How We Name Living Things
Invention of the Linnaean System
Classification - Multilevel grouping of
individuals.
Organisms first classified by Aristotle over 2,000
years ago.
Eventually groups started to be formed and referred to
as genera (singular, genus).
Starting in middle ages, names began to be systematically
written down using Latin.
Invention of the Linnaean System
Classification scheme of the Middle Ages
(polynomial system) was used replaced with
a binomial system by Linnaeus about 250
years ago.
Polynomial - Strings of latin words and phrases
containing up to 12 words.
Binomial - Two-part name for each species.
Species Names
Taxa - Group of organisms at a particular
level in a classification system (Taxonomy).
By convention:
First word of binomial name is genus and is
always capitalized.
Second word refers to particular species and is
not capitalized.
Together form Scientific Name, written in italics.
Species Definition
Biological Species Concept (Ernst Mayr)
Species are groups of actually or potentially
interbreeding natural populations which are
reproductively isolated from other such groups.
Problems
Assumes regular outcrossing
Assumes strong reproductive barriers
Hybrids ?
Higher Categories
Species
Genus
Family
Order
Class
Phylum
Kingdom
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Hierarchical Classification System
Kingdoms of Life
Most Biologists use a six-kingdom system.
Animalia
Plantae
Fungi
Protista
Archaebacteria
Eubacteria
Domains - taxonomic level above kingdoms.
Evolutionary Relationship
Domain Bacteria (Eubacteria)
Most abundant organisms on earth.
Most taxonomists recognize 12-15 major
groups.
Domain Eukarya (Eukaryotes)
Appear in fossil record only about 1.5 billion
years ago. Complex cellular organization.
Fungi, Plants, and Animals are well-defined
evolutionary groups.
Largely multicellular
Domain Eukarya (Eukaryotes)
With few exceptions, all modern eukaryotic
cells possess energy-producing organelles
(Mitochondria).
Some protist phyla have also acquired
chloroplasts and are photosynthetic.
Mitochondria and chloroplasts are both believed to have
entered early eukaryotic cells by endosymbiosis.
Advent of The Eukaryotes
Endosymbiosis
Most biologists believe mitochondria
originated as symbiotic, aerobic eubacteria
(endosymbiosis).
Bacteria thought to have been engulfed by
ancestral eukaryotic cells early in the history of
eukaryotes.
Endosymbiosis
Kingdoms of Life
Most Biologists use a six-kingdom system.
Animalia
Plantae
Fungi
Protista
Archaebacteria
Eubacteria
Multicellular
Organisms Individuals composed of many
cells that interact and
coordinate their activities.
Classifying Protists
Most diverse of four kingdoms in the domain
Artificial group formed for convenience.
Five general groups according to major shared
characteristics.
Presence or absence of cilia / flagella
Presence and kind of pigment
Type of mitosis
Kinds of cristae in mitochondria
Protist Reproduction
Multicellularity - Composed of many permanently
associated cells with integrated activities. Allows for
specialization.
Occurs only in eukaryotes
Colonies - Permanent association, but no integration of cell
activities.
Aggregates - Transient collection of cells.
Movement accomplished by various means.
Flagella
Lobopodia
Filopodia
Axopodia
Heterotrophs Lacking
Permanent Locomotor Apparatus
Largest of the five groups.
Amoebas - Lack flagella and cell walls, and
move with pseudopodia.
Forams - Possess rigid shells and move by
cytoplasmic streaming (podias).
Marine with pore-studded shells (tests).
Radiolarians - Phylum Actinopoda
Glassy skeletons with many needlelike
pseudopods.
Heterotrophs With Flagella
Zoomastigotes
Ancestor of all animals appears to have been a
member of this group.
All have at least one flagellum.
Heterotrophs With Flagella
Ciliates
Possess large number of cilia, fixed cell shape,
and two nuclei per cell.
Reproduction usually by fission.
Move by beating cilia.
Photosynthetic Protists
Dinoflagellates
Photosynthetic unicellular protists, most with two
flagella of unequal lengths.
One flagella beats in a groove circling body, while the
other beats in a groove perpendicular to it.
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Photosynthetic Protists
Euglenoids
Freshwater protists with two flagella.
One-third are photosynthetic, while others are
heterotrophic.
Reproduction by mitotic cell division.
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Photosynthetic Protists
Diatoms
Photosynthetic unicellular protists with unique
double shell of silica.
Golden Algae
Named for yellow and brown accessory pigments
in chloroplasts.
Photosynthetic Protists
Green Algae
Ancestor of true plants is a member of this group.
Contain chlorophyll a and b.
Most are microscopic and unicellular.
Photosynthetic Protists
Red Algae
Contain red pigments
(phycobilins).
Almost all multicellular and live at
sea.
Brown Algae
Life cycle employs alteration of
generations. (Kelp)
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