Reviewer

in
General
Biology II
 Classification
By:
Aldren R. Beliber Jr.
Aristotle’s System of Classification Samantha P.
Aceron
Stem- Magaling

Linnaean System of Classification

Classification- is the process of arranging objects, ideas or information into groups based
on shared characteristics or criteria.

Aristotle- a Greek philosopher, proposed a system of classifying living things.

 He grouped the organisms into plants and animals.

 Species are distinct, separate, and unchanging.
 His classification ns had many limitations and many organisms did not fit easily into
his classifications.
 It was used for almost 2000 years.
Species Concepts

Carolus Linnaeus- is a Swedish naturalist, who built upon the work of Aristotle and
developed the first formal and scientific system of classification.

 It was a taxonomic system of classification.

 He also grouped organisms based on observed morphology and behaviour.
 Before the Linnaean system of classification, plants and animals were identified
by a series of descriptions, sometimes numbering as many as 12 organisms, using
Latin words. It described the physical features of the organism.
 Systema Naturae (1758)- In this book he introduced the naming system called
binomial nomenclature. It is a system of giving organisms two names, thus the
term binomial nomenclature. Similar in a human naming systems which consist of
a given name and a family name.
 In binomial nomenclature, the first name refers to the genus group to which the
organism belongs and the second name refers to the species group of the
organisms.
 Latin is the language used in binomial nomenclature.

 Biologists use scientific names mainly to avoid confusion with common names.
 Scientific name is the genus name and not the species name, which vividly
describes the characteristics of an organism.
Writing scientific names:
1. The first letter of the genus name is capitalized but the species name begins with
a small letter.
2. If printed to books or magazines, both names are italicized
3. If handwritten, both names should be underlined.
4. After the scientific name has been written in full, the genus name may be
abbreviated to the first letter in the succeeding citations. For example, the
scientific name of domesticated dog, which is Canisfamiliaris can be written as C.
familiaris.
  Each organism has only one scientific name.
 No two organisms have the same scientific name.
 The scientific names are stable and unchanging
 It also reflects the way the organism is classified.

Linnaean system of classification

 Species- is the smallest and the most basic unit or category of classification.
 Genus- (plural, genera) is defined as a group of species that shares a common
ancestor.
 Family- consists of related genera
 Order- consists of related families.
 Class- consists of related orders.
 Phylum- consists of related classes, and in more traditional classification is
composed of related phylum (plural, phyla) or division.
 Domain- becomes the broadest taxa or taxonomic category, which contains
related kingdoms.

1. Typological species concept- This species concept traces its roots to the philosophy of Plato.
It is based on the idea that each species is a distinct group of organisms that shares certain
characteristics, which distinguish them from other species.
2. Biological species concept- This species concept came from the definition of two
evolutionary biologists, Theodosius Dobzhansky in the 1930s and Ernst Mayr in the 1940s.
According to Dobzhansky and Mayr, a species is a group of organisms that are able to
interbreed and produce fertile offspring.
3. Evolutionary species concept- A species is a single lineage of ancestor descendant sequence
of population with distinct identity and evolutionary tendencies.
4. Phylogenetic species concept- This species concept was developed from the evolutionary
species concept which defines a species as a cluster of organisms that are distinct from other
cluster organisms.
  Two major factors have had a major effect on the classification system
1. Introduction of the evolutionary theory of Charles Darwin
2. Advancement in technology

Modern Classification System- based on a variety of techniques that compare DNA sequences in
assessing evolutionary relationships.

 DNA and RNA analyses are powerful tools in establishing genealogy.

 Greater number of DNA sequence the greater the number of share genes, thus the greater
the evidence that the species share a recent common ancestor.

Modern Classification System Anton van

Leeuwenhoek-
Discovers the first unicellular organisms in 1674.

Ernst Haeckel- Proposed a third kingdom, which he called protista. The kingdom include not
just bacteria but all unicellular organisms.

Edouard Chatton- a French marine biologist, introduced the terms prokaryotes and
eukaryotes in 1937. He defined prokaryotes as organisms without a distinct nucleus (plural
nuclei) inside their cells ad eukaryotes as organisms with a distinct nucleus inside their cells.
Both prokaryotes and eukaryotes were then placed under Kingdom Protista.

Herbert Copeland-

Six-Kingdom Classification Scheme an American

biologist who
proposed a four kingdom scheme. He classified prokaryotic organisms (bacteria and blue-
green algae) into a separate kingdom called Monera.

Two empires or superkingdoms, namely, Prokaryota, which includes Monerans, and , and
Eukaryota, which includes Protista, Plantae and Animalia.

Robert Whittaker- proposed a fifth kingdom called Fungi. Kingdom Fungi included mushrooms,
yeasts, and molds.
 Carl Woose- proposed the division of Prokaryota into Eubacteria and Archaebacteria.

Most widely use and accepted biological

classification system has six kingdoms and
Basis of Classification three domains.

1. Domain Bacteria- This group includes all prokaryotic, single-celled bacteria whose cell
walls are composed of a polysaccharide called peptidoglycan. The kingdom under this domain
is the Eubacteria, which is also known as the true bacteria. Members of this group are so diverse
that they can survive different environmental conditions.

 Aerobic Bacteria- Needs oxygen to survive.

 Anaerobic Bacteria- Dies in the presence of oxygen.

2. Domain Archaea- Organisms

Three Domain System that are classified under this
domain are perceived to be more
primitive than bacteria. They are considered to be more closely related to eukaryotes. Their cell
walls do not contain peptidoglycan, but a complex form of glycoprotein called pseudo
peptidoglycan. They are diverse in shape and mode of nutrition.

