Transcript Kingdom Protista

Kingdom Protista
Protists
Even a low-power microscope
–Can reveal an astonishing menagerie of
organisms in a drop of pond water
50 m
Protist Diversity
•Protists are more diverse than all other
eukaryotes
–And are no longer classified in a single
kingdom
•Most protists are unicellular
–And some are colonial or multi-cellular
Protist Diversity
• Organisms that range in size from
single cells to complex structures
more than 100 meters long.
• They show a variety of reproductive
and nutritional strategies.
Protist Diversity
•Protists, the most nutritionally diverse of all
eukaryotes, include
–Photoautotrophs, which contain chloroplasts
–Heterotrophs, which absorb organic molecules
or ingest larger food particles
–Mixotrophs, which combine photosynthesis and
heterotrophic nutrition
Protists are also diverse in habitat
•Including freshwater and marine species
(a) The freshwater ciliate Stentor,
a unicellular protozoan (LM)
100 m
100 m
4 cm
(b) Ceratium tripos, a unicellular marine dinoflagellate (LM)
(c) Delesseria sanguinea, a multicellular marine red alga
500 m
(d) Spirogyra, a filamentous freshwater green alga (inset LM)
ProtistA Evolution
•There is now
considerable
evidence
–That much of
protist diversity
has its origins in
endosymbiosis
ProtistA Evolution
•The plastid-bearing lineage of protists
–Evolved into red algae and green algae
•On several occasions during eukaryotic
evolution
–Red algae and green algae underwent
secondary endosymbiosis, in which they
themselves were ingested
2˚ Endosymbiosis
Plastid
Alveolates
Dinoflagellates
Apicomplexans
Secondary
endosymbiosis
Cyanobacterium
Ciliates
Red algae
Primary
endosymbiosis
Stramenopiles
Heterotrophic
eukaryote
Plastid
Euglenids
Secondary
endosymbiosis
Green algae
Chlorarachniophytes
Diplomonadida and parabasala
•Have modified mitochondria
–Are adapted to anaerobic environments
–Lack plastids
–Have mitochondria that lack DNA, an electron
transport chain, or citric-acid cycle enzymes
•A tentative phylogeny of eukaryotes
–Divides eukaryotes into many clades
Diplomonads
–Have two nuclei and multiple flagella
(a) Giardia intestinalis, a diplomonad (colorized SEM)
5 µm
Zooflagellates
· Move by flagella
· They may enter into symbiotic
relationships with other organisms.
Parabasalids
-include trichomonads
–Which move by means of flagella and an
undulating part of the plasma membrane
Euglenozoa
•Have flagella with a unique internal structure
•Euglenozoa is a diverse clade that includes
–Predatory heterotrophs, photosynthetic
autotrophs, and pathogenic parasites
•2 Types
–Kinetoplastids & Euglenids
Euglenozoa
•The main feature that distinguishes protists
in this clade
–Is the presence of a spiral or crystalline rod
of unknown function inside their flagella
Flagella
0.2 µm
Crystalline rod
Ring of microtubules
Kinetoplastids
–Have a single, large mitochondrion that
contains an organized mass of DNA called a
kinetoplast
–Include free-living consumers of bacteria in
freshwater, marine, and moist terrestrial
ecosystems
Tsetse fly
Trypanosoma
–Causes sleeping sickness in humans
9 m
Euglenids
Long flagellum
Eyespot: pigmented
organelle that functions
as a light shield, allowing
light from only a certain
direction to strike the
light detector
Light detector: swelling near the
base of the long flagellum; detects
light that is not blocked by the
eyespot; as a result, Euglena moves
toward light of appropriate
intensity, an important adaptation
that enhances photosynthesis
Short flagellum
Euglena (LM)
Nucleus
Contractile vacuole
5 µm
Plasma membrane
Figure 28.8
Pellicle: protein bands beneath
the plasma membrane that
provide strength and flexibility
(Euglena lacks a cell wall)
Chloroplast
Paramylon granule
Euglenids
Euglenids
Only one third of the species of Euglenoids are
photosynthetic.
·
·
Euglena stores glucose in a polymer called Paramylon
An eyespot with a photoreceptor is capable of
detecting the presence of light.
