Download Classifying Plants - Toronto District Christian High School

S E C T I O N
14.1
Classifying Plants
E X P E C TAT I O N S
Distinguish between nonvascular and vascular plants
and between gymnosperms
and angiosperms, based on
structural differences.
Understand differences
between monocots and dicots.
Figure 14.1 Scientists think
that terrestrial plants have
descended from a type of
green algae.
Scientists think it is probable that vascular and
non-vascular plants have common ancestors with
one group of the plant-like protists, the green algae
(see Figure 14.1). Members of the plant kingdom
have characteristics that they share with algae. For
example, both plants and algae use starch as their
primary food resource, they have cellulose in their
cell walls, and they use chlorophylls a and b
during photosynthesis. Protists, which can be
unicellular or multicellular organisms, have no
roots, stems, or leaves. Algae do not need to
develop sophisticated systems to transport
nutrients and water because they live in a medium
of water and dissolved nutrients. The algae absorb
nutrients and water directly from the external
environment, and the material diffuses from one
cell to another. There are no specialized cells to
move materials within the organism.
In contrast, members of the plant kingdom live
in terrestrial environments, from wetlands to
deserts and from tundra to tropical rain forests.
They have adapted many ways to survive these
environments, such as protecting their reproductive
cells and having more sophisticated ways of
transporting material both to and from their
environment and within the plant.
In Chapter 13, you studied the different groups
of plants in the plant kingdom and the general
characteristics of each group. Now, you will
examine how plants are classified by their structures.
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REWIND
Turn to Chapter 13, Section 13.2, to review the differences
between non-vascular and vascular plants, gymnosperms
and angiosperms, and monocots and dicots.
Non-vascular Plants
Non-vascular plants, such as the mosses,
liverworts, and hornworts (shown in Figure 14.2),
require a moist environment for two reasons. First,
they cannot reproduce unless a film of moisture is
available to carry gametes between plants. Second,
they lack vascular tissue. That is, they have no
system of tubes to carry water and dissolved
substances through the plant.
Although some non-vascular plants appear
to have root-like, stem-like, and leaf-like parts or
structures, these are not true roots, stems, and
leaves because they do not contain vascular tissue.
The root-like structures anchor the plant but do not
absorb water for other parts. The stem-like
structures hold the leaf-like parts up to the light,
but they cannot transport food or water. The leaflike structures carry out photosynthesis and make
food, but the dissolved food must diffuse to the
other parts of the plant.
Non-vascular plants are restricted in size. Even
in a very moist environment, they cannot grow
very tall because they have no specialized vascular
tissue to support them or to transport water
upward. Non-vascular plants play only a minor
role in providing food or other materials for people.
Sphagnum moss, for example, is used as a base for
flower arrangements, used as a source of organic
material for potting and gardening soils, and, in
countries such as Ireland, “mined” and cut into
blocks as fuel. The princess pine, despite its name,
is a non-vascular plant that is used in winter
flower arrangements. All trees and many of our
food plants are vascular, as are the food plants
used to nourish domestic animals such as poultry
and cattle.
BIO
FACT
Peat makes up almost 10% of Ireland’s primary energy
consumption. Raw peat is formed into pellets, sod, and
briquettes. These fuel products yield from 7 to 22 MJ/kg of
raw peat found in Ireland. In comparison, coal has a value
of about 25 MJ/kg and wood has a value of about 12 MJ/kg.
Vascular Plants
Some plants developed a specific system of
vascular tissue to transport materials within the
plant. Many early forms of vascular plants are now
extinct. Only a few of these groups of plants still
exist today — they are the whisk ferns, club
mosses, horsetails, and ferns.
Figure 14.2 Mosses, liverworts, and hornworts are
non-vascular plants.
A
B
C
D
Figure 14.3 Gymnosperms include conifers (A), which have specialized leaves and
cones (B). Angiosperms, such as oak trees (C) have leaves and acorns (D).
