Plant Evolution
http://www.earthtimes.org/climate/canplants-evolve-fast-cope-climate-change/269/
• Darwin (1859) "If variations useful to any
organic being do occur, individuals thus
characterized will have the best chance of
being preserved in the struggle for life, and
from the strong principle of inheritance they
will tend to produce offspring similarly
characterized."
http://www2.estrellamountain.
edu/faculty/farabee/BIOBK/bio
bookdiversity_5.html
http://eclecticlimpet.wordp
ress.com/
Plant Evolution
• We will look at leaf and
reproductive evolution
• Woody Angiosperms Bark bearing flowering
plants
http://arboretum.harvard.edu/visit/hotline/
Leaves
• Earliest land plants had stomata on cuticles on
their stem
• Were leafless or had spine like parts
• Photosynthetic leaf like structures began to
appear ~390 - 354 million years ago
• Leaves were divided into 2 types: microphylls
& megaphylls
– These different types can still help identify leaves
today
Leaf Type
Microphylls
• small leaves that grow
directly from the stem
Megaphylls
• attached to the stem by a
petiole
http://www.studyblue.com/notes/note/n/bota
ny-test-1/deck/6281065
Leaf Evolution
• Where discovered?
– Russia - Asia - Portugal - USA
• Why compare leaves?
http://en.wikipedia.org/wiki/Photo
synthesis
– Shape of leaf features will tell us whether fossils
(extinct) live in a similar environment to modern
(extant) plants
Leaf Evolution
• Features we look at:
• - Presence or absence
of drip tips
– What might this tell us
about a climate?
http://www.imagejuicy.com/images/plants/c/c
eratozamia/8/
Leaf features
• Entire / dissected margins (teeth)
1. Smooth (entire). 2. Serrate. 3. Double serrate. 4.Saw-shaped. 5. Toothed. 6.Crenate. 7. Lobed.
8. Parted. 9. Pinnately (like a feather) incised. 10. Palmately (like a hand) incised. 11.Palmately
(like a hand) lobbed.
http://www.vcbio.science.ru.nl/en/virtuallesso
ns/leaf/dicot/
Size of leaf blade
http://www.vectorfree.com/leaf-collection
Creative Thinkers
• Imagine different parts of the world and then
think of the plants / leaves in that area.
– Where else might you see these leaves?
– What kind of climate conditions do you associate
with these areas?
http://tofspot.blogspot.ie/2012/04/where-doyou-get-your-ideas.html
Leaf Analysis
• Using modern plants to predict mean average
temperature
• If we can do it using modern plants, we can do
the same using fossils for times past
• 2 methods
– Leaf margin analysis
– CLAMP
What kind of information are we
looking for?
• A connection has been found between leaf
shape and climate
– Different plants grow in different biomes e.g. no
palm trees in the Arctic
– Toothier plants tend to live in colder climes
http://www.grantsgardens.com/blog/post/496/Know-Your-Palm-Trees-Bismarck-Palm--Cuban-Royal-Palm-and-Canary-Island-DatePalm#.UfZpJ42Hs3w
Interactive Leaf Analysis
• http://www.smithsonianeducation.org/studen
ts/ideaLabs/prehistoric_climate_change.html
http://thepetmandlma.wikispaces.com/What+i
s+Leaf+Margin+Analysis%3F
Leaf Margin Analysis
• Practical:
– Part 1: Nature walk &
gather leaf samples (20 –
30 samples)
– Part 2: Analysis of leaves
• Toothed
• Untoothed
Remember: leaves gathered
should be from woody
angiosperms
Leaf Margin Analysis
• Formula: y = 3.2093x - 2.7844
• Y = the percentage of leaves that are untoothed
in the formula.
• X = the mean annual temperature that you wish
to work out.