·
Reproduction is asexual.
Alveolates
Members of the clade Alveolata
–Have membrane-bounded sacs (alveoli) just
under the plasma membrane
Includes:
•Dinoflagellates
•Apicomplexans
•Ciliates
0.2 µm
Flagellum
Alveoli
Dinoflagellates
–Are a diverse group of aquatic
photoautotrophs and heterotrophs
–Are abundant components of both marine
and freshwater phytoplankton
•Shape is reinforced by internal plates of cellulose
•Two flagella
–Make them spin as they
–move through the water
Dinoflagellates
Some species are responsible for red tides that kill fish
and shellfish
Toxins
released can
kill aquatic
&
terrestrial
animals
(aerosols)
Apicomplexans
–Are parasites of animals and some cause serious
human diseases
–Are so named because one end, the apex, contains
a complex of organelles specialized for penetrating
host cells and tissues
–Have a non-photosynthetic plastid, the apicoplast
Apicomplexans
Most apicomplexans have intricate life cycles
–With both sexual and asexual stages that often require
two or more different host species for completion
–Plasmodium causes malaria
Plasmodium
Anopheles
mosquito
Sporozoans
• Parasitic
• Complicated life cycle that usually involves the
formation of infective spores.
e.g. malaria - The parasite is injected into a
human by a mosquito. The parasite then invades
red blood cells and ruptures them.
Ciliates
–Are named for their use of cilia to move and feed
–Have large macronuclei and small micronuclei
•The micronuclei
–Function during conjugation, a sexual process that
produces genetic variation
•Conjugation is separate from reproduction
–Which generally occurs by binary fission
Ciliates
• Example - Paramecium
• The outer covering of paramecium is covered
with hundreds of cilia
• They have numerous organelles including a
gullet (oral groove) and an anal pore
• The macronucleus controls the cell's activities.
• The micronucleus is involved in cell reproduction
(sexual & asexual).
CONJUGATION AND REPRODUCTION
Meiosis2 of micronuclei
produces four haploid
micronuclei in each cell.
MEIOSIS
3 micronuclei in each cell
disintegrate. The remaining
micro-nucleus in each cell
divides by mitosis
Macronucleus
Compatible
mates
Haploid
micronucleus
Diploid
micronucleus
Diploid
micronucleus
The cells swap
one micronucleus
MICRONUCLEAR
FUSION
Two rounds of cytokinesis
partition one macronucleus
and one micronucleus
into each of four daughter cells.
The original macronucleus disintegrates.
8
Four micronuclei
become macronuclei,
while the other four
remain micronuclei.
7
Micronuclei fuse,
forming a diploid
micronucleus.
The cells
separate
Key
Three rounds of
mitosis without
cytokinesis
produce eight
micronuclei.
Conjugation
Reproduction
Paramecium
FEEDING, WASTE REMOVAL, AND WATER BALANCE
50 µm
Stentor (Type of ciliate)
Stramenopila
•Stramenopiles have “hairy” and smooth
flagella
•The clade Stramenopila Includes:
–Water molds
–Diatoms
Hairy
flagellum
–Golden algae
–Brown algae
Smooth
flagellum
5 µm
Oomycetes
–Include water molds, white rusts, and downy
mildews
–Were once considered fungi based on
morphological studies
–Are decomposers or parasites
–Have filaments (hyphae) that facilitate nutrient
uptake
–Have cell walls
made of cellulose
Diatoms
•Are unicellular algae
–With a unique two-part, glass-like wall of
hydrated silica
–major component of phytoplankton
Diatoms
·
·
·
·
Most numerous unicellular algae in the oceans
and are an important source of food and
oxygen.
Also important in freshwater environments.
Glucose stored as polysaccharide laminarin (Same
as golden & brown algae)
Their remains form diatomaceous earth.
Diatoms
~ 100 000 species
50 µm
25 µm
Golden Algae
•Or chrysophytes
–Are named for their color,
which results from their
yellow & brown carotenoids
•The cells of golden algae
–Are typically bi-flagellated, with both flagella
attached near one end of the cell
Brown algae
•Or phaeophytes
–Are the largest and most complex algae
–Are all multicellular, and most are marine
–Include many of the species commonly called
seaweeds
•Seaweeds
–Have the most complex multi-cellular anatomy of
all algae
Brown Algae
Photosynthetic & multicellular
· Range in size.
