Download Review Ecosystems

Review Ecosystems
Key Information
Types of Symbiosis
Species A
Species B
Mutualism
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Commensalism
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0
Parasitism
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Roles in Ecosystem
ROLES
Producer
Consumer
Decomposer
Competition
• Populations compete for limited resources such as water, energy,
living space, and mates. Competition within a species may result in
the better-adapted individual (better able to get food, water, territory,
mates, etc.) eliminating the less fit competitor.
• Interspecific (between species) competition negatively effects both
competing populations. Both populations will be reduced in number
due to competition for limiting resources.
Competition
Succession
• Minor changes occur as one species slowly replaces another in
response to such factors as climate changes, human impact, or
introduction of foreign species.
• In land environments, succession is driven by the plants.
• There are two main types of succession, primary and secondary.
Primary Succession
• Primary succession occurs when no soil is present. Therefore, the
organisms that migrate into the area must contribute to soil
formation before other, larger plants can move in. Weathering begins
breaking down the bare rock into smaller particles, and then pioneer
species can move in. Lichens are a good example of a pioneer species.
Lichens attach themselves to rocks with root-like rhizoids. They
secrete acids onto the rock surface, dissolving the rocks. This begins
the formation of soil.
Primary Succession
Secondary Succession
• Secondary succession that takes place when soil is already present,
usually following a catastrophic event that partially or completely
removes the existing vegetation. Secondary succession occurs much
faster than primary succession because soil already exists, a healthy
seed bank in the soil may be present, or rootstocks of previous plants
may still be viable. Secondary succession usually begins with fast
growing herbaceous ground cover that stabilizes the soil.
Interactions of Biotic and Abiotic Factors within an Ecosystem
SOIL – Has both biotic and abiotic components
Changes in Ecosystems
• Humans have impacted practically every ecosystem on Earth.
• Humans have over-fished the oceans, polluted water sources, caused
deforestation, eradicated entire species, or introduced new invasive
species. Most human activities cause changes to the ecosystem in
one way or another.
• Natural forces are also factors that cause ecosystems to change. They
can be large scale natural changes such as fire or they can be slow
changes such as erosion.
Biodiversity
• Biodiversity describes the variation of organisms found in an
ecosystem.
• Biodiversity is the foundation to a healthy ecosystem and may be
impacted by pressures that cause environmental change such as
habitat loss, the introduction of invasive species, climate change, fire
and resource management.
• The development of roads, pipelines, and power lines causes natural
habitats to become fragmented into islands and negatively impacts
the natural flora and fauna of the area.
Invasive species
• Invasive species are also a threat to biodiversity and impose
enormous costs to agriculture, forestry and fisheries.
• The introduction of the alien species may be accidental or intentional.
• The introduction of non-native animals, plants or microbes can result
in serious problems.
• For example, if the non-native species does not have natural
predators in their new environment, then they may potentially rapidly
reproduce, out-compete the native species in the area and alter
natural habitats. The spread of invasive species is a serious problem
and may cause extensive damage to ecosystems.
Climate Change
• Climate change is another factor that impacts ecosystems.
• The effects of climate change are already evident in some
ecosystems.
• According to the EPA, “As the climate continues to warm, major
changes may occur in ecosystem structure and function, species’
ecological interactions, and species’ geographic ranges, with
predominantly negative consequences for biodiversity. In addition,
climate changes such as increased floods and droughts are predicted
to increase the risk of extinction for some plant and animal species,
many of which are already at-risk due to other non-climate related
factors.”
FIRE
• Fire is another important natural occurrence that causes drastic
changes to ecosystems.
• While many mistakenly believe that fire only causes danger, this is far
from the truth.
• Fire helps maintain such ecosystems as grasslands from turning into
forests or scrublands.
• Fire also helps to promote new growth in forest by clearing debris
from the forest floor and allowing the germination of seeds. In fact,
some trees like the redwoods and giant sequoias need their seeds
“heat treated” by fire to germinate.
Humans
• There are trade-offs associated with resource management and
protecting the environment. Overall, the impact that humans have on
the environment is negative.
• However, humans have taken action to improve the ecosystems that
were damaged or destroyed by human activities. Examples of humans
changing the environment to make a positive impact are
natural/wildlife preserves and national parks. These are areas of land
that are protected, managed, and conserved for the benefit of the
environment. Many cities participate in recycling programs, which
limit the amount of trash that enters the landfills and decreases the
demand for non-renewable resources. New fuels and improved
engines reduce pollutants into the atmosphere.
Ecology
• Ecology is the study of interactions between living organisms in a
given area and their surroundings.
• Organisms are impacted by their environment and in turn, impact
their environment.
• The living part of this world is referred to as the biotic community.
Biomes of the World
• Biomes are recognized as the broadest area of interactions in ecology.
• These areas such as deserts, rainforests or grasslands are defined by
two major climatic factors: precipitation and temperature.
