Science High School Reviewer | Grade 4 Science | Life Science | Kingdoms of Life | Lesson 3: Classification of Plants

3.1 Classifying by structure

All plants need to move water and nutrients from the ground to their cells. Plants with roots, stems,
and leaves have a system of tubes for this. Mosses and other plants that lack such structures grow close to the ground. They don’t need a tube system. They take in water directly from the soil.

3.1.1 Vascular – Plants with roots, stems, and leaves

The vascular tissue does more than help the organs
of the plant get the materials they need. The vascular tissue
also adds support to the stems and leaves of the plant.
Because of the added support, the plant can grow larger.

Grass, ferns, dandelions, celery, and trees are all
vascular plants.

3.1.2 Non-vascular – Plants without roots, stems, and leaves

Nonvascular plants do
not have true roots, stems, or leaves. They can pass water and
nutrients only from one cell to the cell that is next to it. That
means that water and nutrients do not travel very far or very
quickly. These plants are usually small.
Nonvascular plants do not have a system of tubes to help
support their organs. As a result, they don’t grow very tall. But,
sometimes they grow so close to each other that they look like
one plant. Most nonvascular plants live in moist places.

Examples are mosses, hornworts, liverworts

Mosses –

Mosses form the largest group of nonvascular plants. They
often look like a velvety green mat. They sometimes live in
places with low temperatures where other plants cannot
survive.

Hornworts –

Hornworts are another group of nonvascular plants. Do you
wonder how hornworts got their name? At one stage in its life
cycle, part of a hornwort looks like a cattle horn. And the old
English word for plant is wort.

Like mosses, hornworts don’t have
true stems or leaves. Hornworts usually live in warm places.

Liverworts –

The liverwort is a nonvascular plant that often grows on
moist rocks or soil along the sides of a stream. Some liverworts
look like flat leaves that are connected to the ground. Some
have parts that look like little umbrellas. Some species have a
spicy smell. And, as you may have guessed, some species are
shaped like a liver.

3.2 Classifying by mode of reproduction

Another way that scientists classify plants is by
how they make new plants, or reproduce. Plants with
flowers or cones produce seeds. Other plants reproduce
using spores.

Flowers and Seeds
Plants in one group make seeds. A seed has many
cells. It has a young plant and stored food inside a
protective covering. Seeds are different shapes and
sizes. You can see most seeds without using a hand
lens. Flowering plants are the largest group of plants
that make seeds. The seeds and other parts of flowering
plants provide food for people and animals. A cactus,
a fruit tree, a poppy, and wheat are examples of
flowering plants.

Cones and Seeds
Pine trees belong to the group of plants that make
seeds but do not have flowers. These plants are called
conifers. Conifers grow two kind of cones. One cone
makes pollen and the other makes seeds. Most conifers
are evergreen plants. Evergreen plants keep their
leaves, or needles, year-round.

Spores
Ferns and mosses are two kinds of plants that do
not make seeds. They reproduce by forming tiny cells
that can grow into new plants. Each cell is called a
spore. Spores are different sizes and shapes. Each one
is a single cell surrounded by a protective cell wall. To
begin growing into a new plant, a spore needs a moist, shady place where it can get nutrients.
Spore cases in most ferns form on the underside of
fern leaves. They look like brown dots or streaks. In
mosses, spores are in cases at the tips of short stalks.