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The Importance of Plants, their origins and ways of life
Objectives of the lecture:
1. Describe some ways that plants provide the foundation of life.
2. Provide the basic sequence of plant evolution and its relationship
to changes in earth landforms and environment.
3. Describe the endosymbiosis theory.
4. Identify important adaptations of plants that enable them to live on
land.
Text book pages:
548-553
604, 609,
626-639,
Ginkgo biloba
Motile male sperm
The only surviving species of a diverse group originating in
the Permian, closely related fossils 200m ybp
Illustration in Pen Tsao
Kang Mu of Ginkgo with
seeds (1578)
Ginkgo biloba extract (Gbe) and two ingredients, bilobalide
and ginkgolide B, are part of a review of botanicals being used
as dietary supplements in the United States. Deregulation of
botanicals now permits Gbe to be sold as a dietary
supplement to a willing public eager to "improve brain
functioning" or "promote radical scavenging activity".
Ginkgo biloba- the wonder drug!
Medicinal!!
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you're wrong. Ginkgo can be a
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Plan for Biology 220 Spring 2010
Wk
5
6
7
8
9
10
Th April 29
M May 3
Tu May 4
W May 5
Th May 6
M May 10
Tu May 11
W May 12
Th May 13
M May 17
Tu May 18
W May 19
Th May 20
M May 24
Tu May 25
W May 26
Th May 27
M May 31
Tu June 1
W June 2
Th June 3
W June 9
Importance of plants, their origins and problems.
Exam
The Dicot plant, morphology, meristems, cell types, and tissues
Cellulose, wood structure and water transport in the plant
Structure and function of the leaf.
Stomata: structure, control, CO2 exchange and transpiration
Photosynthesis I: Chemistry, chloroplast, chlorophyll, action spectra
Photosynthesis II: continued
Photosynthesis III: C4 and CAM photosynthesis, photo-inhibition
Photosynthesis IV: canopy photosynthesis and global change.
Translocation
Plant nutrition
Exam #3 on lectures May 3 through May 17.
Plant reproduction and diversity.
Plant reproduction continued
Seed formation, dormancy and germination.
Plant hormones and development
Memorial Day
Plant hormones and development continued.
Fungi, decomposition, mycorrhizae, and lichens.
Fungi continued.
Final Exam: Cumulative Plant 2:30-4:20.
Why are plants important for human life?
Page 627-630
How do they do that?
1. Plants produce oxygen
2. Plants build soil
3. Plants hold soil
4. Plants hold water
Green plant photosynthesis
Rock weathering and carbon build-up and decomposition
Root strength and ramification through soil
The “reservoir” function of plants and soil
4. Plants moderate the local climate
Evapo-transpiration and particle capture
6. Plants provide food, fuel and fibre
7. Plants provide drugs
Next slide
Figure 30-4-Table 30-1
Know 5 of these
What functions might these substances have in plants?
Opium poppy, Papaver somniferum
The opium poppy is the principal source of all natural opiates. Opiates are
extracted from opium and poppy straw. Opium is the latex harvested by
making incisions on the green capsules (seed pods).
Evolution?
Mature seed pod of the opium poppy (Papaver somniferum) with milky latex
sap dripping from a recent cut. The latex sap contains a mixture of naturallyoccurring narcotic alkaloids including morphine and codeine. Morphine is
acetylated to produce diacetylmorphine, better known as heroin.
Figure 30-8
Seed fern leaves
Cooksonia pertoni
Origin
of land
plants
475 mya
Carboniferous:
Lycophytes and
horsetails abundant
Silurian-Devonian
explosion
444
First evidence
of land plants:
cuticle, spores,
sporangia
359
Most major
morphological
innovations:
stomata, vascular
tissue, roots, leaves
Cones from Araucaria mirabilis,
an early gymnosperm
Extensive coalforming swamps
Angiosperms abundant
Gymnosperms abundant
299
145
Both wet and dry environments
blanketed with green plants for
the first time
Archaefructus, an early angiosperm
Present
Diversification of flowering plants
History of evolution of major plant types on land
Life’s Timeline: The Precambrian
How did multi-cellular green organisms develop?
How did multi-cellular green organisms develop?
Endosymbiosis
An endosymbiont is any organism that lives within the body or cells of
another organism, i.e. forming an endosymbiosis (Greek: ἔνδον endon
"within", σύν syn "together" and βίωσις biosis "living").
