OUTLINE: BIO102, Chapt 29 & 30

Plant Diversity: Colinization of Land and Evolution of Seed Plants

A. Chemical Evolution (abiotic)
B. Biotic Evolution

1. Prokaryote
2. Eukaryote
3. Multicelluar Eukaryotes

C. Compartmentalization

1. prokaryotes
2. eukaryotes
3. multicellular eukaryotes -

D. Phylogeny based on complexity, organelles, etc., lost traits

A.Diploid (2N) / Haploid (N), Mitosis / Meiosis, gametes / spores
B. Review: Meiosis and Mitosis
C. In Plants: ALTERNATION OF GENERATIONS:

SPOROPHYTE & GAMETOPHYTE

SHIFT from AQUATIC to TERRESTRIAL

IV. Basic Organizational Points:

A. Form / Body Plan / Support
B. Nutrition / Excretion / Digestion
C. Circulation / Transport
D. Respiration
E. Communication:
F. Reproduction
G. Motility / Behavior

A. Light to O2 and Sugar: Two step process
B. C3 vs. C4 pathways
C. Stomata:

LECTURE NOTES: BIO102, Chapt 29 & 30

I. PREVIOUSLY...

History of Life...

A. Chemical Evolution (abiotic)
B. Biotic Evolution

"invention" of photosynthesis: atmospheric shift from reducing to O2
Cell

1. Prokaryote

Cell membrane, skeleton (extracellular : cell wall)
DNA, RNA, protein, sugars, metabolic pathways, behavior, reproduction
nutrition, digestion, metabolic byproducts, waste, secretion, consumption.

2. Eukaryote

Nucleus, organelles (mitochondria, chloroplasts : from endosymbionts?)
Single cells - "jack of all trades"
Multicellularity - compartmentalization, specialization

C. Compartmentalization

1. prokaryotes

• single space, molecular pathways all interact, limited separation
  
• change in one pathway (genetic) affects other pathways
  
2. eukaryotes -

• nuclei and organelles package certain conserved reaction centers
  
• changes can now occur in cytoplasm that do not influence critical processes
  in nuclei, mitochondria (or chloroplasts)
  
3. multicellular eukaryotes -

• complex processes can be relegated to different structural compartments
  
• external space/environment:
  
• space external to cell can be INTERNAL to organism
  
• secretion, mechanisms for secretion (golgi, membrane bound ribosomes)

D. Phylogeny based on complexity, organelles, etc. note lost traits
Refer to Fig. 26.26 p.542

II. REPRODUCTIVE DIVERSITY

Much focus in chapts on reproductive mechanisms,

especially life cycles and where meiosis, vs. mitosis occurs

Life History: when, where, how:

Diploid (2N) / Haploid (N), Mitosis / Meiosis, gametes / spores

SPOROPHYTE (2N)

Meiosis
Haploid Spores

GAMETOPHYTE (N)

Mitosis
Haploid Gametes
Fertilization

SPOROPHYTE (2N) ...

Must produce reproductively viable offspring.

III. PLANT DIVERSITY

      
"Higher" Eukaryote Phylogeny
             
           |-----------------Diatoms      |
           |                              |
     |-----|     |-----------Golden Algae | distinguished by pigment
     |     |     |                        |  & reproduction
     |     |-----|     |-----Brown Algae  |
     |           |-----|                  | 500-600my
     |                 |-----Water Molds  |
     |                                    |
     |                                    |
     |-----------------------Red Algae    |
     |                                    |
-----|                                    |
     |-----------------------Green Algae  |
     |                 |
     |                 |-----PLANTS      |
     |                                    |
     |                                    |
     |-----------------------FUNGI        |
     |                                    |
     |                                    |
     |-----------------------ANIMALS      |
           


Plant Phylogeny / Evolution

----------------------------Green Algae
     |
     |475my
     |-----------------------Bryophytes (mosses, liverworts)
             |                  [18,600 named species]
             |400my
             |---------------Seedless Vascular Plants (ferns, horsetails)
                  |             [13,015 named species]
                  |360my
                  |----------Gymnosperms (Cycads, Gymnosperms)
                       |        [721 named species]
                       |130my
                       |-----Angiosperms (flowering plants)
                                [250,000 named species]




A. In Plants: evolutionary shift towards SPOROPHYTE DOMINANCE



		Non-Vascular Plants:  Mosses (ca. 12,000 extant species), Liverworts (6500), Hornworts (100)
	
			plant you see is the GAMETOPHYTE (N) 

				produce sperm (from antheridium) & egg (from archegonium) 

	
				fertilization in female archegonium (SPERM SWIM TO EGG!) 

