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Algae and the origin of eukaryotic cells (Characteristics of various…
Algae and the origin of eukaryotic cells
Origin of eukaryotic cells
Nuclear structure and division
DNA of prokaryotes lies in nucleus, separated from cytoplasm by 2 nuclear membrane
Nuclei of dinoflagellates have no histone
DNA of prokaryotes lies directly in cytoplasm, no nucleus
Some have both intracellular and extracellular spindle
Organelles
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All eukaryotes have nuclei and mitochondria, plants and algae have plastids
Flagella and cilia are remarkably uniform in eukaryotes
Prokaryotes lacks membrane bound organelles
DNA structure
In eukaryotes
Each DNA is long, capable of carrying thousands of genes
At lease 2 occur per haploid set, and 10-20 are more common
More elaborately packaged
In prokaryotes
Contains few introns, and mRNA processing is relatively simple
Each genome is just a short circle of DNA
DNA is naked, not complexed with proteins
The Endosymbiont theory
Deals with the origins of mitochondria and chloroplasts
Mitochondria and chloroplasts are believed to have developed from symbiotic bacteria
Evolutionary theory of the origin of eukaryotic cells from prokaryotic organisms
Characteristics of various groups of algae
Do have chlorophyll and other pigments for carrying out photosynthesis
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A nucleus is present, and multiple chromosomes are observed in mitosis
Algae are eukaryotic organisms that have no roots, stems, or leaves
Consist of seven divisions of distantly related organisms
some species have flagella with the “9‐plus‐2” pattern of microtubules
Algae are most prominent in bodies of water but are also common on land
Green algae include many single-celled, motile organisms
Red Algae
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Photosynthetic pigments of red algae are chlorophylls a & d
Red algae are 4,000 species of mostly marine algae
Example-: Pleonosporum spp, Porolithon spp, Chondrus crispus
Lack flagella, and they store energy as a specialized polysaccharide
Green Algae
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Life cycle
Sometimes, spores are formed from the meiotic products
After fertilization the zygote soon goes through meiosis
Representative genera
It has mitosis, meiosis and syngamy
Cells recognize each other by reaction at the tip of their flagella
Unicellular species, Chlamydomonas
Bogy construction
Nonmotile colonies
Filamentous body
Motile colonies
Membranous body
Parenchymatous body
Siphonous body
Green algae and embryophytes
Embryophytes are complex multicellular eukaryotes
Embryo is retained within maternal tissue, which include the bryophytes and tracheophytes
Form monophyletic clad and called Streptophytes
Brown algae and Heterokonts
Yellow-green algae
Thought green algae until chlorophyll c was discovered
Eg-: Vaucheria, Zooxanthella, Xanthophyta.
Occur mostly in freshwater
Diatoms
Eg-: phytoplankton
responsible for 20% of global carbon fixation and 40% of marine primary productivity
A single-celled alga which has a cell wall of silica
Golden-brown algae
Consist of 33 genera and some 1,200 species of algae
Has two hair-like short tails used for swimming and to attach to things
Golden algae is also commonly used to refer to a single species, Prymnesium parvum
Brown algae
Multicellular, from branched filaments to massive and complex kelp
Reproduction is Isogamous, anisogamous, or oogamous.
1,100 and 40,000-100,000 species of unicellular algae
Dinoflagellates
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unicellular protists that can be identified using the light microscope
Oomycetes
Most are marine plankton, but they also are common in freshwater habitats
large group of flagellate eukaryotes
