Transcript Ecosystems and Communities Chapter 4

Ecosystems and Communities
Chapter 4
The Role of Climate - Sec. 4.1
Organisms vary in their adaptations to
temperature, rainfall, and other
environmental conditions.
Species also vary in their tolerances for
conditions outside their normal ranges.
Weather – day to day conditions of the
Earth’s atmosphere at a particular place and
time.
Climate – average, year to year conditions of
temperature and precipitation in a particular
region.
The Greenhouse Effect
 The atmosphere traps heat energy and
maintains Earth’s temperature range.
 Top three gases: carbon dioxide, methane,
water vapor.
 Sunlight enters the atmosphere as short
wavelength radiation and is converted to
long wavelength heat which can not escape
back out into space.
 Without the greenhouse effect the Earth
would be too cold to sustain life.
The Effect of Latitude on Climate
Because Earth is a sphere that is tilted on
its axis, solar radiation strikes the surface at
an angle that varies throughout the year.
The further you move away from the equator
the more solar radiation varies during the
seasons.
This divides the Earth into three main
climate zones:
1. Polar – cold areas where light hits at low
angle
2. Temperate – affected by tilt of Earth so
seasonal change is great
3. Tropical – near equator from 23.5 degrees
north to 23.5 degrees south.
 Because the sun is directly overhead year
round at the equator climatic conditions
vary very little.
Heat Transport in the Biosphere
Unequal heating of the atmosphere drives
winds and ocean currents.
Warm air rises and cold air sinks.
As warm air rises it is replaced by heavier cold
air – creates prevailing winds.
Cold water at the poles sinks and flows toward
the equator where it warms and rises.
These air and water movements transfer heat
throughout the world.
• Continents and other land masses can also
affect winds and ocean currents.
• Winds over the oceans influence currents.
• As air rises over mountains, it cools and
often loses its moisture as precipitation.
• This causes a dry area on the leeward side
of the mountains = Rain Shadow Effect
Rain Shadow Effect
What Shapes an Ecosystem? – Sec. 4.2
Biotic Factors
- biological influences affecting an organism
in its environment
- all of the living organisms in an ecosystem
Abiotic Factors
- physical, or nonliving, factors that affect
an organism in an ecosystem
- climate, nutrient availability, soil type,
sunlight, rainfall, etc.
Habitat
= where an organism lives
Together, biotic and abiotic factors determine
the survival and growth of an organism and
the productivity of the ecosystem in which
the organism lives.
Niche
- an organism’s habitat and its role in the
habitat
- includes biotic and abiotic factors, its role
in the food web, its physical tolerances,
its reproductive methods, etc.
- no two species can share the same niche
in the same habitat. Fig. 4-5
- Many species have similar, but slightly
different niches
- Fundamental niche – the complete
niche that a species could occupy
- Realized niche – the niche that a
species occupies when in competition
with other species.
Community Interactions
- refers to interactions between organisms
A. Competition
- occurs when organisms of the same or
different species try to use the same
resource in the same place at the same time.
- Competitive Exclusion Principle
- no two species can occupy the same
niche in the same habitat at the same
time
Resource partitioning in Anolis lizards.
A. distichus
A. insolitus
B. Predation
- where one organism eats another
- predator vs. prey
C. Symbiosis
- relationships in which two species live
closely together.
A) Mutualism
- both species benefit
B) Commensalism
- one organism benefits and the other
has no positive or negative effect
- oxpeckers on grazers
- barnacles on whales
C) Parasitism
- one organism lives on or in another
organism and harms it.
- host vs. parasite
Ecological Succession
- ecosystems constantly change in response
to natural and human disturbances.
- results in a replacement of one community
of species by another community
- as organisms live in an area they make the
area better suited to other species
- Primary Succession
- when succession occurs where no soil
previously exists
- lava flows, sand dunes, bare rock, etc.
- pioneer species = first species to populate
- lichen are often pioneer species
- composed of a fungus and algae
- begin breaking down rock and forming
soil
- prepare the area for small grasses or
herbs, which further prepare the area
for other species
Secondary Succession
- when disturbance changes an existing
community but does not remove the soil
- after fires, cutting forests, abandoned
farmland
Secondary Succession
Primary
Succession
Alders to cottonwood
Spruce into Forest
Mount Saint Helens
Biomes – Sec. 4.3
* complex of terrestrial ecosystems that cover
a large area and is characterized by certain
soil and climate conditions and particular
communities of plants and animals.
- organisms are adapted to certain biomes
- an adaptation is an inherited characteristic
that increases an organism’s ability to
survive and reproduce.
