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PLANT LIFECYCLES 2003 SchoolMedia, Inc.
Learning Objectives
1)
Understand that a lifecycle consists of the different
parts of an organism’s life as it grows and changes.
Lifecycles occur over and over again.
2)
Describe the four-stage lifecycle of a typical plant.
a) Seeds: Most plants begin as seeds. The outside
part of the seed is called the seed coat; it is a sheath
that protects the seed. Inside the seed coat, there is
an embryo and a food source. The embryo, a tiny
plant, is made up of a small root, a small stem, and
very tiny leaves. The food source provides the plant
with nutrition as it begins to grow. When the
conditions are right, the seed will germinate.
b) Germination/seedling: Germination is the
process by which a seed becomes a sprout
(seedling). After the seed coat splits open, the root
of the embryo grows down into the soil. Then the
stem grows, bringing the tiny leaves up through the
soil with it. In addition, the food sources are pushed
out of the soil on the stem; they become green and
look like leaves. Called “seed leaves,” they will
provide the plant with food until it grows new
leaves. The plant’s new leaves will make the food it
needs to grow. The tiny plant that emerges after
germination is known as a seedling, or sprout.
e) Cones/seed production: Some plants do not use
flowers to produce seeds; they use cones instead.
These plants are called conifers. A pine tree is an
example of a conifer. Conifers produce two types of
cones; small cones, which make pollen, and large
cones which make seeds. Wind blows pollen from
the small cones to the large cones (pollination), and
seeds begin to grow inside the large cones. When
the weather becomes dry, the woody scales of the
cones open and the seeds fall out. These seeds may
become new plants.
3)
4)
c) Full-grown plant: As the seedling grows, it
produces more leaves, roots, and stems, which get
thicker and stronger. The result is an adult plant.
d) Flowers/seed production: When most plants are
fully grown, they produce flowers. Flowers are the
reproductive structures that make seeds. A flower
consists of a pistil, several stamens that surround
the pistil, and petals. The tips of each stamen make
pollen, which is transferred to the tip of the pistil
and on to the center of the flower (pollination).
Soon, the flower dies off, but the part where the
seeds develop grows into a fruit. The seeds will
eventually grow into new plants.
TEACHER’S GUIDE
5)
Realize that a new seed needs the right conditions to
start growing; that is, it needs the right amount of
water, the right temperature, and the right amount of
light. Not all seeds require the same conditions to
germinate. Most seeds germinate in warm
temperatures, but some seeds need a period of cold
temperatures before they germinate. Some seeds will
not grow until the intense heat of a forest fire
stimulates them.
Understand that some plants can pollinate
themselves while others require pollination from
separate individuals. The problem is moving pollen
from the stamen/small cone of one individual to the
pistil/large cone of another individual. Plants have
solved this problem in a couple of ways. Confers, for
example, developed wing-like structures on their
pollen grains that allow the wind to carry the pollen
from plant to plant. Flowering plants use insects,
birds, and other animals to move pollen, which
sticks to the animals, from one flower to another.
Note that a seed will only grow into the type of plant
from which it came. For example, a pine seed will
not grow into an iris.
Suggested Activities
1)
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overlap. Tape the diagram on the board in front of
the class. Have a class discussion comparing and
contrasting Flowering Plants and Conifers. Here are
some questions to help lead the discussion: How are
their life cycles the same? How are they different?
Do they have similar structures? What are their
defining structures? Write the answers under their
respective headings on the diagram.
2)
Plant lifecycle picture: Provide the students with
paints, markers, or crayons and a piece of white
paper. Ask them to choose a type of plant
(Flowering Plant or Conifer) and illustrate its
lifecycle. The students should draw a Seed stage, a
Germination/Seedling stage, a Full-Grown stage,
and Flower/Cone stage.
Vocabulary
Embryo — The tiny plant inside a seed
Flowering Plant — A plant that produces
flowers
Fruit — the part of the plant that contains the
seed(s)
Germinate — To become a sprout
Pollen — Male spores used to fertilize the seed
Pollination — The moving of pollen from the
male part of the plant (stamens/small cones) to
the female part of the plant (pistils/large cones)
Seed — A structure containing a plant embryo
that may germinate into a new plant
Seedling/Sprout — The tiny plant that
emerges after the seed germinates
Flowering plants vs. conifers: Obtain a large piece
of butcher paper and draw a Venn diagram on it.
Give one circle the heading, “Flowering Plants” and
the other circle the heading, ”Conifers”. Write
“Similarities” above the point where the two circles
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