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About 67% of Canada’s forest area is made up
of softwoods, a forestry term for gymnosperms.
Figure 14.4 Gymnosperms and angiosperms produce seeds.
Gymnosperm or Angiosperm?
All trees living today are either gymnosperms or
angiosperms (Figure 14.3 on the previous page and
Figure 14.4). The “sperm” ending indicates that
both groups grow from seed. A seed is a complex
multicellular structure that contains an embryo and
a food supply (Figure 14.5). The embryo includes
an immature root, an immature shoot, and one or
two “seed leaves” or cotyledons. Inside the seed,
the food supply consists of nutritive tissue made
up of starch, oils, and other molecules needed for
development of the embryo. As you learned in
Chapter 13, gymnosperms have seeds without a
seed coat and are attached to the scales of cones.
embryo
seed
coat
food
supply
Figure 14.5 A seed contains an embryo and a food supply.
Many gymnosperms, such as conifers, are
adapted to thrive in environments with long cold
winters and low amounts of nutrients in the soil.
Gymnosperms dominate in large parts of Canada,
northern Europe, and northern Asia.
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MHR • Plants: Anatomy, Growth, and Functions
The gymnosperms
contribute a large
portion of Canada’s
forestry exports, in
total valued at
almost $45 billion.
Coniferous trees are
used for pulp and
paper, lumber, wood pulp,
furniture, other construction
materials, fuel for heating,
and many other products.
Figure 14.6 Gymnosperms are important to Canada’s
economy.
The boreal forest, which is characterized by
conifers, is the largest biome in Canada. In
addition, gymnosperms are vital to Canada’s
economy. Gymnosperms provide fibre for making
paper and wood for building materials. Figure 14.6
illustrates the importance of gymnosperms to
Canada’s economy.
The total number of angiosperm species is far
greater than the total number of gymnosperm
species. Angiosperms as a group are more diverse
in structure than gymnosperms. As well,
angiosperms are so widely distributed around the
world that their total biomass exceeds that of
gymnosperms. Thus, angiosperms dominate
many parts of the biosphere and they are
important as a source of food for many organisms,
including humans.
Angiosperms are also known as flowering plants.
Flowers are the angiosperm’s reproductive organs,
which mature into a seed-containing fruit. The
extra protection of the surrounding fruit gives
angiosperm seeds a strong adaptive advantage over
gymnosperm seeds, which lack an enclosing fruit.
Once gymnosperm seeds fall or are blown out of
their cones, they have only a thin cover to protect
them. As well, the fruits of angiosperms are
adapted to facilitate seed dispersal. Some fruits are
tasty (like apples), and the seeds are dispersed
when the fruit is eaten. Some are sticky (like burrs)
and are dispersed in the feathers or fur of animals.
Others are shaped for flight, such as maple keys,
and are dispersed by the wind.
The group of plants we call angiosperms
includes trees, grasses, vegetables, wildflowers, and
herbs. All angiosperms produce fruits, many of
which are edible. In addition, the roots, leaves, and
stems of many angiosperms provide food for
humans and other animals.
The number of angiosperm species is so large
that biologists needed a way to group them for
study purposes. They found that all angiosperm
seeds have either one or two (never more)
embryonic seed leaves, or cotyledons, inside the
seed, and agreed to use this difference as a basis for
classification. The two major angiosperm classes
are the monocots, which have one cotyledon, and
the dicots, which have two cotyledons. Figure 14.7
shows the major differences between monocots and
dicots, including some of the structural differences
in the leaves, stems, and roots.
Monocots
About 10% of all monocots have woody (tough and
rigid) stems. Examples of woody monocots include
Seed leaves
palms and bamboos. Such species are grown for
ornamental purposes in Canada, but only where
the climate is mild. Most woody monocots grow in
warmer climates and are sources of food such as
dates, coconuts, bananas, palm oil, and sugar.
Sugar cane, a woody monocot, is a type of grass.
