lecture #10 – 2/11 – dr - university of...
Post on 15-Feb-2018
215 Views
Preview:
TRANSCRIPT
Lecture #10 – 2/11 – Dr. Kopeny
Locomotion and Structures for Support and Protection
Pseudopodia
flagella
cilia
Structure of microtubules in cilia and flagella
Modes of Locomotion in Protists
2 single microtubules (red) surrounded by
nine paired microtubules (yellow)A ciliatedProtist
An Amoeboid Protist
reference: chapter 4 in textbook
A ciliated protist
Paramecium can swim in either direction relative to its long axis by beating its cilia in rhythmic, coordinated fashion that progresses from one end of the cell to the other.
Amoeba extends a pseudopodium toward a Pandorina colony. At right, the amoeba surrounds colony before engulfing it
Proposed mechanism of psuedopodial movement. In endoplasm, actin subunits are bound to regulatory proteins that keep them from assembling.
Source: Hickman et al 2001
External Structures for Support and Protection
Forams; shells are made from protein hardened with calcium carbonate
Amoeba; shell made of cemented sand grains
Radiolarians; glassy skeletons allow light penetration for photosynthetic endosymbionts
Diatoms
foraminiferan with calcium carbonate tests
diatomshave glass-like silicon containg sructures
Dinoflaggelates surrounded by cellulose plates
Sources: Purves et al (2002), Freeman (2002)
Multicellularity
Clamydomonas Gonum Pandorina Volvox
Multicellular Green Alga (Coleochaete orbiculairs)
Morphological continuum in Volvocales from unicellular to multicelluar.
True multicellarity is defined functionally
Differentiation of cell function (specialization, division of labor)
Differential gene expression
Multicellularity has evolved independently multiple times in Protistan lineages
Multicelluarity confers advantages by allowing for increased size, specialization, and complexity
The initial evolution towards multicellularity begins with differentiation of gamete-producing cells, the consequence of the uniquely eukaryotic reduction division process; meiosis
Source: Freeman 2002
Reproduction, Life Cycles and Alternation of Generations
Meiosis and Sexual reproduction were important Protistan innovations
Life Cycle of Chlamydomonas
http://megasun.bch.umontreal.ca/protists/chlamy/introduction.html
http://www.ucmp.berkeley.edu/greenalgae/greenalgae.html
Life cycle of Laminaryia: an example of alternation of generations
Sporophytes of this seasweed are usually found in water just below the line of the lowest tides, attached to the rocks by branching holdfasts
In early spring, at end of the main growing season, cells on the surface of the blade develop into sporangia
sporangia produce zoosporres by meiosis
Zoospores are all structurally alike, but about half of them are capable of developing into a male gametophyte and half into a femlel gametophye. Gametophytes look nothing like the sporophytes, being short, branched filaments that grow on the surface of subtidal rocks
Male gametohytes release sperm, and female gametophytes produce eggs, which remain attached tot eh gametophyte. Eggs secrete a chemical signal that attracts sperm of the same species, thereby increasing the probability of gametic union in the ocean.
Sperm fertilize the eggs
The zygotes grow into new sprorophytes, starting life attached to the remains of the old female gametophyte
Gametophytes (n)
Sporophytes (2n)
Lines of evidence indicating mitochondria and chloroplasts arose as prokaryotic symbionts
-membranous enzymes and transport systems
-replication process
-genome
-protein translation machinery, including ribosomes, t-rna
-similarities of mitochondrial and chloroplast ribosomes to prokaryote ribosomes
Endosymbiotic Theory
2.5 um 80 um
Margulis webpagewww.bio.umass.edu/faculty/biog/margulis.html
Lynn MargulisU. Mass., Distinguished Professor and Member of the National Academy of Science – developed endosymbiotic theory
Proteobacteria Cyanobacteria
Phylogenetic analyses using small subunit RNA
Ribosomes are comprised of one small and one large subunit. The single rRNA molecule of the small subunit
Ribosomes are
Gene for small subunit r-RNA is present in all organism –good gene for determining deep branching in tree of life
Sequence comparisons show that closest prokaryote relatieves of mitochondria are altpha proteobacteria.
