Transcript Protist Diversity II

Protist diversity II
Level 1 Biological Diversity
Jim Provan
Phylogeny of eukaryotes
Diplomonads and Parabasala
Amitochondriate:
Originally believe to have
diverged before acquisition
of mitochondria
Presence of nuclear gene
homologues now suggests
that mitochondria have been
lost
Diplomonads have multiple
flagella and two separate
nucleii
Infectious
Euglenozoa
Contain flagella
Two main groups:
Euglenoids:
—
—
Paramylon (glucose polymer)
used as a storage molecule
Anterior pocket with one or
two flagella
Kinetoplastids:
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—
Contain a single large
mitochondrion and a unique
organelle (kinetoplast)
Symbiotic / pathogenic
Alveolata
Encompasses:
Photosynthetic flagellates
(dinoflagellates)
Parasites (apicomplexans)
Group that move by cilia
(ciliates)
Have small, membranebound cavities under cell
surfaces (alveoli)
Dinoflagellates
Components of phytoplankton – may cause red tides
Most are unicellular, some are colonial
Some are photosynthetic symbionts, some are nonphotosynthetic parasites
Plastids are brownish and contain chlorophylls a and c
and a mix of carotenoids (including peridinin)
Food stored as starch
Chromosomes lack histones and are always condensed
Have no mitotic stages
Apicomplexans
All parasites of animals:
Infectious cells called sporozites
Apex of sporozites has organelles for penetrating host cells
Life cycles have both sexual and asexual reproduction, often
requiring more than one host
Several species of Plasmodium cause malaria:
Anopheles mosquitoes serve as intermediate host
New, resistant forms of Plasmodium are appearing
Little success in developing a vaccine:
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Plasmodium spends most of its life cycle in blood or liver cells
—
Has the ability to alter its surface antigens
Life history of Plasmodium
Ciliates
Species use cilia to move and
feed
Most solitary cells in fresh water
Cilia are short and beat in
synchrony
Submembraneous system
coordinates beating
Some species move on leg-like
cirri
Others have rows of tightly
packed cilia which act as
locomoter membranelles
Among most complex of cells
Two types of ciliate nuclei
Macronucleus:
Is large and has over 50 copies of the genome
Genes packaged into units, each with hundreds of copies of just a
few genes
Controls everyday functions by synthesising RNA
Necessary for asexual reproduction – macronucleus elongates and
splits instead of undergoing mitosis
Micronucleus:
Small and present in 1-80 copies
Does not function in growth, maintenance or asexual reproduction
Functions in the sexual process of conjugation
Conjugation and genetic
recombination in Paramecium
Stramenopiles
Includes several heterotrophic groups as well as a
variety of photosynthetic protists (algae):
Oomycota (water moulds etc.):
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—
Heterotrophic
Ostensibly similar to fungi but have analogous hyphae, cellulose
cell walls (as opposed to chitin), prevalent diploid stage and
biflagellated cells (true fungi have no flagellated stages)
Heterokont algae:
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—
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Diatoms have hydrated silica shells and generally reproduce
asexually
Chrysophytes (golden algae) have carotene and xanthophyll
accessory pigments and are mostly unicellular
Phaeophytes (brown algae) are all multicellular and mostly marine
Seaweeds
Have differentiated tissues
and organs similar to plants:
Analogous:
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—
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Holdfast  root
Stipe  stem
Blade  leaf
Commercially important:
Food (Laminaria and Porphyra)
Agar
Thickeners
Lubricants
Alternation of generations in algae
Rhodophyta (red algae)
Have no flagellated stages
Accessory pigment:
phycoerythrin
Not always red: dependent
on depth
Mostly multicellular
Diverse life cycles but
alternation of generations
is common
Chlorophyta (green algae)
Two main groups:
Chlorophyceae
Charophyceae
Share a common ancestor
with green plants
Unicellular, colonial or
multicellular
Nearly all reproduce
sexually by way of
biflagellated gametes
Life cycle of Chlamydomonas
Rhizopods (amoebas)
Simplest unicellular protists
No flagellated stages
Pseudopodia used in
feeding and movement
All reproduction is asexual
Inhabit freshwater, marine
and soil habitats
Most are free living,
although some are parasitic
Actinopods
Possess axopodia, slender
form of pseudopodia
Increase surface area which
helps floating and feeding
Some prey may stick to
axopodia and be
phagocytosed
Two main groups:
Heliozoans (primarily
freshwater)
Radiolarians (primarily
marine)
Plasmodial slime moulds (Myxomycota)
Cellular slime moulds (Acrasiomycota)