Transcript classificationstx

CLASSIFICATION
Mikael Mara
Species
A species is a population of organisms that share similar
characteristics and can breed with one another, producing fertile
offspring.
Biologists have already identified and named about 1.5 million
species. They estimate that anywhere between 2 and 100 million
additional species have yet to
be discovered!
Through the discipline of
taxonomy, scientists classify
organisms and assign each one
a universally accepted name.
Why Classify?
By using a scientific name, biologists can be certain that everyone is
discussing the same organism.
The organisms are classified, or organized, in a manner that has
biological significance. Organisms placed into a particular group are
more similar to each other than they are to organisms in other
groups.
Two birds have more similarities than a bird and a mammal.
Assigning Scientific Names
Scientists recognized that using common names was a problem since the
same animal could have multiple common names, such as a mountain lion
which is also called a cougar, a puma, or a panther depending on where you
live.
They decided to use a single word for each species, and since 18 th century
scientists understood
Greek and Latin, they chose to
use those two languages in
naming organisms—a practice
that is still followed today:
Felis concolor ->
Binomial Nomenclature
Carolus Linnaeus developed a two-word naming system called
binomial nomenclature.
Binomial = two words
Nomenclature = naming system
Each species, even today, is assigned a
two-part scientific name which is:
1. written in italics.
2. the first word is Capitalized
3. the second is lowercased
Binomial Nomenclature
The grizzly bear is called Ursus arctos using binomial nomenclature.
The first part of the name is called the genus. A genus is a group of closely
related species. The genus Ursus, for example, contains five other kinds of
bears, including the polar bear—Ursus maritimus.
The second part of the name, arctos or maritimus, is the organism’s unique
species.
A species’ name is often a Latinized
description of some important trait of
the animal. The Latin word maritimus,
referring to the sea, comes from the fact
that polar bears often live on pack ice that
floats in the sea.
Linnaeus’ System of Classification
Linnaeus’ classification system is hierarchal—meaning it consists of levels.
It includes seven levels, or taxa (plural of taxon) from largest to smallest:
Kingdom
Phylum
Class
Order
Family
Genus
Species
Linnaeus’ System of Classification
Species: the smallest and most exclusive group; organisms here can breed
to produce fertile offspring.
Genus: group of closely related species.
Family: genera (plural of genus) that share many characteristics.
Order: broad category composed of similar families.
Class: composed of similar orders.
Phylum: composed of many different classes.
Kingdom: the largest and most inclusive of Linnaeus’ taxonomic categories.
Linnaeus’ System of Classification
Grizzly bear
Black bear
Giant
panda
Red fox
KINGDOM Animalia
PHYLUM Chordata
CLASS Mammalia
ORDER Carnivora
FAMILY Ursidae
GENUS Ursus
SPECIES Ursus arctos
Abert
squirrel
Coral
snake
Sea star
Modern Evolutionary Classification
Linnaeus’ system used the physical
traits of animals to characterize
organisms into different taxa,
however that is not always the best
way of classifying animals, since many
animals which look similar are not
related, and many who look dissimilar
are related.
Phylogeny is a line of evolutionary
descent, and it is the way which
biologists now group organisms.
The strategy of grouping organisms
together based on their evolutionary
history is called evolutionary
classification.
Modern Evolutionary Classification
Species within a genus are more closely related to each other than to
species in another genus, even if they do look physically different. This is
because all members of a genus share a recent common ancestor.
The higher the level of the taxon, the further back in time is the common
ancestor of all the organisms in the taxon.
Due to natural selection, different organisms living in similar environments
develop similar body structures—convergent evolution.
Barnacles and limpets used to be grouped together due to their physical
characteristics, however through the use of phylogeny, scientists now say
that barnacles are more closely related to crabs than they are to limpets.
Barnacles and clams actually share a more recent ancestor, making them
both crustaceans, whereas clams and limpets share a more distant
ancestor. Instead, limpets are mollusks.
Modern Evolutionary Classification
Classification Using Cladograms
To refine the process of evolutionary
classification, scientists now use cladistic
analysis, which categorizes organisms
using evolutionary innovations—new
characteristics that arise as lineages
evolve over time.
Characteristics that appear in recent parts
of a lineage but not in its older members
are called derived characters.
These derived characters are used to
construct a cladogram, a diagram that
shows the evolutionary relationships
among a group of organisms.
Cladogram is derived from the Greek
“κλάδος” which means “branch.”
Kλάδος and Cladograms
Just like a family tree shows the relationships among different lineages
within a family, a cladogram represents a type of evolutionary tree,
showing evolutionary relationships among a group of organisms.
Similarities in DNA and RNA
Because DNA and RNA are so similar across all forms of life, these molecules
provide an excellent way of comparing organisms at their most basic level—
their genes.