	
			SPOROPHYTE (2N) grows from zygote (female archegonia) into stalk/capsule 

					capsule (SPORANGIUM) produces spores (N, via meiosis) 

					spores grow into male or female gametophytes

					HOW IS SEX DETERMINED? 

	

		Seedless Vascular Plants: Ferns (12,000), Horsetails (15), Lycophytes (1,000) 

		
		plant you see is the SPOROPHYTE (2N) 

					capsules (sporangia) produce spores (N, following meiosis) 

					spores grow into gametophyte (small, male and female parts on same plant) 

					gametes produced (antheridia, archegonia) 

		
			fertilization in female archegonium (SPERM SWIM TO EGG!) 

		
		SPOROPHYTE (2N) grows from zygote (in archegonium) 


		Seed Plants - Gymnosperms:  Conifers (550), Cycads (100), Ginkgo(1), Gnetae (70)

	
			plant you see is SPOROPHYTE (2N) 

					male and female cones >> meiosis

	
				pollen (N) = male gametophyte (multicellular) 

						ovule (N) = female gametophyte (multicellular) 

	
			fertilization occurs in female cones (WIND BLOWN POLLEN) 

					embryo to new plant


		See Plants - Angiosperms: flowering plants ( ca. 250,000 extant species) 

	
			similar to gymnosperms (details later)

					


	B. SHIFT from AQUATIC to TERRESTRIAL

	Dehydration

		Neutrally buoyant vs. Gravity: Structural adaptations 

		Water & nutrient acquisition, transport: Vascular System 

		Fertilization (male gamete migration through water (sperm) vs. through air (pollen) 

		Multiple tissues: requirement for coordination / communication: hormones, homeostasis




Success of Angiosperms

1. Gamete Dispersal - Directed, energy effecient

	Plant-Animal Coevolution: pollenators

Major animal pollenators include insects, bats, hummingbirds.  Plants attract animal pollenators with nutritional rewards supplemented by advertisement in the form of olfactory and visual cues.  Flower shape and scent production have been strongly selected for pollenator attraction and pollen attachment (tubular flowers require pollenators to "dig deep" and contact pollen).  Regarding insects, the majority of insect Orders existed prior to the acendancy of flowering plants.  However, the tremendous diversification within insect Orders was likely stimulated by the diversification of flowering plants.

	Many plants, especially certain trees, rely on wind for pollen distribution


2. Seed Dispersal - Fruit

	Plant-Animal Coevolution: seed dispersal

Fruit is for seed dispersal (not for embryo nutrition).  Fruit may have hooks (burrs) for attachment to body surface, or be food to encourage animals to injest.  Result is animals carry seeds elsewhere, dispersing the plant.


	Fruits may also function in wind dispersal - maple "propellers", dandelion fluff


Environmental Impact: Change in Global CO2

Atmospheric CO2 levels declined >100 fold as a consequence of photosynthetic consumption by land plants! (300-450my ago) (p. 571, Figure 30.10)






V. Basic Organizational Points: 
 A. Form / Body Plan / Support 
  
                 1. Eukaryotes / Multicellular (except some unicellular algae)

                     2. Photosynthetic organelles(e.g. chloroplasts) 

                     3. Cell Walls: 

                                 a. Cellulose (glucose polymer) 

                                            - glucose polymer, indigestible

                                                - some fungi and some protists have cellulase

                                                - termites: gut protozoans 

                                b. Lignin

                                            - non-carbohydrate polymer; complex carbon backbone

                                                - structural support in vascular plants

   4. Tissues: specialization

                                 a. algae

                                            - aquatic, neutrally buoyant

                                                - typically single or double cell layered

                                                - filaments, sheets

                                                - special parts: e.g. holdfasts

                                                - the brown algae (kelps): most complex 

                                                    -- holdfasts, stipes, blades ("leaves"), air bladders (floats) 

                   b. land plants

                                            - below ground (roots), above ground (e.g. leaves) 

                                                - complex circulatory/transport systems 

                                                            -- for water, nutrients 
                                    
                                                                -- from / to roots

                                                                -- from / to leaves (photosynthetic centers) 

