Download Classes of Plants: Non-seed Plants and Seed Plants

Grade 11 College Biology – Unit 4
Classes of Plants: Non-seed Plants and Seed Plants
Plants were the first multicellular organisms to live out of water. Over 500 million years ago, plants
successfully invaded land, and since that point, they have evolved to occupy a wide range of
environmental conditions.
Almost all life on Earth depends on the ability of plants to use water and carbon dioxide during
photosynthesis to produce food and oxygen.
BIODIVERSITY is the number of different species and number of individuals of each species found in an
area. The 15 million species of animals depend on the 300,000 species of plants. Thus, the loss of one
plant species can significantly reduce biodiversity. In general, an area with high plant biodiversity (e.g.,
rainforest) can support many species of animals, while an area of low plant biodiversity (e.g., mountain
tops, desert, polar regions) cannot support a wide range of animal species.
By growing only one crop in a region, humans have impacted biodiversity. Crop growing can be thought
of as a MONOCULTURE (i.e., only one plant type).
Plant Kingdom
• Plants belong to the Kingdom Plantae
• They share the following characteristics: (1) multicellular, (2) most are autotrophs (i.e., produce
their own food), (3) reproduce sexually and asexually and (4) most are terrestrial.
• During asexual reproduction, a new individual is produced by one parent AND the new individual
is genetically identical to the parent. A SPOROPHYTE is the form of plant capable of asexual
reproduction. In sexual reproduction, a new individual arises by the union of a male and female
sex cell AND it is not genetically identical to the parents. A GAMETOPHYTE is the form of a
plant that produced sexually. A life cycle that involves stages of both asexual and sexual
reproduction is called ALTERNATION OF GENERATION.
• They can be placed into two groups: (1) seed producers and (2) non-seed producers. A SEED is
a specialized plant structure that contains an embryonic plant and a supply of food.
Classes of Plants: Non-seed Plants
• There are two groups of non-seed plants; (1) mosses and (2) ferns.
Mosses and their relatives
• Mosses do NOT have a vascular system. A VASCULAR SYSTEM is a system of specialized
cells or tissues that transport water and dissolved materials between cells in the body of an
organism. Plants lacking a vascular system are called BRYOPHYTE.
• They lack true leaves and roots. Instead, they have RHIZOIDS, small root-like structures that
absorb water like a sponge
• Osmosis, diffusion and active transport are needed to move water and nutrients between cells.
Mosses grow close to the ground. How does this mode of water/nutrient transport help explain
the height of a moss? Clue: Lack of vascular means the plant lacks a tube or channel to
transport materials
•
Life Cycle
o In a spore capsule, sporophyte
produces and releases asexual
spores
o Spore germinate and develop into
gametophytes
o Mature gametophyte produces
both egg and sperm cells (female
and male plants, respectively)
o Sperm reach and fertilize the egg
(often after a rain event when a
water canal forms between the two
sexual parts of the plant). A
zygote forms.
o The zygote develops into a
sporophyte.
Ferns and their relatives
• Ferns have a vascular system. This
system enhances the plant’s ability to transport water and nutrients to the many cells of the plant.
• Ferns often have large leaves called FRONDS. What is the advantage of a frond?
• Many ferns also have RHIZOMES, stems running under the soil surface.
•
Life Cycle
o Spores are produced in sporangia
located on the underside of the
frond
o Spores are released and develop
into small, heart-shaped
gametophytes.
o The gametophyte produces sperm
and egg cells
o Mature sperm cell joins with the
egg to form a zygote
o The zygote develops into a
sporophyte. As the sporophyte
grows, the gametophyte is
destroyed by the growth of the
rhizome and roots.
Classes of Plants: Seed Plants
• Seed plants have roots, stems and leaves. Yet, there are many adaptations (e.g., leaf size, plant
size, colour).
• The most important adaptation of the seed plants is the SEED. Seeds allow the plant to
reproduce without free water, over great distances and under ideal growing conditions.
• There are two types of seed plants: (1) GYMNOSPEMS that are plants with a vascular system
that produce seeds that are NOT in an enclosed structure, and (2) ANGIOSPERMS that are
plants with a vascular system that produce enclosed seeds.
Gymnosperms
• They are WOODY (wood-producing) trees or shrubs
• Many are CONIFERS such as pines and cedars. These have needle-like leaves and are
evergreen (i.e., they do NOT drop their leaves in the fall).
• Needle-like leaves are adaptations to reduce surface area of the leaf and lower water loss. This
allows the plant to survive cold, dry winters.
•
Life cycle
o The life cycle is an ALTERNATION OF GENERATIONS
o The sporophyte is the tree or shrub. Many make cones.
o The gametophytes are tiny, microscopic plants found on the sporophyte. The female
gametophyte is found inside the female cone, while the male gametophytes are the
POLLEN GRAINS found in the male cone. The male sex cells in the pollen grains are
carried by wind to the female cones. After pollination, the zygote forms a small embryo
within a seed. When released, it develops into a sporophyte.
Angiosperms (Flowering Plants)
• Angiosperms are the largest plant group on Earth
• Many are HERBACEOUS PLANTS, plants that lack woody tissue.
• Many produce large flowers that attract insects and birds to aid in pollination. Other plants have
small flowers, and pollination is often wind-aided. POLLINATE is to transfer pollen from one plant
to another plant.
•
Life Cycle
o The male gametophytes are the pollen
grains. They are produced on the
STAMEN (male part of the flower).
o The female gametophytes are found in
the PISTIL (female part of the flower).
o The pollen germinates and produces a
POLLEN TUBE which grows down into
the ovary of the pistil. The pollen
fertilizes an egg cell.
o After fertilization, a seed is developed
containing an embryo and food supply
inside a FRUIT.
o The seed is released and develops into a
new sporophyte.
•
MONOCOTS and DICOTS
o Angiosperms are subdivided into two groups: monocots and dicots
o A MONOCOT is an angiosperm that produces seeds containing embryos with one
cotyledon. Most of the monocot seed is ENDOSPERM, a tissue that stores food
materials.
o A DICOT is an angiosperm that produces seeds containing embryos with two cotyledons.
The bulk of the dicot seed is the two cotyledons that store food for the developing
embryo.
FOR PRACTICE
Answer the following questions from your textbook
• Section 4.2 Page 279 Questions 1-3
• Section 4.3 Page 284 Questions 1-2, 4-5