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What is Your
Ecology IQ?
CHAPTER 5
HOW ECOSYSTEMS WORK
Ecology
the scientific study of interactions among
organisms and their environment
 such as the interactions organisms (biotic)
have with each other and with their abiotic
environment.

Environment?
The external conditions or surroundings in
which plants or animals live
 Air, water, minerals, other organisms, and all
other external factors surrounding and
affecting a given organism at any time.
 Which influence development and behavior
of an organism

Ecosystem
a community of living organisms
 (plants, animals and microbes)
 in conjunction with the nonliving
components of their environment
 (things like air, water and mineral soil)
 interacting as a system (ie. habitat)

Biological Community vs Population?
Community
 an interacting group of various species in a
common location.
 For example, a forest of trees and
undergrowth plants, inhabited by animals
and rooted in soil containing bacteria and
fungi
 Population
 a group of organisms belonging to the same
species that are living in the same area

What is succession?

the observed process of change in the
species structure of an ecological
community over time
Succession after disturbance: a boreal
forest one (left) and two years (right) after
a wildfire
What is succession?
community begins with relatively few
pioneering plants and animals and develops
through increasing complexity until it
becomes stable or self-perpetuating as a
climax community
 The ʺengineʺ of succession, the cause of
ecosystem change –
 is the impact of established species upon their
own environments

Predictable changes following a
disturbance or initial colonization of
new habitat

lava flow or a severe landslide, or by some
form of disturbance, such as from a fire,
severe windthrow, logging, of an existing
community
Introduction of Invasive
Species
Kudzu
Types of Succession
Primary succession
 Begins in new habitats, uninfluenced by
pre-existing communities
 Secondary succession
 follows a disruption of a pre-existing
community

An example of Secondary
Succession by stages:
.

1 A stable deciduous forest community

2. A disturbance, such as a wild fire, destroys the forest
3. The fire burns the forest to the ground
4. The fire leaves behind empty, but not destroyed, soil
5. Grasses and other herbaceous plants grow back first
6. Small bushes and trees begin to colonize the area
7. Fast growing evergreen trees develop to their fullest, while shade-tolerant trees
develop in the understory
8. The short-lived and shade intolerant evergreen trees die as the larger deciduous
trees overtop them. The ecosystem is now back to a similar state to where it began
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Secondary succession: trees are colonizing
uncultivated fields and meadows
The study of succession
remains at the core of
ecological science
Where would an ecologist be
least likely to go to study
primary succession?
 A.
A locked, abandoned asphalt
parking lot in New York City
 B. The Amazon Rain Forest
 C. A new island formed by a
volcanic eruption
 D. A gravel-filled valley that had
been covered by a glacier until
recently
B. The Amazon Rain Forest
If an insect eats a plant and a
bird eats the insect, about how
much energy from the plant is
stored in the insect for the bird
to use?
 A. 90%
 B. 50%
 C. 10%
 D. 1%
C. 10%
Plants play a crucial role in the
carbon cycle because they
 A.
Allow carbon to enter an
ecosystem through photosynthesis
 B. Have special bacteria that live in
their root systems
 C. Do not release carbon dioxide
during cellular respiration
 D. Are chemically converted into
fossil fuels when burned.
A. Allow carbon to enter an
ecosystem through
photosynthesis
Which of the following is one of
the largest carbon reservoirs on
Earth?
A.
Oceans
B. Limestone
C. Amazon rain forest
D. Fossil fuels
A. Oceans
What term is used to refer to
the many feeding relationships
that are possible in an
ecosystem?
A.
Energy transfer
B. Energy pyramid
C. Food chain
D. Food web
D. Food web
Which of the following
statements is NOT correct
A. Rare bacteria that live deep in the
ocean get their energy from hydrogen
sulfide in hot water
 B. Plants and other producers get their
energy directly from the sun
 C. Animals get their energy from the sun
indirectly
 D. Consumers get their energy directly
from the sun.

