Classification and Protista
Why do Scientists Classify?
Imagine a grocery store…
How are they organized?
What would happen if they were not
organized?
How is your life organized?
Why do Scientists Classify?
Almost 13 billion known species of organisms
Need to keep organized! (Easier to study!)
• Classification the grouping of information or
objects based on similarities.
Why do Scientists Classify?
• Taxonomy is the science of grouping and
naming organisms.
Useful because:
once classified, scientists will know a lot about
an organism
Early Classification Systems
Aristotle (4th century B.C.)
-observed animals
-watched appearance, behavior,
movement
-fly, swim, and walk/crawl/run
-observed similarities and differences
-used differences to divide into smaller
subgroups
Linnaeus
Carolus Linnaeus (1750s)
-used observations as basis of his system
-placed organisms based on observable
features
Devised naming system for organisms:
Binomial Nomenclature
Linnaeus
Binomial Nomenclature- 2 part naming system
-uses Latin words
First name (genus); second name (species)
Genus species
Felis concolor
Genus is capitalized; species is NOT.
If you can’t italicize, underline the genus and
species!
Classification Today
Species with similar evolutionary histories are
classified more closely together.
-when organisms share a common ancestor,
they share an evolutionary history
Levels of Classification
-based on contributions of both Aristotle and
Linnaeus
There are 7 levels of classification.
Remember the first letter of this sentence:
King Philip Came Over For Good Spaghetti.
7 Levels of Classification
Kingdom
Phylum
Class
Order
Family
Genus
Species
broadest level
most specific
Levels of Classification
Taxonomic Categories
• Taxon- a named group of organisms
– Taxa range from having broad diagnostic
characteristic to having specific characteristics
• Genus- is defined as a group of species that
are closely related and share a common
ancestor
Taxonomic Categories
• Family- is the next higher taxon, consisting of
similar, related genera.
– Ursidae family contains 9 species of bears
Higher Taxa
• Order- contains related families
• Class- contains related orders
– Bears belong to order carnivora and class
mammalia
Higher Taxa
• Phylum or division- contains related classes
• Kingdom- contains related phlya or divisions
• Domain is the broadest of all taxa and
contains one or more kingdoms
• Bears are classified in phylum chordata,
Kingom Animalia, and Domain Eukarya
Using the Classification System
Field guides help identify organisms.
-they highlight differences between similar
organisms (like trees)
Taxonomic Key (AKA Dichotomous Key)
-paired statements that describe the physical
characteristics of different organisms
Taxonomic Key
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•
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•
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1. Fruits occur singly ....................................................... Go to 3
1' Fruits occur in clusters of two or more ......................... Go to 2
2. Fruits are round ....................................................... Grapes
2' Fruits are elongate ................................................... Bananas
3. Thick skin that separates easily from flesh .............Oranges
3' Thin skin that adheres to flesh .............................. Go to 4
4. More than one seed per fruit ............................ Apples
4' One seed per fruit ............................................ Go to 5
5. Skin covered with velvety hairs .................... Peaches
5' Skin smooth, without hairs ........................... Plums
Domains
• Broadest, most inclusive taxon
• Three domains
• Archaea and Eubacteria are
unicellular prokaryotes (no nucleus
or membrane-bound organelles)
• Eukarya are more complex and
have a nucleus and membranebound organelles
19
Archaea live in harsh environments and may
represent the first cells to have evolved.
Sewage
treatment
plants, thermal
vents, etc.
20
Eubacteria, some of which
cause human diseases, are
present in almost all habitats on
earth.
Live in the
intestines
of animals
Many bacteria are important
environmentally and commercially.
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Domain Eukarya is Divided into
Kingdoms
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Protista (protozoans, algae…)
Fungi (mushrooms, yeasts …)
Plantae (multicellular plants)
Animalia (multicellular
animals)
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Protista
•Most are
unicellular
•Some are
multicellular
•Some are
autotrophic, while
others are
heterotrophic
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Fungi
• Multicellular,
except yeast
• Absorptive
heterotrophs
(digest food
outside their
body & then
absorb it)
• Cell walls made
of chitin
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Plantae
•Multicellular
•Autotrophic
•Absorb sunlight to
make glucose –
Photosynthesis
•Cell walls made of
cellulose
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Animalia
• Multicellular
• Ingestive
heterotrophs
(consume food
& digest it
inside their
bodies)
• Feed on plants
or animals
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Similarities and Differences in the
Protist Kingdom
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All are eukaryotes (cells with nuclei).
Live in moist surroundings.
Unicellular or multicellular.
Autotrophs, heterotrophs, or both.
