Module 3.2
Plant diversity
Plant classi cation
- bryophytes, pterophytes, gymnosperms, angiosperms
Classi ed by:
• Vascular tissue (xylem and phloem)
• True leaves and roots
• Dependable on water to reproduce
• Seeds or spores
• Cones or owers
• Fruit Vascular plants
- adaptations to dry environment
Adaptations needed:
• Prevent desiccation ( cuticle to decrease water loss)
• Aid nourishment ( roots to absorb water and minerals)
( vascular tissue xylem and phloem to move water and
food around the plant) ( types to carry liquid)
( supporting tissue(xylem)to hold up leaves for sunlight)
• Aid reproduction (spores and seeds)
The ability of vascular plants to do well in di erent
habitats = become dominate terrestrial group of plants
Di erences in non vascular and vascular tissue
- possess vascular tissue (xylem and phloem) to form central
No vascular plants column (stele)
- brtophytes - Sporophyte phase is larger and more conspicuous
- Poorly adapted to life on land generation of life cycle
- Live on moist, shady places growing on rocks, trees and
soil How are they classi ed:
- Mosses, liverworts and hornworts - seedless (pterophyte)
- All stay close to ground - Seed bearing (angiosperms and gymnosperms)
Characteristics Seedless plants
No vascular tissue = unable to transport water and food Pterophytes (ferns)
around plant - 12 000 fern species
No true roots, stems or leaves = they have rhizoids ( ne - Some endemic to South Africa
outgrowths of “stem” to anchor plant - More evolved for terrestrial life than bryophytes = much
No cuticle = no means to prevent water loss larger but still only grow up to 1m tall
No strengthening tissue = canʼt grow tall
Homosporous = spores are same size Characteristics
Depend on water for fertilisation ( male gametes swim Ferns are either terrestrial or epiphytic (grow upon
to female gametes) another plant)
Have life cycle with well de ned alternation of Have roots, stems and leaves (roots grow horizontally
generations from stem thatʼs partially underground) ( leaves, fronds
are deeply divided and characteristically coiled in the
bud = cucinate vernation
When dry moss plants = look brown and dead but if Have vascular tissue (xylem and phloem) xylem
splash water = revive green
tracheids are strengthened by lignin. No vessels
A sign of their aquatic origin is a motile sperm which Have thin cuticle and stomata
depends on water for fertilisation Reproduce by means of spores. Spores are released
from bursting open sporangia which grow on back of
sporophylls.
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, They produce motile gametes which rely on water for Seed bearing plants
fertilization and therefore are found in moist A. Cone bearing plants (gymnosperms)
environments B. Flowering plants (angiosperms)
They have a independant sporophyte (life cycle)
Habitats = shady forests, crevices, rock faces, acid Seed bearing plants share with Ferns:
wetlands - plant body with roots, stem and leaves
- Presence of vascular tissue
- Dominate and independent sporophyte
Seed plant di er from mosses and ferns:
- gametophyte in seed plants is reduced in size only to a
few dozen cells = female gametophyte is not
independent and is vulnerable to environmental stress
- Gametes do not depend on water for fertilization
- Spores are make (microspores) or female (megaspores)
= heterosporous
Megaspore = produced by meiosis, forms female gametophyte
and part of ovule
Microspore = produced by meiosis, forms male gametophyte or
pollen grains
Evolutionary advancements of seed plants:
Plant body is generally more complex (stems branch
laterally and has second growth) = letʼs grow taller =
receive more sunlight
Pollen grains produced from microspores. Pollen grains
are transported by wind, water, animals to female where
fertilization takes place. Pollen tube through which non
motile male gametes are carried directly to female
gametes in ovule. = pollen tube eliminates need for
water for fertilization
How to recognize ferns
- no owers, seeds or cones Resistant seeds are produced. Seed includes embryonic
- New leaves are coiled up and unroll from base to tip = plant (sporophyte), food storage tissue and hardened
circinate vernation protective covering (seed coat)
- Sporangia found on undersurface of leaves clusters = sori
(sorus)
The seed:
Why can they grow
- allows plant embryo to remain dormant until suitable
conditions for germination
on drier places than - Has food for embryos needs in early growth
mosses? Seed represents an important improvement over spores of
-have proper roots ferns and mosses which have limited capacity for survival
with water
conducting tissue
xylem to absorb and
transport water from
soil
-And they have a
waxy cuticle which
helps prevent water
loss
