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Algae & the Origin of Eukaryotic Cells (Euglenoids (example Euglena,…
Algae & the Origin of Eukaryotic Cells
Origin of Eukaryotic Cells
Nucleus Structure & Division
as prokaryotic cells grows
its plasma membrane expands
gap may form in nuclear envelope & bundles of microtubules
nuclei of plant is identical to nucleus of animals & fungi
unusual nuclear characteristics may represent lines of evolution
Organelles
only 70s ribosomes
80s cytoplasmic & 70s in organelles ineukaryotes
prokaryotes lack membrane bound organelles
DNA Structure
Prokaryotes DNA
introns are rare
histone is absent
small circles
Eukaryotes DNA
introns are common
histone is present
chromesomes
Origin of Mitochondria & Plastids: The Endosymbiont Theory
origin of plastids
types of cytokinesis
origin of mitochondria
Euglenoids
example Euglena
swim actively with two flagella
36 genera & 800 species
green photosynthetic euglenoids have chlorophyll a & b
carbohydrate is stored as glucose polymer paramylon not as starch
Brown Algae & their relatives
The Heterokonts
Diatoms
200 genera & 5000 species
they die & decomposed into ocean floor known as diatomaceous earth
Yellow-Green Algae
mostly freshwater
Brown Algae
mostly marines
found in rocky coasts in littoral zone
Golden-Brown Algae
consist of about 70 genera & 325 species
Red Algae
red color is due to presence of phycoerythrin
they are often purple, brown or black due to additional presence of phycocyanin
constitue large group of algae
excess photosynthate stored in Floridian starch
life cycle is poorly known
Dinoflagellates
Oomycetes
oomycetes are diverse in structure & nutrition
lack chloroplast
are parasitic or saprophytic
sexual reproduction in most of oomycetes
Green Algae
Life Cycles
monobiontic species
haploid phase
represent the individual
diploid phase
zygote, capable of meiosis
dibiontic species
there is no alternation of generation
alternation of isomorphic generation
during the easiest stage of evolution
gametes were isogamous (identical) but anisogamy(slight difference in gamete)
gametes formed in gametangia
spores formed in sporangia
Representative Genera
motile colonial species
filamentous species
unicellular species
laminar species
coenocytic species
parenchymatous species
Body Construction
filamentous body
if cell heads tightly by middle lamella & cells divides transversely
membraneous body
if orientation of cell divisions is controlled precisely
non-motile colonies
occurs this if cell loose their flagella
parenchymatous body
if cell division occurs regularly in all three planes , a bulky 3-dimensional
motile colonies
there may be differentiation into 2 or 3 distinct cell type
coenocytic or siphons body
if karyokinesis occurs without cytokinesis & giant multinucleate cells results
Green Algae & Embryophytes
archaeplastids
monophyletic clade consist of red algae + green algae + embryophytes & glaucophytes
streptrophytes
monophyletic clade
