ECOLOGY
Core Concepts
1. Ecology is the scientific study of interactions among organisms
and between organisms and their environment.
2. Biotic and abiotic factors influence life in the biosphere, such as
the distribution of biological communities.
3. An organism’s niche refers to the conditions in which an
organism lives and the way in which the organism uses those
conditions.
4. Ecosystems constantly change in response to natural or human
disturbances.
5. Energy flows through an ecosystem in one direction: from the
sun or inorganic compounds to autotrophs (producers) and
then to various heterotrophs (consumers).
Keywords
ecology pioneer species
ecosystem autotroph
biotic factor heterotroph
abiotic factor species
ecological niche population
ecological succession community
biome biosphere
climax community
- study of the interactions between organisms and their environment
(both living and non-living)
- “oikos” (house) + “logos” (study)
- scope of ecology:
organism
population
community
ecosystem
biosphere
ECOSYSTEM
- biological community + physical environment (biotic and abiotic factors)
ECOLOGY
ECOLOGICAL NICHE
- the status/role of an organism in its environment
- Competitive Exclusion Principle:
a fundamental rule in ecology stating that no two organisms can occupy
the exact niche for an indefinite amount of time because competition for
resources would lead to the death of one.
ECOLOGICAL SUCCESSION
- the sequence of communities that develops in an area from the initial
stages of colonization until a stable climax community is achieved
- series of changes in the species composition of living communities, often
following ecological disturbance of the community
- pioneer species vs. climax community
- primary vs. secondary succession
- an environment that has a characteristic climax community
- organisms are of the same general type, being adapted to the particular conditions in which they occur
BIOMES
A. Land Biomes1. Tundra2. Taiga3. Temperate deciduous forest4. Grassland5. Tropical rainforest6. Desert
B. Aquatic Biomes1. Freshwater 2. Marine3. Estuary
BIOMES
Characteristics used to distinguish
Types of Land Biomes/Ecosystems:
Climatic conditions
Temperature
precipitation/rainfall
location, altitude, topography, etc.
Climax community
Vegetation
Animals
Adaptations of Flora and Fauna
Matter/Biogeochemical Cycles
Carbon cycle
Nitrogen cycle
Water cycle
Mineral cycles:
Phosphorus
Calcium
Sulfur
etc.
Energy Flow
Trophic levels: producers, consumers
Feeding relationships: food chains, food webs
Ecological pyramids:
Energy pyramid
Pyramid of Biomass
Pyramid of Numbers
Terrestrial vs. Aquatic ecosystems
Evolution and Ecological Succession
Life originated in water and evolved there for almost
3Billion years before plants and animals began moving
onto land.
Coverage
Aquatic Biomes occupy the largest part of the biosphere
covering about 75% of the Earth’s surface
Aquatic biomes are less affected by climate change
than land ecosystems. Why?
Nature of water
Abiotic and Biotic Factors
of Aquatic Biomes Water Chemistry
Salinity, pH, ions, nutrients,
pollutants
Temperature
Depth of Water
Light penetration
Turbidity
O2 content
Wind action
Water current/flow rate
Microbial action
Water pressure
Salinity of Aquatic Biomes:
<1% - 3%
Freshwater – about <1%
Estuary – variable (Why?)
Marine – about 3%
BOD
Biological Oxygen Demand
Eutrophication
Turn-over/Upwelling
Zonations and Thermal Stratification
Affect Interactions
in Aquatic Ecosystems/Biomes
Standing (Lentic)water : ponds, lakes
Isolated/land-locked ;
low species diversity
Life Zones/Zonations based on:Light Penetration:
Photic Zone
Aphotic Zone
Distance from shoreline, Depth, Sunlight, Temperature:
Littoral Zone:
near shore; sunlight abundant; photosynthesis high ; high species diversity
Limnetic Zone:
near-surface open water ; w/ plankton at the base of food chain
Profundal Zone:
deep water ; aphotic; low temp; no photosynthesis; no O2 (only anaerobic
organisms live here), low species diversity
Thermal Stratification: Eutrophic vs. Oligotrophic vs. Mesotrophic Lakes
Epilimnion
Thermocline
Hypolimnion
Abiotic - Biotic Interactions in
Freshwater based on Life Zones
Oligotrophic lakes are generally newly formed lakes with
relatively small supply of nutrients (poorly nourished); they are
often deep, with steep banks. They are usually crystal-clear blue
or green water due their relatively low net primary productivity.
Spring overturnIn spring, when the atm. warms, the lake’s surface water warms to 40C, reaches maximum
density, and sinks through and below the cooler, less dense water, bringing the bottom
water to the surface. During this spring turnover, DO in the surface layer is moved
downward, and nutrients released by decomposition on the lake bottom are moved
upward toward the surface.
The Thermocline acts as a barrier to the transfer of nutrients
and dissolved O2 from the epilimnion to the hypolimnion.
In summer, such lakes become stratified into different temperature layers
that resist mixing. These lakes have and epilimnion, an upper layer of warm
water with high levels of dissolved O2 (DO ), and a hypolimnion, a lower
layer of colder,denser water, usually with a lower concentration of dissolved
O2, because it is not exposed to the atmosphere.
In the fall the temp. begin to drop, the surface layer sinks to the bottom
when it cools to 40C and the thermocline disappears. This mixing or fall
turnover, brings nutrients from bottom sediments to the top and sends DO
from the top to the bottom.
Water is densest as liquid at 40C(390F) or Solid ice at 00C (320F)is less dense than
liquid water at 40C, which is why ice floats on water. This is fortunate for us and
most freshwater organisms; otherwise, lakes and other bodies of freshwater in
cold climates would freeze from bottom up instead of from surface down, which
would push fish and other organisms to the top, killing them. This unusual
property of water causes thermal stratification of deep lakes in northern
temperate areas with cold winters and warm summers.
Flowing (Lotic) water: streams, rivers ;conditions at different points
(headwater, middle reaches, lower reaches) with
different adaptations of organisms
depth + width high species diversity
Slow flow low O2 low species diversity (e.g.,
catfish, carp)
slow flow high sediments low light low
photosynthesis low species diversity
fast flow animals w/ hooks, suckers, flattened
bodies
Slow flow species similar to pond/lake inhabitants
Marine Biome Salinity: >3%
Distance from shoreline, depth, sunlight, temp determine life zones:
Spray zone: constantly sprayed with salt water by wave action in the intertidal zone
Intertidal zone: low/high tide area
constantly changing conditions constantly changing communities
high light + highO2 + high nutrients highly productive ecosystem
Pelagic zone: open ocean
producers limited to photic zone
remains sink to ocean floor low nutrients (unless there is an upwelling)
Benthic zone: ocean floor
high remains + decomposers low nutrients (stuck here)
Abyssal zone: deep ocean
Low temp (3oC) + high PH2O + no light very low species diversity
hydrothermal vents w/ chemosynthetic bacteria (use H2S)
Zones in a Marine Biome
Estuarine Biome
Salinity: freshwater < estuarine < marine
organisms highly tolerant to salt
Organic material deposited by river/stream; depth:
relatively shallow compared to marine biome
High amount of sunlight
highly productive ecosystem
spawning & nursing grounds
Major Environmental Problems
Habitat destruction
Deforestation
Soil erosion
Desertification
Flooding
Climate change
Pollution
Invasive and Introduced
species
Wildlife trade
Coral reef and Mangrove
destruction
Eutrophication
Overfishing
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