                                           -       multiple cell layers    
                    
                                                            -- epidermis (specialized to prevent drying), stomata

                                                                -- endodermis, etc. 

                   c. specific regions of growth (e.g. meristem of flowering plants) 

                                     d. photosynthetic areas:  concentrated, all over, or varied

                   5. Alternation of Generations

                                    a. Very different forms

                                        b. Specialized reproductive structures 

                        6. Complex Developmental and Morphogenic Mechanisms

                             7. Evolutionary trends: mostly terrestrialization

                            a. root-like structures for anchorage and for absorption of water and nutrients

                                     b. conducting vessels to transport water and nutrients throughout plant

                                     c. stiffening substance called lignin to impregnate the vessels and support the plant body

                                     d. waxy cuticle to slow loss of water through evaporation

                                     e. stomata that can open allowing gas exchange and close preventing water loss




     B. Nutrition / Excretion / Digestion        

                    1. carbon: autotrophic (photosynthetic) 

                        2. nitrogen, phosphorous, sulfur, etc: medium (water) / soil

                        3. stomata: gas exchange

                        4. some: salt secretion

                                                
C. Circulation / Transport          
                            
         1. Aquatic algae: diffusion

             2. Land plants / vascular plants: 

                         a. complex circulatory / transport systems

                                 - xylem (water, dissolved minerals from roots) 

                                             - phloem (water, sugars, amino acids, hormones) 


     D. Respiration

                 1. Aquatic algae: diffusion

                                    a. intertidal algae - complex problems re. heat and desiccation

                2. Vascular plants: stomata / ("open" gas circulatory) system) 

   
     E. Communication: 

                    1. hormones (via phloem)

                        2. electrical (action potentials - like nerves but slower) 

                        3. plant - plant communication (pheromones?) 

        

     F. Reproduction             

                    1. Sporophytes (2N) / Gametophytes (N) 

                        2. motile gametes in algae, mosses and liverworts, ferns

                        3. aquatic transfer of gametes in all but conifers and flowering plants

                        4. Pollen (wind or animal dispersed) in conifers and flowering plants

                        5. Evolutionary shift from dominant gametophyte to dominant sporophyte

                        6. Evo. shift towards large, stationary egg | "female" gametophyte


     G. Motility / Behavior

                    1. motile gametes (flagella) 

                        2. movement towards light: growth or cell shape change

                        3. evolved chemical communication with insects

                        4. carnivorous plants: Venus fly traps, sun dews, pitcher plants


II.  Photosynthesis (Review)
        

     A. Light to O2 and Sugar: Two step process

                 1. Light Dependent Reaction

                                                    Light + H2O >>> O2 | ATP, NADPH

                        2.  Carbon Fixation

                                                    CO2 | ATP & NADPH >>> C3 or C4 sugars        
                                                     
                              
     B. C3 vrs C4 pathways

                                    1. Different tissues, different species

                                        2. C4: less water, more light

                                            a. drought tolerant plants / desert environment

                                        b. crab grass vs. blue grass


                                      
     C. Stomata:  

                  1. terrestrial plants 

  
                       a. CO2 limiting, dehydration a risk 

                             b. leaves water proof, regulated openings: stomata 

 
                2. Guard Cells = stomata / regulated opening and closing 

 
                        a. openings in plant epidermis 

 
                            - pair of "guard cells" swell and shrink to open and close 

                        b. Stomata open in daylight (light response) 

 
                            - allow CO2 entry for photosynthesis 

 
                       c. Stomata will close under water stress, even in light 

                             d. Stomata close in dark 


  






VOCABULARY

chemical evolution 

abiotic evolution

biotic evolution 

photosynthesis: atmospheric shift from reducing to O2

carbon fixation

cell

prokaryote

eukaryote

cell membrane

skeleton 

cytoskelaton

cell wall

intracellular

extracellular

DNA

RNA

protein

sugars

metabolic pathway

nucleus

organelles

mitochondria

chloroplast

endosymbiont theory

compartmentalization

secretion

golgi

ribosomes

life cycle

meiosis

mitosis

diploid 

haploid

2N / N

gamete

sperm

egg

zygote

spore

sporophyte

gametophyte

alternation of generations

fertilization

sporophyte dominance

antheridium

archegonium

moss

fern

gymnosperm

angiosperm

conifer

embryo

terrestrial adaptation

vascular system

meiosis

mitosis

germ line tissue

somatic tissue

chromosomes

chromatids

homologous

analagous

cross over


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