Few monocots are suitable to use as building
materials. However, the hollow stems of bamboo
provide a light, strong structural material often
used in Asia for scaffolding and furniture. In
contrast, the stems of palm trees are heavy and
crumbly, with little strength for their weight.
Bamboo shoots are used as food by humans and by
giant pandas (see Figure 14.8).
Figure 14.8 Bamboo shoots and roots are the only food
giant pandas can eat in the wild.
Veins in leaves
Vascular bundles
in stems
Flower parts
Monocots
one
cotyledon
usually parallel
scattered
multiples of
threes
Dicots
two
cotyledons
usually netlike
arranged in ring
multiples of
fours and fives
Figure 14.7 Distinguishing characteristics of monocots and dicots
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Two monocots, bananas and their near relatives,
plantains, are a major source of carbohydrates for
many of the world’s people. During the 1980s,
agronomists feared that a fungal infection would
wipe out these important food plants. They were
able to develop a new disease-resistant banana
variety. This proved to be much more difficult than
developing a new wheat variety, for instance,
because cultivated bananas and plantains do not
contain seeds. Why do you think this is so?
Investigation
We b
LINK
Researchers established a banana breeding program by going
back to early wild varieties, which do contain seeds. However,
developing plump, sweet, cultivated bananas from wild ones
presents a considerable challenge. How do researchers
overcome the challenge? Go to the web site shown below to
find the answer. Go to Science Resources, then to BIOLOGY 11
to find out where to go next.
www.school.mcgrawhill.ca/resources/
SKILL FOCUS
1 4 • A
Performing and recording
Comparing Monocots and Dicots
Analyzing and interpreting
In this investigation, you will compare the parts of monocot and dicot
plants. Apart from differences in their number of cotyledons, monocots
and dicots differ in the appearance of their flowers and leaves. In
monocots, the flower parts (such as petals) occur in groups of four or
five (or multiples of four or five), while dicots have parts that occur in
groups of three (or multiples of three). As shown below, the vascular
tissue in the leaves of monocots is found in parallel veins; vascular
tissue in dicot leaves is found in branching veins.
Communicating results
Prediction
Predict which external characteristics of
angiosperms can be used to determine if the
plant is a monocot or a dicot.
CAUTION: Wash your hands thoroughly after the
investigation. Use care when cutting the seeds.
Scalpel blades are very sharp, so follow your
teacher’s instructions.
Monocot leaves (A) have parallel veins. Dicot leaves (B)
have branching veins.
What characteristics distinguish a monocot
and a dicot? Refer to Figure 14.7 on page 525
to review these characteristics.
pre-soaked seeds of beans, corn, peas, etc.
stem, leaves, and flowers of various plants (such
as onion, herbs, house plants, and others)
magnifying glass
sketching materials
scalpel
Are there any differences in growth patterns
between monocots and dicots?
Procedure
Pre-lab Question
Problem
Use live plant specimens and photographs of
plants to determine whether a plant is a
monocot or a dicot.
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Materials
MHR • Plants: Anatomy, Growth, and Functions
1. Dissect one sample of each type of seed to
find out whether its embryo has one or two
cotyledons. Alternatively, if you let the
seeds germinate, the number of cotyledons
Most monocots are non-woody or herbaceous —
that is, their stems are soft and fleshy. Ornamental
examples include orchids, lilies, tulips, and other
spring bulbs. In terms of food for land animals, the
most important monocots are the grasses. Cows and
rabbits eat grasses, and so do you. However, there
is a difference in what plant parts are eaten.
Rabbits and cows obtain energy from the leaves of
grass. They are able to do this because both have
bacteria in their digestive systems that produce
enzymes able to cut the “crossties” in cellulose
will be obvious once the young plants
emerge from the ground.
Post-lab Questions
2. Obtain samples of stems, flowers, and leaves
of various plants. Use their characteristics to
classify the plants as monocots or dicots.