Biomes
• Other local factors such as topography, wind patterns and ocean
currents will have modifying effects on regions.
• In addition to particular climate factors, each biome is defined by its
major vegetation type, which influences the types of animals and
other organisms living in that biome.
• Biomes can be subdivided into smaller units called ecosystems.
Growth of Populations
• An organism’s maximum ability to increase its population size is
referred to as its biotic potential.
• This occurs under optimal conditions such as no limits to food, water,
living space, diseases and predation.
• This type of growth pattern is called exponential growth and is
illustrated with a J-shaped curve.
Growth of Populations
Environmental Resistance
• While populations may experience this type of growth, it is often only
for brief periods.
• Seldom do all of these optimal conditions exist at any one time.
• More often, an organism’s growth meets environmental resistance,
which results in decreases in birth rates or increases in death rates.
• These decreases or increases are related to environmental conditions
such as availability of food or predation.
• In this case, the growth of the population is represented by an Sshaped curve.
S-shaped curve showing a population has reached
its carrying capacity.
Abiotic and Biotic Factors Affecting Population
Growth
• The carrying capacity is the size of the population or community that
can be supported by the surrounding environment.
• In determining the carrying capacity of any environment, biologists
identify limiting factors to population growth.
• These either promote or hinder growth and can be divided into
abiotic or biotic factors.
Abiotic Factors Affecting Population Growth
• Temperature
• Precipitation
• Soil pH
• Soil nutrients
• Space availability
• Length of growing season
• Light availability
• Water availability
Wind Effect on Tree Growth
Biotic Factors Affecting Population Growth
• Disease
• Competition
• Predation
• Behaviors of living organisms
Once a population reaches its carrying capacity, the size of a population
might fluctuate due to interplay of the limiting factors within the
environment.
An environmental carrying capacity is subject to change
• Environments may degrade resulting in the shrinking of the carrying
capacity.
• In this case, the environment is no longer able to support a
population of organisms that formerly have lived in an ecosystem on
a sustainable basis.
• No population can live beyond the environment's carrying capacity
for very long.
• Over grazing by herbivores or the introduction of a new disease or
predator may reduce the carrying capacity. This may lead to a drop in
the number of organisms in the ecosystem. After this drop in the
population, a new carrying capacity may be established.
Change in the carrying capacity over time
Both abiotic and biotic factors can be limiting
• Since ecology focuses on the interaction of organisms with their
environment and to other living organisms, these factors (abiotic and
biotic) cannot be viewed in isolation.
• Both types are also referred to as limiting factors, since they
determine the types and number of organisms in the environment.
• For example, plant growth is restricted in the tundra due to the short,
cool summers, coupled with harsh winters and permafrost in the soil.
Trees cannot survive under these conditions. However, the plants that
are present grow low to the ground and tend to be annuals.
The actions of living organisms will have
similar effects - Predation
• In certain environments, keystone predators are important in
restricting the population sizes of some organisms and preventing the
disappearance of other populations.
• This can be seen in the kelp forests along the Pacific coastline in
California. Young kelps are grazed by sea urchins. If left unchecked,
the sea urchins can overgraze the kelp beds leading to their reduction
in size. This normally does not happen because in this situation, the
sea otter acts as a keystone predator and preys upon the sea urchins
keeping their populations in check. This allows a kelp forest to
maintain itself and provide a habitat for many other organisms.
Predation can also lead to fluctuations in
population size of both predator and prey
• The Canadian lynx and snowshoe hare is a classic example of how
populations of predators and prey can fluctuate. The population
peaks for these two organisms is offset. The rise in the lynx
population occurs only after the hare population has begun to rise.
Then as the lynx population increases, predation upon the hare
reduces its population.
• Other limiting factor like climate or disease could also affect the
numbers of both organisms.
Canadian lynx and snowshoe hare
Plants and animals in each biome have
developed specific adaptations for survival
• To survive the harmful effects of fire, grasses have their growing
regions located below the surface of the soil. Therefore, the growing
regions are protected from the fires that periodically burn across the
grasslands.
• In another example, deciduous trees drop their leaves in the fall to
avoid damage to during the cold winters. Also, cold winters reduce or
stop the ability of deciduous tree to carryout photosynthesis. In a
sense, these trees “hibernate” to overcome their ability to function
normally during winter conditions.
• In addition, some organisms may migrate or hibernate to avoid harsh
winter conditions.
Adaptive Strategies of Desert Plants
Succulence
Drought Tolerance
Drought Avoidance
Absorb large amounts
Grow annually, grow
Shed leaves during dry
of water in a short
and die quickly. Shed
periods
period of time
seeds for next season
Have extensive
system horizontal,
shallow roots
Larger, deeper roots
Have a thick waxy
cuticle
Develop mechanism
to absorb moisture
from dry soils
Stomata open at
night rather than the
day
Germinate when soil
moisture conditions
are optimal
Not all seeds
germinate, even
under optimal
conditions