Please enable JavaScript.
Coggle requires JavaScript to display documents.
Algae and the Origin of Eukaryotic Cells (Green Algae (Body Construction…
Algae and the Origin of Eukaryotic Cells
Origin of Eukaryotic Cells
DNA Structure
In prokaryotes DNA is "naked"
In eukaryotes DNA is elaborately packaged
Nuclear Structure and Division
DNA prokaryotes
Directly in cytoplasm
Nuclei of plants and animals
Virtually identical
DNA eukaryotes
Located within a nucleus
Separate from cytoplasm
Organelles
Prokaryotes lack membrane-bounded organelles
Flagella and cilia uniform in eukaryotes
Origin of Mitochondria and Plastids
The Endosymbiont Theory
Plastids and mitochondria
Prokaryotes living inside eukaryotes
Prokaryotes represent first organisms
Became eukaryotes gradually
Autogenous theroy
Origin of Mitochondria
Prokaryotic cells evolved to eukaryotic features
#
Origin of Plastids
Primary endosymbiosis
Gave rise to a clade containing
Red algae
Green algae
Small group called glaucophytes
Secondary endosymbiosis
Other lines of algae
Group of early eukaryotes
Heterokonts
Types of Cytokenesis
Several types occur in algae
Cell division in algae is like plants
In green algae cytokinesis occurs by phycoplast
Microtubules oriented parallel to the plane
Where the new wall will form
Green Algae
Constitute an extremely important group
Remarkable developmental and metabolic plasticity
Resilient and survive many disturbances
Body Construction in Green Algae
Numerous green algae are unicellular
Motile colonies
#
Cells adhere loosely
Resulting structure is a colony
Not an individual organism
Nonmotile colonies
Cells lose their flagella or never develop them
Filamentous body
Cells are held tightly by a middle lamella
If all cells divide transversely
Portions of the body differ from others
Membranous body
Orientation of cell divisions all new walls occur in two planes
Sheet of cells
Parenchymatous body
Cell division occurs regularly in all three planes
Bulky and three-dimensional
Coenocytic or siphonous body
Karyokinesis occur without cytokineses
Giant multinucleate cell results
Life Cycles of Green Algae
Angiosperm type of life cycle
Dibiontic
Alternation of generation between haploid and diploid
Both stages are multicellular
Alternation of isomorphic generations
Monobiontic species
Specialization occurs
Only one free-living generation exists
Earliest stages of evolution of sexual reproduction
Gametes were isogamous
Identical
Oogamy
Anisogamy
Slight differences in gametes
Produced in gametangia
Spores were formed in sporangia
Representative Genera of Green Algea
Unicellular species
Motile Colonial Species
Filamentous species
Undergo conjunction
Zoospores
Four haploids
Laminar species
Coenocytic species
Parenchymatous species
Charophytes
Cell division by means of phragmoplast
Green Algae and Embryophytes
Streptophytes
Monophyletic clade
Considered true plant
Brown Algae and Their Relatives: The Heterokonts
Brown Algae
Almost exclusively marine
Only a few fresh water species are known
Prefer cold water that is agitated
Found on rocky coasts
Growing in littoral zone
Region between low tide and high tide
Storage product
Laminarin
34% of body weight
Diatoms
Distinct morphology
Each wall composed of two halves
Deposits
Diatomaceous earth
Can become hundred of meters thick
Yellow-Green Algae
#
Occur mostly in fresh water
Thought to be green algae
Until chlorophyll c was found in them
Golden-Brown Algae
Consists of about 70 genera
Cells may be uniflagellate or biflagellate
Coccolithophorids
Relatively inert and do not decompose
Dinoflagellates
Have many unusual characteristics
Nuclear envelope and nucleolus persists
Throughout mitosis
Typical spindle does not form
Oomycetes
Thought to be fungi for many years
Diverse in structure and nutrition
