2. Evolution and
Diversity of Plants
Outline
Evolutionary History
Alternation of Generations
Nonvascular Plants
Vascular Plants
Seedless
Seed
Angiosperms
Monocots and Eudicots
Flowers
3. Evolution and
Diversity of Plants
Evolutionary History of Plants
More than 98% of all biomass is plants
Multicellular photosynthetic eukaryotes
280,000 known species
Thought to have evolved from freshwater algae
over 500 mya
Evolution of plants marked by four evolutionary
events associated with four major groups of
plants
Nonvascular Plants
Advent of nourishment of a multicellular embryo
5. Evolution and
Diversity of Plants
Evolutionary History of Plants
Seedless vascular plants
Advent of vascular tissue
Gymnosperms and angiosperms
Produce seeds
Flowering Plants
Attract pollinators that give rise to fruits
7. Evolution and
Diversity of Plants
Life cycle involves of Generations
Alternation alternation of generations
Multicellular 1n individuals (gametophytes)
produce multicellular 2n individuals
(sporophytes)
Multicellular 2n individuals (sporophytes)
produce multicellular 1n individuals
(gametophytes)
Sporophyte (2n):
Multicellular individual that produces spores by
meiosis
Spore is haploid cell that will become the
gametophyte
Gametophyte (1n):
Multicellular individual that produces gametes
Gametes fuse in fertilization to form zygote
9. Evolution and
Diversity of Plants
Alternation of Generations
Appearance of generations varies widely
In ferns, female portions are archegonia
and are fertilized by flagellated sperm
In angiosperm, female gametophyte
(embryo sac), consists of an ovule
Following fertilization, ovule becomes
seed
In seed plants, pollen grains are mature
sperm-bearing male gametophytes
11. Evolution and
Diversity of Plants
Other Terrestrial Adaptations
Vascular tissue transports water and
nutrients to the body of the plant
Cuticle provides an effective barrier to
water loss
Stomata bordered by guard cells that
regulate opening, and thus water loss
14. Evolution and
Diversity of Plants
Nonvascular Plants
Nonvascular plants (bryophytes)
Lack specialized means of transporting
water and organic nutrients
Do not have true roots, stems, and leaves
Gametophyte is dominant generation
Produces eggs in archegonia
Produces flagellated sperm in antheridia
Sperm swim to egg in film of water to
make zygote
15. Evolution and
Diversity of Plants
Nonvascular Plants
Hornworts (phlym Anthocerophyta) have
small sporophytes that carry on
photosynthesis
Liverworts (phylum Hepatophyta) have
either flattened thallus or leafy
appearance
Mosses (phylum Bryophyta) usually have
a leafy shoot, although some are
secondarily flattened
Can reproduce asexually by fragmentation
Dependent sporophyte consists of foot,
19. Evolution and
Diversity of Plants
Vascular Plants
Xylem conducts water and dissolved
minerals up from roots
Phloem conducts sucrose and other
organic compounds throughout the plant
Lignin strengthens walls of conducting
cells in xylem
Most seedless vascular plants are
homosporous
Windblown spores are dispersal agents
All seed plants are heterosporous and
have male and female gametophytes
Seeds disperse offspring
22. Evolution and
Diversity of Plants
Seedless Vascular Plants
Club Mosses (phylum Lycophyta)
Typically, branching rhizome sends up
short aerial stems
Leaves are microphylls (have only one
strand of vascular tissue)
Sporangia occur on surfaces of
sporophylls
Grouped into club-shaped strobili
24. Evolution and
Diversity of Plants
Seedless Vascular Plants
Ferns and Allies
Horsetails (phylum Sphenophyta)
Rhizome produces tall aerial stems
Contains whorls of slender, green branches
Small, scalelike leaves also form whorls at
the joints
30. Evolution and
Diversity of Plants
Seed Plants
Seed plants are the most plentiful plants
in the biosphere
Seed coat and stored food allow an
embryo to survive harsh conditions during
long period of dormancy
Heterosporous
Drought-resistant pollen grains
Ovule develops into seed
32. Evolution and
Diversity of Plants
Gymnosperms
Gymnosperms have ovules and seeds
exposed on the surface of sporophylls
Confiers
Cycads
Ginkgoes
Gnetophytes
33. Evolution and
Diversity of Plants
Conifers
Conifers, as well as other gymnosperm
phyla, bear cones
Tough, needlelike leaves of pines
conserve water with a thick cuticle and
recessed stomata
Considered a “soft” wood because it
consists primarily of xylem tissue
35. Evolution and
Diversity of Plants
Cycads
Cycads (phylum Cycadophyta)
Large, finely divided leaves that grow in
clusters at the top of the stem
Pollen and seed cones on separate plants
Pollinated by insects
37. Evolution and
Diversity of Plants
Ginkgoes
Ginkgoes (phylum Ginkgophyta)
Dioecious
Some trees producing seeds
Others producing pollen
One surviving species ( Gingko biloba )
41. Evolution and
Diversity of Plants
Gnetophytes
Gnetophytes (phylum Gnetophyta)
Have similarly structured xylem
None have archegonia
Strobili have similar construction
42. Evolution and
Diversity of Plants
Angiosperms
Angiosperms (phylum Anthophyta)
An exceptionally large and successful
group of plants
Ovules are always enclosed within diploid
tissues
Became dominant group of plants in the
late Cretaceous and early Paleocene
periods
44. Evolution and
Diversity of Plants
Monocots and Eudicots
Two classes of flowering plants
Monocotyledones (Monocots)
One cotyledon in seed
Eudicotyledones (Dicots)
Two cotyledons in seed
46. Evolution and
Diversity of Plants
The Flower
Peduncle (flower stalk) expands at tip
into a receptacle
Bears sepals, petals, stamens, and
carpels, all attached to receptacle in
whorls
Calyx (collection of sepals) protect flower
bud before it opens
Corolla (collection of petals)
47. Evolution and
Diversity of Plants
The Flower
Each stamen consists of an anther and a
filament (stalk)
Carpel has three major regions
Ovary - Swollen base
Fruit
Style - Elevates stigma
Stigma - Sticky receptor of pollen grains
50. Evolution and
Diversity of Plants
Flowers and Diversification
Wind-pollinated flowers are usually not
showy
Bird-pollinated flowers are often colorful
Night-blooming flowers attract nocturnal
mammals or insects
Usually white or cream-colored
Fruits of flowers protect and aid in
dispersal
Utilize wind, gravity, water, and animals
51. Evolution and
Diversity of Plants
Review
Evolutionary History
Alternation of Generations
Nonvascular Plants
Vascular Plants
Seedless
Seed
Angiosperms
Monocots and Eudicots
Flowers
