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CHAPTER 4
Ecosystems and
Communities
4.1 Climate
Weather vs. Climate
Weather
• Day to day conditions
Climate
• Average conditions over a long period
• Year to year patterns of temperature and
precipitation
“Weather is how you pack your suitcase;
climate is how you shop for a wardrobe”
4.1 Climate
Solar Energy
Some energy is reflected
back into space and some is
absorbed
• Absorbed energy is
converted into heat
 Some radiates into space
 Some is trapped in the
biosphere
Greenhouse Effect
Greenhouse Gasses
• Carbon dioxide,
methane, & water vapor
• Allows visible light to
enter but traps heat
 Different wavelengths
Figure 4.1
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4.1 Climate
Latitude and Solar Energy
Creates 3 different
climate zones
• Tropical
• Temperate
• Polar
Depends on amount of
direct sunlight
• Due to tilt and curvature of
Earth
Figure 4.2
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4.2 Niches and
Community Interactions
Tolerance
Range of conditions
under which it can
grow and reproduce
Habitat
The place where a
species lives
Determined by the
tolerance of the species
4.2 Niches and
Community Interactions
Niche
An organisms “role” in the ecosystem
How it interacts with biotic and abiotic factors
as it obtains resources
• What it needs to survive and reproduce
 Food, water, nutrient, space, etc.
Encourages competition
4.2 Niches and
Community Interactions
Competitive Exclusion Principle
No two organisms can occupy exactly the same niche in
exactly the same habitat at the same time
Competition causes one species to die out or move
4.2 Niches and
Community Interactions
Dividing Resources
By causing species to
divide resources,
competition helps
determine the number
and kinds of species in
a community and the
niche each species
occupies
4.2 Niches and
Community Interactions
Predation
One organism captures
and eats another
• Predator-prey relationship
Affect the size of prey
populations
4.2 Niches and
Community Interactions
4.2 Niches and
Community Interactions
4.2 Niches and
Community Interactions
Herbivory
An animal(herbivore) feeds
on a producer(plant)
Affect the size and
distribution of plant
populations
4.2 Niches and
Community Interactions
Keystone Species
Population of a single
species can cause dramatic
changes in the structure of
the community
4.2 Niches and
Community Interactions
Symbiosis
Any relationship in
which two species live
closely together
Three main classes of
symbiotic relationships
in nature:
• Mutualism
• Parasitism
• Commensalism
4.2 Niches and
Community Interactions
Mutualism
Both species benefit
from the relationship
• Crocodile and Plover
4.2 Niches and
Community Interactions
Parasitism
One species benefits
and the other is harmed
• Leech and human
• Parasite does not want
to kill host
 WHY?
4.2 Niches and
Community Interactions
Commensalism
One organism is
benefited and the other
is neither benefited nor
harmed
• Barnacle and whale
4.3 Succession
Ecological Succession
• Video
4.3 Succession
Ecological Succession
A series of changes that occur in a community
over time
Some species die out and some new species
move in
• Number of species typically increases
Example: Krakatau
4.3 Succession
Primary Succession
Succession that begins in an area with no remnant of an
older community
Making of new land or sterilizing existing areas
• After volcanic eruptions
Pioneer species
• Breakdown rock and add organic material to form soil
• Lichens
4.3 Succession
Secondary Succession
Existing communities are not completely
destroyed
Proceeds faster because soil survives
Fire, hurricane, logging, farming
3 years
5 years
40+ years
4.3 Succession
Five stages of succession
Stage 1
• Grasses and weeds begin to grow and scatter seeds
• Insects, worms, and birds return
• Lasts about 2 years
Stage 2
• Dense shrubs, vines and non-woody short plants
appear
• Rabbits, snakes, and mice move in
• Lasts about 5 years
4.3 Succession
Five stages of succession
Stage 3
• Fast growing thin trunk trees take over (birch and
popple)
 Habitat for squirrels
• Larger animals return
• Lasts about 15 years
Stage 4
• Diverse species of diverse ages,
 From ground cover and undergrowth plants to tall trees
• Lasts about 40 years
4.3 Succession
Five stages of succession
Stage 5
• Climax community
• Most diverse forest ecosystem
4.4 Biomes
Biomes
Described in terms of
abiotic and biotic factors
• Abiotic factors
 Climate
 Soil types
• Biotic Factors
 Plant life
 Animal life
4.5 Aquatic Ecosystems
Water Depth
Photic Zone
• Region near the surface
where photosynthesis
can occur
Aphotic Zone
• Dark region below the
photic zone where
photosynthesis can not occur
Benthic Zone
Rocks and sediments at the bottom of a body of water
4.5 Aquatic Ecosystems
Why are some
photic zones much
deeper than others?
4.5 Aquatic Ecosystems
Temperature
Colder at poles and warmer near equator
Warmer at surface and colder at greater depths
Currents
Carry nutrients
Affected by water temperatures
4.5 Aquatic Ecosystems
Marine Ecosystems
Ocean zones are divided into zones based on
depth and distance from shore
• Intertidal Zone
 Submerged in high tide and exposed at low tide
• Costal Ocean
 Brightly lit and well supplied with nutrients
• Open ocean
 Broken into two regions:
 Photic zone
 Aphotic zone
4.5 Aquatic Ecosystems
Marine Ecosystems