Plant Evolution plants-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."

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Plant Evolution We will look at leaf and reproductive evolution Woody Angiosperms - Bark bearing flowering plants

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 ~ 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 ny-test-1/deck/

Leaf Evolution Where discovered? – Russia - Asia - Portugal - USA Why compare leaves? – Shape of leaf features will tell us whether fossils (extinct) live in a similar environment to modern (extant) plants synthesis

Leaf Evolution Features we look at: - Presence or absence of drip tips – What might this tell us about a climate? 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. ns/leaf/dicot/

Size of leaf blade

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? you-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 Bismarck-Palm--Cuban-Royal-Palm-and-Canary-Island-Date- Palm#.UfZpJ42Hs3w

Interactive Leaf Analysis ts/ideaLabs/prehistoric_climate_change.html ts/ideaLabs/prehistoric_climate_change.html

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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 = x 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 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 = x – Rearrange maths formula to find x X = / X = 7.01 degrees Celcius Check this with your local annual mean temperature to compare results

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 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 g_the_hidden_beauty_of_pollination.html 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 council.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 student-sheet-4-pollen-tube-growth

Dont 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

Dont 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

Childs Play! Click on links for more ideas flora leaves-animal-by-mehdi-moeeni.html

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