Download The Protista: Evolution`s 2nd Wave Evidence for the Endosymbiotic

The Protista: Evolution’s 2nd Wave
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100,000 living species, 35,000 fossilized
members
Ancestors to metazoans: plants, fungi,
animals
Low specialization, high complexity
The origins of Eukaryotic complexity:
Two trends allowed the eukarya to arise
from the eubacteria
υ Compartmentalized cell structure
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Increased genomic size
The Evolution of Compartmental Organellar
Structure: The Autogenesis Theory
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1. Increased membrane surface area
2. Compartmentalization w/ regional specialization:
Nuclear membrane, endoplasmic reticulum, Golgi
apparatus, others
Evidence for the Endosymbiotic
Theory:
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1. size
2. homology to prokaryotic
plasma membranes
3. replication: binary fission,
not de novo synthesis
4. DNA structure: circular
loop and packing
5. complete “intracellular”
intracellular”
protein synthesizing
machinery
6. ribosomal structure,
sequence and Abx
sensitivity
Traditional hypothesis for how the three domains
of life are related. Note how the Eukarya are
monophyletic.
monophyletic.
The Origins of Eukaryotic Diversity: K. Protista
ν I. Evolutionary Trends:
Proks.
Proks. to Euks.
Euks.
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A. Comparmentalized Cell
Structure
Φ Autogenesis Theory
Φ Serial Endosymbiotic
Theory
B. Genome Size and Sex
Φ Archezoans:
Diplomonads
Φ 3 Life Cycles: Meiosis,
sex and genetic variation
Evolution of Compartmentalized Structure:
Serial Endosymbiotic Theory - Lynn Margulis
1. Parasites or prey are internalized
2. Mutualistic relationship develops
Serial Endosymbiosis: Primary and
secondary endosymbiosis form the basis
for the origin of algal diversity
A hypothetical proposal toward the rapid evolution
of complex eukaryotic structure and diversity:
An alternative “polyphyletic” hypothesis for
how the three domains of life are related
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Consider the concept of
“horizontal evolution”
evolution” - the
wholesale incorporation of
genomes
Consider the evolutionary
process brought about by SET:
“Symbiogenesis”
Symbiogenesis” - the origin or
new organelles or life forms
via symbiotic relationships b/w
previously independent
organisms (networking instead
of competition)
Margulis - Euks are better
conceived as microbial
communities rather than as
individuals
Margulis - Among early euks,
euks,
SET has greater importance
than random mutations
Protistans are NOT monophyletic
Archaebacterium:
provides cytoplasm
Autogensies:
expands
mesosome to
provide
membranes
Daptobacter or Bdellovibrio
bacteria: provide O2respiring functions
(mitochondria)
Cyanobacteria: provide
photosynthetic
functions
Protists w/ aerobic
metabolism
Fungi
Chloroplast
containing
algae
Animals
Plants
The Nuclear Lineage: Genomic Size,
Mitosis, Meiosis and Sex
Among bacteria: Is more DNA
adaptive?
Archezoans: Giardia a
diplomonad
What are the advantages of
diploidy?
diploidy?
υ More genes and vegetative
life style
υ Ability to mask bad genes
and test new genes
υ Prerequisite for sexual
reproduction
3 Patterns of cell division:
υ Binary fission
υ Mitosis
υ Meiosis
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Note: These groups only represent a sample of protist diversity; many
other lineages are not shown on the tree.
A comparison of mitosis and meiosis:
Identical duplication versus guaranteed variation through
recombination and gametic fusion
Eubacterium: spirochete
provides undulopodium
(flagellum) and
eventually mitosis
The Evolution of Sexual Reproduction:
Life Cycles of Protists and Other Eukaryotes
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1. The Gametic Cycle: diploid dominant
υ protozoans, all animals, a few algae
2. The Zygotic Cycle: haploid dominant
υ some fungal protists, fungi, some algae
3. The Sporic Cycle: Alternation of Generations
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algae and higher plants, 1n and 2n adult
stages, shift in dominance
3 Patterns of Sexual Reproduction
2n adult
meiosis
mitosis
GAMETIC
n gametes
2n zygote
2n adult
mitosis
meiosis
2n zygote
SPORIC
n adult
mitosis
n gametes
mitosis
n spores
ZYGOTIC
meiosis
n gametes
2n zygote
mitosis
n adult
n spores
mitosis