3. Sketch an example of each structure you
examined. Identify as many differences
among the samples as you can.
blue flag
wild rose
pitcher plant
1. What differences did you observe in the
external appearance of monocot and dicot
plants?
2. Which class dominates the official list of
floral emblems? Identify the province or
territory for each floral emblem.
Conclude and Apply
4. Each of the plants shown below is the floral
emblem of a Canadian province or territory.
Look at the photos and determine whether
the floral emblems are monocots or dicots.
Use Figure 14.7 (on page 525) to help you in
your classification.
trillium
molecules, and thereby release glucose units. (This
relationship between bacteria and animals such as
rabbits and cows is one that benefits both species;
it is called mutualism.)
Humans do not have bacteria that can digest
grass blades (leaves), even if the leaves are boiled
or chopped. Our bodies cannot produce the enzymes
needed to break down the cellulose of grass leaves
into simple glucose units. We do, however, eat the
seeds of grasses as you will learn next.
3. Create a chart or table listing the differences
you noted between monocots and dicots.
Name the most significant differences.
4. Develop a hypothesis to test whether or not
there are any functional differences between
monocots and dicots.
prairie crocus
(pasque flower)
lady slipper
purple
saxifrage
violet
dogwood tree
fireweed
mountain avens
prairie lily
mayflower
Plant Characteristics and Functions • MHR
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A
B
C
Figure 14.9 Important monocot species in many countries include rice (A),
wheat (B), and corn (C).
Humans can digest most of the matter in the
seeds of grass plants such as wheat, corn, and rice
(see Figure 14.9). Each of these seeds has large
stores of carbohydrates, along with smaller
amounts of protein and oils. Wild grasses produce
seeds much smaller than those of today’s prairie
wheat. Varieties have been developed that produce
more usable human food per plant. As well,
hybridization techniques have produced new
varieties of wheat, oats, and barley that are both
more climate-tolerant and disease-resistant than
earlier varieties.
About 15% of Canada’s forest area is made up of
hardwoods, a forestry term for angiosperm trees.
FAST FORWARD
Turn to Chapter 15, Section 15.2, to learn about the
technologies for increasing production or quality of crops.
Dicots
Most of Canada’s native tree species are dicots.
Some of these deciduous trees are important
economic resources in Canada (see Figure 14.10).
Most native wildflower species are also dicots
(see Figure 14.11) and a typical salad contains a
diversity of dicots such as lettuce, tomatoes,
radishes, and sunflower sprouts. Only the onions
are monocots. The staple foods of many cultures,
past and present, are dicots — yams, potatoes,
rutabaga, and cabbage are all rich in starch. Bean
seeds are rich in protein, while bean pods are rich
in vitamins.
The wholesale
value of Canada’s
maple products is
about $150 million.
Deciduous trees
contributed a portion
of Canada’s forestry
exports, in total valued
at almost $45 billion.
Deciduous trees are
used to make furniture,
hockey sticks, fuel for
heating, carvings, and
many other products.
Figure 14.10 Deciduous trees are important to Canada’s
economy.
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MHR • Plants: Anatomy, Growth, and Functions
Figure 14.11 Most native wildflowers are dicots.
Figure 14.12 Which produce are dicots?
Canadians in Biology
Naturalist and Artist
Many know him best for his animal art, but Robert
Bateman thinks of himself as a naturalist. He spends just
as much time studying and painting rocks and plants as
he does on the animals that are featured in most of his
paintings.
shared the birds’ habitats. Bateman chose to study
geology at university, “because I knew there would be
lots of field trips — I would get outdoors.” He went on to
become a teacher of art in his home province of Ontario,
painting whenever he could find time. By the time he
reached his 40s, he was able to earn his living solely
through artistic endeavours.
Robert Bateman believes that the biological knowledge
gained by observing the organisms that share our world
could be used by high school graduates throughout their
lives. When speaking in public, he urges people to go
outdoors and “meet the neighbours.” Plants would make
a good starting point because they are much easier to
observe and identify than birds or other animals. Even if
you are a city dweller, you may have access to natural
areas set aside by your city’s parks department. In
addition, some public gardens have signs identifying
the different kinds of plants.