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Plant diversity
Plant classi cation
- bryophytes, pterophytes, gymnosperms, angiosperms
Classi ed by:
• Vascular tissue (xylem and phloem)
• True leaves and roots
• Dependable on water to reproduce
• Seeds or spores
• Cones or owers
• Fruit Vascular plants
- adaptations to dry environment
Adaptations needed:
• Prevent desiccation ( cuticle to decrease water loss)
• Aid nourishment ( roots to absorb water and minerals)
( vascular tissue xylem and phloem to move water and
food around the plant) ( types to carry liquid)
( supporting tissue(xylem)to hold up leaves for sunlight)
• Aid reproduction (spores and seeds)
The ability of vascular plants to do well in di erent
habitats = become dominate terrestrial group of plants
Di erences in non vascular and vascular tissue
- possess vascular tissue (xylem and phloem) to form central
No vascular plants column (stele)
- brtophytes - Sporophyte phase is larger and more conspicuous
- Poorly adapted to life on land generation of life cycle
- Live on moist, shady places growing on rocks, trees and
soil How are they classi ed:
- Mosses, liverworts and hornworts - seedless (pterophyte)
- All stay close to ground - Seed bearing (angiosperms and gymnosperms)
Characteristics Seedless plants
No vascular tissue = unable to transport water and food Pterophytes (ferns)
around plant - 12 000 fern species
No true roots, stems or leaves = they have rhizoids ( ne - Some endemic to South Africa
outgrowths of “stem” to anchor plant - More evolved for terrestrial life than bryophytes = much
No cuticle = no means to prevent water loss larger but still only grow up to 1m tall
No strengthening tissue = canʼt grow tall
Homosporous = spores are same size Characteristics
Depend on water for fertilisation ( male gametes swim Ferns are either terrestrial or epiphytic (grow upon
to female gametes) another plant)
Have life cycle with well de ned alternation of Have roots, stems and leaves (roots grow horizontally
generations from stem thatʼs partially underground) ( leaves, fronds
are deeply divided and characteristically coiled in the
bud = cucinate vernation
When dry moss plants = look brown and dead but if Have vascular tissue (xylem and phloem) xylem
splash water = revive green
tracheids are strengthened by lignin. No vessels
A sign of their aquatic origin is a motile sperm which Have thin cuticle and stomata
depends on water for fertilisation Reproduce by means of spores. Spores are released
from bursting open sporangia which grow on back of
sporophylls.
Page 1
ff fi fl fi fi fi ff fi
, They produce motile gametes which rely on water for Seed bearing plants
fertilization and therefore are found in moist A. Cone bearing plants (gymnosperms)
environments B. Flowering plants (angiosperms)
They have a independant sporophyte (life cycle)
Habitats = shady forests, crevices, rock faces, acid Seed bearing plants share with Ferns:
wetlands - plant body with roots, stem and leaves
- Presence of vascular tissue
- Dominate and independent sporophyte
Seed plant di er from mosses and ferns:
- gametophyte in seed plants is reduced in size only to a
few dozen cells = female gametophyte is not
independent and is vulnerable to environmental stress
- Gametes do not depend on water for fertilization
- Spores are make (microspores) or female (megaspores)
= heterosporous
Megaspore = produced by meiosis, forms female gametophyte
and part of ovule
Microspore = produced by meiosis, forms male gametophyte or
pollen grains
Evolutionary advancements of seed plants:
Plant body is generally more complex (stems branch
laterally and has second growth) = letʼs grow taller =
receive more sunlight
Pollen grains produced from microspores. Pollen grains
are transported by wind, water, animals to female where
fertilization takes place. Pollen tube through which non
motile male gametes are carried directly to female
gametes in ovule. = pollen tube eliminates need for
water for fertilization
How to recognize ferns
- no owers, seeds or cones Resistant seeds are produced. Seed includes embryonic
- New leaves are coiled up and unroll from base to tip = plant (sporophyte), food storage tissue and hardened
circinate vernation protective covering (seed coat)
- Sporangia found on undersurface of leaves clusters = sori
(sorus)
The seed:
Why can they grow
- allows plant embryo to remain dormant until suitable
conditions for germination
on drier places than - Has food for embryos needs in early growth
mosses? Seed represents an important improvement over spores of
-have proper roots ferns and mosses which have limited capacity for survival
with water
conducting tissue
xylem to absorb and
transport water from
soil
-And they have a
waxy cuticle which
helps prevent water
loss
Page 2
fl
ff
