Protists
•Historically a ‘catch all’ category
•Are neither animals, plants, fungi, nor prokaryotes.
•Are the first eukaryotic organisms to evolve from
prokaryotes. They gave rise to all other eukaryotic
lifeforms (plants, animals, fungi, modern protists).
•All protists are eukaryotic, the only unifying feature
of the group.
A eukaryotic cell
Figure 28.2 A model of the origin of eukaryotes
Membrane infolding
Endosymbiotic theory
Some general protist features
•Eukaryotic
•Most are aerobic (cellular respiration occurs in mitochondria)
•Most are motile (e.g, flagella/cilia)
•Most are unicellular (some may be colonial or multicellular)
•Most live in aquatic habitats (wherever there is moisture)
•Reproduction occurs both asexually and sexually:
asexually: budding, fission, multiple fission
*sexually: production of diploid cells via meiosis
Kingdom Protista
• All protists are
eukaryotes. This means
that their cells contain a
nucleus, a membrane-
bounded structure that
encloses the cell's genetic
material.
• Some protists are
autotrophs like plants,
others are consumers like
animals. Unlike plants
and animals, however,
protists do not have cells
organized into specialized
tissues.
Unicelluar Algae Protozoans
Multicellular algae
Slime molds
Protist Kingdom
Brum et al, 1994
Protista Classified by Nutrition
• The first detailed descriptions of protists
were made in 1676 by the inventor of the
microscope, Dutch naturalist
Leewenhoek.
• The term Protista was first used in 1862
by the German biologist Haeckel to
describe microscopic organisms that were
neither animallike nor plantlike
• The classification is currently based on
the structure and organization of the cell,
the presence of organelles, and the pattern
of reproduction or life cycles. The five-
kingdom system divides the Protista into
27 phyla. However, classifications based
on comparisons of cell physiology and
DNA sequences suggest that many protist
phyla may be sufficiently large and
diverse to be classified as kingdoms.
• Autotrophic Protists are called “Algae”.
Scientists believe they gave rise to the
kingdom Plantae
• Ingestive Heterotrophic protists are called
“Protozoa”. Scientists believe they gave rise
to the kingdom Animalia
• Absorptive heterotrophic protists are called
“Slimemolds”. Scientists believe they gave
rise to the kingdom Fungi
Protozoa classified by locomotion
• The word protozoa means "little
animal." They are so named
because many species behave
like tiny animals—specifically,
they hunt and gather other
microbes as food.
• Protozoa mainly feed on
bacteria, but they also eat other Actinophrys feeding on Colpidium
protozoa, bits of stuff that has
come off of other living
things—what's generally called
organic matter—and sometimes
fungi.
• Sarcodines, Flagellates,
Ciliates, Sporozoans,
• Food Vacuoles
1. Amoebas
Pseudopodia
Phylum Sarcodinia
• Engulf prey with pseudopodia
• Some naked and ameboid (Ameba proteus)
• Foraminiferans, warm oceans secrete calcium
carbonate shells w/ holes for pseudopodia
• Form chalk/limestone such as White Cliffs of
Dover
• heliozoans “sun animals” in fresh water
• free or attached by a stalk, some naked some silica
skeletons
• radiolarians secrete elaborate silica shells
2) Flagellates
a. Giardia
Purves et al., 2001
Phylum Zoomastigina (zooflagettes)
• Heterotrophic flagelleates
• Both free living and parasitic
• Trypanosoma sleeping sickness and
Chaga’s disease
• Giardia lakes and reservoirs causes
diarrhea, cramps, fatigue, loss of weight
b. Trypanosoma, causes African sleeping sickness
Parasitic protists infect more than
half the world’s population!!
Phylum Euglenophyta
• Freshwater, especially polluted habitats
• 2 flagella, one for locomotion one to detect
light
• lack cell walls but have a transparent
pellicle made of pp
• chlorophyll a & b & carotenoids
• can be autotrophic or heterotrophic
b. Euglena
Apicomplexans
• Spore forming parasites
of animals (including
humans).
• Have complex life
cycles.
• Plasmodium the cause
of malaria transferred
from mosquito to human
to mosquito.
4. Ciliates
II. Slime Molds
• Heterotrophs
• Not closely related to fungi, appear similar
due to convergent evolution.
• Probably evolved from an ameoboid
ancestor.
• Two types:
– 1. Cellular
– 2. Plasmodial
1. Cellular Slime Molds
2. Plasmodial Slime Molds Brum et al, 1994
Plasmodia have syncytial structure- Sporangia - stalked fruiting bodies
One huge cell with many nuclei
Shirley Owens, Center for Electron Optics, Michigan State University
Slimemolds, Watermolds & Mildews
• Slime molds have traits like both
fungi and animals. They have very
complex life cycles involving
multiple forms and stages. During
good times, they live as independent,
amoeba-like cells, dining on fungi
and bacteria. But if conditions
become uncomfortable—not enough
food available, the temperature isn't
right, etc.—individual cells begin
gathering together to form a single
structure.
