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Chapter 3
Classification of Organisms
ECOSYSTEMS
• An ecosystem includes biotic and abiotic components
interacting together.
ABIOTIC = NON-LIVING
BIOTIC = LIVING
• Abiotic elements of a community change over time, affecting
organisms and their interactions on all levels.
The number and type of species
change over time as land is
exposed by a melting glacier.
ABIOTIC FACTORS
• Abiotic factors such as climate, latitude, elevation,
temperature, humidity, moisture, salinity, and light affect
patterns of distribution of life.
• Abiotic factors are NONLIVING.
Temperature and Precipitation and their
Effects on Biomes of the World
Biomes of the World
BIOME – An ecosystem or group of ecosystems in a specific region on
Earth that has a particular combination of biotic and abiotic factors;
for eg, tundra, desert, rainforest, taiga, etc.
HABITAT
• A habitat is a place or area within a biome or ecosystem
that has a particular set of biotic and abiotic
characteristics.
• It is an organism’s “home”.
RANGE
• An organism’s range is the geographical area where the
organism is found.
The hoary marmot (Marmota
caligata) feeds on plants found in
high altitude meadows.
Range of the hoary marmot
NICHE
• The ecological niche of a population is the role that its
members play in an ecosystem.
• The variety of niches and habitats within an ecosystem allow
it to support a diversity of organisms.
These two species of ocean
barnacles have similar niches, but
the two niches differ enough that
both species are able to establish
populations at different depths of
the rocky shore.
LIMITING FACTOR
• A limiting factor is any biotic or abiotic element that controls
the number of individuals in a population. Biotic limiting
factors include competition, predation, and parasites.
Limiting factors prevent these
bacteria from reproducing
infinitely.
PREDATORS
PREDATORS
COMPETITION
• For mates,
food, territory
COMPETITION
• Intraspecific competition – competition
WITHIN a species
(Example:
• Interspecific competition – competition
BETWEEN 2 or more species
(Example:
PARASITISM
• The “parasite” lives and feeds off of a “host”
• The parasite rarely kills the host, but will weaken it
• The parasite is generally smaller than the host
ANIMAL PARASITES
HUMAN PARASITES
Head lice feeding on a human scalp
ABIOTIC LIMITING FACTORS
• Abiotic (non-living) factors include:
3.3 Studying Organisms in Ecosystems (cont’d)
• Organisms can be sampled using transects or quadrats
situated randomly in a sample area. From these samples, the
density of a population can be estimated.
A 5m × 100m transect
Chapter 3 Summary
• An organism’s environment includes biotic and abiotic
components. Organisms affect and are affected by their
environment. Organisms are part of a population, a
community, an ecosystem(s), and Earth’s biosphere.
Abiotic factors in the environment affect the distribution
of organisms.
• Biologists use a hierarchical system to group organisms.
Naming and categorization must sometimes be changed
to accommodate new discoveries. A universal, two-word
naming system is used, giving each organism a genus and
species name in Latin.
Chapter 3 Summary
(cont’d)
• Biologists use dichotomous keys to identify organisms. Each
step in the key has only two choices.
• Unequal heating of the Earth creates different climates and
distinct biomes that support the growth of certain groups of
organisms. Within biomes and ecosystems, there is a great
deal of variation in habitats and niches.
• A population’s growth in a particular habitat is limited by
biotic and abiotic factors.
• Biologists use sampling techniques to estimate population size
in large ecosystems. Transects are often used for mobile
populations, while quadrats are used for sessile populations,
such as plants.