3.2: The Plant Kingdom
pg. 96
Non-vascular Plants: Bryophytes
There are three phyla of non-vascular plants, mosses, liverworts, and
hornworts. These plants are dependent on osmosis and diffusion to
obtain their water and nutrients from the surrounding environment.
These plants develop along the ground, and do not have roots but rely
on rhizoids to act like roots.
These plants present the pioneers the converted barren terrestrial
landscape of 460 millions ago into a green environment.
Seedless Vascular Plants
Ferns formed the first forests about 350 million years ago. These
seedless vascular plants were different from the non-vascular plants.
They developed vascular tissue which also allowed them to grow tall,
greater then a metre in height.
Table 3.2: Features of Seedless Vascular Plants
pg. 98
Seed-producing Vascular Plants: Gymnosperms and Angiosperms
Gymnosperm: a vascular plant with non-enclosed seeds.
Angiosperm: a vascular plant with seeds enclosed in a protective
tissue.
There are two groups of plants that disperse by seeds, gymnosperms
and angiosperms. Seeds allow plants to reproduce sexually, without
needing water and are protected from harsh environments. The seeds
can survive without water for many years, they can be dispersed by
different means across continents. The first seed bearing plants first
appeared about 280 million year ago.
Gymnosperm Diversity
Gymnosperms (naked seeds) have seeds that are exposed on the
surface of cones. Cone bearing trees (conifers), such as; pines, firs,
yew, spruce, cedar, and redwood.
(A) Coniferous trees produce seeds on the surface of cone scales, making them a target for
animals such as birds.
(B) Cycadophytes are short, palm-like trees with scaly trunks, but they are not closely related
to palms.
(C) Ginkgo biloba is the only living species in the ginkgophyte group.
Reproduction in Gymnosperms: Cones and Pollen
The reproductive structures are cones. Male cones are usually soft
and short-lived. The female cone are hard and longer-lasting, made up
of scales where the eggs develop.
Sexual reproduction in seed plants requires a mechanism to transport
sperm from the male cone to the unfertilized egg of the female cone
for fertilization. Pollen grains are tiny, reduced gametophytes that
travel from the male cone to the female cone. The wind is usually the
dispersing method.
Angiosperm Diversity
Angiosperms, commonly known as flowering plants, are vascular
plants. These plants have flowers used for reproduction a fruit, where
the seed are contained.
90 % of all plants are angiosperms (250 000 species), roses, trilliums,
oaks, maples, and birches. A long with grasses and weeds. Flowering
plants first appeared 150 million years ago.
Angiosperm Characteristics
Flower: collection of structures in angiosperms used for sexual
reproduction.
Plants that developed many large colourful flowers are dependent on
animals for the transfer of pollen, insects collect pollen as they look
for food, nectar. Other angiosperms that produce non-colourful
flowers are reliant on the wind to disperse pollen.
Angiosperms have both male and female housed within the flower,
although there are a few angiosperms that have separated male and
female plants.
Figure 3.14: The typical flower has four organs: sepals at the base, attractive petals, male
stamens that produce pollen, and the female pistil that contains the ovary.
Fruits
Fruit: a mature ovary of a flower that protects and dispersed dominant
seeds.
Different types of fruit will help support the dispersion of seeds. Fruits
eaten by animals will have seeds dispersed when the animal excretes
later. Burrs may stick to animal fir and drop off later in different areas.
Other seeds may float in water and are washed a shore in different
areas, like the coconut.
Angiosperm Classification
Monocot: a major cluster of flowering plants that have one cotyledon.
Dicot: a major cluster of flowering plants that have two cotyledons.
Angiosperms are divided into two groups based on their structure of
their seed leaf or cotyledon. The cotyledon of the embryo helps to
nourish the plant as it starts to grow. Angiosperm embryos can have
one (monocot) or two (dicot) cotyledons.
Other characteristics expressed by angiosperms; monocots vs. dicots
are listed below in Table 3.
Table3.3: Differences between Monocots and Dicots.
Learning Check: Questions 13 – 18
pg. 101
Section 3.2 Review: Questions 1 – 13
pg. 104