Transcript Earth: A Living Planet

The Biosphere
Earth: A Living Planet
General Vocabulary
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Ecology: The study of how living organisms
interact with each other and with their
surroundings.
Biosphere: Part of the Earth in which life exists
(water, land, air)
Ecosystem: Area defined by its abiotic and biotic
traits
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All ecosystems overlap with neighboring
ecosystems ex. forest and a pond found within
the forest
Traits of an
ecosystem
Biotic
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Plants:
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Trees
Shrubs
Grasses
Fungi
Animals:
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Rodents
Insects
Large animals
Abiotic
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Soil type
Amount of sunshine
Amount of rain
Rock types
Temperature
Succession
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Changes in an ecosystem where one type of
organism replaces another over 100’s of years.
Pioneer Species: colonizes an area for the first
time (ex. first plants to grow after a volcanic
eruption)
Climax community: “end point” – organisms
found in a climax community do not continue to
change – they are very stable
Energy and Nutrients
Flow of Energy
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Plants convert sunlight into usable energy for
animals (photosynthesis)
After energy is used by an organism, it cannot
be re-used…energy FLOWS it does not CYCLE!
Trophic (feeding) Levels
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Producer: (photosynthetic plants) – uses
sunlight to make its own food
Consumer: organism that gets energy from a
producer
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Primary, secondary, tertiary…
Decomposer: live on non-living organisms
10% Rule
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At each trophic level, only 10% of the energy
that is consumed is available to the next
trophic level
WHY?
– Because most of what the animal eats is
used by the animal (doing life processes…
running, hiding, eating, breathing etc… all of
this uses energy!)
Ecological Pyramid
Tertiary Consumers
Secondary Consumers
Primary Consumers
Producers
At each level: biomass, numbers and energy are reduced
Food Webs
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Ecological pyramid demonstrates a single food
chain…
Food Chain: sequence of organisms that eat
one another BUT
Food chain is oversimplified. Weaving food
chains together is called a food web and
reflects true relationships within an ecosystem
Nutrient Cycles
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Because nutrients are used and re-used, they
form cycles
Nutrients in
soil used by
plants
Animal dies &
decomposes
Nutrients returned
to soil
Animal eats
animals and uses
nutrients
Animal eats
plants and uses
nutrients
Nutrient Cycles
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Limiting Factor: a nutrient that is found in small
amounts and limits the growth of a population
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Ex. Nitrogen usually limits algae growth in
ponds. By adding more nitrogen, algae no
longer has limited growth and results in algae
blooms… leads to fish death
Populations and Communities
Population Growth
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Population: group of the same species that
live in the same area in a given time.
If living conditions are IDEAL, growth will be
exponential… there is nothing to inhibit growth!
In reality – exponential growth is not
sustainable – there will always be a limiting
factor
– Can you think of an exception to this??
Logistic Growth
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Real growth curves will eventually reach a
steady state = the carrying capacity of the
environment for that species
A population cannot continue to grow forever
because of:
– Lack of food
– Overcrowding (lack of space)
– Competition within the population
Factors that control population
growth
Density-Dependent
Limiting Factors:
Factors that affect
large and/or
overcrowded
populations
DensityIndependent
Limiting Factors:
Weather and natural
occurrences that
have nothing to do
with the density of a
population
Density-Dependent Limiting
Factors
1. Competition (for food, space, water,
sunlight…)
 Remember: if two species compete for the
same niche, one will lose. Natural selection
allows for both species to survive if one
species evolves and adapts to a different
niche
Density-Dependent
Limiting Factors
2. Predation
 Predator-prey relationships keep both
populations in balance
 As prey pop. increases… the predator pop. will
increase… as predator pop. increases, prey
pop. will decrease… as prey pop. decreases,
predator pop. will decrease… this allows prey
pop. to increase… and the cycle begins again
Density-Dependent Limiting
Factors
3. Parasitism
 Parasites: live off host organism without killing it
 Thrive best in large, stressed populations
(stressed populations are susceptible to
disease)
 More easily spread in overcrowded populations
Density-Dependent Limiting
Factors
4. Crowding and Stress
 Smaller area per animal in which to find home
and/or hunt for food
 Crowded populations tend to fight
Interactions within and between
Communities
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Community: all the populations that live
together within an area.
– They live together – therefore they interact
Interactions include:
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Competition
Predator/prey relationship
Symbiosis
Ecosystems are Connected!
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Ecosystems are studied as isolated systems
BUT
All ecosystems are interconnected by
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Proximity
Migratory patterns
Atmosphere (wind patterns)
Hydrology of Earth (groundwater flows, rivers)
THE END!