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