MAIN TOPIC 1: ECOLOGICAL CONCEPTS
EVOLUTION, BIOLOGICAL COMMUNITIES, AND SPECIES INTERACTIONS
ADAPTATION
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One of the most important concepts in biology.
The acquisition of traits that allow a species to survive
in its environment.
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WAYS OF USING THE TERM “ADAPT”
1.
Acclimation – When an individual organism can
respond immediately to a changing environment.
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Genetic traits passed from generation to
generation and allow a species to live more
successfully in its environment. This process of
adaptation to environment is explained by the theory
of evolution.
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Evolution – the basic idea is that species
change
over
generations
because
individuals compete for scarce resources.
Natural Selection – the process of betterselected individuals passing their traits to
the next generation.
Mutations – changes to the DNA coding
sequence of individuals that occurs
occasionally, and the changed sequences
are inherited by offspring.
ECOLOGICAL NICHE
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LIMITING FACTORS OF SPECIES
Pressure and influence to fitness of an individual and
their offspring are exerted by factors such as environmental.
With this, species have limitations in where they can live. These
limiting factors are:
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Physiological stress due to inappropriate levels of
some criticalnenvironmental factor, such as moisture,
light, temperature, pH, or specific nutrients.
Competition with other species
Predation, including parasitism and disease
Luck.
TOLERANCE LIMITS
Ecologist Victor Shelford (1877-1968)
o stated that each environmental factor has both
minimum and maximum levels, called tolerance
limits, beyond which particular species cannot
survive or is unable to reproduce.
o The single factor closest to these survival limits is
the critical factor that limits where a particular
organism can live.
o In some species, tolerance limits affect the
distribution of young differently than they affect
adults.
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Habitat – the place or set of environmental conditions in
which a particular organism lives.
Ecological Niche – describes both the role played by a
species in a biological community and the set of
environmental factors that determine its distribution.
Charles Elton (1900-1991)
o British Ecologist who defined the concept of niche
in 1927.
o each species had a role in a community of species,
and the niche defined its way of obtaining food, the
relationships it had with other species, and the
services it provided to its community.
G. E. Hutchinson (1903–1991)
o American limnologist who, thirty years later,
proposed a more biophysical definition of niche.
o Every species exists within a range of physical and
chemical conditions such as temperature, light
levels, acidity, humidity, or salinity. It also exists
within a set of biological interactions such as
predators and prey present, defenses, or nutritional
resources available.
Generalists – species that tolerate a wide range of
conditions or exploit a wide range of resources.
o Example: Species that thrive in broad variety of
environments such as weedy species or pests (rats,
cockroaches, or dandelions).
Specialists – species that have a narrow ecological niche.
o Examples are Giant Panda and Giant Saguaro.
SPECIATION
CRITICAL FACTOR
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SPECIATION
Justus von Liebig (1840)
o the single factor in shortest, supply relative
to demand is the critical factor determining
where a species lives.
o Temperature, moisture level, nutrient supply,
soil and water chemistry, living space, and
other environmental factors must be at
appropriate levels for organisms to persist.
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The development of a new species.
As a population becomes more adapted to its ecological
niche, it may develop specialized or distinctive traits that
eventually differentiate it entirely from its biological
cousins.
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2 KINDS OF SPECIATION
Allopatric Speciation – speciation that occurs when
populations are geographically separated.
o *Geographic Isolation – when the habitat are far
enough apart that population were genetically
isolated; they couldn’t interbreed with populations
on the other habitat.
Sympatric Speciation – speciation that occurs within one
geographic area.
o *Behavioral Isolation – when two identical species
live in similar habitats but have different mating
calls. This difference is enough to prevent
interbreeding.
DIRECTIONAL SELECTION
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Directional Selection – the shift toward one extreme of a
trait.
TAXONOMY
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The study of types of organisms and their relationships.
With this, organisms can be traced which common
ancestors they have descended.
BINOMIALS
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also called Scientific or Latin Name
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Identify and describe species using Latin or Latinized
nouns and adjectives, or names of people or places.
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Scientists communicate using scientific names instead of
common names like lion, dandelion, or ant to avoid
confusion.
SPECIES INTERACTIONS
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Competition leads to resource allocation.
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Predation is an important type of selective pressure.
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Symbiosis benefits both species involved.
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COMPETITION
A type of antagonistic relationship within a biological
community.
Organisms compete for resources that are in limited supply
such as energy and matter in usable forms, living space,
and specific sites to carry out life’s activities.
Competition shapes a species population and biological
community by causing individuals and species to shift their
focus from one segment of a resource type to another.
TYPES OF COMPETITION
Intraspecific competition – competition among members
of the same species.
Interspecific competition – competition between
members of different species.
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Any organism that feeds directly on another living
organism, whether or not this kills the prey.
Herbivores, carnivores, and omnivores, which feed on live
prey, are predators.
Predation is a powerful but complex influence on species
populations in communities.
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PREDATION AFFECTS:
1. All stages in the life cycles of predator and prey species.
2. Many specialized food-obtaining mechanisms.
3. The evolutionary adjustments in behavior and body
characteristics that help prey avoid being eaten and help
predators more efficiently catch their prey.
