Transcript Biology\Ch.4 Ecosystems

Ecosystems
Objectives: I can …
• Describe the factors affecting the weather and climate of an area.
• List the major climate zones and biomes.
• Explain the types of relationships that can occur in a community.
• Compare and contrast primary and secondary succession.
• Develop a likely succession scenario of species.
• Evaluate the role of various biomes on global conditions.
• Characterize the conditions and species found in each major biome.
• List the factors that help determine which life forms will exist in a
freshwater environment.
• Compare and contrast wetlands: bogs, marshes, swamps, and
estuaries.
• Explain the importance of aquatic ecosystems.
Vocabulary:
ecosystem * biotic factors * climate * latitude * conduction *
convection currents * radiant energy * shore breeze * sea
breeze * microclimate * niche * symbiotic * mutualism *
commensalism * parasitism * pioneer species * primary and
secondary succession * climax communities * dominant species *
abiotic factors * biome * transpiration * canopy * emergent
layer * understory * deciduous * succulents * temperate *
freshwater * plankton * phytoplankton * zooplankton *
wetlands * bogs * marshes * swamps * estuaries * marine *
continental slope * continental rise * abyssal plain * midocean
ridges * photic * aphotic * benthos * open ocean
An ecosystem (a collection of all of the biotic and abiotic factors in an
area) has specific life forms (biotic factors) based primarily on the
area’s climate (average daily weather conditions/seasonal changes
over years). All weather, and the resulting climate, is affected by the
sun’s energy. How direct the sun hits an area is dependent on the tilt
of the Earth and the Earth’s position in its revolution around the sun.
Therefore, the northern hemisphere experiences summer during June,
July, and August because the Earth is tilted toward the sun during this
part of Earth’s revolution around the sun. This is true in spite of the fact
that the Earth is actually FURTHER AWAY from the sun during our
summer. The sun’s heat also affects evaporation (and therefore
rainfall) and wind generation (hot air rises and the surrounding air
moves in, creating wind). Wind patterns can also be affected by
mountains, etc. And, atmospheric gases and cloud cover can affect
temperatures.
Abiotic and Biotic Factors
Section 4-2
Abiotic Factors
Biotic Factors
ECOSYSTEM
Go to
Section:
Sunlight
Some heat
escapes
into space
Greenhouse
gases trap
some heat
Earth’s surface
CO2 and water vapor (greenhouse gases) help hold heat in the
atmosphere, away from outer space. Cloud cover at night also helps
hold heat in.
Latitude (distance from the equator) plays an important role in how
directly the sun’s rays hit an area. This creates different climates at
different latitudes. The three main climate zones are the polar,
temperate, and tropical zones.
The polar zones fall between 66.5 and 90 degrees North and South
latitudes. Between 23.5 and 66.5 degrees North and South latitude lies
the temperate zones. These are characterized by warm summers and
colder winters. The tropical zones fall between 23.5 degrees North and
23.5 degree South latitude. These areas are characteristically warm
year round but often have wet and dry seasons instead.
The rotation of and unequal heating of the Earth drives winds and
ocean currents. Air heated near the equator rises and travels toward
the poles while cold air from the poles sinks and travels toward the
equator. But, the flow is not directly north or south due to the spin
(rotation) of the Earth.
Polar
Temperate
Tropical: direct sunlight
Temperate
Polar
The ocean warms from the sun’s radiant energy (electromagnetic
waves - the only form of heat transfer that can occur in the vacuum of
outer space). Warm ocean waters keep coastal areas warmer during
the winter than inland areas. Warm water heats the air above it via
conduction (heat transfer due to direct contact). The warm air rises
above cold air due to convection currents (hot air is less dense and
therefore rises). The warm air over the water is then replaced by the
flow of cool air along the surface from the land. This is called a shore
breeze. However, in Spring, water is slow to warm up after winter but
the sun’s heat quickly heats the landmasses. This makes the hot air
over the land rise and the breeze from the ocean (or Great Lakes in
Wisconsin) moves in, cooling the air (hence, “cooler near the lake” in
Wisconsin). These “sea breezes” can dramatically affect temperatures
on shore.
Heat Transport
The currents in the ocean will transport heat throughout the Earth
Ocean Currents
Microclimates along shorelines or in mountains, due to altitude (higher
altitudes are colder due to fewer air molecules vibrating in the sun’s
radiant heat energy), are common. But other factors can create small
areas with significantly different climates from the surrounding area
(aka microclimates) too.
Microclimates may help provide a niche (the right climate and other
physical conditions to support a species) for a particular species that
might not otherwise live in that area. For example, much of the ocean
has very little life, but coral reefs provide a niche suitable for many
species to survive. A species’ niche will provide the right food, shelter,
climate, etc. for its survival.
Many organisms living in the same community must compete for
resources such as light (plants), food, etc. Often there are
predator/prey relationships. And, symbiotic (living together)
relationships which include mutualism (both organisms benefit),
commensalism (1 benefits, the other is neither harmed nor helped), and
parasitism (the parasite benefits, the host is harmed).
