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Sylvia S. Mader
Immagini e
concetti
della biologia
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
A9 - Life history
and biodiversity
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Geologic timescale
Units in geochronology:
Relative time system
•Eras
•Periods
•Epochs
Absolute time system
•Million Years (MA)
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Geologic timescale
Eras:
Cenozoic,
Mesozoic,
Paleozoic.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Geologic clock
In a 24-h geologic clock:
•Life started at 5 a.m.
•Prokaryotes dominated for a large part of history.
•Humans only appeared one minute before midnight.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Continental drift - A.L. Wegener, 1912
Movements of the continents have affected the history of
life.
“The position of continents has changed over
time and is still changing.”
The Earth’s Crust is a fluid mosaic of many irregular rigid
plates (continental or oceanic).
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Continental drift - A.L. Wegener, 1912
Tectonic movements from 225 MA ago till now
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Extinctions: the press/pulse model
“Species are pressed to the brink of extinction by
environmental changes.
Then a cataclysmic event (meteorite impact or climate
change) pulse them to die out.”
Mass extinction is a sharp decrease in the diversity and
abundance of macroscopic life.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Five major mass extinctions
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Five major mass extinctions
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Humans as extinction factor
Some scientists believe that humans are
pressing Earth’s life toward the sixth mass
extinction.
The pressure is due to the impact of
agriculture, deforestation, urbanization
and pollution.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Classification of the organisms
Carl Von Linnaeus (1707-1778)
All living organisms can be categorized into
taxa.
A taxon is a group of organisms which have
characters in common.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Classification of the organisms
The main Linnaean taxa are:
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
Organisms of the same species interbreed
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Classification of the organisms
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Systematics reflects phylogeny
Systematics is the study of organisms diversity at all
levels of organization.
Linnaean classification utilizes characters which reflect
phylogeny, the evolutionary history of a group of
organisms.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Systematics reflects phylogeny
Phylogenetic trees indicate common ancestors and
lines of descent.
Derived characters: particular
characteristics of a group.
derived characters
Ancestral characters: shared
with a common ancestor.
Divergence
Common ancestor
(ancestral characters)
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
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Human phylogeny
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Viruses
Viruses are non-cellular simple identities and reproduce
by using metabolic machineries of the host cell.
Therefore they are not classified using traditional
systematics.
Structure of a virus
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Viruses
Viruses are specific and
some of them reproduce
inside animal cells causing
diseases.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Viruses
Each virus infects a certain
organism or tissue;
bacteriophages parasitize
bacteria.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Three domains classification system
1 BACTERIA
is composed of a diverse group of prokaryotes.
2 ARCHAEA
encompasses prokaryotes that are chemically different
from bacteria and thrive in extreme environments.
3 EUKARYA
wide variety of unicellular to multicellular organisms that
have a membrane-bounded nucleus but different life
cycles.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Three domains classification system
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Prokaryotes: Bacteria and Archaea
Unicellular
Lack a nucleus
Do not have
complex
organelles
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Anatomy of prokaryote
Nucleoid: contains a single
chromosome consisting of a
circular strand of DNA.
Cell wall: strengthened by
peptidoglycan.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Anatomy of prokaryote
Prokaryotes may be round (Cocci), rod-shaped (Bacilli) or
spiral (Spirilla).
Cocci
Bacilli
Spirilla
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Anatomy of prokaryote
Prokaryotes reproduce asexually by binary fission
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Anatomy of prokaryote
Under unfavorable environmental conditions, bacteria can
reduce itself to a dormant form called endospore. The
endospore consists of the bacterium's DNA and part of its
cytoplasm, surrounded by a very resistant outer coating.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Prokaryote’s nutrition strategies
Aerobes (most of the organisms): live and grow in an
oxygenated environment.
Obligate anaerobes: cannot tolerate the presence of
oxygen.
Facultative anaerobes: can use oxygen but also have
anaerobic methods of energy production.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Prokaryote’s nutrition strategies
Autotrophs
Chemosynthetic
use inorganic
compounds (as
CH4 or NH3)
Photosynthetic
use solar energy to
make organic
compounds
Heterotrophs
Decomposers
Break down
dead
organisms
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Cyanobacteria
Cyanobacteria (or blue-green algae) are ecologically
important as they produce oxygen through photosynthesis, fix atmospheric nitrogen and form symbiotic
relations in lichens.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Archaea live in extreme environments
Methanogen Archaea produce methane in anaerobic
environments.
Halophiles live in high-salt environments.
Thermoacidophiles inhabit extremely hot, acid
environments.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Prokaryotes and medicine
Prokaryotes can cause many human diseases
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Microbes at our service
Viruses and bacteria can be very useful in gene
research, as decomposers in water treatment, in
bioremediation and can produce antibiotics.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012