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TYPES OF SYMBIOSIS
Mutualism – type of symbiosis in which both members’
benefits. (e.g. Dogs and Humans)
Commensalism – type of symbiosis in which one member
clearly benefits and the other apparently is neither
benefited nor harmed. (e.g. a spider building a web on a
tree)
Parasitism – a form predation may also be considered
symbiosis because of the dependency of the parasite on
its host. (fleas and mosquitoes feed on blood from other
organisms
Endosymbiosis – one species living inside another one.
(e.g. Protozoans that live inside termites and help them
digest wood)
Ectosymbiosis – one species living on the surface of the
other species. (e.g. Lice that feed on the skin, blood, or oil
secretions of the host)
KEYSTONE SPECIES
Plays a critical role in a biological community that is out of
proportion to its abundance.
Thought to be the top predators like lions, wolves, and
tigers that limited herbivore abundance and reduced the
herbivory of plants.
Scientists now recognize that less-conspicuous species
also play keystone roles.
COMMUNITY PROPERTIES
Productivity is a measure of biological activity.
Abundance and diversity measure the number and variety
of organisms.
Resilience and stability make communities resistant to
disturbance.
PRIMARY PRODUCTIVITY
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PREDATOR
SYMBIOSIS
Two or more species live intimately together, with their
fates linked.
Symbiotic relationships often enhance the survival of one
or both partners.
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The rate of biomass production.
An indication of the rate of solar energy conversion to
chemical energy.
The energy left after respiration is net primary production.
ABUNDANCE AND DIVERSITY
Abundance is an expression of the total number of
organisms in a biological community.
Diversity is a measure of the number of different species,
ecological niches, or genetic variation present.
The abundance of a particular species often is inversely
related to the total diversity of the community.
Communities with a very large number of species often
have only a few members of any given species in a
particular area.
Diversity decreases but abundance within species
increases as we go from the equator toward the poles.
ECOLOGICAL STRUCTURE
Ecological structure refers to patterns of spatial
distribution of individuals and populations within a
community, as well as the relation of a particular
community To its surroundings.
At the local level, even in a relatively homogeneous
environment, individuals in a single population can be
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distributed randomly, clumped together, or in highly regular
patterns.
In randomly arranged populations, individuals live
wherever resources are available.
Ordered patterns may be determined by the physical
environment but are more often the result of biological
competition.
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Ecological development or facilitation - In both kinds of
succession, when organisms change the environment by
modifying soil, light levels, food supplies, and
microclimate, the change permits new species to colonize
and eventually replace the previous species.
Pioneer species - In primary succession on land, the first
colonists (microbes, mosses, and lichens) that can
withstand a harsh environment with few resources.
RESILIENCE AND STABILITY
Many biological communities tend to remain relatively
stable and constant over Btime.
Robert MacArthur (1955) - a graduate student at Yale,
proposed that the more complex and interconnected a
community is, the more stable and resilient it will
be in the face of disturbance.
THREE KINDS OF STABILITY OR RESILIENCY IN
ECOSYSTEMS
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Constancy – lack of fluctuations in composition or
functions
Inertia - resistance to perturbations
Renewal - ability to repair damage after disturbance
EDGES AND BOUNDARIES
The boundary between one habitat and its neighbors is an
important aspect of community structure. These
relationships are called edge effects.
The edge of a patch of habitat is sometime relatively sharp
and distinct.
In moving from a woodland patch into a grassland or
cultivated field, you sense a dramatic change from the
cool, dark, quiet forest interior to the windy, sunny, warmer,
open space of the meadow.
In other cases, one habitat type intergrades very gradually
into another, so there is no distinct border.
Ecotones are what the ecologists call the boundaries
between adjacent communities.
Closed Community - a community that is sharply divided
from its neighbors.
Open Community - a community with gradual or indistinct
boundaries over which many species cross.
o *Often this distinction is a matter of degree or
perception.
DYNAMIC AND CHANGING COMMUNITIES
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Some biological communities are dependent on periodic
disturbance.
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Introduced species can cause profound community
change.
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ECOLOGICAL SUCCESSION
Climax Community is the community that developed last
and lasted the longest.
Ecological Succession is the history of community
development. When a succession occurs, organisms
occupy a site and change the environmental conditions.
An example of primary succession, shown in five stages (left
right). Bare rocks are colonized by lichens and mosses, which
trap moisture and build soil for grasses, shrubs, and eventually
trees.
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DISTURBANCE
Any force that disrupts the established patterns of species
diversity and abundance, community structure, or
community properties.
Disturbances on earth: landslides, mudslides, hailstorms,
earthquakes, hurricanes, tornadoes, tidal waves, wildfires,
and volcanoes.
Animals can cause disturbance too.
Disturbance-adapted species - species that can survive
periodic disturbance (survive fires underground, or resist
the flames, and then reseed quickly after fires).
INTRODUCED SPECIES
Continuous introduction of new community members and
the disappearance of previously existing species are
requirements of succession.
New species move in as conditions become suitable;
others die or move out as the community changes.
New species can be introduced after a stable
community already has become established. Some of
them cannot compete with existing species and fail to
become established. Others are able to fit into and become
part of the community, defining new ecological niches.
If an introduced species preys upon or competes more
successfully with one or more populations that are native
to the community, the entire nature of the community can
be altered.
TWO KINDS OF SUCCESSION
Primary succession - Land that is bare of soil (a sandbar,
mudslide, rock face, and volcanic flow) is colonized by
living organisms where none lived before.
Secondary succession - When an existing community is
disturbed, a new one develops from the biological legacy
of the old.
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