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Ecology
Ecological valance
M. Saadatian
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1
Ecological valance
Ecological balance is an balance within a community where the
organisms remain stable and the changes are slow and gradual. A
ecological balance must be retained in order for species to thrive
comfortably in their habitat. Removal of things like plants, animals,
trees and other natural items can shift the balance. This shifting can
lead to a loss of something. The loss may be something like lost
vegetation or animals or an increase in pollution.
Stenoece: a species do not ability to stable with environmental
(weak dispersion)
Euryece: a species ability to stable with environmental (wide
dispersion)
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Liebig rule
• Liebig's law of the minimum, often simply called Liebig's law or
the law of the minimum, is a principle developed in agricultural
science by Carl Sprengel (1828) and later popularized by Justus von
Liebig. It states that growth is controlled not by the total amount of
resources available, but by the scarcest resource (limiting factor).
• This concept was originally applied to plant or crop growth, where it
was found that increasing the amount of plentiful nutrients did not
increase plant growth. Only by increasing the amount of the limiting
nutrient (the one most scarce in relation to "need") was the growth
of a plant or crop improved.
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Blackman rule
• According to this law, when a process depends
on a number of factors, its rate is limited by
the pace of the slowest factor. Blackman's law
of limiting factors determines the rate of
photosynthesis.
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Shelford rule
• It states that an organism's success is based on a complex set
of conditions and that each individual or population has a
certain minimum, maximum, and optimum environmental
factor or combination of factors that determine success.
Increasing in ecological agent can be effects on life of
organism.
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Environmental selection
• Ecomorphological selection: environmental
effects on morphological style in plants and
stable to tolerance environmental conditions
• Genetic selection: changes in environmental
factors due to change in gene expression
(ecotype).
• Variety: in a communication a species plant
have a minor different from each other.
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Evolution
• Evolution is the change in the inherited characteristics of
biological populations over successive generations.
Evolutionary processes give rise to diversity at every level of
biological organization, including species, individual
organisms and molecules such as DNA and proteins.
Evolution agents:
1: mutation
2: natural selection
3: genetic drift
4: migration
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1. Mutation
• In genetics, a mutation is a change of the nucleotide
sequence of the genome of an organism, virus, or
extrachromosomal genetic element. Mutations result
from unrepaired damage to DNA or to RNA genomes
(typically caused by radiation or chemical mutagens),
errors in the process of replication, or from the
insertion or deletion of segments of DNA by mobile
genetic elements. Mutations may or may not produce
discernible changes in the observable characteristics
(phenotype) of an organism.
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2. Natural selection
• Natural selection is the gradual process by
which biological traits become either more or
less common in a population as a function of
the effect of inherited traits on the differential
reproductive success of organisms interacting
with their environment.
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3. Genetic drift
• Genetic drift or allelic drift is the change in
the frequency of a gene variant (allele) in a
population due to random sampling. The
alleles in the offspring are a sample of those in
the parents, and chance has a role in
determining whether a given individual
survives and reproduces.
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4. Migration
• Migration, as it is now known among modern
birds and mammals, probably appeared gradually
by stages. Some animals changed their habitat
only slightly, never leaving the same general
region. The movements of other animals were
more erratic, their dispersal being oriented toward
the most favorable places. Such movements are
the first stages of true migration—a phenomenon
characterized by elaborate mechanisms—which
gradually acquired stability through natural
selection.
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Adoption
• Change in an organism so that it is better able
to survive or reproduce, thereby contributing
to its fitness.
• Adaptedness is the state of being adapted: the
degree to which an organism is able to live and
reproduce in a given set of habitats.
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Extinction
• In biology and ecology, extinction is the end
of an organism or of a group of organisms
(taxon), normally a species. The moment of
extinction is generally considered to be the
death of the last individual of the species,
although the capacity to breed and recover
may have been lost before this point.
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