- each species has a range of tolerance for
every environmental factor
- microclimate is often very important
(insert graph of Law of Tolerances)
Terrestrial Biomes
Climatograph
1. Tropical Rain Forest (pg. 100)
2. Tropical Dry Forest (pg. 100)
3. Tropical Savanna (pg. 101)
4. Desert (pg. 101)
5. Temperate Grassland (pg. 102)
6. Temperate Woodland and Shrubland
7. Temperate Deciduous Forest (pg. 103)
8. Northwestern Coniferous Forest (pg. 103)
9. Boreal Forest (Taiga) (pg. 104)
10. Tundra (pg. 104)
Aquatic Ecosystems – Sec. 4.4
- are grouped according to abiotic factors
which affect them.
- determined primarily by depth, flow,
temperature, and chemistry of the water
- depth determines light penetration
- water chemistry refers mostly to the
amount of dissolved chemicals in the
water – salts, nutrients, and oxygen
- water covers approximately 75% of
Earth’s surface
-about 3% of Earth covered by fresh water
Aquatic Ecosystems
Freshwater Ecosystems
- divided based on if water is flowing or still
1. Flowing-water ecosystems
- rivers and creeks
- change along their length
- headwaters often cold and turbulent
with lots of dissolved oxygen but
little plant life (trout)
- further down soil builds up, water
slows, more plants grow (catfish)
- organisms are well adapted for speed of
water
2. Standing-water ecosystems
- lakes and ponds
- still water is good habitat for plankton
* tiny, free-floating or weakly swimming
organisms in both freshwater and
saltwater environments
* phytoplankton – single-celled algae –
base of most aquatic ecosystem food
chains
* zooplankton – planktonic animals which
feed on the phytoplankton
Freshwater Pond
3. Freshwater Wetlands
- ecosystems in which water either covers
the soil or is present at or near the
surface of the soil for at least part of
the year
- often very productive
a. bogs – dominated by sphagnum moss
- form in depressions where water
gathers – often acidic soils/water
b. marshes – shallow wetlands along
rivers
- often contain cattails, reeds, rushes
c. swamps – water slowly flows through
- often look like flooded forests
Estuaries
* wetlands where rivers meet the sea
- mixed fresh and salt water
- affected by rise and fall of tides
- often shallow, so they support many
producers and are extremely
productive
- detritus feeds many of the lower levels
of the food chains
- important spawning and nursery areas
a. Salt marshes
- temperate zone estuaries dominated
by salt-tolerant grasses above the
low-tide line and seagrasses below
* much of Texas Coast
b. Mangrove swamps
- tropical wetlands dominated by salttolerant trees called mangroves
- seagrasses below low-tide line
- valuable nurseries for fish and
shellfish
* coast of Everglades N.P.
Estuaries
Marine Ecosystems – pg. 109
Marine Ecosystems
* Photic Zone – area where light penetrates
- photosynthetic producers
* Aphotic Zone – below light penetration
- chemosynthetic producers and detritus
1. Intertidal zone
- area between high and low tide
- organisms adapted to being exposed for
part of the day
- clear zonation of organisms
Marine Ecosystems
2. Coastal Ocean
- extends from low-tide mark to outer
edge of continental shelf
- often all in the photic zone
- kelp forests
3. Coral Reefs
- warm, shallow tropical waters
- coral animals’ hard calcium carbonate
skeletons make up the reef base
4. Open Ocean
- low productivity, but huge area makes it
important for worldwide photosynthesis
5. Benthic Zone
- ocean floor ecosystem
- usually depends on detritus “raining
down”
- benthos – organisms which live on the
ocean floor
Characteristics of Populations
1. Population Density
- number of individuals per unit of area
2. Geographic Distribution
- range
- the area inhabited by a population
3. Growth Rate
- depends on birth rates, death rates, and the number
of individuals moving into or out of a population
Populations in nature grow in two ways:
1. Exponential Growth
- occurs in populations with abundant
space, resources, and few predators or
disease
- individuals in a population reproduce at
a constant rate.
- at first population grows slowly, but
steadily increases at an accelerating
speed.
Exponential Growth – Whooping Cranes
2. Logistic Growth
- after a period of exponential growth,
resources become limited and
population growth slows or stops.
- slows due to decrease in birthrate,
increase in death rate, or both
- eventually the population reaches a
maximum size that the environment
can support = Carrying Capacity
Logistic Population Growth
Limiting factors cause population growth to decrease.
Density-Dependent Factors
- limiting factors that depend on population size
- become limiting only when the population density
reaches a certain level and as population grows the
factor becomes more limiting.
* competition, predation, parasitism, disease
Density-Independent Factors
- affect all populations in similar ways, regardless of
population size
* weather, natural disasters, seasonal cycles, and human
activities
Human Population growth has historically been exponential.
Age-structure diagrams give a view of what a population is like now and what
might happen in it in the future.