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Chapter 19: Algae and the Origin of Eukaryotic Cells (Characters of…
Chapter 19: Algae and the Origin of Eukaryotic Cells
Origin of Eukaryotic Cells
Nuclear Structure and Division
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Most of the DNA of eukaryotes are located within a nucleaus
The nuclei of plants are virtually the same to those of animals and fungi in
Metabolism
Mitosis
Structure
Meiosis
The DNA of prokaryotes lies directly in the cytoplasm; no nucleus is present
Its plasma membrane expand;
The DNA circles attached to it are separated from each other by cell growth
As a prokaryotic cell grows -
Organelles
Prokaryotes lack membrane-bounded organelles
Flagella and cilia are remarkably uniform in eukaryotes
Consisting of a 9+2 arrangement of microtubules
Plastids and mitochondria also have 70S ribosomes instead of 80S ribosomes
Their cytoplasm is rather homogenous, containing only ribosomes and storage granules
DNA Structure
Prokaryote DNA contains few introns, and mRNA processing is relatively simple
In Eukaryotes
DNA is more elaborately packaged, being complexed with nucleosome histones and forming chromosomes
Each DNA molecule is long, capable of carrying thousands of genes
Many eukaryotic genes contain introns, and large segments of DNA do not code for any type of RNA
Each genome is just a short circle of DNA
Often containing only approximately 3,000 genes
In prokaryotes, DNA is "naked," not complexed with proteins, its numerous negative charges being neutralized by calcium ions instead
Origin of Mitochondria and Plastids: The Endosymbiont Theory
Types of Cytokinesis
Several types of cytokinesis occur in algae
In some green algae, cytokinesis occurs by a phycoplast
A group of microtubules that helps with cell division after mitosis in specific algae.
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The division of the cell cytoplasm that usually follows mitotic or meiotic division of the nucleus.
The differences between prokaryotes and eukaryotes are deep seated, involving many of the most basic metabolic processes and cellular organization
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Characters of Various Groups of Algae
Red algae are described after that, and then attention is turned to the lines that resulted from the secondary endosymbiosis of plastids
The descriptions of algae will begin with green algae because they are in the clade the encompasses not only the ancestors of embryophytes but also the primary endosymbiosis that originally produced chloroplasts
Division Euglenophyta
Euglenoids
There are many nonpigmented euglenoids
The photosynthetic species have pigments similar to green algae
Seem to extremely sufficient
Phylum Protozoa
Division Pyrrhophyta
Also called Dinoflagellates
Lack histones
Have intranuclear mitosis with chromosomes that never decondense during interphase
Division Chrysophyta
This is a diverse group, sometimes divided into several separate divisions, sometimes included with the brown algae
Diatoms, golden-brown algae, yellow-green algae
Division Chlorophyta
But very homogeneous and well-defined biochemically
They are universally considered to be the ancestors of true plants
Green algae are extremely diverse structurely
Green Algae
Green Algae
Diversity is tremendous
Examining it will give you a basis for understanding the diversity possible among living organisms
Body Construction in Green Algae
Filamentous Body
Membranous Body
Nonmotile Colonies
Parenchymatous Body
Motile Colonies
Coenocytic Body
Green algae have remarkable developmental and metabolic plasticity
They are resilient and survive many types of disturbances and changes
Life Cycles of Green Algae
Filamentous Species
Unicellular Species
Dibiontic Life Cycles
Motile Colonial Species
Monobiontic Life Cycles
Constitute an extremely important group
Green Algae and Embryophytes
Archaeplastids
The clad is based on the original plastid endosymbiosis
Primoplantae
Streptophytes
A clad of plants
