1) An ecosystem consists of all the organisms in a particular environment and their physical environment. It includes communities of species and populations of each species. 2) Energy from the sun is the main input that drives ecosystems. Through photosynthesis, producers like plants convert the sun's energy into organic molecules and provide a food source. 3) Energy and matter are transferred between trophic levels in an ecosystem, from producers to primary, secondary, and tertiary consumers. Decomposers break down dead organic material and release nutrients.

1. Ecology: Ecosystems
 Ecosystem: all of the organisms in a
particular environment and their physical
environment
 Community: all of the species in an area
 Population: all the members of a species
in an area
 # pops = community; # comm + env =
ecosystem

2. In a Sense, the Earth Is a Closed Ecosystem
with Energy as the Only Input
Figure 23.1

3. The Biosphere Is a Part of the
Earth Where Life Exists
 Consists of many ecosystems (rem: the
organisms in a specific geographic area and
their physical environment)
 A couple of terms that the book brings up
here:
 Niche: organism’s role in ecosystem
 E.g., herbivores: prey, consumers
 Habitat: the environment in which the
organism lives: e.g., rainforest canopy

4. Ecosystems are Dynamic
 Chemicals cycle through ecosystems –
cycles affect populations/communities
 Humans can upset biogeochemical cycles

5. Ecosystems are Dynamic
 Ecological succession: The sequence of
changes in the species composition of a
community over time
 Example: Mount St. Helens
Now
check out
how it
looks on
google
maps
today ~
30 years
later

6. Ecological Succession
 Primary succession
 The change in
species making up a
community where no
previous community
existed
 Pioneer
Communities:
Dynamic
assemblages that
change during
succession

7. Ecological Succession
Question:
How do
plants get
there?
Figure 23.2 (2 of 2)

8. Ecological Succession
Figure 23.2 (3 of 2)

9. Ecological Succession
 As time goes on, the an ecosystem’s
organismal makeup progresses from a
pioneer community to a climax community

10. Climax Communities
 Relatively stable community over long term
 The nature of the climax community depends largely
upon geography
Temperate deciduous
forest. These forests
receive 75–125 cm (30–50
in.) of rainfall per year.
Summers are hot, and
winters are cold. Trees
lose their leaves in the
winter so as to avoid water
loss when it is too cold to
photosynthsize. Insects,
mice, squirrels, and many
species of birds are
common in these forests.
Figure 23.3 (1 of 5)

11. Climax Communities
Temperate grasslands.
These grasslands receive
25–75 cm (10–30 in.) of
rainfall per year. Long dry
periods and fire are
important factors in
maintaining grasslands.
Grazing animals such as
antelope and burrowing
animals such as prairie
dogs are common.
Figure 23.3 (2 of 5)

12. Climax Communities
Desert. Lack of water
defines the desert
community. Deserts receive
less than 25 cm (10 in.) of
rain each year. Most deserts
are hot, but some are cold.
Both plants and animals
must be able to conserve
water. Many desert plants
are succulents with leaves
that retain and store water.
Animals may tend to avoid
the sun by foraging at night.
Figure 23.3 (3 of 5)

13. Climax Communities
Taiga. The taiga is
composed of evergreen
forests with variable
rainfall of 50–100 cm
(20–40 in.) per year.
Winters are long and cold,
and summers are short.
The needles on evergreen
trees help save water by
providing little surface
through which water can
leave. Animals such as the
grizzly bear, moose, wolf,
and snowshoe hare are
common.
Figure 23.3 (4 of 5)

14. Climax Communities
Tropical rain forest.
Tropical rain forests may
receive 200–1000 cm
(80–400 in.) of rain each
year. It is hot throughout
the year. Tropical rain
forests have a tremendous
diversity of life.
Figure 23.3 (5 of 5)

15. Ecological Succession
 Secondary succession
 Occurs when an existing community
becomes cleared and then undergoes a
sequence of events leading once again to a
climax community
 Soil is already present in secondary
succession

16. Ecological Succession
Figure 23.4

17. Energy Flows through Ecosystems
from Producers to Consumers
 The only input to the Ecosystem of Earth?
 Then? How does this input drive other
processes? … focus on life process
 Photosynthesis

