1. 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).

2. Keywords
ecology pioneer species
ecosystem autotroph
biotic factor heterotroph
abiotic factor species
ecological niche population
ecological succession community
biome biosphere
climax community

3. ECOLOGY
- 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)

4. 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

6. BIOMES
- 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

7. BIOMES
A. Land Biomes
1. Tundra
2. Taiga
3. Temperate deciduous forest
4. Grassland
5. Tropical rainforest
6. Desert
B. Aquatic Biomes
1. Freshwater
2. Marine
3. Estuary

8. 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

9. Matter/Biogeochemical Cycles
 Carbon cycle
 Nitrogen cycle
 Water cycle
 Mineral cycles:
 Phosphorus
 Calcium
 Sulfur
 etc.

10. Energy Flow
 Trophic levels: producers, consumers
 Feeding relationships: food chains, food webs
 Ecological pyramids:
 Energy pyramid
 Pyramid of Biomass
 Pyramid of Numbers

11. 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

12. Abiotic and Biotic Factors
of Aquatic Biomes
 Water Chemistry  Salinity of Aquatic Biomes:
 Salinity, pH, ions, nutrients, <1% - 3%
pollutants Freshwater – about <1%
 Temperature Estuary – variable (Why?)
 Depth of Water Marine – about 3%
 Light penetration
 BOD
 Turbidity
 O2 content
Biological Oxygen Demand
 Wind action  Eutrophication
 Water current/flow rate  Turn-over/Upwelling
 Microbial action
 Water pressure

13. Zonations and Thermal Stratification
Affect Interactions
in Aquatic Ecosystems/Biomes

14. Standing (Lentic)water :
ponds, lakes
Isolated/land-locked ;
low species diversity

15. 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

16. Abiotic - Biotic Interactions in
Freshwater based on Life Zones

17. 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.

18. Spring overturn
In 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.

19. The Thermocline acts as a barrier to the transfer of nutrients
and dissolved O2 from the epilimnion to the hypolimnion.

20. 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.

22. 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.

23. 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.

24. 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

25. 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 H 2S)

26. Zones in a Marine Biome

27. 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

29. Major Environmental Problems
 Habitat destruction  Coral reef and Mangrove
 Deforestation destruction
 Soil erosion  Eutrophication
 Desertification
 Overfishing
 Flooding
 Climate change
 Pollution
 Invasive and Introduced
species
 Wildlife trade