• Rework the formula to find a value for X, this is
your answer
• Be sure to check online if your answer is similar
to a given mean annual temperature for the area
• http://www.met.ie/default.asp is an example
Leaf Margin Analysis Example
• 30 leaf samples
– 24 toothed
– 6 untoothed
– 6 / 30 = 20%
– Fill in formula using this
value for y
– Y = 3.2093x – 2.7844
• Rearrange maths
formula to find x
• X = 22.7844 / 3.2093
• X = 7.01 degrees Celcius
• Check this with your
local annual mean
temperature to
compare results
http://www.q4s.eu/GB/resources/self_review/numeracy.html
Method 2: What is CLAMP?
• - Climate Leaf Analysis Multivariate Programme
• - uses leaf characters to calculate the mean
annual temperature of a site where plants are
growing
• - can therefore be used with fossils from a certain
area to predict the temperature of that time
• Example: Leaves of woody angiosperms tend to
have more "leaf teeth" in colder climates than in
warmer ones
CLAMP
• CLAMP is more detailed than Leaf Margin
Analysis alone – it takes into account much
more than just the teeth / no teeth of a leaf
• Several characteristics are looked at – shape,
the way the leaf joins the petiole, the tip of
the leaf.
• Leaves are never just leaves again after you do
this analysis!
Plant Evolution: Reproduction
Plant Reproduction and Evolution
• Development of seeds has been recorded ~
395 – 286 million years ago
• This meant:
– plants no longer needed excess water for sexual
reproduction
– Seed gave protection for the developing embryo
– Nutrients were provided within the seed
As a result, plants began to move from water
sources to drier, inland environments
Former Plant Reproduction
• Plants that produced one spore were known
as homosporous (1 spore size)
• Plants that produced two spores were known
as heterosporous (2 spore sizes)
• Important development for the plant kingdom
– Larger megaspore  ovule (female)
– Smaller microspore  pollen (male)
Ovule (Female)
• Megaspores:
– 3 out of 4 spores were aborted to allow all energy
into one functional megaspore
– An outer, protective seed coat soon followed
http://faculty.clintoncc.suny.edu/faculty/micha
el.gregory/files/bio%20102/bio%20102%20lec
tures/seed%20plants/seed%20plants.htm
Pollen (Male)
• Pollen evolved in such a way that allowed it to
produce a tube towards the female ovule
• Plants had several techniques to ensure pollen
and ovule could meet
– A funnel to attract wind-borne pollen
– Hairs lining the integument lobes
– Sticky pollination droplets (on tentacle like
projections outside of the integument)
Passionate about Pollination
• http://www.ted.com/talks/louie_schwartzber
g_the_hidden_beauty_of_pollination.html
• Video clip showing the interaction of animals
and their importance in pollination
Modern Plants (Angiosperms)
• The seed coat is fully enclosed, the
integument lobes are fused and there is a
pore (micropyle) to allow the tube to go in
http://www.field-studiescouncil.org/breathingplaces/food_
for_us.htm
Practical – Grow your own pollen
tube
• We will take pollen from our collected
flowers and allow them to build a tube in a
solution that replicates the female one
• In this way we can mimic the action of a
pollen grain and observe the growth of a
pollen tube
L. Bailey & E. Nertney 2013
Pollen Tube Practical
• Pollen grains are partially dehydrated when
they leave the anther.
• On the stigma, they become rehydrated and
are therefore able to begin growth of the
pollen tube
http://www.saps.org.uk/secondary/teaching-resources/222student-sheet-4-pollen-tube-growth
Don’t throw out left over leaves!(1)
• Use keys to identify as many leaves as you can
• Check these using online images / more keys /
mobile phone app e.g. Leaf snap
Don’t throw out left over leaves!(2)
• Competition time
– Can be team work or individual
– Make leaf shapes (see next slide for ideas)
– Paste to paper for a showcase in the classroom
Child’s Play! Click on links for
more ideas
• http://
http://www.designswan.com/archives/lovelyleaves-animal-by-mehdi-moeeni.html
http://www.scribbleshop.com/content/faunaflora
References
• Willis, K.J and McElwain, J.C (2002). The
Evolution of Plants. New York: Oxford
University Press
• Personal Communication:
– Dr. Karen Bacon, UCD
– Dr. Caroline Elliott-Kingston, UCD
– Palaeobotany department, UCD
L. Bailey & E. Nertney 2013