2. 290, 000 known plant species
Land plants enabled survival of other life
forms on land – including animals
Roots provide habitats, stabilize landscapes
Oxygen supply
Ultimate provider of food eaten by terrestrial
animals
3. Common (derived) traits of land plants –
separate them from ancestral plants (algal
relatives):
Alteration of generations & multicellular,
dependent embryo’s
Walled spores produced in sporangia
Multicellular gametangia
Apical meristems
4. Alteration of Generations
The life cycle includes both
multicellular haploid (n) &
multicellular diploid (2n)
organisms
5. Multicellular, Dependent Embryos
After fertilization zygote develops into
a multicellular embryo within maternal
structures.
Maternal tissues provide nutrients.
Embryo is dependent
Land plant called embryophytes.
6. Walled Spores Produced in Sporangia
Sporophyte produces spores in organs called
sporangia
Diploid cells called sporocytes undergo
meiosis – generate (n) spores
Spore walls contain
sporopollenin:
resistant to harsh
environments
7. Multicellular Gametangia
Gametes produced in multicellular organs – gametangia.
Female gametangia – archegonia – produce single egg
Male gametangia – antheridia - produce & release sperm
– fertilize egg internally
within the archegonium
8. Apical Meristems
Plants sustain continual growth in
apical meristems
Cells from apical meristems differentiate into various
tissues
1) Elongation of the roots
Nutrients & water from soil
2) Growth of stems & leaves
More area for photosynthesis
9. GROUPING OF LAND PLANTS
• Ancestral species gave rise to a vast diversity of
modern plants
• Land plants informally grouped based on
presence or absence of vascular tissue
• Most plants have vascular tissue; these constitute
the vascular plants
• Nonvascular plants are commonly called
bryophytes
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10. GROUPING OF LAND PLANTS
• Seedless vascular plants can be divided:
– Lycophytes (club mosses and their relatives)
– Pterophytes (ferns and their relatives)
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11. GROUPING OF LAND PLANTS
• Seed plants
• A seed is an embryo and nutrients surrounded by
a protective coat
• Seed plants can be divided into:
– Gymnosperms, the “naked seed” plants, including
the conifers
– Angiosperms, the flowering plants
13. Bryophyta (non-vascular plants)
(p. 606 – 609)
• Phylum includes all mosses (Bryophyta)
• Bryophytes: all non-vascular plants
– Include liverworts, hornworts & mosses
• Mosses show alternation of generations
– i.e. have sporophyte & gametophyte generation
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14. Bryophyta
• In all bryophytes gametophytes are dominant
in life cycle
• Larger & longer living than sporophyte
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19. VASCULAR PLANTS
LIVING VASCULAR PLANTS CHARACTERISED BY:
• Life cycles with dominant sporophytes
– Fern life cycle
• Transport in vascular tissues
– Xylem and phloem
• Well-developed roots and leaves
– Including spore bearing leaves called sporophylls
20. Pterophyta
(p. 610 – 615)
• Phylum includes all ferns, horsetails & whisk ferns
• Vascular seedless plants
– Vascular means plants could grow taller than bryophytes
• Ferns show alternation of generations (dominant sporophyte)
• Sperm flagellated – must swim through water to reach eggs
i.e. found in damp environments
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25. Transport in Vascular Tissues
• Two types of vascular tissue:
• Xylem and phloem
• Xylem conducts water & minerals
• Dead cells called tracheids
• Phloem distributes sugars, amino acids, & other organic
products
• Consists of living cells
• Water-conducting cells are strengthened by lignin
and provide structural support
26. Evolution of Roots
• Benefits of lignified vascular tissue below
ground
• Instead of rhizoids, roots evolved
– May have evolve from subterranean stems
• Roots: organs to absorb water & nutrients
from soil
• Also anchor vascular plants
27. Evolution of Leaves
• Leaves increase surface area of plant body
• Main photosynthetic organ of vascular plants
• Classified as:
– Microphylls (only lycophytes) – leaves with a
single vein
– Megaphylls (all vascular plants) – highly branched
vascular system
• Greater photosynthetic productivity
28. Sporophylls and Spore Variations
• Sporophylls are modified leaves with
sporangia
• Sori are clusters of sporangia on the
undersides of sporophylls
• Strobili are cone-like structures
formed from groups of sporophylls
29. • Most seedless vascular plants are homosporous
• Produce one type of spore that develops into a bisexual
gametophyte
• All seed plants (and some seedless vascular plants)
are heterosporous
• Produce megaspores that give rise to female
gametophytes
• And microspores that give rise to male gametophytes
Sporophylls and Spore Variations
30.
