Download Ecosystems and Environments (7

Ecosystems and Environments (7.10ABC)
Student Expectation
The student is expected to observe and describe how different environments, including
microhabitats in schoolyards and biomes, support different varieties of organisms,
describe how biodiversity contributes to the sustainability of an ecosystem, AND
observe, record, and describe the role of ecological succession such as in a microhabitat
of a garden with weeds.
Key Concepts







Key Concept 1: Earth’s biomes, including freshwater, marine, desert, forest,
grassland, and tundra and their main vegetation type support organisms that are
adapted to that particular environment.
Key Concept 2: Like a habitat, a microhabitat is a specialized space with food,
water, and shelter for organisms to survive and interact with biotic and abiotic
factors. An example of a microhabitat includes a garden or the space between two
rocks.
Key Concept 3: Biodiversity, or biological diversity, is the variety of life and the
intricate interactions that support and link organisms together in a geographical
region.
Key Concept 4: Biodiversity includes a variety of genes, species, and
ecosystems. The higher the biodiversity of an ecosystem, the better that
ecosystem can withstand environmental stress. Hence, if biodiversity is lost, that
ecosystem has less ability to withstand the same environmental stress.
Key Concept 5: The biodiversity of an ecosystem depends on limiting factors, or
factors that limit the ability of that habitat to sustain a population.
Key Concept 6: Ecological succession is the dynamic and predictable transition
of organisms that make up a community after a disturbance (either natural or
human-caused) as it reaches its climax community.
Key Concept 7: Succession can be primary, beginning with rock exposed by
geologic activity, or secondary, where the existing community’s soil is intact.

Key Concept 8: A microhabitat’s transition over time can be observed and
recorded to identify the role of ecological succession as new habitats and niches
are created
Teacher Background
Objective(s):
7.10A Observe and describe how different environments, including microhabitats in
schoolyards and biomes, support different varieties of organisms.
7.10B Describe how biodiversity contributes to the sustainability of an ecosystem.
7.10C Observe, record, and describe the role of ecological succession such as in a
microhabitat of a garden with weeds.
Foundation:
Organisms are well-adapted to the environments in which they live. Earth's biomes,
including desert, forest, grassland, marine, freshwater, and tundra, support different
varieties of organisms. Even in America's national parks, habitats vary and different types
of animals live in different areas within the same park.
On the microscopic scale, there are also environmental variations that differentiate types
of habitats. Microhabitats exist in gardens and in the spaces between rocks, for example.
A variety of organisms live in these microhabitats, where they interact with different
biotic and non-biotic factors (resources) such as water, food, and shelter.
Biodiversity is a shortened term for biological diversity, and it can be observed and
measured on a large scale — such as in the ocean or a national park or on a smaller scale,
such as in a microhabitat. In a certain geographical region, the variety of life and the
intricate interactions between them indicate the level of diversity present in an area. A
variety of genes, different kinds of species, the ecosystems and the relationship between
all of these factors form biodiversity. The stability of the ecosystem is tightly linked to its
diversity. Simply put, the lower the biodiversity of an ecosystem, then the more
vulnerable it is to environmental change and imbalance. If an ecosystem has a higher
biodiversity, which means more genetic diversity, more varieties of species and so on,
then the ecosystem can withstand more environmental stress. Thus, if certain genes or
species are lost permanently, then the biodiversity is reduced. With the same
environmental stress, this ecosystem will have less ability to withstand. The biodiversity
of an ecosystem depends on those factors that limit the ability of the habitat to sustain a
population.
Following a major disturbance, such as natural disaster, a progression of re-building
occurs. Weeds, small insects, and other pioneers will move into the disturbed area first.
This literally lays the foundation for other species to move into the area, and the progress
continue. This is referred to as ecological succession. Based on F.E. Clement’s theory,
succession is a dynamic process with several steps, such as the bare site, migration,
habitation, competition, reaction, and stabilization. Stabilization is the process of
reaction, when an area reaches a climax community. There are different types of
climaxes, such as Catastrophic Climax, Pre-climax and Post-climax, and Climatic
Climax. The Climatic Climax means the climax community’s progress is solely
controlled and influenced by the local climate.
There are also different kinds of successions. Generally, if the development happens on a
bare site, which has not been occupied before, it is considered as primary succession. A
succession which begins on the rock exposed by geologic activity would be this kind. On
the other hand, if the community develops and proceeds on a site from which another
community was removed, it is secondarysuccession, as it develops on the existing soil.
The transitions of microhabitats can be a record to recognize the role of ecological
succession. New habitats and niches are created, and the microhabitat is transformed. The
observation of a microhabitat’s transition could potentially tell the history of ecological
succession. This philosophy is to make use of a small sample to identify what happens for
the whole system.
Entire species, populations, and individual organisms are directly and indirectly
dependent on their environment. Thus, if environmental conditions change, then these
changes will affect the animals and plants living there. There are generally two types
environmental change, short-term and long-term. Climate change is considered long-term
change. Many scientists have concluded that the Earth’s average temperatures are rising
and predict that they will continue to do so. One consequence of this, many believe, is
that terrestrial ecosystems generally experience an earlier arrival of spring. Such dramatic
shifts in seasonal conditions may lead to extinctions. Existing food chains or food webs
may become broken. However, this is still a gradual change over a long period of time
during which the genetic variations could become more or less favorable towards the new
environment. Although this long-term change may permanently alter an ecosystem,
depending on which those living things may not be able to survive, adaptation to these
changes may allow some species to survive.
Short-term change happens in a relatively short period of time, and commonly forces
populations to move or perish. Along marine coastlines, populations and entire species
often suffer from floods, hurricanes, tsunamis, and human-caused disasters. Many Texans
may still remember Hurricane Katrina's devastation in 2005. Millions of people were
evacuated. This short-term environmental change not only affected humans, but also
other species. Those who could not flee, such as reptiles, may have their population
numbers reduced. If the populations were small and the species isolated to that area, then
an entire species could go extinct from one catastrophic, short-term event.
In addition to natural forces influencing environmental change, human activities are also
often responsible for both short-term and long-term environmental changes. Burning
fossil fuels, cutting large tracts of forest, and unsustainable agricultural practices all affect
the natural environment. Over-consumption and waste also harm the environment. Plastic
bags, for example, are used and discarded daily by the millions and may take hundreds of
years to decompose. Such waste degrades the environment quality and harms food webs.