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Topic 13 Introduction to the Kingdom Plantae

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Title: Topic 13 Introduction to the Kingdom Plantae


1
Topic 13Introduction to the Kingdom Plantae
  • Biology 1001

November 2, 2005
2
LAND Plants The Tree of Life
3
13.1 What Are Plants?
  • Plants colonized land approximately 500 MYA
  • Land plants are a monophyletic group!
  • Land plants evolved from aquatic green algae
  • 290,000 living species
  • Producers sources of O2 and food for land
    animals

4
General Features of Land Plants
  • Multicellular, eukaryotic photoautotrophs
  • Cell walls containing cellulose
  • Chloroplasts containing chlorophylls a and b
  • What Features DEFINE plants?
  • The Evolution of Land Plants
  • Features shared with charophyceans
  • Terrestrial adaptations that characterize land
    plants
  • Origin and diversification of land plants

5
Land Plants Evolved From Green Algae
  • Green algae called charophyceans are the closest
    living relatives of land plants
  • Evidence
  • Rosette cellulose-synthesizing complexes
  • Peroxisome enzymes that minimize photorespiration
  • Similarity of sperm structure
  • Formation of a phragmoplast
  • Similar nuclear and chloroplast genomes
  • Adaptation to a dry environment sporopollenin

6
Adaptations to a Terrestrial Environment
  • Defining the plant kingdom
  • Five key derived traits of plants
  • Apical meristems
  • Alternation of generations
  • Walled spores produced in sporangia
  • Multicellular gametangia
  • Multicellular, dependent embryos

7
Land vs. Water
  • Some combination of characteristics allowed the
    first plants to survive and reproduce on land
    once there the many benefits of this new
    environment led to the evolution of this
    successful and diverse group of organisms
  • Aerial and subterranean environments
  • Aerial CO2 and light
  • Soil minerals and H20
  • Bright sunlight unfiltered by water or plankton
  • Plenty of CO2, soil rich in nutrients
  • Initially few herbivores and pathogens

8
APICAL MERISTEMS
  • Figure 29.5a (!)
  • Localized regions of cell division at the tips of
    roots and shoots
  • Produce roots and leaf-bearing shoots
  • Structural specialization that allows plants to
    flourish in separate aerial and subterranean
    environments

9
ALTERNATION OF GENERATIONS
  • Figure 29.5b (!)
  • Also evolved in various groups of algae but does
    not occur in the charophyceans
  • In some groups of plants the gametophyte
    generation is dominant, in others the sporophyte
  • In flowering plants, the gametophyte generation
    is highly reduced

10
WALLED SPORES PRODUCED IN SPORANGIA
  • Figure 29.5c (!)
  • Spores are produced in organs called sporangia
  • Spore walls are enriched with sporopollenin
  • Allows them to survive the dry terrestrial
    environment
  • Charophycean sporopollenin protects the zygote,
    and they lack sporangia

11
MULTICELLULAR GAMETANGIA
  • Figure 29.5d(!)
  • Gametes are produced in multicellular organs of
    the gametophyte called gametangia
  • Male antheridia
  • Female archegonia
  • The sperm fertilizes the egg in the archegonia,
    and that is where the zygote develops

12
MULTICELLULAR, DEPENDENT EMBRYOS
  • Figure 29.5e(!)
  • The embryo (developing young sporophyte) is
    retained within the tissues of the female parent
  • Nutrients are transferred from parent to embryo
    through placental transfer cells
  • This is why land plants are embryophytes

13
Other Terrestrial Adaptations
Cuticle
  • Have evolved in many but not all plant species
  • An epidermal covering known as a cuticle prevents
    dessication
  • Secondary compounds such as
  • Alkaloids, terpenes, and tannins defend against
    herbivores and parasites
  • Flavenoids absorb harmful UV rays
  • Phenolics prevent bacterial infections

Tannins
Lignin a phenolic
14
Origin and Diversification of Plants
  • Fossilized sporophyte tissue molecular evidence
    place the origin of plants at 475 MYA
  • The first plants were nonvascular
  • There have been three subsequent major
    evolutionary adaptations or adaptive radiations
    of plants
  • Vascular plants evolved 420 MYA
  • Seed plants evolved 360 MYA
  • Flowering plants evolved 130 MYA

Figure 29.7 (!) Highlights of Plant Evolution
15
Highlights of Plant Evolution
  • Nonvascular and all subsequent plants have the
    five key terrestrial features
  • Vascular plants have complex vascular tissue
    systems composed of xylem and phloem
  • Seed plants package their embryos with a supply
    of nutrients into a seed
  • Flowering plants develop their seeds inside a
    chamber called the ovary

16
Some Examples of Land Plants
Pterophytes and Lycophytes
Bryophytes
Lycopodium a club moss
Pallavicinia a thalloid liverwort
Psilotum a whisk fern
Porella a leafy liverwort
Equisetum - a horsetail
Phaeoceros - a hornwort
Polypodium vulgare a fern
Polytrichum commune star moss
17
Some Examples of Land Plants
Gymnosperms
18
Some Examples of Land Plants
Angiosperms 250,000 species!
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