Many are 50-100 m long.
· Found along rocky shores
The thalus (plant like body) contains:
· Holdfasts for attachment
· Blades and air bladders that function in floatation
· A stem-like structure that holds the blades is called a
stipe.
Fucus
Common "seaweed" found along the rocky coast.
Blade
Stipe
Holdfast
Brown Algae
•Kelps, or giant seaweeds
–Live in deep parts of the ocean
–Can grow as long as 60m
Cell walls are composed of
cellulose and gel forming
polysaccharides which
cushion the algae in the
intertidal zone
Brown Algae - Macrocystis and
Nereocystis (Deep water Kelp)
Nereocystis
Macrocystis
A variety of life cycles
Have evolved among the multi-cellular algae
•The most
complex life
cycles include an
alternation of
generations
–The alternation
of multi-cellular
haploid and
diploid forms
Sporangia
Sporophyte
(2n)
Developing
sporophyte
MEIOSIS
Zoospores
Female
Gametophytes
(n)
Zygote
(2n)
Egg
Mature female
gametophyte
(n)
Key
Haploid (n)
Diploid (2n)
Male
FERTILIZATION
Sperm
Cercozoans
•Cercozoans and radiolarians have threadlike
pseudopodia
•A newly recognized clade, Cercozoa
–Contains a diversity of species that are among
the organisms referred to as amoebas
•Amoebas were formerly defined as protists
–That move and feed by means of pseudopodia
•Cercozoans are distinguished from most other
amoebas
Foraminiferans, or forams
–Are named for their porous, generally
multichambered shells, called tests
20 µm
Pseudopodia extend through the pores in the test
Radiolarians
•Marine protists
–Whose tests are fused into one delicate piece,
which is generally made of silica
–Phagocytize microorganisms with their
pseudopodia
•The pseudopodia of radiolarians, known as
axopodia
–Radiate from the central body
Axopodia
200 µm
Radiolarians
Marine plankton (float in marine environments) with
a skeleton composed of silica, and numerous needlelike pseudopodia.
Amoebozoans
• Have lobe-shaped pseudopodia
–rather than threadlike, pseudopodia
–Include gymnamoebas, entamoebas, and slime
molds
Protozoans
· Do not have a cell wall
· Heterotrophic
· Usually motile
· Food vacuoles
· Contractile vacuole (water elimination)
Reproduction is usually asexual but many also reproduce
sexually during some part of their life cycle.
Gymnamoebas
–Are common unicellular amoebozoans in soil as
well as freshwater and marine environments
•Most are
heterotrophic
–And actively seek
and consume
bacteria and
other protists
Pseudopodia
40 µm
Entamoeba
–Are parasites of vertebrates and some invertebrates
•Entamoeba histolytica
–Causes amebic dysentery in humans
Amoeboids
Amoeba
Move by cytoplasmic extensions called pseudopodia.
Feed by phagocytizing (engulfing) their prey.
Most amoeboids are marine organisms;
Amoeba proteus is found in freshwater
Amoeboids
Slime molds, or mycetozoans
–Were once thought to be fungi
•Molecular systematics
–Places slime molds in the clade Amoebozoa
–Plasmodial & Cellular types
The plasmodium
–Is undivided by membranes and contains
many diploid nuclei
–Extends pseudopodia through
decomposing material, engulfing food by
phagocytosis
Protists that are Decomposers
(Saprotrophs)
·
Slime molds play an ecological role similar to that of fungi.
·
They are decomposers, feeding on dead organic material.
·
They differ from fungi in that slime molds ingest their food.
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·
·
·
Slime molds are masses that creep along the substrate and phagocytize
dead organic material and microorganisms.
The mass is one large cell referred to as a plasmodium.
Spores are resistant to environmental extremes (Food and moisture)
and germinate when environmental conditions become favorable
Saprotrophic; they live off of dead organic matter.