31. SEED PLANTS
• Seeds changed the course of plant evolution
– Plants with seeds would become dominant
producers in most terrestrial ecosystems
• Living seed plants can be divided into two:
– Gymnosperms
– Angiosperms
• A seed consists of an embryo and nutrients
surrounded by a protective coat
32. SEED PLANTS
5 DERIVED TRAITS:(COMMON TO ALL SEED PLANTS)
1. Reduced gametophytes
– Develop in walls of spores that are retained in tissues of
parent sporophyte
2. Heterospory
– Megasporangia produce megaspores (female
gametophytes)
– Microsporangia produce microspores (male gametophytes)
33.
34. SEED PLANTS
3. Ovules
– An ovule consists of a megasporangium, megaspore, and
one or more protective integuments
• Gymnosperm megaspores have one integument
• Angiosperm megaspores usually have two integuments
35. SEED PLANTS
4. Pollen
– Microspores develop into pollen grains – contain male
gametophytes
– Pollination is the transfer of pollen to the part of a seed
plant containing the ovules
Pollen eliminates need for film of water
Can be dispersed great distances by air or animals
If a pollen grain germinates, it gives rise to a pollen tube
that discharges two sperm into the female gametophyte
within the ovule
36.
37. SEED PLANTS
5. Seeds
• Evolutionary
advantages over
spores:
– May remain dormant for
days to years, until
conditions are favorable
for germination
– Transported long
distances by wind or
animals
40. Gymnosperms
(p. 618 – 625)
• Plants with ‘naked seeds’ not enclosed in
ovaries
• Include conifers (pine tree) and cycads
• Three key features of the gymnosperm life cycle
are:
1. Dominance of the sporophyte generation
2. Development of seeds from fertilized ovules
3. The transfer of sperm to ovules by pollen
• The life cycle of a pine provides an example
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46. Angiosperms
(p. 625 – 634)
• Most widespread and diverse of all plants
• Are seed plants with reproductive structures
called flowers and fruits
• Characterised by enclosed seeds
• The flower is an angiosperm structure
specialized for sexual reproduction
• Pollinated by insects, animals or wind
47. Angiosperms
(p. 625 – 634)
• A flower is a specialized shoot with up to four
types of modified leaves:
– Sepals, which enclose the flower
– Petals, which are brightly colored and attract
pollinators
– Stamens, which produce pollen on their terminal
anthers
– Carpels, which produce ovules
• A carpel consists of an ovary at the base and a style
leading up to a stigma, where pollen is received
48.
49. Angiosperms
(p. 625 – 634)
• A fruit typically consists
of a mature ovary but
can also include other
flower parts
• Fruits protect seeds and
aid in their dispersal
• Mature fruits can be
either fleshy or dry
50. Angiosperms
(p. 625 – 634)
• Various fruit
adaptations help
disperse seeds
• Seeds can be carried by
wind, water, or animals
to new locations
56. Angiosperm Diversity
Monocots (one cotyledon)
¼ of angiosperm species
Eudicots (“true” dicots)
More than 2/3 angiosperm
species
TWO MAIN GROUPS OF ANGIOSPERMS
57.
58.
59. HUMAN WELFARE
• No group of plants is more important to
human survival than seed plants
• Plants are key sources of food, fuel, wood
products, and medicine
• Our reliance on seed plants makes
preservation of plant diversity critical
60. PRODUCTS FROM SEED PLANTS
• Most of our food comes from angiosperms
• Six crops (wheat, rice, maize, potatoes, cassava, and
sweet potatoes) yield 80% of the calories consumed
by humans
• Modern crops are products of relatively recent
genetic change resulting from artificial selection
• Many seed plants provide wood
• Secondary compounds of seed plants are used in
medicines
