Flow
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Ecological Pyramids
 Pyramid
of Biomass
 Pyramid of Productivity
 Pyramid of Numbers
4a. Ecosystems- Energy Flow
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Pyramid of Biomass:
 shows
the relationship between biomass and trophic
level by quantifying the amount of biomass present at
each trophic level of a community at a particular
moment in time.
4a. Ecosystems- Energy Flow
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Pyramid of Biomass
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Typical units are grams per meter
4a. Ecosystems- Energy Flow
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Pyramid of Production
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Illustrates the cumulative loss of energy with each transfer in a food
chain.
Each tier of the pyramid represents one trophic level, and the width of
each tier indicates how much of the chemical energy of the tier below is
actually incorported into the organic matter of that trophic level.
Note that producers convert only about 1% of the energy in the sunlight
available to them to primary production.
In this idealized pyramid, 10% of the energy available at each trophic
level becomes incorporated into the next higher level.
The efficiencies of energy transfer usually range from 5 to 20%.
In other words, 80 to 95% of the energy at one trophic level never
transfers to the next.
4a. Ecosystems-Energy Flow
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Pyramid of Production:
Units can be Joules or calories
4a. Ecosystems- Energy Flow
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Pyramid of Numbers
 shows
graphically the population of each level in a
food chain.
4b. Ecosystems- Chemical Cycling
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Chemical cycling: involves the transfer of materials within the ecosystem.
 An ecosystem is more or less self-contained in terms of matter.
 Chemical elements such as carbon and nitrogen are cycled between
abiotic components (air, water, and soil) and biotic components of the
ecosystem.
 The plants acquire these elements in inorganic form from the air and soil
and fix them into organic molecules, some of which animals consume.
 Detrivores return most of the elements in inorganic form to the soil and
air.
 Some elements are also returned as the by-products of plant and animal
metabolism.
4b. Ecosystems- Chemical Cycling
4b. Ecosystems- Chemical Cycling
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Biogeochemical cycles:
 Water
cycle
 Carbon cycle
 Nitrogen cycle
 Phosphorous cycle
4b. Ecosystems- Chemical Cycling
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General Model of Nutrient Cycling:
1. Producers incorporate chemicals from the abiotic reservoir (where a
chemical accumulates or is stockpiled outside of living organisms) into organic
compounds.
2.Consumers feed on the producers, incorporating some of the chemicals into
their own bodies.
3. Both producers and consumers release some chemicals back to the
environment in waste products (CO2 and nitrogen wastes of animals)
4. Detritivores play a central role by decomposing dead organisms and
returning chemicals in inorganic form to the soil, water, and air.
5. The producers gain a renewed supply of raw materials, and the cycle
continues.
4b. Ecosystems- Chemical Cycling
General Model of Nutrient Cycling:
Water Cycle
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1.Precipitation
2.Condensation (conversion of gaseous water vapor into liquid water)
3. Rain Clouds
4. and 5. Evaporation (conversion of water to gaseous water vapor) from ocean
6. and 7. precipitation over ocean
8. evaporation from land
9. Transpiration
10. Transpiration
11. evaporation from lakes, rivers
12. surface runof
13. infiltration (movement of water into soil)
14. Water locked in snow
15. Precipitation to land
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**refer to diagrams in handout
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Water Cycle
Carbon Cycle
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1. Carbon in plant and animal tissues
2. fossilization (preserved remains or traces of animals, plants, and other organisms)
3. Death and excretion
4. Decomposers (breakdown organic materials to inorganic ones)
5. coal
6. photosynthesis
7. atmospheric CO2
8. Dissolving
9. combustion (burning of wood and fossil fuels)
10. diatoms (major group of algae, and are one of the most common types of phytoplankton)
11. drilling for oil and gas
12. fossilization
13. oil and gas
14. limestone
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**refer to diagrams in handout
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Carbon Cycle
Nitrogen Cycle
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1. Nitrogen in plant and animal tissue
2. Excretion
3. Ammonia (NH3)
4.Dead organisms
5. decomposers
6. Nitrifying bacteria (convert ammonia to nitrate)
7. nitrogen fixing bacteria (convert N2 to ammonia)
8. nitrate (NO3-)
9. nitrate (NO3-) available to plants
10. swampy ground
11. denitrifying bacteria (return fixed nitrogen to the atmosphere)
12. lightning (atmospheric nitrogen fixation)
13. atmospheric nitrogen (N2 gas)
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**refer to diagrams in handout
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Nitrogen Cycle