18. Energy Flows through Ecosystems
from Producers to Consumers
 Food chains and food webs depict feeding
relationships
 (Both tend to be oversimplified and based
on incomplete understanding)

19. Energy Flows through Ecosystems
from Producers to Consumers
Falcon Sparrow
 Photosynthetic organisms =
Producers = 1st trophic level
 All other organisms are Tertiary consumers
are carnivores that feed
Secondary consumers
are carnivores that feed
on secondary consumers.
consumers on herbivores.
 Herbivores = 1 consumers;
eat plants
 Carnivores = 2 consumers;
feed on herbivores
Grasshopper
Primary consumers
(herbivores) consume
Producers use the energy producers.
of the sun to produce
organic molecules.

20.  Omnivores: Eat both plants
and animals
 Decomposers
 Consume dead organic
material for energy
 Release inorganic material
that can be used by
producers

21. Energy Flows through Ecosystems
from Producers to Consumers
Tertiary
consumer
Tuna Secondary
(secondary consumer
consumers)
Chicken Primary
Fish (primary
(primary consumer
consumers)
consumers)
Algae Grain Vegetables Human
(producers) (producers) (producers)
Figure 23.6

22. Energy Flows through Ecosystems
from Producers to Consumers
 Food chains
 Linear patterns that describe the flow of
energy through an ecosystem
 Food webs
 The complex interrelationships of many food
chains
 More realistically describes the trophic
relationships in an ecosystem

23. Energy Flows through Ecosystems
from Producers to Consumers
Transfer of energy from producer
Transfer of energy from primary
consumer to secondary consumer
Transfer of energy from secondary
consumer to tertiary consumer
Transfer of energy from tertiary
Hawk consumer to quarternary consumer
(tertiary and
quaternary consumer)
Red-winged blackbird
(primary and secondary Snake
consumer) (tertiary
consumer)
Duck
(secondary Heron
Grasshopper consumer) (secondary,
(primary consumer) tertiary, and
Grass quarternary
(producer) Frog consumer)
(secondary
Large fish consumer)
Small fish
(tertiary
(primary
consumers)
consumer)
Small fish
(secondary
consumers) Algae
(producer) Snail
(primary Bacteria
Diatoms
consumer) (decomposers)
(producers)
Zooplankton
(primary consumers)
Decomposing
underwater plants
Figure 23.7

24. Energy Flow and Food Webs
PLAY Animation—Energy Flow and Food Webs

25. Energy Flows through Ecosystems
from Producers to Consumers
 Most energy is lost
when it is transferred
from one trophic level Energy to carnivores
to the next
 Only the energy
Heat energy to
Growth and
environment
reproduction
converted to biomass Cellular
respiration
is available to the next
higher trophic level
 (life is inefficient)
Food eaten by herbivore
Energy to decomposers
(fungi, insects, worms, etc.)
Figure 23.8

26. Energy Flows through Ecosystems
from Producers to Consumers
Energy (calories) Biomass
 Ecological Only 10% of the energy
available at the trophic
pyramid: level becomes biomass
Diagram depicting Tertiary consumers
that is available to the
(falcon)
the energy next higher tropic level.
available to each
successive trophic 10
level (pyramid of Secondary consumers
(sparrow)
energy) or the
biomass at each 100
trophic level Primary consumers
(pyramid of 1000 (grasshopper)
biomass)
Producers
10,000 (grass)
Most of the energy in
a grassland is in
green plants.
Figure 23.9

27. Energy Flows through Ecosystems
from Producers to Consumers
 Both nutrients and
nondegradable
substances are passed
from one organism to
the next
 Biological
magnification:The
tendency of
nondegradable
chemicals to become
more concentrated in
organisms in each
successive trophic
level

28. Energy Flows through Ecosystems
from Producers to Consumers
 Rem: Only about 10% of the energy
captured by one trophic level is available
to the next
 It takes a greater investment of energy
 More energy is lost as one eats higher on
the food chain

29. Energy Flows through Ecosystems
from Producers to Consumers
 Rem: Only about
10% of the
energy captured
by one trophic
level is available
to the next
 It takes a
greater
investment of
energy
 More energy
is lost as one
eats higher on
the food chain
Figure 23.11