CHAPTER
1
Classifying Life’s Diversity
Specific Expectations
In this chapter you will learn how to . . .
• B1.1 analyze some of the risks and
benefits of human intervention to the
biodiversity of aquatic and terrestrial
ecosystems (1.4)
• B2.1 use appropriate terminology
related to biodiversity (1.1, 1.4)
• B2.4 create and apply a dichotomous
key to identify and classify organisms
from each of the kingdoms (1.3)
• B3.1 explain the fundamental principles
of taxonomy and phylogeny (1.1, 1.2)
• B3.2 compare and contrast the
structure and function of different
types of prokaryotes, eukaryotes, and
viruses (1.3)
• B3.5 explain why biodiversity is
important to maintaining viable
ecosystems (1.4)
This blind, white crab, known as the yeti crab (Kiwa hirsuta), is
covered in hair-like structures that are home to millions of bacteria.
Living more than 2 km under the ocean’s surface, this crab is a new
species discovered during the Census of Marine Life. The Census is
a 10-year project with the goal of learning more about the diversity
and distribution of marine life.
The yeti crab is one example of that diversity. Based on genetic
analysis, it is so different from other crabs that a new family,
Kiwaidea, was created to help classify it. Identifying and classifying
this crab, along with more than 5000 other new species discovered
by the Census, helps scientists learn more about the history and
biodiversity of life on Earth. It also helps people make decisions
about how to ensure that ocean biodiversity endures for the future.
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Launch Activity
Organizing Life
When you think of biodiversity, you may think of the ocean or a
rainforest. However, biodiversity exists in your area as well. Think
about the different types of birds, insects, or plants that you see when
you are outside in your neighbourhood. How many different kinds of
organisms live in your neighbourhood? In this activity, you will list and
classify local species.
Procedure
1. Make a list of all the different plants, animals, and fungi that you
observe during a 15-minute trip around your school or home.
Include indirect evidence of organisms as well, such as tracks, animal
droppings, nests, and sounds. Aim for at least 15 species in your list.
2. Organize your list into three main groups: plants, animals, and fungi.
Within each main group, create subgroups based on the similarities
and differences you observe or infer among the various kinds of
organisms. Begin by choosing a characteristic that lets you divide
each group into two subgroups: one that has the characteristic and
one that does not. For example, one characteristic could be wings
and no wings.
3. Next, decide if you can divide any of your groups and subgroups
further using another characteristic. If so, list the organisms in each
new group or subgroup.
4. Continue dividing your lists until you cannot see another way to do so.
Questions
1. What characteristics did you use to define your groups? How many
different subgroups did you make?
2. Exchange your lists with a partner. Interpret and discuss each other’s
system of classification.
3. Compare the similarities and differences among the classification
systems in the class. Why were so many systems invented?
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SECTION
1.1
Key Terms
species
morphology
phylogeny
taxonomy
binomial nomenclature
genus
classification
hierarchical classification
rank
taxon
species a group of
organisms that can
interbreed in nature and
produce fertile offspring
Identifying, Naming, and Classifying Species
Take a moment to think about the great variety of organisms that inhabit Earth. From
microscopic bacteria to carnivorous plants that capture insects, whales that migrate
thousands of kilometres, and fungi that help break down dead trees, there are millions
of species on Earth. To date, scientists have identified about 2 million species on Earth.
Although 2 million is a large number and new species are discovered every day, it is
thought that this is just a fraction of the total number of species on Earth. Scientists
estimate that the total number of species on Earth ranges from 5 million to 20 million.
Knowing the identity of Earth’s species is important not just to biologists or other
scientists, but to everyone in society. Farmers and gardeners need to be able to identify
weeds that might be growing next to their crop plants. Doctors need to know which
species of bacteria a patient is infected with in order to prescribe the correct medication
for treatment. Many people, including Aboriginal peoples, collect plants for medicinal
use. It is critical for them to correctly identify the species they need. Border inspection
officials must check incoming goods to prevent the introduction of an invasive
species. Because species have been identified, defined, and named by scientists, people
worldwide can communicate about all of the different organisms that live on Earth.
Identifying and Naming New Species
Suppose you are a scientist who discovers a new species, such as the woolly rat found
in the crater of a volcano in New Guinea or the pink iguana found on only one of the
Galapagos Islands, both of which are shown in Figure 1.1. Although it seems obvious that
the rat is a mammal and the iguana is a reptile, how would you determine exactly what
species these organisms are? What methods would you use to determine how closely
they are related to other species? What methods would you use to classify them and give
them scientific names? Throughout history, scientists have used different methods, and
examined and compared different characteristics, to define and classify a species.
A
B
Figure 1.1 (A) The Bosavi woolly rat, about 1.5 kg in mass and 80 cm in length, is one of the
largest rats in the world. Despite its size, it is closely related to the rats and mice most people
are familiar with. (B) This pink iguana is found only in the crater of Wolf Volcano on Isabela
Island in the Galapagos Islands.
