Plants
Objective

Students will be able to

Describe the characteristics of
plants
An Overview of Plants

Plants
Between 260,000 and 300,000 different
species
 Have adapted to almost every
environment

An Overview of Plants

Plants have some general
characteristics:
Roots or root-like structures
 Can perform photosynthesis
 Has cells that are different from those
of other organisms

An Overview of Plants

Plant cells
Cell walls, which provide structure and
protection.
 Green pigment chlorophyll
 Central vacuole, which regulates water
content.

An Overview of Plants
Earliest plants were probably green
algae, dating back to 420 m.y.a.
 Cone-bearing plants show up around
300 m.y.a.
 Flowerings plants came into existence
around 120 m.y.a.

An Overview of Plants
An Overview of Plants

Scientists think plants probably
evolved from green algae in the sea
because:
Plants and green algae have the same
types of chlorophyll and carotenoids.
 Fossils of early plants are similar to the
ancient green algae.

An Overview of Plants

When plants moved to land, they
had to adapt to new conditions.
More sunlight and carbon dioxide were
available.
 Plants developed a cuticle—a waxy,
protective layer secreted onto the surface
of the plant which holds water in and
allows plants to live in drier conditions.

An Overview of Plants

When plants moved to land, they
had to adapt to new conditions.
Cell walls developed cellulose, a
chemical compound that provides
structure and support, which allows plants
to stand upright on land.
 Water-resistant spores and seeds enabled
plants to reproduce on land.

An Overview of Plants

Plant classification
Vascular plants use tube-like structures that
carry water and nutrients throughout the
plant.
 Nonvascular plants lack tube-like
structures and use other ways to move water
and nutrients.

Objective

Students will be able to:
Identify seedless plants
 Distinguish between vascular and
nonvascular seedless plants
 Explain a pioneer species
 Explain how humans use seedless
plants

Seedless Plants

Nonvascular plants


Very small plants that have rhizoids
rather than roots
Seedless Vascular plants

Reproduce by spores, but have vascular
tissue that carries water and nutrients
throughout the plant
Nonvascular plants
Water is absorbed and distributed
directly through cell membranes and
cell walls.
 Grow in damp environments
 Reproduce by spores rather than
seeds

Nonvascular plants

Examples of
nonvascular plants:

Mosses - green,
leaflike growths
arranged around a
central stalk
Nonvascular plants

Examples of
nonvascular plants:

Liverworts flattened, leaflike
bodies
Nonvascular plants

Examples of
nonvascular plants:

Hornworts - have
only one chloroplast
in each of their cells
Nonvascular plants

Pioneer species

Organisms that are the first to grow in
new or disturbed areas and which
change environmental conditions
Seedless Vascular plants
Reproduce by spores, but have vascular
tissue that carries water and nutrients
throughout the plant
 Can grow bigger and thicker than
nonvascular plants

Seedless Vascular plants

Examples of seedless vascular
plants

Ferns - largest group of
seedless vascular plants
Have stems, leaves, and roots
 Leaves are called fronds
 Reproduce by spores found on
the back of their fronds

Seedless Vascular plants

Examples of seedless vascular
plants

Club mosses - needlelike leaves
Seedless Vascular plants

Examples of seedless vascular
plants

Horsetails - jointed stem with a
hollow center
Seedless plants

Seedless plants are important because
they have many useful purposes
Fuel—decaying seedless plants are
compressed into peat and eventually
coal
 Soil conditioners
 Ferns can be used for weaving material
and basketry.

Objective

Students will be able to:
Describe the characteristics of a seed plant
 Describe the anatomy of a seed plant
 Distinguish between gymnosperms and
angiosperms
 Compare and contrast monocots and dicots
 Explain how humans use seed plants

Seed Plants

Have leaves, stems, roots, and
vascular tissue

Reproduce by seeds, which contain
an embryo and stored food
Seed Plants

Leaves

Trap light and
make food
through
photosynthesis.
Seed Plants

Leaves

Epidermis - a thin layer of cells on the
upper and lower surfaces of a leaf
May have a waxy cuticle coating the epidermis
 Stomata—small openings in the epidermis that
allow carbon dioxide, water, and oxygen to
enter and exit a leaf
 Each stoma is surrounded by two guard cells
that open and close it.

Seed Plants

Leaves
Palisade layer contains
chloroplasts, where
most food is made
 Spongy layer loosely arranged
cells and air

Seed Plants

Stems
allow the movement of materials
between leaves and roots.
 Usually above ground
 Support the branches, leaves, and
flowers
 May store food

Seed Plants

Stems:

Herbaceous stems—soft and green

Woody stems—hard, rigid, and woody
Seed Plants

Roots
Roots collect water and nutrients from
the ground.
 Roots anchor plants so they don’t blow
away.
 May store food or water.

Seed Plants

Vascular tissue
Xylem tissue—transports water
from the roots throughout the
plant
 Phloem tissue—moves food
from where it is made to other
parts of the plant
 Cambium tissue—produces new
xylem and phloem cells

Seed Plants

There are two kinds of seed plants
Gymnosperms
 Angiosperms

Gymnosperms

Vascular plants that produce seeds
that are not protected by fruit
Oldest trees alive
 Gymnosperms have no flowers.
 Leaves are often needlelike or scalelike

Gymnosperms

Four divisions:
Conifers
 Cycads
 Ginkgoes
 Gnetophytes

Gymnosperms

Conifers
Cone-bearing, reproducing because of
male and female cones
 Woody
 Most are trees, some are shrubs
 First trees on earth

Gymnosperms

Conifers are the oldest living things
on earth


Left: oldest tree is a
bristle-cone pine, the
Methuselah tree is 4,839
years old
Right: Newly
discovered in Sweden,
this spruce has a root
system that is 9,600
years old.
Gymnosperms

Conifers are the oldest living things
on earth

NOVA Online |
Methuselah Tree
Gymnosperms


Conifers are the tallest living things
on earth
Hyperion is the newly
discovered sequoia that is
379.1 feet tall, beating out
the Stratospheric Giant at
370.5 feet.
Gymnosperms

Conifers are the widest living things
on earth


Left: the General
Sherman Redwood at
102 ft. around
Right: The Tree at
Santa Maria del Tule,
a Montezuma Cypress
at 164 ft. in
circumference
Gymnosperms




Conifers are the widest living things
on earth
This is known as the
“Tree of a hundred
horses.”
At 204 ft around it
was the widest tree
ever measured
It now grows in three
pieces
Angiosperms

Vascular plants that flower and have
fruit that contains seeds
Fruit develops from flowers.
 Most fruit contains seeds.

Angiosperms

Two groups:

Monocots
One cotyledon in seed
 Vascular bundles scatteres
 Flower parts in multiples of three
 Parallel veins on leaves

Angiosperms

Two groups:

Dicots
Two cotyledons inside their seeds
 Vascular bundles in rings
 Flower parts in multiples of four or five
 Branching veins

Angiosperms

Different angiosperms have different
life cycles:
Annual - the plant’s life cycle is completed
within one year
 Biennial - the plant’s life cycle is completed
in two years
 Perennial - takes more than two years to
grow to maturity

Seed Plants

Seed plants are very important
because they have useful purposes
Wood for construction
 Paper products.
 Angiosperms form the basis of diets for
most animals, including humans.