D. Consumers get their
energy directly from the
sun.
Which of the following is NOT
a true statement about cellular
respiration?
A. It is essentially photosynthesis in
reverse
 B. Sugar molecules are its primary
products
 C. Oxygen is one of the primary reactants
 D. It produces energy for organisms to
use

B. Sugar molecules are
its primary products
Consumers are organisms that
 A.
Occupy an ecosystem’s lowest
energy level
 B. Get solar or other energy
indirectly
 C. Are also known as self-feeders
 D. Eat only other animal species
B. Get solar or other
energy indirectly
Succession is possible because
 A.
Climate change over time
 B. It is a rapid and chaotic process
that is very difficult to control
 C. Existing plants reproduce
quickly
 D. New species make the
environment less suitable for
previous ones
D. New species make the
environment less
suitable for previous
ones
Which of the following is NOT
a likely component of soil
formed during primary
succession?
 A.
Broken bits of stone and rock
 B. Decayed lichens and bacteria
 C. Cast-off parts of shrubs and
trees
 D. Dust particles from the air
C. Cast-off parts of
shrubs and trees
Which item is a carbon sink
and NOT part of the carbon
cycle?
A. Consumers breaking down
carbohydrates into carbon dioxide
during respiration
 B. Carbon dioxide being converted into
carbohydrates during photosynthesis
 C. Carbon in the atmosphere in the form
of carbon dioxide
 D. Carbon found within limestone rocks

D. Carbon found within
limestone rocks
Which gas makes up 78% of
our atmosphere but can be
used by plants only when
transformed by bacteria first?
 A. Nitrogen
 B. Oxygen
 C. Carbon dioxide
 D. Hydrogen
A. Nitrogen
Which statement describes how
humans are affecting the balance
of carbon in the atmosphere?
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A. Fewer agricultural crops are planted,
reducing the amount of CO2 released into
the atmosphere
B. Burning fossil fuels in great quantities has
increased the amount of CO2 in the
atmosphere
C. Overgrazing of grasslands has reduced the
amount of CO2 in the atmosphere
D. Severe drought in large areas of the world
has decreased the amount of CO2 that is
released into the atmosphere
B. Burning fossil fuels in great
quantities has increased
the amount of CO2 in the
atmosphere
What type of succession occurs
after a natural process such as
a volcanic eruption or flood?
 A.
Old-field succession
 B. Climax community
 C. Primary succession
 D. Secondary succession
D. Secondary
succession
The bacteria that live within
the roots of a soybean plant are
a critical part of the nitrogen
cycle because they
A. Provide the plant with sugars needed
for growth
 B. Transform nitrates into nitrogen gas
for release
 C. Change atmospheric nitrogen into a
usable form
 D. Release nitrogen by decomposing
dead plant parts

C. Change atmospheric
nitrogen into a usable
form
Which of the following is an
example of secondary
succession?
A. Pioneer plants begin to grow after
glacial melting
 B. Appearance of weeds in cracks in a
concrete surface
 C. Breaking down of bare rock by fungi
and mosses
 D. Growth of plants after a forest is
destroyed by fire.

D. Growth of plants after a
forest is destroyed by fire.
Which kind of organism
obtains energy only from
producers?
A.
Omnivores
B. Decomposers
C. Herbivores
D. All of the above
C. Herbivores
What kind of natural disaster
helps some forest communities
by allowing some trees to
release their seeds, by clearing
away deadwood, and by
encouraging new growth?
 A.
Fire
 B. Flood
 C. Windstorm
 D. Drought
A. Fire
The energy consumed by
organisms
A. Is not partially lost during digestion
 B. Can be stored in fat and sugar
molecules
 C. Remains constant at all trophic levels
 D. undergoes magnification in food
chains

B. Can be stored in fat and
sugar molecules
What type of vegetation would
you expect to find on an
abandoned farm that has
remained undisturbed for 150
years
 A.
Short grasses
 B. Shrubs
 C. Young pine trees
 D. Tall, mature oak trees
D. Tall, mature oak trees
Which of the following does
NOT contain carbon from the
bodies of plants and animals
that died millions of years ago?
 A.
Coal
 B. Oil
 C. Natural gas
 D. Phosphate salts
D. Phosphate salts
Which of the following are
photosynthetic organisms?
 A.
Intestinal bacteria
 B. Freshwater algae
 C. Deeply buried soil bacteria
 D. Fungal decomposers
B. Freshwater algae
Which of the following is
responsible for making
nitrogen in the atmosphere
usable by living organisms?
 A.
Nitrogen-fixing bacteria
 B. Absorption of nitrogen into water
systems
 C. Decomposing bacteria
 D. Conversion of nitrogen into
carbohydrates by photosynthesis
A. Nitrogen-fixing bacteria
Which organism is likely to be
in the bottom trophic level of a
food chain?
A.
Leopard seal
B. Algae
C. Krill
D. Killer whale
B. Algae
Which of the following plants is
likely to be a pioneer species?
A.
Grass
B. Shrub
C. Lichen
D. Oak tree
C. Lichen
lichens are really fungi containing
photosynthetic algal cells
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conveniently grouped into 3 characteristic growth forms:
Foliose lichens have a leaf-like or lobed thallus, loosely
attached to the substrate by root-like rhizines or by a
central stalk-like umbilicus.
Fruticose lichens have an intricately branched upright
or pendulous thallus.
Crustose lichens are low-growing, with the entire
thallus firmly attached to the rock or other substrate.
The thallus of crustose lichens may be squamulose
(composed of crowded, overlapping scales) or areolate
Foliose lichen
Lichens as bioindicator
Scientists use lichens as bioindicator species
to assess air quality
 Lichens vary in their ability to survive in
areas exposed to pollutants such as sulfur
dioxide, fluoride, and ammonia
 They tend to concentrate heavy metals
 Lichens also serve as recorders of these
other contaminants.