Slime Molds
Plasmodial Slime mold life cycle
Feeding
plasmodium
Zygote
(2n)
Mature
plasmodium
(preparing to fruit)
Young
sporangium
SYNGAMY
1 mm
Mature
sporangium
Amoeboid cells
(n)
Key
Flagellated cells
(n)
Germinating
spore
Spores
(n)
MEIOSIS
Haploid (n)
Diploid (2n)
Stalk
Cellular slime molds
•Form multicellular aggregates
–In which the cells remain separated by their
membranes
–Has become an
experimental
model for
studying the
evolution of
multi-cellularity
Cellular Slime Mold
Life Cycle
SYNGAMY
Emerging
Spores amoeba
(n)
Solitary amoebas
(feeding stage)
600 µm
Zygote
(2n)
SEXUAL
REPRODUCTION
MEIOSIS
Amoebas
Fruiting
bodies
ASEXUAL
REPRODUCTION
Aggregated
amoebas
Migrating
aggregate
Key
200 µm
Haploid (n)
Diploid (2n)
Algae
The word algae refers to aquatic (freshwater or marine)
protists.
Algae photosynthesize like plants. They produce much
of the oxygen in the atmosphere.
· Algae provide food for aquatic food chains.
Red & Green Algae
•Are the closest relatives of land plants
•Over a billion years ago, a heterotrophic protist
acquired a cyanobacterial endosymbiont
–And the photosynthetic descendants of this ancient
protist evolved into red algae and green algae
Red Algae
• Are reddish in color
–Due to an accessory pigment call phycoerythrin,
which masks the green of chlorophyll
Red Algae
• Red algae are found mainly in warmer, tropical oceans.
• Accessory photosynthetic pigments are called
phycobilins which allow some species to survive in deep
waters where blue and green light predominates.
• Some species are filamentous but most have a complex
pattern of branching.
• Some coralline forms deposit calcium carbonate in
their cell walls, making coral reefs.
Green Algae
–Are named for their grass-green chloroplasts
–Are divided into two main groups: chlorophytes
and charophyceans
–Are closely related to land plants
Green Algae
Single-celled and multicellular forms.
·
Ancestors of the first plants, both have the following
characteristics in common:
They have a cell wall that contains cellulose.
They have chlorophyll
They store their food as starch inside the chloroplast.
Chlorophytes
(green algae)
•Include:
–Unicellular,
colonial, and
multicellular
forms
20 µm
50 µm
(a)
)
Ulva
• Multicellular with a leaf-like body that is
two cells thick but up to one meter long
• Common name: Sea lettuce
Volvox
· Colonial green algae
· They divide asexually to
produce a daughter colony.
Notice the daughter colonies
within the larger colonies.
Volvox
• Some cells are specialized to produce sperm
and eggs for sexual reproduction which is a
characteristic of multicellular organisms.
• Considered to be a colony because it appears
to be intermediate between a group of
individual cells and a multicellular organism.
Spirogyra
· Filamentous form of green algae.
· Has a ribbonlike spiral-shaped chloroplast.
· Sexual reproduction occurs by conjugation.
·
The zygote is resistant and overwinters.
Spirogyra
Conjugation
Chlorophyte Life Cycle
Harsh environmental
conditions
Flagella

1 µm
Cell wall
+
Nucleus

+
Zoospores
Regions
of single
chloroplast
ASEXUAL
REPRODUCTION
Mature cell
(n)
SEXUAL
REPRODUCTION
+
Key
+
Haploid (n)
Diploid (2n)
Normal environmental
conditions
SYNGAMY

MEIOSIS
Zygote
(2n)
Protists Compared to Plants,
Animals, and Fungi
• Characteristics resemble plants, animals, or fungi.
• Photosynthetic protists differ from plants in that they do
not have structures that protect the gametes or zygote.
• Plants and animals undergo a period of embryonic
development but protists do not.
• Fungi have cell walls composed of chitin; protists do not
have chitin in their cell walls
• Fungi do not have cilia or flagella. Many kinds of protists
have cilia or flagella.
Trophic Levels
·
·
·
·
·
·
Autotrophs:
green algae
brown algae
red algae
diatoms
dinoflagellates
euglenoids
·
·
·
·
·
Heterotrophs:
amoeboids
ciliates
zooflagellates
sporozoans
slime molds