Examples:
nitrogen-fixing bacteria (called rhizobia) that live in root nodules
on legume roots,
single-celled algae inside reef-building corals,
and bacterial endosymbionts that provide essential nutrients to
about 10%–15% of insects.
Andreas Schimper observed in 1883 that the division of chloroplasts in green
plants closely resembled that of free-living cyanobacteria (blue-green algae)
and tentatively proposed that green plants had arisen from a symbiotic union
of two organisms.
Margulis and Sagan (2001) "Life did not take over the globe by combat, but by networking"
Page 604
THE ENDOSYMBIOSIS THEORY FOR MITOCHONDRIA
AND CHLOROPLAST EVOLUTION
Proposed evolutionary origin for mitochondria
Aerobic
bacterium
Anaerobic
eukaryote
Pyruvate
and O2
ATP
1. Eukaryotic cell
2. Bacterium lives
3. Eukaryote supplies
surrounds and
engulfs bacterium.
within eukaryotic
cell.
bacterium with protection
and carbon compounds.
Bacterium supplies
eukaryote with ATP.
Each would have performed mutually benefiting functions from their symbiotic
relationship.
The aerobic bacteria would have handled the toxic oxygen for the anaerobic
bacteria, and the anaerobic bacteria would utilize ingested food and protected the
aerobic "symbiote".
p609
Secondary Endosymbiosis
Serial ingestion of photosynthetic
bacteria by endosymbiontic
prokaryotes or eukaryotes led to the
ancestors of eukaryotic plants.
As the ingested photosynthetic
bacteria adapted to the ingesting
prokaryotic host cell, plastids, such
as the chloroplast evolved.
Primary plastids are found in some
algae because their plastids are
derived directly from a
Cyanobacterium.
All other lineages of plastids have arisen through secondary (or tertiary)
endosymbiosis, in which a eukaryote already possessing plastids is engulfed
by a second eukaryote. Considerable gene transfer has occurred among
genomes and, at times, between organisms.
Mitochondria and chloroplasts contain DNA
The most convincing evidence of the descent of these organelles from
bacteria is the position of mitochondria and plastid DNA sequences in
phylogenetic trees of bacteria.
Mitochondria have sequences that clearly indicate origin from a group
of bacteria called the alpha-Proteobacteria.
Chloroplasts have DNA sequences that indicate origin from the
cyanobacteria (blue-green algae).
There are also organisms alive today, called
living intermediates, that are in a similar
endosymbiotic condition to the prokaryotic cells
and the aerobic bacteria. For example, the giant
amoeba Pelomyxa lacks mitochondria but has
aerobic bacteria that carry out a similar role. A
variety of corals, clams, snails, permanently
host algae in their cells.
Multiple nuclei
Multiple ingestions lead to a
variety of endosymbiotic
structures
Figure 30-39
Plant of the Day
Lycopodium species
Life’s Timeline: The Paleozoic Era
Atmospheric O2 and CO2 concentrations through geological time
Widespread arthropod
gigantism
Origin of
insect flight
Carboniferous coal
formation
70cm wing dragonfly
1m long millipede
and giant spiders
Denser atmosphere,
Greater O2 partial pressure
CO2 removed from the
atmosphere by plant
synthesis and limestone type
rock formation
Devonian plant community found at Rhynie, in Scotland.
marsh, 370-380 million years ago.
A reed-like
Asteroxylon
MAIN FEATURES
Simple dichotomous branching
Sporangia
15 to 30 cm tall
No roots
Stomata with guard cells
Most had a central vascular strand
Cuticle
Devonian
plant
community
Asteroxylon had leaves –without a
vascular connection
Life’s Timeline: The Mesozoic Era
Life’s Timeline: The Cenozoic Era
Adaptation to living on land
The land that plants colonized was hostile to life.
Soil development was minimal.
Land plants required several adaptations to be successful that require
multi-cellular tissues
mechanical strength for support,
exposed light catching surfaces,
anchoring system,
conducting system for water,
system for obtaining mineral nutrients,
a way to restrict water loss in desiccating air,
a means of reproducing and dispersing on land
Things you need to know ...
1. Why plants are important for human life.
2. Some drugs derived from land plants.
3. The geological time periods when plants of different types were
abundant and how this relates to the environment of those periods.
4. The adaptations shown by plants to living on land.