KEY CONCEPT Plant life began in the water and became adapted to land. Plant Evolution
Jan 05, 2016
KEY CONCEPT Plant life began in the water and became adapted to land.
Plant Evolution
Plant Evolution• Land plants evolved from
green algae (450 mya)– Both have same type of
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)
• True plants evolved through natural selection. – True plants have embryos that develop while attached to female
parent.– 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.
Land plants had to overcomemany challenges. We’ll takea look at the adaptations…
Land Adaptations
stoma
• Challenge = Retaining Moisture– Early plants grew near waters edge
• Adaptation:– Cuticle: Waxy coating– Stomata: Pores to allow gas exchange
Land Adaptations
• Challenge = Transporting Resources• Adaptaion:– Vascular system: tissue to transport nutrients
• Up from the roots (ex: water)• Down from the leaves (ex: sugars)
– Allows taller growth
water
glucose
Land Adaptations
• Challenge = Growing Upright• Adaptation:– Large plants need to support own weight– Lignin: hardens cell wall; gives wood strength
• Challenge = Reproduction on Land• Adaptation:– Pollen: Allow for reproduction without free-standing water.
• Can be carried by wind/animals.– Seeds: Hard coated storage device for a plant embryo.• Protects embryos from drying wind and sunlight.
– Embryo then develops when environment is favorable.
Land Adaptations
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
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?