Ch.8
Plants
Section 4: Gymnosperms and
Angiosperms
• Gymnosperms
– A gymnosperm is a seed plant that produces
naked seeds (not being enclosed by a protective
fruit)
– Every gymnosperm produces naked seeds. In
addition, many gymnosperms have needle-like or
scale-like leaves, and deep-growing root systems
– Oldest type of seed plant
– Four types: cycads, conifers, ginkgoes, and
gnetophytes
Section 4: Gymnosperms and
Angiosperms
• Gymnosperms
– Cycads
• Grow mainly in tropical and subtropical areas; look like palm trees
w/ cones, & grow as big as a football
– Conifers
• Cone-bearing, & largest/most diverse groups
• Ex: pines, sequoias, junipers, are evergreens
• Keep there leaves year round
– Ginkgoes
• Only one species living today & are planted along city streets
because they can tolerate air pollution
– Gnetophytes
• Live in hot desert & tropical rain forest
Section 4: Gymnosperms and
Angiosperms
• Reproduction in Gymnosperms
– Most gymnosperms have reproductive structures called cones
(are covered with scales)
– Form two types of cones: male and female
– Single plants produce both male/female but some trees
produce either male/female but some produce no cones at all
– The female gametophyte develops in structures called ovules (is
a structure that contains an egg cell)
– First, pollen falls from a male cone onto a female cone. In time,
a sperm cells and an egg cell join together in an ovule on the
female cone
– After fertilization occurs, the seed develops on the scale of the
female cone
Section 4: Gymnosperms and
Angiosperms
• Reproduction in Gymnosperms
– Pollination
• The transfer of pollen from a male reproductive
structure to a female reproductive structure is called
pollination; wind carries the pollen from male to
female; the pollen collects is a sticky substance
produced by each ovule
– Fertilization
• The ovule closes and seals in the pollen; the scale close,
and a sperm cell fertilizes an egg cell inside each ovule;
then develops into the embryo part of the seed
Section 4: Gymnosperms and
Angiosperms
• Reproduction in Gymnosperms
– Seed Development
• Female cones remain on the tree while the seeds
mature; the seed develops increasing in size which
could take up to two years
• Males cones fall off the tree after they have shed their
pollen
– Seed Dispersal
• When the seeds are mature, the scales open; the wind
shakes the seeds out of the cone and carries them away
Section 4: Gymnosperms and
Angiosperms
• Angiosperms
– All angiosperms, or flowering plants, share two
important traits. First, they produce flowers.
Second, in contrast to gymnosperms, which
produce uncovered seeds, angiosperms produce
seeds that are enclosed in fruits
Section 4: Gymnosperms and
Angiosperms
• The Structure of Flowers
– Flowers come in all sorts of shapes, sizes, and colors.
But, despite their differences, all flowers have the
same function – reproduction
– A flower is the reproductive structure of an
angiosperm
– Sepals and Petals
• When a flower is still a bud, it is enclosed by leaflike
structures called sepals (protect the developing flower and
are often green in color)
• When the sepals fold back, they reveal the flower’s colorful,
leaflike petals (most colorful part of the flower)
Section 4: Gymnosperms and
Angiosperms
• The Structure of Flowers
– Stamens
• The stamens are the male reproductive parts
• The thin stalk of the stamen is called the filament
• Pollen is produced in the anther, at the top of the filament
– Pistils
• The female parts, or pistils are found in the center of most
flowers (some flowers have 2 or more)
• The sticky tip of the pistil is called the stigma
• A slender tube, called a style, connects the stigma to a
hollow structure at the base of the flower
• This hollow structure is the ovary, which protects the seeds
as they develop
Section 4: Gymnosperms and
Angiosperms
• The Structure of Flowers
– Pollinators
• To ensure that pollination occurs the colors and shapes
of most petals and the scents produced by most
flowers attract insects and other animals
• Reproduction in Angiosperms
– First, pollen falls on a flower’s stigma. In time, the
sperm cell and egg cell join together in the
flower’s ovule. The zygote develops into the
embryo part of the seed
Section 4: Gymnosperms and
Angiosperms
• Reproduction in Angiosperms
– Pollination
• Pollinated when a grain of pollen falls on the stigma, by the
wind, birds, bats, or insects
• Nectar, a sugar-rich food, is located deep inside a flower;
when an animal enters a flower to get the nectar, it brushes
against the anthers and becomes coated with pollen
dropping the pollen onto the stigma
– Fertilization
• Fertilization occurs when pollen falls on the stigma
• A sperm cell joins with the egg cell inside the ovule, then the
zygote begins to develop into the seed’s embryo
Section 4: Gymnosperms and
Angiosperms
• Reproduction in Angiosperms
– Fruit Development and Seed Dispersal
• As the seed develops after fertilization, the ovary changes
into a fruit – a ripened ovary and other structures that
enclose one or more seeds
• Fruits are the means by which angiosperm seeds are
dispersed
• Types of Angiosperms
– Angiosperms are divided into two major groups:
monocots (are angiosperms that have only one seed
leaf) and dicots (produce seeds with two seed leaves)
Section 4: Gymnosperms and
Angiosperms
• Types of Angiosperms
– Monocots
• Ex: corn, wheat, rice, lilies, and tulips
• Have 3 petals or a multiple of three petals
• Have long, slender leaves with veins that run parallel to one
another
• Stems are scattered randomly throughout the stem
– Dicots
• Ex: roses, violets, dandelions, oak/maple trees, beans, and
apples
• Four or five petals
• Leaves are wide, with veins that branch many times
• Stems have bundles of vascular tissue arranged in a ring
Section 4: Gymnosperms and
Angiosperms
• Seed Plants in Everyday Life
– Provide useful products such as paper and the
lumber used to build homes
– Conifers are used to produce turpentine, & rayon
– Angiosperms are important source of food,
clothing, and medicine
– People eat vegetables, fruits, and cereals, which
all are angiosperms