BE101 Introduction to Biological Systems Dr. Michael Parkinson.
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Transcript of BE101 Introduction to Biological Systems Dr. Michael Parkinson.
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BE101 Introduction to Biological Systems
Dr. Michael Parkinson
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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).
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Schedule of topics
• Evolution of eukaryotes and protists
• Fungi
• Plant Evolution
• Plant reproduction
• Plant Structure
• Plant growth and development
• Photosynthesis
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The origins of eukaryotic diversity
Dr Michael Parkinson
School of Biotechnology
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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
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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
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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
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1. Nucleus formation
Phagocytosis is a very common phenomenon in Protists. Invagination of the plasma-membrane is expected to giverise to: a double membrane covering around the nucleus, a system of membranes within the cell continuous with the nucleus and the plasma membrane.
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2. Origin of organelles
Phagocytosisof an aerobicbacterium
Heterotrophiceukaryote
Photoautotrophic eukaryote
Phagocytosisof cyano-bacterium
c.f. Archezoa
c.f. Forams
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Features of ‘Protists’
• All eukaryotes
• Mostly unicellular
• ‘Primitive’ and thought to have diverged early from a ‘universal ancestor’
• Very diverse
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Types of ‘Protist’
Euglenozoa Alveolata Rhodophyta Plantae
GreenAlgae
RedAlgae
Dinoflagellates
Ciliates
Apicomplexans(sporozoans)
Euglenoids
Kinetoplastids
Stramenopila = Diatoms+Golden Algae+Brown algae+Water moulds
Archezoae.g Giardia
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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.
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Summary of evolutionary relations
Archezoa
Euglenozoa
Stramenopila
Green algae
Plants
Fungi
Animals
time
Distance apart
Alveolates
Red algae
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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
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Giardia
• An important parasite
• Transmitted by both water and animals
• Probably the most important source of holiday diarrhea
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Trichomonas
• An STD
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EUGLENOZOA
• Flagellates• 2 sub-groups
– euglenoidsPhotosynthetic but may beheterotrophic or mixotrophic
– KinetoplastidsSymbiotic or parasitic e.g. Trypanosoma, Leishmania
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Trypanosoma
• Causes sleeping sickness in cattle and man in Africa transmitted by the Tsetse Fly
• In Americas, Chagas disease
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Chagas disease / Sleeping Sickness
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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
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Cutaneous Leishmaniasis
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ALVEOLATA
• All have small membrane bound cavities (Alveoli) beneath the cell surface.
• 3 subgroups• Ciliates• Apicomplexans• Dinoflagellates
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Ciliates
• All have cilia for locomotion and feeding
• Reproduce by binary fission
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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.
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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)
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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
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Malaria - Plasmodium/mosquito
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Malaria - infection with an Apicomplexan, Plasmodium
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Dinoflagellates• Abundant components of the phytoplankton
• Blooms cause red tides in coastal waters
• Can be an important symbiont in coral reefs