Similarities in DNA can be used to help determine classification and
evolutionary relationships.
Scientists can now compare the DNA of
different organisms to trace the history
of genes over millions of years and group
organisms together.
Ex: Both humans and yeast have a gene which
codes for myosin, a protein found in our muscles.
The same protein helps internal cell parts in yeast
to move.
This indicates a common ancestor between humans and yeast!
Similarities in DNA and RNA
In addition, the more similar the DNA of two species, the more
recently they shared a common ancestor, and the more closely
related they are in evolutionary terms.
Even though the African vulture (left) and the American vulture
(center) have been traditionally grouped together, DNA analysis has
showed that the American vulture is more related to the stork
(right)!
Draw Two Cladograms!
In the traditional cladogram, the two vultures were grouped
together under the family of “falcons;” however, both the American
vulture and the stork have a curious tendency to urinate on their own
legs in order to cool off.
On a piece of paper draw two cladograms. The first cladogram is the
traditional one which depicts the two vultures being grouped
together, whereas the second cladogram should show the American
vulture and stork grouped together.
Make sure you include important details such as the behavior of the
American vulture and stork!
Molecular Clocks
DNA comparisons can also allow us to
estimate the length of time that has
passed since two species have been
evolving independently.
This is called a molecular clock.
A molecular clock relies on continued
mutations to estimate the time that
the two species have diverged from a
single one.
Some mutations cause major
phenotypic changes in animals—
natural selection then chooses the
more beneficial mutation to allow the
organism to survive.
Molecular Clocks
Other mutations have no effect on
phenotype!! These “neutral”
mutations accumulate in the DNA of
different species at about the same
rate.
A comparison of these neutral
mutations between two species can
reveal how dissimilar the genes are.
The degree of dissimilarity is an
indication of how long ago the two
species shared a common ancestor.
Kingdoms and Domains
Linnaeus had grouped living organisms
into two different kingdoms: Animalia and
Plantae; animals could move and used
food for energy, and plants were green
and used the energy of the sun.
Upon the discovery of microorganisms
such as protists and bacteria, scientists
created a third kingdom—Protista.
Soon afterwards mushrooms, yeasts and
molds were placed in their own kingdom—
Fungi.
After that scientists noticed that bacteria
lacked many features of other cells, and
were placed in their won kingdom—
Monera.
The process produced five kingdoms:
Monera, Protista, Fungi, Plantae and
Animalia.
Kingdoms and Domains
In recent years, scientists have
discovered further differences
between the organisms in the
kingdom of Monera—some of these
microorganisms are as different as
plants and animals!
Monera has thus been broken into
two kingdoms called:
Eubacteria
Archaebacteria
There are now a total of 6 kingdoms!
Kingdoms and Domains
Due to DNA analyses, an even more inclusive group than kingdom
has been created—domain.
The three domains are:
Bacteria
• Corresponds to kingdom Eubacteria
Archaea
• Corresponds to kingdom Archaebacteria
Eukarya
• Corresponds to kingdoms Protista, Fungi, Plantae and Animalia
Domain Bacteria
Members of the domain Bacteria:
•
•
•
•
Unicellular
Prokaryotic
Thick, rigid cell walls
Cell walls made of peptidoglycan
• Big diversity among them
• Soil organisms – deadly parasites
• Some photosynthesize, others do not
• Some aerobic, some anaerobic
Domain Archaea
Members of the domain Archaea:
•
•
•
•
Unicellular
Prokaryotic
Live in extreme environments
Many are anaerobic
• Cell walls lack peptidoglycan
• Cell membranes contain unusual lipids not found in other
organisms
Domain Eukarya
Members of the domain Eukarya:
• All organisms contain a nucleus
• Protista, Fungi, Plantae, Animalia Kingdoms
Protista:
• Eukaryotes that cannot be classified as animals, plants, or fungi.
• Members display the greatest variety.
• Most are unicellular, some multicellular
Fungi:
• Heterotrophs
• Feed on dead or decaying organic matter
• Secrete digestive enzymes into their food before ingesting
• Most multicellular, some unicellular
Domain Eukarya
Members of the domain Eukarya:
•
•
All organisms contain a nucleus
Protista, Fungi, Plantae, Animalia Kingdoms
Plantae:
• Multicellular
• Photosynthetic (Autotrophs)
• Non-motile (they cannot move)
• Cell walls that contain cellulose
Animalia:
• Multicellular
• Heterotrophic
• Cells lack cell walls
• Motile (they can move about)
• Extreme diversity within this kingdom: birds, mammals, reptiles, amphibians, etc.
DOMAIN
ARCHAEA
DOMAIN
EUKARYA
Kingdoms
DOMAIN
BACTERIA
Eubacteria
Archaebacteria
Protista
Plantae
Fungi
Animalia