Botany Unit Notes

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Botany Unit Notes

• Part I

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What is a Plant?

• When you are asked, what color is life?, the
  color that comes to mind is usually green!
• It is no wonder that all of Earths living
  systems ultimately depend upon plants

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What is a Plant?

• Plants are multicellular eukaryotes that have
  cell walls made of cellulose
• Many plants undergo photosynthesis
• Plants include trees, shrubs, and grasses
• Also ferns and mosses
• Most are autotrophs except for a few parasitic
  plants and saprobes
• Saprobes feed on decaying organic material

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What Plants Need to Survive

• Sunlight plants use the energy from the sun to
  carry out photosynthesis
• Water and Minerals all cells require water and
  it is used during photosynthesis plants absorb
  minerals from the soil needed for plant growth

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What Plants Need to Survive

• Gas Exchange plants need Carbon Dioxide and
  even Oxygen to carry out photosynthesis
• Movement of Water and Nutrients The water and
  minerals taken up by the roots of plants needs to
  be transported to the structures that carry out
  photosynthesis
• These are hundreds of feet in the air sometimes!

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The Origin of Plants

• It all started in the water
• Some scientists believe that the first plants
  came from ancient, photosynthetic prokaryotes
• The oldest known fossils of plants show them to
  be around 500 Million years old

Green Algae
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The Origin of Plants
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Overview of the Plant Kingdom

• Botanists divide the Plant Kingdom into 4 groups
  based upon three features
• Water-conducting tissues
• Seeds
• Flowers
• The Four Groups
• Cone bearing 760 species
• Ferns their relatives 11,000 species
• Mosses their relatives 15,600 species
• Flowering plants 235,000 species
• The most abundant plants of today are the
  flowering plants making up 90 of all plants on
  Earth

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Overview of the Plant Kingdom
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Evolution of Land Plants

• As plants evolved they obtained important traits
• Non-vascular tissues (primitive)
• Early plants that needed to be near water to
  diffuse it into their cells (bryophytes mosses,
  liverworts, hornworts)
• Vascular plants (seedless came first)
• Plants that have specialized tissues capable of
  drawing water up from the soil through roots
  (Ferns horsetails)
• Seed producing plants
• Plants able to protect their young in a durable
  seed (Gymnosperms Cycads, Gnetophytes, Conifers,
  etc)
• Seeds enclosed in fruits (advanced)
• Plants that adapted an attractive fruit to have
  animals disperse their young (Angiosperms
  Grasses, fruit trees, shrubs, etc)

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Seedless Vascular Plants

• The first seedless vascular plants arrived on
  land around 420 million years ago
• The new adaptation of transporting water and
  nutrients through the plant using vascular tissue
  allowed them to grow much taller than the mosses
  and other bryophytes

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Vascular Tissues

• Vascular tissues allowed plants to grow taller
  transport water and nutrients
• Xylem moves water up the plant from the roots
• Phloem transports sugars and nutrients of
  photosynthesis down through the plant

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Seedless Vascular Plants

• This group contains the club mosses, horsetails,
  and ferns
• What makes them different from the earlier plants
  is that they have true roots, stems, and leaves
• Club Mosses Phylum Lycophyta, millions of years
  ago they existed as tall plants towering over 100
  ft!
• Today they are small plants living in moist
  woodlands

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Seedless Vascular Plants

• Horsetail Phylum Arthrophyta
• The only living species left of this phylum
• All plants in this Phylum belong to the Genus
  Equisetum and has true roots, leaves, and stems
• They reproduce by way of spores released from
  specialized structures
• They look like tall grasses and are found near
  water most often
• They are popular pond plants and used for
  decoration in Asian gardens

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Seedless Vascular Plants

• Ferns are members of the Phylum Pterophyta
• Thought to have begun around 350 mya
• Survivors of millions of years and having 11,000
  different species existing today
• True vascular tissues, strong roots, and
  underground stems called rhizomes

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Life Cycle of Ferns

• Ferns and relatives are actually the final stage
  of their lifecycle
• Called a Diploid Sporophyte
• Spores are haploid forming young gametophytes
• The gametophytes produce sperm and egg and then
  fertilize the egg
• After fertilization, a mature sporophyte grows
  from the gametophyte