Some can move - others cannot.
3 categories of Protists:
• Animal-like
•Fungus-like
•Plant-like
Animal-like Protists (Protozoans)
*Unicellular Heterotrophs
*Four groups based on movement: those
with flagella, cilia, pseudopods, and the
‘others’.
Protozoans with Pseudopods
• Pseudopods also called ‘false
feet’
• Cell membrane pushes in one
direction & the cytoplasm flows
into the bulge.
• This allows the protozoan to
move, dragging the rest of the
cell behind it.
Pseudopod Movement
EXAMPLE OF HOW
PSEUDOPODS MOVE
FLOW
PUSH
DRAG
Pseudopods & Feeding
They can form pseudopods to
surround & trap food. Then
form a food vacuole to break
down food in the cytoplasm.
Pseudopods
• Reproduce by mitosis
• Contractile vacuole - it
collects extra H2O &
expels it from cell
• Thin cell membrane
• No definite shape.
• Example - Amoeba
Protozoans with cilia
• Cilia - hairlike structures - help organisms
move, get food and sense environment.
• Multicellular with 2 nuclei.
• 1 nuclei controls everyday functions
• 1 nuclei is for reproduction.
• Reproduce by mitosis or
conjugation.
Ciliates
• Oral groove lined with cilia moves H20 containing food into
food vacuole at end of oral
groove.
• Food vacuole breaks down food
and sends through cell.
• Anal pore sends out waste.
• Example of protozoan w/ cilia:
paramecium.
CONTRACTILE
VACUOLE
CILIA
FOOD
VACUOLE
ORAL
GROOVE
FOOD
VACUOLE
ANAL PORE
Protozoans with flagella
• Organisms called zooflagellates
• Use long whiplike part called flagella
to move.
• These usually live inside other
organisms.
Other Protozoans
• Called sporozoans - parasites
• Feed on cells & body fluids of hosts
Sporozoans like
Plasmodium
(causes malaria)
have more than 1
host: mosquitoes
and then humans
Examples of Animal-like Protista
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Cilates- move by cilia
Sarcodines- pseudopods
Sporozoans- spores
Zooflagellate- Flagella
Plantlike Protists
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Better known as algae
Autotrophs
Size: unicellular to very large
Contain different pigments so they come
in different colors.
• Euglena: special type of algae -when there
is no sunlight they become heterotrophic.
• Plant-like protists are algae.
• Algae are eukaryotic autotrophs.
• They, along with other eukaryotic autotrophs,
form the foundation of Earth’s food chains.
• They produce much of Earth’s oxygen.
• There are three unicellular phyla of algae:
– Phylum Euglenophyta
– Phylum Bacillariophyta
– Phylum Dinoflagellata
• Members of first phylum of algae,
Euglenophyta, are both plant-like and
animal-like.
• Euglena are autotrophs since they make food
from sunlight and
• Heterotrophs since they ingest food from
surrounding water.
• The second unicellular algae, Bacillariophyta,
are photosynthetic autotrophs.
• They have shells of silica.
• They make up a large portion of the world’s
phytoplankton which is Earth’s largest
provider of oxygen.
DIATOMS
• The third unicellular algae, Dinoflagellata,
are a major component of marine
phytoplankton.
• These algae have at least two flagella set at
right angles to each other and thick cell walls
made of cellulose plates.
• Blooms of dinoflagellates cause “Red Tide.”
• Multicellular algae are classified by color.
• Rhodophyta are red seaweeds.
• They are found in warm or cold marine
environments along coast lines in deeper
water.
• They absorb green, violet, and blue light
waves. These light waves are able to
penetrate below 100 meters.
• Phylum Phaeophyta is made up of the brown algae.
• They are found in cool saltwater along rocky coasts.
• Giant Kelp are the largest and most complex brown
algae. They have hold fasts and air bladders.
• The last of the multicellular algae are the green
algae from the Phylum chlorophyta.
• Most green algae are found in fresh water
habitats.
A Volvox is a hollow boll composed of hundreds of
flagellated cells in a single layer.
Chlamydomonas are actually unicellular and
flagellated.
Funguslike Protists
• Like animals, they are
heterotrophs
• Like plants, they have cell walls
• Reproduce by spores (tiny cells
that can grow into a new
organism)
• Not in fungi kingdom because
they can move at one point in
their lives.
• Example are water or slime
molds.
• Fungus-like protists, Myxomycota and
Oomycota are decomposers.
• Phylum Myxomycota are made up of
plasmodial slime molds.
• Phylum Oomycota is made up of water molds
and downy molds.