Plant Bio Day 1

I. Importance of plants II. Botany, the study of plants III. What is a plant? IV. Ancestors of land plants V. Land plants, the embryophyta

Botany

Evolution, Ecology, Molecular Genetics, Mathematical Modeling, Morphology, Anatomy, Physiology, Cell Bio, Systematics, Development

Importance of Plants

1. Energy: Food
2. Energy: Fossil fuels
3. Clothing
4. Drugs, meds
5. Ecosystem functioning
6. Biodiversity

Plants evolved from what

Algae

Plants evolved from what/how

Algae, Eukaryote engulfment of cyanobacteria (plastid) Red/Green split

Streptophytes

Fresh water (Charophytes) & Land plants (Embryophytes)

Plants = all organisms within clade ___

Viridiplantae

Primary Endosymbiosis

Prokaryote + Eukaryote = Eukaryote (plastid)

Secondary endosymbiosis

Eukaryote (nonphotosynthetic) + Eukaryote (photosynthetic) = Eukaryote

Plants 1500 MYA

* Single cell & multicellular
* Marine
* Moist environments 

Plants 500 MYA

Colonization dryer environments

Cuticle
Vascular tissue: roots & shoots
Relationship w fungi
Seeds & pollen

Oxygen Revolution

Cyanobacteria changing O2 levels

* Plants created (2400 MYA)
* Plants move to land (700MYA)
* Results in Oxygen spikes

Features of plants

Starch, Chlorophyll b, Cellulose, Thylakoids in stacks

Starch

* Amylose (20%) chain
* Amylopectin (80%) Branches
* Sugar stored as starch

Chlorophyll b

* Chl a: all photosynthetic eukaryotes
* Chl b: accessory pigment; passes energy to Chl a

Cellulose

* Polysaccharide: unbranched glucose residues
* Most common polymer

Thylakoids in stacks

* Rather than as simple bands
* Membranes inside chloroplast - contain chlorophyll

Common ancestor of plants (not descended from)

Charophytes

Features of charophytes & land plants

1. Cell plate & phragmoplast (short microtubules)
2. Plasmodesmata
3. Rose-shaped cellulose synthesizing complexes
4. Sporopollenin

Plasmodesmata

Extensions of cell membrane thru pores in cell wall

Sporopollenin

* Durable polymer
* Found in walls of plant spores & pollen
* Chemically inert (stable, persists in environment)
* Protects from desiccation, decay, etc.

Move to land: Advantages

* Air filters less sunlight than water
* Air has more CO2
* No predators/herbivores on land
* More nutrient rich soil

Plants in water:

Supported, retain water, Reproduction easier

Plants on land

Not supportive, Lose water, Reproduction Harder

Land Plant Adaptations

Turgor (+ pressure),

Cuticle; vascular tissue; roots; stomates

Egg & embryo retained on parent; sporopollenin; protected embryo; seed coat; pollen; flower; fruit

Cuticle

Waxy covering

Antheridium

Male sex organ (produces sperm)

Archegonium

Female sex organ, produces egg

All sexual reproduction

diploid → haploid

Alternation of generations

mulitcellular diploid → Multicellular haploid

The alternating generations are

Gametophyte (haploid 1n)

Sporophyte (diploid 2n)

Origination of alternation of generations

* Zygote delays meiosis & instead divides and grows.
* Result: Multicellular diploid

Meisis makes _# cells

4

Green alga w/o alt of generations

Chlorophyta