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

Figure 23.1

In a Sense, the Earth Is a Closed Ecosystem

with Energy as the Only Input

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

Ecosystems are Dynamic

Chemicals cycle through ecosystems –

cycles affect populations/communities

Humans can upset biogeochemical cycles

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

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

Figure 23.2 (2 of 2)

Ecological Succession

Question:

How do

plants get

there?

Figure 23.2 (3 of 2)

Ecological Succession

Ecological Succession

As time goes on, the an ecosystem’s

organismal makeup progresses from a

pioneer community to a climax community

Figure 23.3 (1 of 5)

Climax Communities

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.

Relatively stable community over long term

The nature of the climax community depends largely

upon geography

Figure 23.3 (2 of 5)

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 (3 of 5)

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 (4 of 5)

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 (5 of 5)

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.

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

Figure 23.4

Ecological Succession

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

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)

Energy Flows through Ecosystems

from Producers to Consumers

Photosynthetic organisms =

Producers = 1st trophic level

All other organisms are

consumers

Herbivores = 1 consumers;

eat plants

Carnivores = 2 consumers;

feed on herbivores

SparrowFalcon

Grasshopper

Secondary consumers

are carnivores that feed

on herbivores.

Primary consumers

(herbivores) consume

producers.Producers use the energy

of the sun to produce

organic molecules.

Tertiary consumers

are carnivores that feed

on secondary consumers.

Omnivores: Eat both plants

and animals

Decomposers

Consume dead organic

material for energy

Release inorganic material

that can be used by

producers

Figure 23.6

Energy Flows through Ecosystems

from Producers to Consumers

Vegetables

(producers)

Grain

(producers)

Algae

(producers)

Chicken

(primary

consumers)

Fish

(primary

consumers)

Tuna

(secondary

consumers)

Secondary

consumer

Primary

consumer

Tertiary

consumer

Human

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

Figure 23.7

Energy Flows through Ecosystems

from Producers to Consumers

Bacteria

(decomposers)

Decomposing

underwater plants

Diatoms

(producers)

Algae

(producer) Snail

(primary

consumer)

Zooplankton

(primary consumers)

Grasshopper

(primary consumer)

Grass

(producer)

Small fish

(secondary

consumers)

Small fish

(primary

consumer)

Large fish

(tertiary

consumers)

Heron

(secondary,

tertiary, and

quarternary

consumer)Frog

(secondary

consumer)

Duck

(secondary

consumer)

Snake

(tertiary

consumer)

Red-winged blackbird

(primary and secondary

consumer)

Hawk

(tertiary and

quaternary consumer)

Transfer of energy from producer

Transfer of energy from primary

consumer to secondary consumerTransfer of energy from secondary

consumer to tertiary consumerTransfer of energy from tertiary

consumer to quarternary consumer

Animation—Energy Flow and Food WebsPLAY

Energy Flow and Food Webs

Energy Flows through Ecosystems

from Producers to Consumers

Most energy is lost when it is transferred from one trophic level to the next

Only the energy converted to biomassis available to the next higher trophic level

(life is inefficient)

Figure 23.8

Food eaten by herbivore

Heat energy to

environment

Energy to decomposers

(fungi, insects, worms, etc.)

Energy to carnivores

Cellular

respiration

Growth and

reproduction

10,000

10

100

1000

Producers

(grass)

Primary consumers

(grasshopper)

Secondary consumers

(sparrow)

Tertiary consumers

(falcon)

Energy (calories) Biomass

Only 10% of the energy

available at the trophic

level becomes biomass

that is available to the

next higher tropic level.

Most of the energy in

a grassland is in

green plants.

Energy Flows through Ecosystems

from Producers to Consumers

Ecological pyramid: Diagram depicting the energy available to each successive trophic level (pyramid of energy) or the biomass at each trophic level (pyramid of biomass)

Figure 23.9

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

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

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