Evolution of multicellular plants

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Evolution of multicellular plants
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Evolution of a multicellular organism from a
unicellular protist
Fig 16.27
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Going from unicellular to multicellular
Going from unicellular to multicellular
Advantages
Organization and specialization of plant parts
Permanent colonization of land becomes possible
Disadvantages
Loss of mobility evolution of specialized plant
parts is essential for nutrition and reproduction
Reduction in individual plant growth rate
Challenges
Communication between cells
The development of tissue systems
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Photos of slime moulds
Photos of slime moulds by Clive Shirley
Organisms with both unicellular and multicellular
stages
http//www.hiddenforest.co.nz/slime/intro.htm
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Slime moulds have structural adaptations
Slime moulds have structural adaptations and life
cycles that enhance their ecological role as
decomposers
Two main groups. 1 - Plasmodial slime moulds or
true slime moulds, are a large single-celled mass
with thousands of nuclei called a plasmodium
formed when individual flagellated cells swarm
together and fuse into one large bag of cytoplasm
with many diploid nuclei. 2 - Cellular slime
moulds spend most of their lives as separate
single-celled amoeboid protists, but upon the
release of a chemical signal, individual cells
aggregate into a great swarm, known as a
pseudoplasmodia and eventually muticellular slugs.
http//www.wvonline.com/myxo/intro.htm
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The life cycle of a cellular slime mold,
Dictyostelium
The life cycle of a cellular slime mold,
Dictyostelium
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Film of Dictyostelium
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Characteristics of Dictyostelium
Dictyostelium amoebae grow as separate,
independent cells but interact to form
multicellular structures when challenged by
adverse conditions such as starvation. Up to
100,000 cells signal each other by releasing a
chemo-attractant and aggregate to form a mound.
Subsequent processes depend on cell-cell
communication. Many of the underlying molecular
and cellular processes appear to have arisen in
primitive precursor cells and to have remained
fundamentally unchanged throughout evolution.
Basic processes of development such as
differential cell sorting, pattern formation,
stimulus-induced gene expression, and cell-type
regulation are common to Dictyostelium and
metazoans.
A model organism for bio-medical research.
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Alternation of Generations
Alternation of Generations
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Origin of alternation of generations?
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Sizes and morphology of generations
Relative sizes and general morphology of
gametophyte and sporophyte generations in
bryophytes, ferns and seed plants
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The life cycle of Ulva
The life cycle of Ulva
Fig 16.26C
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Evolution of a multicellular organism from a
unicellular protist
Fig 16.27
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Sections you need to have read
16.21 16.22 16.23 16.24 16.25 16.26 16.27
16.28
Courses that deal with this topic
MICROM 435 Microbial Ecology