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Reading Assignment: Chapter
17
Learning Outcomes:
By the end of this lecture you should
be able to:
- identify the challenges
faced by land plants and explain how plants have adapted to these challenges
- identify the general characteristics of different plant groups
- identify the components of the shoot and root system of land plants and the
root & shoot modifications of plants
- identify the differences between monocots & dicots
I. Evolution of Land
Plants:
A. Challenges of a
terrestrial existence: water limitation, carbon dioxide and nutrient
availability, structural support and reproduction
B. Terrestrial adaptations
of land plants:
1. Presence of cuticle - reduces water loss due to evaporation
2. Presence of stomata - allows efficient gas exchange for photosynthesis
3. Presence of apical meristems- found at the tips of shoots and roots; allows
efficient growth towards resources
4. Presence of vascular tissue (xylem and phloem) - allows more efficient
transport of water and nutrients
5. Presence of multicellular embryos that are dependent on the parent -
increases survival of the offspring
6. Presence of Alternation of Generations -
both haploid and diploid stages are multicellular; increases # of gametes
produced per individual
II. Plant Diversity:
A. Non-vascular plants
(plants that don’t contain specialized cells for transporting water and
nutrients):
- includes two groups: Liverworts and Mosses
Sphagnum moss – provides important carbon and water storage in ecosystems
B. Seedless Vascular Plants
(plants that contain specialized cells for transporting water and nutrients):
have more complex structures; includes ferns & their relatives
Ferns formed vast “coal forests” – deposits that became a source of fossil
fuel.
C. Seed Plants (vascular
plants that produce seeds):
Includes two groups: Gymnosperms and Angiosperms (flowering plants)
1. Overview of Seed Plant
Evolution:
a.
production of seeds (increases chance of survival for the embryo)
b.
evolution of pollen (eliminates the need for water in plant fertilization)
2. Gymnosperms (“naked
seeds”): seeds develop on the surface of specialized leaves
3. Angiosperms (flowering
plants): have more advanced vascular tissue, evolution of the flower as the
reproduction structure, production of fruits to aid in seed dispersal
4. Flower structure:
Stamen – male reproductive structure;
Carpel – female reproductive structure
Complete flower: sepals, petals, stamens and carpels are all present.
Incomplete flower: lacks one or more of the above structures.
Composite inflorescence: a group of flowers that simulate a single flower. E.g.
sunflower
5. Plant Reproduction:
Flowering plants have adaptations to reduce self-fertilization
- Some plants undergo asexual (vegetative) reproduction – they clone
themselves
- Both animal and wind pollination help transfer pollen from one plant to
another
- Both animal and wind dispersal help distribute seeds to new areas
III. Plant Form and Function
1. Components of the shoot
system (flower, leaf, stem) and the root system (taproot, lateral roots) of a
plant.
Root hairs: absorb water and minerals; increase the surface area of the root
system
Stems can be modified for colonization of new areas, asexual reproduction and
food storage.
Eg. strawberry, ginger, potato
Leaves can be modified for
attachment/support, reduction of evaporation, water storage, attraction of
pollinators and transmission of light. Eg. pea, cactus, ice plant, poinsettia,
cushion plant
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