Sequence comparisons of plastids from various photosynthetic eukaryotes cluster with prokaryotic cyanobacteria (photosyntheitc machinery and metabolic pathways are shared as well.
Protists and Human Health:Plasmodium and Malaria
http://www.malaria.org/lifecycle.html
P. falciparum is the most widespread and dangerous of the four: untreated it can lead to fatal cerebral malaria.
Infected Red Blood Cells
The distribution of malaria varies greatly from country to country and within the countries themselves. In 1990, 75% of all recorded cases outside of Africa were concentrated in nine countries
Infected mosquito bites and infects person; sporozoites and enter liver cells After several days, undergo multiple divisions to become merozoites (specialized spore) that uses apical complex to penetrate RBC
Merozoites reproduce asexually in RBC’s and lyse cells at 48 or 72 hr intervals (species specific); coordinated lysing of cells causes periodic chills and fever.
Some merozoite infect new RBC’s, some divide to form gametocytes; gametocytes that infect a biting female mosquite compete the life cycle in her body.
Gametocytes form gametes and fertilizationoccurs in mosquito digestive tract; zygote is the only dipolid stage in the life cycle
Oocyst develops in wall of mosquito gut. Thousands of sporozoites develop in the oocyst and then migrate to mosquites salivary gland
Merozite
Apex
Red blood cell0.5 um
Plasmodium Infection InterpretationStrain Rate
cp26 Low
cp29 LowHLA-B53 binds to these proteins. Immune resonse is effective
cp26 and cp29 strains together
HighImmune response fails when these strains infect the same person
cp27 Highcp28 Average HLA-B53 does not bind to these
proteins. Immune response is not as effective
Co-evolutonary Arm RaceStrong association between HLA-B53 allele and protection against malaria found in West Africa
HLA-B53 in infected liver cells bind to particular sporozoite protein and display protein-protein complex before they produce merozoites
Recognition breaks down in people co-infected by certain strains
NS leads to iimmune system adaptations for protection – and to pathogen adaptations to overcome them
HUMAN IMMUNE-DEFENSE AGAINST PLASMODIUM
Source: Freeman 2002
Evolution of Land Plants
Artist’s rendering of Carboniferous forest in a tropical river delta. Most of the plants depicted here were nonseed tracheophytes 10 to 20 meters tall. In the distance, earl seed plants up to 40 meters tall towered over the forest.
Prior to the origin and diversitication of green plants in the mid-Silurian(~450 mya), multicellular life was virtually entirely apapted to, and confined to, aquatic lifestyles
Contintnenal Land Masses virtually unoccupied by multicellular organism– multicellular-based ecosystems constituted tremendous potential for adaptive radiation
Terrestrial life in a gaseous medium required evolutionary solutions to structural, physiological and ecological challenges; Many of these innovations can be regarded as exaptations of pre-existing traits of green algae from which green plants diverged
Kingdom Plantae is monophyletic assemblage, descended from Green algae
Chlorophyll a and b are homogous in Chlorophyta, Charaphyta and Plantae
Currently includes over 250,000 described species classified in 12 monophyletic phyla
Most are terrestrial, some are secondarily aquatic
Diversification in plants involved successive adaptive radiations following evolution of key innovations that increased efficiency in an gaseous (air) and solid (Earth) environment
Major problems were posed by gravity and by water loss/availability
-maintain body structure – resist gravity-obtain, transport and retain water-fertilize eggs and produce and protect embryos
Major evolutionary innovations included
-dimorphic body-waxy cuticle and stomata-vascular tissue; -jacketed sex organs; antheridia and -archegonia-life history dominated by sporophytegeneration-seeds embryo with nutritive tissue in protective covering-flowers; vehicles for pollination strategiesGreen algae of phylum Chlorophyta, such as Chara sp.,
are most likely ancestors of plants. Copyright BPS.
top related