1. PLANT EVOLUTION KEY CONCEPTPlant life began in the water and became adapted to land.

2. Plant Evolution • Evolved from green algae (450 mya) • Both have chlorophyll, store energy as starch, DNA similarities • Green algae ancestor • Multicellular body • Cells w/ channels to communicate • Reproduce w/ sperm & egg • Early plants • Low growth

3. True plants evolved through natural selection. • Ancestral charophyceans lived in areas of shallow water. • Those that could survive longer dry periods were favored. • First true plants probably grew at edges of water. • True plants have embryos that develop while attached to female parent. Land plants had to overcome Many challenges. We’ll take a look at the adaptations…

4. stoma Land Adaptations • Retain Moisture • Early plants grew near waters edge • Cuticle: waxy coating • Stomata: pores to allow gas exchange

5. Land Adaptations • Transporting Resources • Vascular system: tissue to transport nutrients • Up from the roots (ex: water) • Down from the leaves (ex: sugars) • Allows taller growth

6. Land Adaptations • Growing upright • Large plants need to support own weight • Lignin: hardens cell wall; gives wood strength

7. Land Adaptations • Reproduction on land • Pollen: carried by wind/animals (no water necessary) • Seeds: hard coat protects embryo inside

8. Alternation of generations • Sporophyte (diploid) • Begins when sperm fertilizes egg (zygote) • Diploid zygote divides by mitosis to create a mature sporophyte • Meiosis produces haploid cells called spores • Gametophyte • Haploid spores released • Spores grow into gametophyte • Male produces sperm • Female produces egg • Sperm and egg make zygote (cycle repeats)

9. Plant Ecology • Mutualistic relationships • Type of symbiosis where both organisms benefit • Ex: Plants (provides living space)/Bacteria (create nutrients) • Ex: Plants (provide food)/Insects (help pollinate) • Herbivore interactions • Defense adaptations • Spines, thorns, chemicals,