• Water mold caused the Irish Potato
Famine in 1846
Plasmodium SlimeMolds
• Form plasmodium: a mass of
cytoplasm that contains many
diploid nuclei but no cell walls or
membranes – its feeding stage
• Creeps by amoeboid movement –
2.5 cm/hour
• May reach more than a meter in
diameter
• Form reproductive structures when
surroundings dry up
• Spores are dispersed by the wind
and grow into new plasmodium
• Tokyo’s Railway System
Cellular Slime Molds
• In feeding mode, they exist as individual
amoebic cells
• When food becomes scarce, they come together
with thousands of their own kind to reproduce
• May look like a plasmodium
Water Molds and Downy
Mildews
• Live in water or moist places
• Feed on dead organisms or
parasitize plants
• Fuzzy white growths
Harmful Protists
• cause mold and
mildew which can
spoil food and cause
allergic reactions
III. Unicelluar Algae
• Most are
photosynthetic, have
chlorophyll.
• Most are unicellular
but can be colonial.
• Abundant in marine
and freshwater
plankton, the bottom
of the food chain.
• Family Tree of
Chloroplasts
Classification of Algae
• When you think of algae, you probably
think of seaweed or the green, slimy
stuff that forms on the walls of
untreated, dirty swimming pools.
• Algae are found in bodies of fresh and
salt water across the globe. They can
also grow on rocks and trees and in soil
when enough moisture is available.
(They also grow on the hair of the South
American sloth, giving the animal a
greenish color.)
• Most algae are able to make energy
from sunlight, like plants do. They
produce a large amount of the oxygen
we breathe. However, at some stages of
their lives, some algae get their nutrients
from other living things.
Figure 28.6b Dinoflagellates: Pfeisteria piscicida
1. Dinoflagellates
Phylum:
Pyrrophyta/dinoflagellata
• 2 flagella, one wrapped around middle in
groove and one projecting
• mostly photosynthetic, chlorophyll a and
c and carotenoids, some heterotrophic
• store food in starch
• abundant in warm oceans
• formed large oil deposits
• reproduce asexually through binary
fission
• “red tide” which accumulates in shell fish
and produces a nerve poison
Harmful algal bloom of the toxic dinoflagellate
Noctiluca, off California
Phylum Chrysophyta (diatoms and
golden algae)
• Marine/wet spots (rocks, plants, wood)
• Chlorophyll a & c & fucoxanthin (gives a
yellow-brown color)
• Store excess food as oil, important in
formation of petroleum deposits
• Diatoms have a rigid cell wall with pectin and
silica glass (SiO2)
• Symmetrical
• Ancient deposits for diatomaceous earth
• mined for abrasives in silver polish and
toothpaste, packing in air and water filters
Phylum Phaeophyta (brown algae)
• 1500 species
• fucoxanthin
• store carbohydrates as
laminarin and mannitol
• flagellated sperm
• marine, especially cold coastal
water
• kelp can be 30m (100ft) tall
• holdfast root, stipes
stems, blades leaves,
bladdersafloat, thallus
entire structure
Phylum Rhodophyta (red algae)
• 4000 species of seaweed
• pigment phycoerythrin from phycobilins (like cyanobacteria)
• store food in a starch like compound called floridan
• produce polysaccharide agar-agar: used to thicken soups
and prepared media for bacterial growth
• harvested for carrageenan, thickening agent in ice cream
• Nori, Japanese seaweed
• Shows alternation of generations
• can be black or green
• absorb blue light
Phylum Chlorophyta (Green Algae)
• 7000 named species, mostly
freshwater a few marine
• unicellular and muticellular
• chlorophyll a & b, store food as
starch
• Volvox simple colonial
suggests arisal of
multicellularity 1: Ulva
2: Chlorella 3: Pediastrum
4: Codium 5: Pterosperma
6: Chlamydomonas
Daughter cells remain attached to the parent cells COLONY
Colonial Green Algae, Volvox
Evolution of multicellularity!
A colonial protist multicellular organism when
some members of the colony took on different
functions.
As cells specialized, they lost some of their previous
functions and so became dependant on the the
colony.
IV. Multicellular Algae: Seaweed
1. Red
3. Green
2. Brown
What distinguishes plants from algae?
1. Roots
2. Stems
3. Leaves
Figure 28.19x Kelp forest: Channel Islands
Multicellular green algae probably gave
rise to plants.
• Have the same type of chlorophyll
as plants.
• Some biologists think that
multicellular green algae should be
considered plants.
• Have alternation of generations.
You use algae everyday
• algae and their by products are ingredients
used in…
– Toothpaste
– Ice cream
– Puddings
– Agar
– Etc...
Beneficial Protists
• Used as insect pathogens
• used in ice cream, soups, nori
(seaweed in sushi), jello,
agar, vitamin supplements
• ancient dinoflagellates
formed oil deposits
• bioluminescent
• diatoms mined for fine
abrasives in silver polish and
toothpaste and as packing in
air and water filters
• marine phytoplankton make
up ~70% of the oxygen on
the planet
Protista Links
• Protist Kingdom:
• Phylogenetic Tree:
• Protozoa Bio 4 Kids:
• Microbe Zoo, Dirtland:
• Campbell's Chapter 28: Protist