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Plant kingdom diversity
Chapters 20-22 Created by Kevin Bleier Milton High School
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Characteristics of Plants
Autotrophs Multicellular Eukaryotes Plant cell walls made of cellulose
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Common Ancestor The common ancestor of ALL plants is thought to be Green Algae In the early evolution of plants, they made the transition from aquatic to land environments
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Water is short on land, so relationships like mycorrhizae are important
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Cuticle Waxy covering that prevents water loss
Crucial for transition to land Also clear … why?
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Cladogram Evolution of cuticle (and specialized cells / tissue)
Gymnosperms Angiosperms Seedless vascular plants Nonvascular plants Evolution of cuticle (and specialized cells / tissue) Green algae
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Plant groups Bryophytes (seedless, non-vascular)
Seedless vascular plants Gymnosperms Angiosperms
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Bryophytes think moss
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Bryophytes Small Found only in damp, moist areas on land
1) Leaves must touch water for photosynthesis 2) Sperm swims through water to reach egg
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Bryophytes
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Seedless vascular plants
Cladogram Gymnosperms Angiosperms Seedless vascular plants Non-vascular plants Evolution of vascular tissue Evolution of cuticle (and specialized cells / tissue) Green algae
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Seedless vascular plants
Think ferns
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Vascular tissue Set of tubes that transport materials around plant
Allows plants to grow taller Water travels up through xylem Sugar travels throughout in phloem
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Ferns live further on land
Mature plant survives fine with vascular tissue But sperm must still swim to egg (needs film of water)
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Seedless vascular plants
Cladogram Gymnosperms Angiosperms Seedless vascular plants Evolution of pollen grains and seeds Non-vascular plants Evolution of vascular tissue Evolution of cuticle (and specialized cells / tissue) Green algae
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Gymnosperms Think cones (any conifer like pine trees) female ovary
male pollen cone
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Gymnosperms Examples: Spruce Tree, Fir Tree, Pine Tree
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Key Adaptations Over Seedless Plants
Seeds Pollen Grains
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Pollen grains Small and lightweight with sperm inside
Removes water requirement for fertilization
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Gymnosperm pollen strategy
Release a lot, hope some pollinate (Meanwhile, irritating everyone else)
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After pollen lands … Builds pollen tube inside female structure to reach egg Sperm still swims to egg inside plant
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Seeds Tough coat protects newly fertilized zygote
Also contains supply of food to survive for a long time without growing (= dormancy) Overall purpose – increases chances that offspring eventually grow
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Seed Dispersal Plants try to disperse offspring far away so they have a higher chance of survival. Dispersal of seeds prevents competition for water, nutrients, light, and living space.
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Seed Dispersal Dispersal by wind – wing-like structures, parachute-like structures
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Seed Dispersal Dispersal by animals – fruits have hooks that cling on animals fur, other fruits provide food for animals
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Seed Dispersal Seeds dispersal is completed by birds, small animals, wind, and water The tough, fibrous outer covering of a coconut provides protection as well as a floatation device
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Gymnosperm cones
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Full colonization of land
Vascular tissue (find water in soil) + Reproduction through air (no need for water for sperm to swim)
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Seedless vascular plants
Cladogram Gymnosperms Angiosperms Evolution of flowers and fruits Seedless vascular plants Evolution of pollen grains and seeds Non-vascular plants Evolution of vascular tissue Evolution of cuticle (and specialized cells / tissue) Green algae
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Angiosperms Think flowers (most diverse plant group)
If you eat it, it’s an angiosperm plant
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Flowers (key adaptation over gymnosperms)
Attract animals to help carry pollen to the next flower Color or scent attractors guide animals to obtain sugar from plant Pollinators also brush by pollen, get on body Overall purpose: reduces amount of pollen that plant has to make (not random wind travel)
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Pollinators
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Advertising in UV color
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After fertilization, ovary becomes fruit
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Fruits Overall purpose: Help get seeds far away from parent plant (why?) Many are sugary fruits – animals eat, seeds pooped out far away from parent (and with free fertilizer!) Other fruits use wind (dandelion fruits), water (coconut fruits)
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Seedless vascular plants
Cladogram Gymnosperms Angiosperms Evolution of flowers and fruits Seedless vascular plants Evolution of pollen grains and seeds Non-vascular plants Evolution of vascular tissue Evolution of cuticle (and specialized cells / tissue) Green algae
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Asexual reproduction Plants can also reproduce asexually
Vegetative reproduction is faster than sexual reproduction. Vegetative reproduction is where many plant parts can regrow to make a whole new organism when separated. Examples: Ivy or Potato
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Overview of plant organs
Our assumption: angiosperms Major organs: 1) Root 2) Stem 3) Leaf 4) Flowers
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Root organ Absorption of H2O and nutrients from soil
Thick root anchors plant, small hairs increase diffusion Fungus threads also help absorption (symbiosis called _______________ ) mycorrhizae
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Modified roots Some species store sugar underground = potato
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Stem organ Xylem moves H2O / minerals up to leaves
Phloem transports sugar to all cells
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Leaf organ Often center of photosynthesis cuticle cuticle stoma (hole)
vascular bundle (xylem + phloem) cuticle stoma (hole) guard cells
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Photosynthesis and leaves
sunlight C6H12O6 H2O CO2 O2 sunlight CO2 + H2O C6H12O6 + O2
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stoma Stomata are tiny holes in the cuticle. can open and close
allow air to move in and out stoma Let in carbon dioxide and let out oxygen and water Guard cells control when stomata are opened vs. closed
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Modified leaves Broad leaves – lots of photosynthesis, but lots of water loss as well Where does this occur? tropical rainforests
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Modified leaves Cactus needles – modified leaves lower transpiration water loss – does photosynthesis in stem
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Water movement up plant
Transpiration creates pull that moves water up a plant
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Transpirational pull (leaf air space) hydrogen
____________ bonds form between H2O molecules (roots)
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Transpirational pull As H2O transpires, it pulls other H2O molecules up Relies on cohesion between water molecules
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Transpirational pull Water moves up plant without energy use
“solar-powered” Plants must still control transpiration rate
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Moving sugar Phloem right next to xylem
Sugar pumped into phloem from leaves, creates __________ solution compared to xylem Water comes in by ___________ hypertonic osmosis
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Plant reproduction Recall purpose of seeds in gymnosperms and angiosperms Recall purpose of fruits in angiosperms Seed dormancy and triggers for germination (water, fire, etc)
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Growth of plants Meristem tissue – cells specializing in mitosis
Plant growth focused on growing taller first – why? Tropisms – directed growth in response to a particular environmental stimulus
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Plant tropisms Phototropism – growth in response to light
Gravitropism – growth in response to gravity (roots “down”, shoots “up”)
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