Introduction to Ecology
Ecology is…
The study of the interactions between
organisms and the living and nonliving
components of the environment.
Levels of Organization in the
Field of Ecology :

Biosphere
Biome
 Ecosystem
 Community
 Population
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
Organism
The Biosphere
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The broadest and most inclusive level
The Earth and its atmosphere
Biome

A very large ecosystem that contains a
number of smaller but related
ecosystems within it.
A certain type of biome may exist in more
than one location on Earth, but biomes of
the same type have similar climates and
tend to have inhabitants with similar
adaptations.
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Types of Marine Biomes

Intertidal zone- area where
land meets water

Neritic zone- shallow regions
over continental shelves

Oceanic zone- very deep water
past the continental shelves

Pelagic zone- open water of any
depth
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Benthic zone- seafloor bottom
Abyssal zone- benthic region in
deep oceans
Some types of terrestrial biomes
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Tundra
Taiga
Temperate Deciduous Forest
Temperate Grasslands
Desert
Savanna
Tropical Rain Forests
Ecosystem

All the biotic (living) and abiotic (non-living)
factors interacting in a particular place.
.
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Community


All the interacting organisms of different
species living in an area.
Example: all the species living in the
woods surrounding Hammond Pond
(gray squirrels, white oak trees, red
maple trees, hair-capped moss, etc).
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Population
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All the members of a species that live in one
place at one time.
Example: all of the gray squirrels in the woods
surrounding Hammond pond.
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Organism

Any living thing
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THE ECOLOGY OF
ORGANISMS
Habitat

The physical area in which an
organism lives.
Biotic & Abiotic Factors

Biotic- all of the
living things that
affect an organism

Abiotic- the nonliving physical and
chemical
characteristics of
the environment:
 Temperature
 Humidity
 pH
 Amount of
sunlight
Ecological Niche


The niche of a species is
 A description of its role in a given ecosystem.
Features of niche include:
 How it obtains food
 Relationships with other species
 Services it provides for the community
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Fundamental Niche - the range of
resources a species can potentially use and
the range of conditions it can tolerate.
Realized- the actual area the species
utilizes for food, reproduction, etc.
Examples of Niches


A panda is a specialist (narrow niche)
 Specialist species may become endangered
if the environment changes.
A mouse is a generalist. (broad niche)
 Eat a wide variety of food
 Occupy a broad range of habitats
COMMUNITY ECOLOGY
Types of Species Interactions
(Symbioses)
1) Predation (+/-): A predator is an
organism that captures, kills, and
consumes another living organism.
 Prey most successfully on
slowest, weakest, least fit
members of target population.
 Reduce competition,
population overgrowth, and
stimulates natural selection.
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2) Parasitism (+/-): One individual feeds on
another individual, but does not necessarily
kill it in the process.
Ectoparasites
Endoparasite
3) Competition- The use of the same limited
resource by two or more species results in
competition for food, living space.
 As a result one species gets more resources and
the other gets fewer resources. ( +/ -)
Competitive Exclusion
Principle

Two (closely related) species cannot coexist in
the same habitat for very long.
 One species will eventually obtain a larger
share of resources (win).
 The other species must then
 Behave in ways so as to minimize
competition
 Migrate
 Become extinct
Resource partitioning

Species behave in ways so as to minimize
competition, for example- Occupy different microhabitats within the
ecosystem
 Feed at different times of day/night
4) Mutualism-a relationship in which both
species benefit (+/+).
5) Commensalism-a relationship in
which one species benefits and the
other species is not affected (+/0).
PROPERTIES OF AN
ECOLOGICAL COMMUNITY
Species Richness


Is the number of species a community
contains.
Varies with latitude (distance from the
equator)

The closer the community is to the equator,
the more species it will contain.

Why? Stable climate; plants can photosynthesize
year-round.
Species Diversity (Biodiversity)

Measures the number of species in a
community (richness) relative to the number
of individuals of each species in that
community (evenness).

This measurement can determine the number of
potential interactions between species.
Community Stability
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Indicates how a community responds to
disturbances, both human-caused or natural.
Greater species richness improves a
community’s stability.
For most communities moderate
disturbance is healthy; severe disturbance is
detrimental.
ENERGY TRANSFER
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The sun is the major source of energy in an
ecosystem.
Energy cannot be recycled. Thus energy in
an ecosystem is referred to as a flow not a
cycle.
Energy in an ecosystem flows from the sun
to producers and then to consumers.
Producers

Use the sun or inorganic compounds to make
food.

Photosynthesis (solar energy)


Chemosynthesis (inorganic compounds)


Plants and algae
Some bacteria
Make up the first link in a food web/ first
trophic level.
Consumers

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Get energy by consuming organic compounds made
by other organisms.
4 Types:
 Herbivores - eat producers
 Carnivores - eat consumers
 Omnivores -eat producers & consumers
 Detritivores - eat dead organisms or decaying
material
1. Decomposers - break down waste (bacteria,
fungi)
2. Scavengers - feed on organisms that have
recently died (vultures)
Measuring Productivity

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
Biomass - the weight of organic material in
an ecosystem.
Gross Primary Productivity - Rate of
biomass production. Indicates the rate of
photosynthesis and chemosynthesis.
Net Primary Productivity - Rate of
biomass accumulation (stored energy).
Trophic Levels


Feeding levels in an
ecosystem.
Usually no more than 5
levels because there is a
low rate of energy
transfer.
Ecological Pyramids
Represent the energy relationships among trophic
levels.
General Patterns in the Eco-Pyramid:


"THE 10% RULE"
 Only 10 % of the stored energy (biomass)
from one level is passed up to the next level.
There are always fewer individuals in the
populations as you go up the pyramid. The
higher you go on the pyramid, the less energy
is available!
Food Chain - a single pathway of feeding
relationships in an ecosystem that results
in an energy transfer.
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Food Web- the interrelated food
chains in an ecosystem.
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Biomagnification
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The process by which pollutants increase
in concentration with each step of the food
chain.
Pollutants accumulate in the fatty tissues of
organisms (sub lethal levels).
Example: DDT and California Condor
Nutrient Cycles
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Nutrients cycle and energy flows.
Examples of nutrients: water, carbon,
oxygen, nitrogen, phosphorus, calcium.
A biogeochemical cycle is the process by
which materials necessary for organisms are
circulated through the environment.
Nitrogen Cycle



Organisms require nitrogen to produce
amino acids.
Nitrogen makes up 79% of the atmosphere,
but most organisms cannot use this form of
nitrogen, and must have it in a fixed form.
The nitrogen cycle produces the fixed form
of nitrogen these organisms need.
Nitrogen Cycle
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Steps of the Nitrogen Cycle
1)
2)
3)
Nitrogen-fixing bacteria take in atmospheric
nitrogen and produce ammonia (NH2).
Other bacteria use ammonia to produce nitrates
and nitrites, which are nitrogen and oxygen
containing compounds.
The nitrates and nitrites are used by plants to
make amino acids which are then used to make
plant proteins.
4) Plants are consumed by other organisms
which use the plant amino acids to make
their own.
5) Decomposers convert the nitrogen found in
other organisms into ammonia and return it
to the soil. A few of these types of bacteria
return nitrogen to the atmosphere by a
process called denitrification.
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