A community or ecosystem develops and changes over time. This is
referred to as ecological succession. Primary succession occurs in
barren areas devoid of soil. Pioneer species are the first to arrive and
begin influencing the environment. For example, lichens can
breakdown rocks and add organic (living or once living) material back
to the soil. Lichens are often the first species in areas covered by a
volcanic eruption. The first species in sandy areas, like beaches or
desert sand dunes, are often grasses.
The pioneer species modify the environment and that allows other
species to take hold. So lichens add soil nutrients that allow mosses
and grasses to grow. These allow insects to move in and help create
deeper soil for shrubs and tree seedlings to start growing. This
provides food and habitat for birds, mice, etc. Then, the shading that
occurs due to the growth of the first sun-loving trees now allows shadeloving species to grow , and so on. Coyotes, etc move in and the
succession of new species continues.
Secondary succession occurs in an area where soil is present but
barren. For example, after a forest fire, plowing a field, a mudflow, etc.
Succession usually occurs faster here than in primary succession.
Eventually, if left undisturbed, an area somewhat stabilizes. This is
seen as old growth forests in some areas, grasslands in the Great
Plains, etc. These stable environments, where changes occur much
more slowly, are sometimes referred to as climax communities. The
dominant species (most prevalent species) gives the area its name (Ex.
grass in a grassland).
Together, the characteristic species living in an area and the physical
(non-living, or “abiotic” factors) environment (weather, etc.) create a
biome. For example, the Great Plains area is a “temperate grassland”,
the very dry areas of Antarctica are “polar deserts”, the deserts in and
near California are “temperate deserts”, etc. Obviously, climate (both
temperature and moisture conditions) has a major impact on what
species survive in an area and what type of biome exists.
Major Biomes
1) Tropical Rain Forest - these constantly warm, wet areas lie close to
the equator. Not only do they provide much of the world’s oxygen
but transpiration (evaporation from plants) from the rain forests
provides much of the moisture in the atmosphere. Tropical rain
forests have more species of plants and animals than any other land
biome. (Coral reefs are the tropical rain forests of the ocean.) The
forest itself is characterized by a canopy (dense tree top leaf
coverings at the same height from mature trees), an emergent layer
(a few tree tops that rise above the canopy layer), and the
understory (shorter plants).
2) Tropical Dry Forest - have less yearly and seasonal rainfall than the
tropical rain forests. During the driest months, trees in these forests
drop their leaves. This is much like our trees losing their leaves
before winter. Trees that lose their leaves are called “deciduous”.
The tropical dry forests are usually found surrounding the tropical
rain forests.
3) Tropical Savannah - also known as tropical grasslands, get little
rainfall. They contain some grass and a few scattered, low growing
trees. Much of Africa and parts of Australia and South America are
covered by tropical savannahs.
4) Deserts - very dry areas whether they are in cold areas (like
Antarctica) or warmer regions. They receive less than 25
centimeters (10 inches) of precipitation yearly. The deserts of the
U.S. can get below freezing at night but over 100 degrees during the
day. The soils have little organic material but many minerals.
Succulents (plants that store water well), like cacti, are found in
parts of some deserts.
5) Temperate Grassland - usually relatively flat plains like in the central
area of North America. The soils are fertile but there is insufficient
rainfall to support trees.
6) Chaparral - occur in temperate, semi-arid (dry) areas. They are
covered with shrubs and other low growing plants.
*** temperate areas have seasonal conditions that are neither
continually hot like the tropics nor continually cold like the polar
regions
7) Temperate Forest - deciduous and coniferous trees dominate. Cold
winters allow the trees to “rest”. The soil has a lot of organic matter
(humus) from leaf and pine needle litter. Precipitation is relatively
good.
8) Temperate Rain Forests - also called northwestern coniferous
forests. Lots of rain, mild seasonal temperature changes, and
characterized by redwoods, spruce, firs, and hemlocks.
9) Taiga - or boreal (north) forests, occur in areas with very cold
winters. Heavily populated by needle bearing trees.
10) Tundra - polar areas with permanently frozen subsoil called the
permafrost. Summers are short and cool. The ground only thaws at
the surface and can get soggy in summer. Plants are very short and
sparse due to cold, windy conditions and frozen subsoil.
Mountains and the surrounding area can provide a vertical shift
(change in altitude) in climate and communities/ecosystems just as
changes in latitudes does. The peak of a tall mountain is much like
the tundra, below that areas resemble the taiga or chaparral, etc.
Ten Major Biomes
Table
Biome
Precip. Compare/Contrast
Temp.