Archaea- are said to be extreme thermopiles because of their ability to survive in extreme
environmental conditions. The kingdom under this domain is the Archaebacteria.

3. Domain Eukarya- The main characteristics of the members of this group is the presence of
membrane- bound nucleus and other membrane-bound organelles. All members of this group
are called eukaryotes. This domain includes K ingdom Protista, Kingdom Fungi, Kingdom Plantae,
and Kingdom Animalia.

Evolutionary Classification- fundamental in classifying relationships.

Phylogeny- a natural classification based on the evolutionary history.

Classification system were introduced by Aristotle and Linnaeus.

Basis of Classification- Scientists are able to infer phylogenies based on the heritable characters
of organisms, which include morphological and molecular data.

Morphological and Biochemical traits- organisms are compared based on similar characters.
Characters are inherited features that vary among species.

Morphological Characters- some traits in organisms may be retained or changed depending on

whether these traits make the organisms fit enough to reproduce and have more offspring that
would pass on the trait to succeeding generations or not.

Homologous structures- are body parts that are similar in structure but may have different
functions.

Morphological divergence- different forms of body parts that emerged from the ancestral form
resulted in an evolutionary pattern.

Analogous structure- may have similar functions but are of different morphological construction.

Morphological convergence- structure that eventually take similar form because of comparable
environmental stresses result in an evolutionary pattern.

Biochemical characters- most convincing evidence for determining evolutionary relationships

among species.

Phlyogenetic Tree- illustrate how related organisms evolved from a common descent based on
the best reliable evidences.

Ancestral characters- found within the entire lineage of descent of a group of organisms.

Derived characters- found in members of one group but not in the common ancestor.

Cladistics- an analytical method of hypothesizing evolutionary relationship.

Cladogram- depicted through branching diagram.

Clade- branch of cladogram with a common ancestor and all the descendants.

- also known as monophyletic group.

Paraphyletic groups- groups of organisms that include an inferred ancestor but not all
descendants of that ancestor.

Polyphyletic- species do not share a common ancestor.

Evolution - change to the genetic composition; gradual process of change over a period of time.

Geologic time scale – presents sequence of events

Biodiversity – number and kinds of organisms in a particular habitat.

 Speciation – emergence of new species a result of divergence between groups that

comprised pre-existing populations
 Extinction – disappearance of species for failing to adapt to changes in the environment
 › Mass Extinction – sudden and cause dramatic loss in biodiversity
o Movement of land into hostile climate, volcanism, global heating or
cooling, and impact of a large meteor “Bolide”

Geologic time scale – presents sequence of events

 Divided into intervals based on the significant events in the history.

Eons – largest intervals

 Hadean Eon, Archean Eon, Proterozoic eon and Phanerozoic Eons

 Eons are subdivided into eras

Eras are subdivided into period

Period in turn are divided into epochs.

FOSSIL STUDIES

Geology – branch of science deals with the study of the earth

Biogeography – study of how species spread across the planet

Fossils – remains of extinct plants and animals embedded in sedimentary rocks.

Paleontology - study of fossils

Radiometric dating – used to estimate the age of specimen through the fixed decay rate of
radioactive isotopes.

Concepts of Evolution

Principle of Uniformitarianism

 James Hutton (1726-1797) and Sir Charles Lyell (1797 -1875)

 Physical, chemical and biological processes that work today are the same forces that
keep on changing the Earth

Theory of the Inheritance of acquired traits

  Organisms adapt to their environment, and the traits they have acquired are passed on to
their offspring
 Jean Baptiste Lamarck

Modern Theory Evolution

 Charles Darwin (1809-1882) - Father of modern theory of evolution

 Five year cruise aboard the H.M.S Beagle – he collected specimen and observed different
organisms,
 Galapagos Island – helped him conceive the idea of natural selection through finches
 1859 – “On the origin of species”
 Alfred Russel Wallace (1858)– wrote to Darwin speculating on evolution by natural
selection

Theory of Natural selection

 Natural Selection – process by which organisms with traits suited to an environment

Mechanism and Evidence of Evolution

 Charles Darwin “On the origin of Species” – described the process of evolution as descent
with modification

Gene frequency – proportion of genes or alleles in a population

Mechanisms of evolution

Genetic Drift – changes in the gene pool

 The genetic makeup consisting of every type of allele in all the members of a population
over time due to chance
 Beetle

Mutation and Recombination

 Mutation – change in DNA that can be passed on the next generation

 Genetic Recombination – gamete formation when genes are moved and interchanged
across chromosomes
 Galapagos Finches

Natural Selection
  Survival of the fittest
 Strongest force of evolution
 Happens when the relative fitness of interacting species in an ecosystem significantly
differs
 Fitness - is the measure of the genetic contribution of a particular species to the next
generation; the rate of survival of a species and its fertility index
 Sickle anemia – where a mutation causes RBC to appear sickle-shaped
 Artificial Selection- driven by propagation

Migration (Gene flow)

 Enables gene flow or the movement of genetic characteristics from on population to

another

Evidence of Evolution

Fossil records – useful sources; show that many extinct organisms were different from chose that
exists today

Comparative anatomy – similarity in the bones, wings and arm suggests a common evolutionary
origin

Genetic Data - provide insight into the evolution of organism as they are used to present gene
trees

Geographical distribution - organisms that have similar characteristic may be found in different
continents