Transcript The origins of eukaryotic diversity

BE101 Introduction to Biological
Systems
Dr. Michael Parkinson
Lecture Structure
• Lectures in QG15 & QG13 each week.
• A round up of points and coverage of
examination type questions on Monday
evening @ 5:00 in QG15
• These overheads are available to view as
powerpoint presentations at:
webpages.dcu.ie/~parkinsm/teaching.htm
• Any standard Biology text will do for
reading around e.g. Mader Biology (all at
570 in the library).
Schedule of topics
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Evolution of eukaryotes and protists
Fungi
Plant Evolution
Plant reproduction
Plant Structure
Plant growth and development
Photosynthesis
The origins of eukaryotic
diversity
Dr Michael Parkinson
School of Biotechnology
What I’m going to cover in this
lecture
• The origin of Eukaryotes
• The classification of Protists
• 3 of the more primitive groups of Protists
– Archezoa
– Euglenozoa
– Alveolates
3 things that you should watch
for in this lecture
• The way that eukaryotes have evolved from
primitive ancestors
• The way that the organisms are classified
and the factors that affect their classification
• The ways that protists can affect public
health
Evolution of eukaryotes by serial
endosymbiosis
• Nuclear membrane and endoplasmic
reticulum formed from invagination of
plasma membrane akin to phagocytosis
• Inclusion of organelles from phagocytosis
of aerobic bacterium / cyanobacterium
• The origin of microtubule structures
(flagellae, cilia, cytoskeleton) is unknown
1. Nucleus formation
Phagocytosis is a very common phenomenon in Protists.
Invagination of the plasma-membrane is expected to give
rise to:
a double membrane covering around the nucleus,
a system of membranes within the cell continuous with the nucleus
and the plasma membrane.
2. Origin of organelles
c.f. Forams
Phagocytosis
of an aerobic
bacterium
c.f. Archezoa
Phagocytosis
of cyanobacterium
Heterotrophic
eukaryote
Photoautotrophic
eukaryote
Features of ‘Protists’
• All eukaryotes
• Mostly unicellular
• ‘Primitive’ and thought to have diverged
early from a ‘universal ancestor’
• Very diverse
Types of ‘Protist’
Archezoa
Euglenozoa
e.g Giardia
Rhodophyta Plantae
Alveolata
Dinoflagellates
Euglenoids
Ciliates
Kinetoplastids
Red
Algae
Green
Algae
Apicomplexans
(sporozoans)
Stramenopila = Diatoms+Golden Algae+Brown algae+Water moulds
Evolutionary relations
• For many years, all
organisms that did not
conveniently fit into
other groups were
placed into the
‘Protists’.
• Classification is in a
very active and
dynamic state.
• Recently, molecular
phylogeny based on
similarity in DNA +
electron microscopy
has led to
reclassification to give
MONOPHYLETIC
groups - organisms are
grouped if they have a
common ancestor.
Summary of evolutionary relations
Animals
Fungi
Plants
Green algae
Red algae
Stramenopila
Distance apart
Alveolates
Euglenozoa
Archezoa
time
ARCHEZOA (from Greek
Arkhaios meaning ancient)
• Considered to be the most primitive of all
eukaryotes
• No mitochondria (some engulf bacteria)
• Mostly parasitic (e.g. Giardia)
• 3 Sub-groups
– Diplomonads (includes Giardia)
– Trichomonads (e.g. Trichomonas)
– Microsporidians
Giardia
• An important
parasite
• Transmitted by
both water and
animals
• Probably the most
important source
of holiday
diarrhea
Trichomonas
• An STD
EUGLENOZOA
• Flagellates
• 2 sub-groups
– euglenoids
Photosynthetic but may be
heterotrophic or mixotrophic
– Kinetoplastids
Symbiotic or parasitic e.g. Trypanosoma,
Leishmania
Trypanosoma
• Causes sleeping
sickness in cattle
and man in
Africa
transmitted by
the Tsetse Fly
• In Americas,
Chagas disease
Chagas disease / Sleeping Sickness
Leishmania
• The life cycles of members of the genus
involve a vertebrate host (e.g., the human)
and a vector (a sand fly) that transmits the
parasite between vertebrate hosts
Cutaneous Leishmaniasis
ALVEOLATA
• All have small
membrane bound
cavities (Alveoli)
beneath the cell
surface.
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3 subgroups
Ciliates
Apicomplexans
Dinoflagellates
Ciliates
• All have cilia for
locomotion and
feeding
• Reproduce by binary
fission
Trichodina sp.
• This genus contains many species, perhaps
as many as 200, most of which are found as
commensals or facultative or obligate
parasites on aquatic invertebrates, fish,
• and amphibians.
Apicomplexans (Sporozoa)
• All parasites of
animals
• All have a complex at
the apex of the cell for
penetrating host
tissues (Apicomplex)
• ‘Relict’ plastids
possibly related to
dinoflagellates with 4
bounding membranes
• Plasmodium
falciparum
• Pneumocystis carinii
(Pneumonia)
• Toxoplasma gondii
(toxoplasmosis)
• Cryptosporidium
parvum
(cryptosporidosis)
Apicoplast (plastid of Apicomplexan)
• 4 membranes
• Genome of circular
plasmid
• Smallest genome of
any plastid (35kb)
• Codes for a number of
genes
• Provides a means of
attacking the parasite
Malaria - Plasmodium/mosquito
Malaria - infection with an
Apicomplexan, Plasmodium
Dinoflagellates
• Abundant components of the phytoplankton
• Blooms cause red tides in coastal waters
• Can be an important symbiont in coral reefs