Soil
Diversity
Tropical Rain
high
hot
poor
high
Section 4-3
Forest
Tropical Dry
variable
mild
rich
moderate
Forest
Tropical Savanna variable
mild
clay
moderate
Desert
low
variable
poor
moderate
Temperate
moderate
summer hot
rich
moderate
Grassland
Temperate
summer low, summer hot
poor
low
woodland and
winter
Shrubland
moderate
Temperate Forest moderate
summer
rich
high
moderate,
winter cold
Northwestern
high
summer mild, rocky,
low
Coniferous Forest
winter cold
acidic
Boreal Forest
moderate
summer mild, poor, acidic moderate
winter cool
Tundra
low
summer mild, poor
low
winter cold
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Section:
Trees
dense
Grasses
sparse
medium
medium
sparse
sparse
absent
dense
sparse
dense
medium
medium
dense
sparse
dense
sparse
dense
sparse
absent
medium
Figure 4-17 The World’s Major Land
Biomes
Section 4-3
Tropical rain forest
Tropical dry forest
Tropical savanna
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Section:
Temperate grassland
Desert
Temperate woodland
and shrubland
Temperate forest
Tundra
Northwestern
coniferous forest
Mountains and
ice caps
Boreal forest
(Taiga)
Aquatic Ecosystems
The Earth’s surface is covered about 70% by oceans and another 3%
by freshwater. Water has a higher specific heat than air. That means
that water gains and loses heat slower than air. This can have a
dramatic effect on climate but can also greatly affect life forms living in
water. (Note: Freshwater does NOT mean clean water. It means it is
not considered “salty.”)
Which life forms can exist in aquatic ecosystems depends on nutrient
availability (Ex: P, K, N for algae), temperature of the water, depth of
sunlight penetration, pH, flow/current, dissolved O2, etc. The smallest
aquatic organisms are the plankton. Phytoplankton are the plant-like
algae. Because water covers such a huge percentage of the Earth’s
surface, algae (phytoplankton) are responsible for much of the oxygen
in our atmosphere. Through photosynthesis, algae also help remove
CO2, the biggest greenhouse gas, from the atmosphere. Zooplankton
are the animal-like organisms. Plankton form the base of aquatic food
webs.
Compared to ponds and lakes, wetlands are relatively shallow areas
with fresh water at or near the soil. These are not only primary feeding
grounds for many types of birds, but are also important areas for
filtering out sediments, contaminants, etc. before surface water soaks
into the soil to become part of the groundwater or before the water
enters another area, like a lake.
Wetlands include bogs, marshes, swamps, and estuaries. Bogs are
usually acidic with a lot of moss growing in these areas - sometimes
creating thick mats dense enough to walk on. Marshes tend to occur
along the edges of rivers. They are often associated with cattails and
reeds. Swamps are similar to marshes however swamps will have
trees and shrubs growing in the water. Estuaries form where flowing
fresh water (rivers, streams) meets the ocean and creates a shallow
area of mixed salt and fresh water.
Marine Ecosystems
“Marine” refers to saltwater. Oceans are divided into zones and
regions based on light, temperature, depth, etc. For example, the area
between high and low tide is called the intertidal zone. This area is out
of water part of each day and under water the rest of the day. Sea
anemones, crabs, clams, etc. can take the crashing waves and
changing water levels found here.
Just beyond the low tide area is the relatively shallow, gently sloping
“continental shelf.” The water here is relatively warm because sunlight
penetrates to the bottom. Plenty of plankton offer food for larger
organisms. Wave action here mixes oxygen into the water. And, water
pressure is minimal. Kelp beds grow rapidly here. It is a very important
area for ocean life. Coral reefs require warm water that is shallow
enough for photosynthesis to occur. So, they often live on the
continental shelf in tropical areas. The coral itself is a symbiotic
partnership between a cnidarian animal and an algae. The coral
provides a great habitat to so many organisms that it is often called “the
rainforest of the ocean.”
The region that quickly slopes down and away from the continental
shelf is called the continental slope. The top reaches of this area has
plenty of sunshine for photosynthesis, wave action for oxygen
distribution, and low pressure. Descending down the slope brings a
proportional drop in ocean temperatures called the thermocline.
Organisms preferring cooler water and tolerant of slightly higher water
pressure, like this environment.
At the base of the continental slope is a huge hill called the continental
rise. This is debris from underwater landslides, dead organisms that
have been carried down the slope, etc. This marks the true edge of the
continental granite based material and the start of the basalt based
oceanic floor.
The abyssal plain is the term for the wide expanse of oceanic floor. It
is dotted with volcanic seamounts, but more importantly, it offers a
unique area called the midocean ridge. This is where magma rises to
the surface between tectonic plates. The warmth and gases here allow
certain bacteria to thrive. These are the basis for tube worm survival
and they are the basis for a whole ecosystem.
Organisms living on the ocean floor must be tolerant of high pressure,
lower oxygen conditions, and lack of sunlight. Organisms from the
photic zone (area of water where light can penetrate for
photosynthesis) often fall into the aphotic zone (area where light can’t
penetrate) when they die. This also provides a food source for
organisms deep in the ocean. Those organisms on the ocean floor are
often referred to as benthos - because they live in the benthic zone
(ocean floor) rather than in the open ocean (area of water extending
from the continental slope outward.