Lichens also have diminutive
animals living on their surface called
“water bears”
peculiar fat body with stubby legs bearing claws
at the tips
2nd stage-
3rd
stage-
colonizers like
herbaceous
larger
plants take
plants take
st
1 stageadvantage of
over and
caused by the improved
compete
soil by
for light –
some sort
macroinvertediversity
of
brates and
increases
disturbance microbes and
weeds of the 1st
stage
4th
4th stageshrubs
provide
protection
for tree
seeds to
grow
stage- increase shade affects the
growth of plants below, dead tree leaves
produce humus lower the pH of the soil
and herbs cannot grow, therefore
conserving nutrients
FINAL stageSlow growing trees,
community reaches
its peak of
productivity and
diversity
Community remains
unchanged unless
disturbed, and then
SUCCESSION starts
over again!
Succession
A series of communities that develop in an
area over time.
 OR Successions are changes in communities
that happen over time
 If the succession develops from an area with
no community, it is called a primary
succession e.g. on exposed rock.
 If the succession develops from an area that
has been prevented from changing e.g. by
agriculture, it is called a secondary
succession.

Primary colonisers
Organisms that are able to colonize a disturbed
habitat such as an area of bare soil or rock.
 They have adaptations that enable them to survive
and reproduce in the harsh environment.
 Primary colonizers typically have effective methods
of dispersal.

Climax community
Succession eventually reaches a stable
community called the climatic climax.
 However, the structure of this community
depends the soil and climate.
 In the temperate forest biome, most
successions lead to woodland.

Pioneer
Some organisms are able to live in
environments where there is no stable soil.
 They have to be able to extract nutrients from
the air and to attach themselves to the surface.
 As they grow and produce dead matter, they
start to develop soil and weather the surface.
 Other colonizers then start to grow in the area
and the pioneers are rapidly out competed.
 Lichens are an example of pioneers of bare
rock.

Herbaceous
A green plant that supports itself with its
cell's turgor.
 Herbaceous plants are often dominant in the
second stage in a succession.
 Later stages become dominated by woody
plants.
 The first stage is often dominated by other
photosynthetic organisms such as algae and
lichens.

Diversity
The diversity of living things in a habitat
increases as the succession takes place.
 The developing soil enables a wider range of
plants to colonize and they provide food and
shelter for animals.
 The animals in turn provide food for secondary
consumers.

Competition
Competition is the primary factor that causes
the change in communities in the succession.
 Each community of plants and animals alters
the environment making it less suitable for
them and more suitable for other colonizers.

Dune Succession
Dune Succession
The sea deposits sand on the beach and the
wind blows it inshore.
 Objects on the strandline reduce wind speed
and the sand is dropped.
 This embryo dune is a very disturbed habitat
with an environment that few plants can
colonize.

A pioneer community – fast growing
annuals w/xerophytic adaptations
Sea sandwort - small surface area and
hairs on the lower surface reduce water loss
The succession from sand to a climax community
The picture shows a dune system
A succession starting with open sand
is a psammosere
A succession starting with bare rock
is a lithosere
A halosere - starts with open salt water
(e.g. the succession that may lead to a
saltmarsh at the edge of an estuary)
A hydrosere develops from open
freshwater (e.g. in a pond)
Agriculture - a large area of land is
really a false climax caused by this
activity
Human Development
People spend a lot of time and money
deflecting successions or halting them
 If this managed ecosystem is left
undisturbed for a few years
 It will develop as a succession until it
reaches the climatic climax
 This is called secondary succession

Ecological Terms to Know
1.
2.
3.
4.
5.
Ecology
Biotic
Abiotic
Environment
Ecosystem
Ecological Terms to Know
6.
7.
8.
9.
10.
Community
Population
Succession
Primary vs secondary succession
Pioneer species
Ecological Terms to Know
11.
12.
13.
14.
15.
Climax community
Invasive species
Habitat
Requirements for a good habitat
Leading cause for extinction or endangerment of an
organism