Plant Evolution

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 (nonvascular)

Land Adaptations

• Challenge: Retain Moisture– Early plants grew near waters edge

• Solutions– Cuticle: waxy coating– Stomata: pores to allow gas exchange

cuticle

water

glucose

• Challenge: Transporting Resources• Solution: Vascular system: tissue to transport nutrients

• Up from the roots (ex: water)• Down from the leaves (ex: sugars)

– Allows taller growth

Land Adaptations

Land Adaptations

• Challenge: Growing upright– Large plants need to support own weight

• Solution– Lignin: hardens cell wall; gives wood strength

mortar

lignin

Land Adaptations

• Challenge: Reproduction on land• Solutions

– Pollen: carried by wind/animals– Seeds: hard coat protects embryo inside

Alternation of Generations

• Plants alternate between a diploid organism and a haploid organism

• Sporophyte (diploid)– Zygote created– Zygote grows into

adult sporophyte– Sporophyte makes

spores by meiosis• Gametophyte (Haploid)

– Spore grows into a gametophyte

– Male gametophyte creates sperm

– Female gametophyte creates egg

• Sporophyte restarts when egg and sperm make zygote

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X

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Plant Ecology• Mutualistic relationships

– Type of symbiosis where both organisms benefit

– Ex: Plants (provides living space)/Bacteria (create nutrients)

– Ex: Plants (provide food)/Animal (help pollinate)

• Herbivore interactions– Defense adaptations– Spines, thorns, chemicals

REview1) What traits do plants and plant-like protista (algae)

share?

2) Name 4 adaptations that plants have for life on land.

3) Which plant adaptation allows them to carry nutrients to great heights?

4) Which plant adaptation allows them to retain moisture?

5) What is the purpose of lignin?

6) Explain a symbiotic relationship between plants and other organisms?

7) How do plants protect themselves from predators?