Chapter 19: Algae and the Origin of Eukaryotic Cells

Origin of Eukaryotic Cells

Characters of Various Groups of Algae

Green Algae

Nuclear Structure and Division #

Organelles

DNA Structure

Origin of Mitochondria and Plastids: The Endosymbiont Theory

The differences between prokaryotes and eukaryotes are deep seated, involving many of the most basic metabolic processes and cellular organization #

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Prokaryote DNA contains few introns, and mRNA processing is relatively simple

In Eukaryotes

Each genome is just a short circle of DNA

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In prokaryotes, DNA is "naked," not complexed with proteins, its numerous negative charges being neutralized by calcium ions instead

Often containing only approximately 3,000 genes

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

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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

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 -

Metabolism

Mitosis

Structure

Meiosis

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Prokaryotes lack membrane-bounded organelles

Flagella and cilia are remarkably uniform in eukaryotes

Plastids and mitochondria also have 70S ribosomes instead of 80S ribosomes

Their cytoplasm is rather homogenous, containing only ribosomes and storage granules

Consisting of a 9+2 arrangement of microtubules

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Types of Cytokinesis

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Several types of cytokinesis occur in algae

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The division of the cell cytoplasm that usually follows mitotic or meiotic division of the nucleus.

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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Red algae are described after that, and then attention is turned to the lines that resulted from the secondary endosymbiosis of plastids

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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

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Euglenoids

There are many nonpigmented euglenoids

The photosynthetic species have pigments similar to green algae

Seem to extremely sufficient

Phylum Protozoa

Division Pyrrhophyta

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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

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Diatoms, golden-brown algae, yellow-green algae

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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

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Green Algae

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Diversity is tremendous

Body Construction in Green Algae

Green algae have remarkable developmental and metabolic plasticity

Life Cycles of Green Algae

Constitute an extremely important group

They are resilient and survive many types of disturbances and changes

Examining it will give you a basis for understanding the diversity possible among living organisms

Filamentous Body

Membranous Body

Nonmotile Colonies

Parenchymatous Body

Motile Colonies

Coenocytic Body

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Filamentous Species

Unicellular Species

Dibiontic Life Cycles

Motile Colonial Species

Monobiontic Life Cycles

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Green Algae and Embryophytes

Archaeplastids

Streptophytes

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A clad of plants

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The clad is based on the original plastid endosymbiosis

Primoplantae