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Ecotoxicology
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Ecotoxicology is derived from the words
ecology a study concerned with howorganisms interact in nature with each other
(the biotic environment) and the physical and
chemical aspects of the environment (abiotic
environment) and toxicology a study of
adverse effects of xenobiotics.
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It is an area of study concerned with the harmful
effects of chemicals within the context of ecology.
It requires an understanding of ecological principles
and theory as swell as a grasp of how chemicals can
affect individuals, populations, communities and
ecosystems.
It is a multidisciplinary subject applying basic
biochemical, chemical, pathological, physiological, and
epidemiological knowledge to gain an understandingof why certain substances cause an untoward
alteration in biological systems which ultimately have
an effect on populations, communities and
ecosystem.
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Ecotoxicology is thus defined as the study of
harmful effects of chemicals upon ecosystem.
These adverse effects occur at various levels
within the body, such as an organ, a type of
cell, or a specific biochemical.
These adverse effects may occur in many
forms, ranging from immediate death to subtle
changes not realized until months or years
later.
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Levels of Biological OrganizationTohelp protectyour privacy, PowerPointprevented thisexternalpicturefrom being automatically downloaded. Todownload and display thispicture, click Optionsin theMessageBar, and then click Enableexternalcontent.
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Macromolecules are substances contributing
to form and organization of cells and tissue.
They are constructed from organic buildingblocks (monomers) linked together by repetitive
formation of covalent bonds to form polymers.
There three main classes:
Sugar monomers made to polysaccharide
polymers (e.g. glucose converted to glycogen
for storage purposes).
Amino acids made into polypeptide chains,
called proteins (e.g. enzymes that catalyze
reactions in the body)
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Nucleotides are polymerized into chains tomake nucleic acids (e.g. deoxyribonucleic acid,DNA, which holds the genetic information in
living organisms and ribonucleic acid, RNA,which is a short lived copy of DNA that is usedfor protein synthesis).
Org
anelles
are structures th
at occur in ne
arly
allcell types and may be regarded as internal
organs.
i.e They are organised units of living substancewith specific functions in cell metabolism.
E.g. mitochondriaan organelle mainlyconcerned in production of energy for drivingcellularactivities.
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The cell is the structural unit of all living things
consisting of cytoplasm and nucleus.
The cell has many critical structures and
processes which are necessary for its normal
function and survival including cell division,DNA replication, energy generation.
Any compound that disrupts one or moreimportant cellular processes may cause cellular
dysfunction which may lead to cytotoxicity
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Tissues are cells serving the same general
function that are grouped together and united
by varying amounts of intercellular substances(e.g. muscle, bone, nerve tissue, etc)
Tissues have many critical structures and
processes which are necessary for the properfunction of the organs they comprise.
Any compound that disrupts the structuralorganization of tissues, or important tissue
functions may cause general organ dysfunction,
which may lead to organ toxicity.
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An organ is derived from a group of cells that
become specialized for a particular function (e.gkidney).
A population can be simply defined as a groupof potentially interbreeding individuals of a
single species.
Communities are collections of interacting
populations in a given place.
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An ecosystem is compose of groups of all
types ( communities) of organisms that function
together as well as interact with the physicalenvironment, including energy flow and cycling
of material between living and nonliving
components.
Biosphere is the whole earth ecosystem.
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Learn also
cytoplasm, nucleus, nucleoli, chromatin,
chromosomes, organelles, mitochondria,endoplamic reticulum, golgi apparatus,
lysosomes, microfilament, centrosome,
microtubules, all stages of mitosis and meiosis).
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Terminology in Toxicology
Bioaccumulate
The increased concentration of harmfulsubstances in tissues of organisms higher up
the food chain
Biotransformation
The sum of the processes by which a
xenobiotic is subjected to chemical change by
living organisms
Carcinogen
Any substance that causes cancer
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Mutagen
Any substance that causes DNA damage,
ranging from changes in one or a few basepairs to gross changes in chromosomestructure or number
Pollutant
A substance present in greater than naturalconcentration as a result of human activity andhaving a net detrimental effect on itsenvironment
Risk
Probability a substance will cause harm underspecific conditions of use, i.e., hazard
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Teratogen
Any substance that causes fetal malformations
(birth defects) Toxicologist
A toxicologist is a scientist that determines the
harmful effects of agents and the cellular,biochemical, and molecular mechanisms
responsible for the effects.
Toxicosis
A diseased condition resulting from poisoning
Toxigenic
An organism producing toxins or poisons
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Toxin, Toxicant, and poison are often used interchangeably in
the literature; however, there are subtle differences as indicated
below
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Toxoid
A toxin that has been treated to destroy its
toxicity.
Xenobiotic
Compounds exogenous (external) to normalmetabolism of the organism, i.e., foreign
compounds
Toxic substances may be organic or inorganic
in composition
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Toxic substances may be systemic toxins or
organ toxins.
Asystemic toxin is one that affects the entire
body or many organs rather than a specific site.
Eg, potassium cyanide is a systemic toxicant inthat it affects virtually every cell and organ in
the body by interfering with the cell's ability to
utilize oxygen.
Lead is a specific organ toxin; (central nervous
system and kidney)
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Germ cells are those cells that are involved in
the reproductive process and can give rise to a
new. Toxicity to germ cells can cause effects on the
developing fetus (such as birth defects,
abortions).
Somatic cells are all body cells except the
reproductive germ cells.
Toxicity to somatic cells causes a variety of
toxic effects to the exposed individual (such as
dermatitis, death, and cancer).