KINGDOM OF PLANTAE
GRADE 11
BIODIVERSITY OF PLANTS
• All plants are thought to have evolved from simple
unicellular algae.
• The kingdom Plantae is divided into four main groups or
divisions:
• Bryophytes – mosses
• Pteridophytes – ferns
• Gymnosperms – conifers, cycads
• Angiosperms – flowering plants
Diagram showing a phylogenetic tree of the evolution of
plants
The characteristics used to place a plant into one of the
four groups depends on:
• The presence or absence of true conducting tissues such
as xylem and phloem
• The presence or absence of true, roots, stems and leaves
• The type of reproduction and reproductive structures
formed and
• The degree of dependence on water for reproduction.
a) Bryophytes (moss)
• They do not have true roots, stems or leaves
(thallus).
• Water can be absorbed directly through the
leaves because there is not a waxy cuticle
covering the leaves.
• The size of mosses is limited because no xylem
or phloem (vascular tissue) is present.
• The gametophyte generation is the dominant
generation.
• No fruits or seeds produced.
b) Pteridophytes (ferns)
• Ferns have true leaves, roots and stems.
• Fern leaves are covered by a waxy cuticle to prevent
excessive loss of water.
• Fern leaves are referred to as a frond.
• The presence of vascular tissues allows ferns to grow
taller than mosses.
• The stems of most ferns grow horizontally and are
called rhizomes.
• The dominant generation in ferns is the sporophyte
generation.
• Spores are produced in sporangia arranged in sori
under the leaf
• No fruit or seeds are produced.
c) Gymnosperms (Conifers)
• Gymnosperms have true roots, stems and leaves.
• Vascular tissues are present.
• The leaves of pine trees are needle-like and have a
cuticle to reduce the loss of water through evaporation.
• Gymnosperms do not produce flowers.
• They form both male and female cones.
• The fertilization in gymnosperms is not dependent on
water.
• The seeds of the pine are said to be “naked” because
they are not protected by a fruit.
• The sporophyte generation is the dominant generation in
gymnosperms.
d) Angiosperms (Flowering plant)
• Angiosperms are commonly referred to
as “flowering plants”.
• The sporophyte generation is the
dominant generation in angiosperms.
• It consists of true roots, stems and leaves.
• Vascular tissues present.
• Angiosperms produce seeds protected
by fruit.
• Gymnosperms and angiosperms are also
known as spermatophytes because they
both produce seeds.
Characteristic Bryophytes (Moss) Pteridophytes Gymnosperms Angiosperms
(Ferns)
Vascular tissue i.e. No true conducting Has well -developed Has well -developed Has well -developed
xylem and phloem tissues vascular tissues (xylem vascular tissues (xylem vascular tissues (xylem
and phloem) and phloem) and phloem)
True leaves and roots Thallus - no true roots, Has true roots, an Has true roots (tap root Has true roots, stems
stems and leaves. underground stem and system, with lateral and leaves
Rhizoids anchor the large compound roots), woody stems
plant in the ground leaves. and small leaves
(needle shaped)
Seeds or spores and Produces spores, no Produces spores, no Produces cones with Produces flowers with
fruit seeds seeds seeds without a seeds enclosed and
The gametophyte protective covering. protected by a fruit.
generation is the Has separate male Has separate male
dominant generation spores (in pollen grain) spores (in pollen grain)
and female spores (in and female spores (in
ovule) ovule)
Dependence on water Depends on water Depends on water for Does not depend on Does not depend on
for reproduction for fertilisation of fertilisation of gametes water for fertilisation of water for fertilisation of
gametes gametes gametes
Table continued…
Reproduction Reproduce Reproduce both Reproduce both Reproduce both
either asexually sexually and sexually and sexually and
or sexually. asexually. asexually. asexually.
The The sporophyte The sporophyte The sporophyte
gametophyte generation is the generation is generation is the
generation is the dominant dominant dominant
dominant generation. generation generation
generation
Reproduction in plants:
• Both animals and plants are capable of asexual and sexual
reproduction.
a) Asexual reproduction:
• In asexual reproduction only one parent is involved and all the
offspring have the same genetic composition as the parent.
• No gametes (sex cells) i.e. sperm and ova are involved and the
process occurs by mitosis.
• Examples of asexual reproduction include binary fusion, vegetative
reproduction, formation of spores, budding and cloning.
Advantages of asexual reproduction:
• A large number of offspring are rapidly produced.
• Energy expenditure is low because no gametes are produced.
• All the offspring are identical.
• Asexual reproduction does not rely on pollinators or dispersion
agents.
Disadvantages of asexual reproduction:
• There is no genetic variation as all offspring are genetically identical.
• Weak characteristics in the parents will be passed on to the
offspring.
• Any change in the environment changes may drastically reduce
the offspring’s chances of survival.
• Rapid multiplication by asexual reproduction may lead to
overpopulation.
b) Sexual reproduction:
• In this type of reproduction two parents are involved and their
genetic material combines.
• Gametes (sex cells) i.e. sperm and ova are produced by meiosis.
• Fertilisation takes place i.e. a haploid male gamete (sperm) and a
haploid female gamete (ovum) fuse to form a diploid zygote.
• The zygote divides by mitosis to form an embryo and later, a new
organism.
Advantages of sexual reproduction:
• The offspring are genetically different and shows greater genetic
variation.
• Farmers can select organisms with desirable characteristics and
cross-breed with them.
Disadvantages of sexual reproduction:
• Sexual reproduction takes longer.
• Fewer offspring are produced.
• Plants that reproduce sexually rely on pollinating agents e.g. wind or
insects and to spread their pollen and seeds.