Knowing the names of the plants around you can be a
great source of personal satisfaction. For example, do you
know the names of the native and ornamental plants that
grow near your home? What about the summer weeds?
Nuisance or not, they are also part of the biosphere.
Robert Bateman’s painting of a Northern saw-whet owl
When Robert Bateman was in high school, he and two
friends used to go on secret bird-watching expeditions.
Why secret? “We were afraid the other fellows would
laugh at us,” he says. In order to locate the birds, the
three friends had to learn how to identify the birds’
habitats: the trees and other plants where the birds lived.
Inevitably, they also learned about the other animals that
To become familiar with plants in your community you
might organize your own field trip, perhaps with a friend,
or relative. You can borrow a field guide to native plants
from a public library. You might want to take a bird guide
along as well. Bird-watching is now one of the fastest
growing activities in North America. When you return the
guides, borrow one of Robert Bateman’s books from the
library. Each one consists mainly of pictures, and each
picture includes meticulous renderings of plants and
animals from around the world.
Plant Characteristics and Functions • MHR
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What factors can contribute to diversity among
organisms? Vascular plants may be either
angiosperms or gymnosperms, and are grouped
according to the number of embryonic leaves the
seeds have. Factors that can contribute to their
diversity are summarized in the Figure 14.13.
How does studying various structures of plants
and other organisms help us to learn about
their functions?
CONCEPT ORGANIZER
COURSE CHALLENGE
Many plants have specific requirements for
survival. In many cases plant species are associated with a
specific geographic area. By identifying a plant species it
may be possible to determine where the plant came from.
How might knowledge of plant biology be useful in
reconstructing past events or environments? Write your
thoughts in preparation for your Biology Course Challenge.
Predicting the Outcome
Plant Vascular Tissue
(Chapter 14, Section 14.1)
Phylum Chordata
(Chapter 13, Section 13.3)
Origins of Diversity
(Chapter 11, Section 11.4)
Cell Structures
(Chapter 2, Section 2.1)
In biology, the structure of an organism, a cell, and even a
molecule is closely related to its function (or functions).
Thus, you can often understand differences in the
appearance and distribution of groups of organisms by
knowing if they have certain key structures or if they lack
them. Why is one species of plant small and delicate while
another species is large and robust? The answer may lie in
the structure of the plant’s vascular tissue. Now consider
differences in the structure and function of plants with
flowers and plants without flowers. Of animals with backbones and animals without backbones. Of eukaryote cells
(with nuclei) and prokaryote cells (without nuclei). Of
organisms with chloroplasts and without chloroplasts. What
other key structures in biology do you know? The origin of
different structures in different groups is explained, in turn,
by differences in their environments and evolutionary history.
Figure 14.13 How diversity originates
SECTION
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REVIEW
1.
K/U What is the main difference between a
gymnosperm and an angiosperm? List five examples
of each type of plant.
2.
K/U An onion seed germinates and a single leaf
emerges from the soil. Is the onion a monocot or a
dicot? What evidence did you use to make your
classification?
3.
C What are some of the differences between
monocots and dicots? List them and give examples
of plants that show these differences.
4.
K/U A shopper notices that alfalfa sprouts have two
leaves each. Classify alfalfa as either monocot or
dicot. What evidence did you use?
MHR • Plants: Anatomy, Growth, and Functions
5.
I You are given seeds from an unidentified plant.
Outline a procedure that you could use to help you
classify the seeds to a major plant group.
UNIT ISSUE PREP
Many industries in Canada are based on resources from
various species of gymnosperm and angiosperm. What
are some of these industries and what is their value to the
Canadian economy? How would you summarize this
information for a brief presentation? Who would you be
addressing? Would this affect how you present your
data? Prepare an outline of your ideas in preparation for
your Unit 5 Project.