Apply How might scientists determine whether this pink iguana is a different species from
other iguanas living on the same island?
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Identifying Species: Using Species Concepts
Despite centuries of thought and research, scientists have been unable to agree on a
single definition of what a species is. Instead, they have proposed various definitions
of species, which are called species concepts. Table 1.1 describes three commonly used
species concepts, along with advantages and disadvantages for each. Notice that each
species concept focuses on a different aspect of organisms.
• The morphological species concept focuses on morphology—body shape, size, and
other structural features.
morphology the
branch of biology that
deals with the structure
or form of organisms
phylogeny the
evolutionary history of
a species
• The biological species concept defines species on the basis of whether two organisms
can produce fertile offspring.
• The phylogenetic species concept examines the phylogeny, or evolutionary history,
of organisms.
Table 1.1 Species Concepts
Species Concept
Morphological species concept
Biological species concept
Advantages and Disadvantages
The morphological species concept
focuses on the morphology of an
organism. This species concept relies
on comparing measurements and
descriptions of similar organisms,
taking into account that species change
over time and that they have variation.
After comparisons are completed,
scientists decide whether similar
organisms represent different species.
Advantage: The relative simplicity of
this species concept makes it the most
widely used, particularly for plants.
The biological species concept focuses
on similar characteristics and the
ability of organisms to interbreed
in nature and produce viable, fertile
offspring. This means that if two
individual organisms can mate under
natural circumstances and they
produce offspring that can successfully
live and reproduce, then those two
individuals are the same species.
Phylogenetic species concept
Bacteria
Archaea
Common
Ancestor
Description
The phylogenetic species concept
focuses on evolutionary relationships
among organisms. A species is
defined as a cluster of organisms
that is distinct from other clusters
and shows a pattern of relationship
among organisms. For example, when
a prehistoric species branches into
two species over time, it becomes
two different phylogenetic species.
This concept has become increasingly
popular as biologists have obtained
more evidence through DNA analysis
about how species are related.
Disadvantage: The challenge in
applying this species concept comes
from having to decide how much
difference between individuals is too
much variation. Almost all populations
are made up of non-identical
individuals.
Advantage: This species concept is
widely used by scientists.
Disadvantages: This species concept
cannot be applied in all cases. For
example, when two populations are
physically separated, they never have
the opportunity to interbreed in
nature. This means that the viable,
fertile offspring requirement cannot
be tested. Also, this species concept
cannot be applied to organisms that
reproduce asexually, nor can it be
applied to fossil species, which are no
longer reproducing.
Advantages: The phylogenetic species
concept can be applied to extinct
species. It also considers information
about relationships among organisms
learned from DNA analysis, a method
scientists are using more and more. For
example, it was through DNA analysis
that scientists were able to classify the
pink iguana from the Galapagos Islands
as a new species.
Disadvantage: Evolutionary histories
are not known for all species.
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Naming Species
Once researchers have decided which organisms qualify as a separate species, a name
must be assigned to the species. Most familiar organisms have been given several—
and sometimes many more—names that differ from continent to continent, country
to country, and often from region to region within the same country. For example,
in English-speaking North America alone, the animal in Figure 1.2 may be known to
different people as a groundhog, a woodchuck, a whistle pig, or a forest marmot. Using
so many names for the same type of organism can cause confusion. Thus, having a
standard system for naming organisms, understood by any scientist, anywhere in the
world, is essential.
Figure 1.2 This animal, made famous every February 2 in Canada and the United States, is
known in English by many names. To biologists around the world, however, it is known only by
one name: Marmota monax.
taxonomy the branch
of biology that identifies,
names, and classifies
species based on natural
features
binomial
nomenclature the
system of giving a
two-word Latin name
to each species—the
first part is the genus
and the second part is
the species
genus (plural genera)
taxonomic group of
a closely related species
A System of Standard Names for Species: Binomial Nomenclature
Taxonomy is the branch of biology that identifies, names, and classifies species.
Swedish scientist Carl von Linné, who is better known by the Latinized version of his
name, Carolus Linnaeus, is often referred to as the Father of Taxonomy. He is credited
with developing the system for naming species: binomial nomenclature. Binomial
refers to something with two parts, and nomenclature means a naming system. Thus,
in this system, each species has a two-part name. The two-part name is known as the
species name, although it is often referred to as the scientific name as well.
The first word in the scientific name is the genus name. The second word in the
scientific name identifies the particular species. The scientific name is italicized when
typed, with the genus name capitalized and the species in lower case. For example, the
scientific name for humans is Homo sapiens. When the scientific name is written by
hand, both parts of the name are underlined.
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Learning Check
1. Explain why it is important to everyone in society
for scientists to identify, define, and name species.
2. Explain why there are several different species
concepts, rather than a single definition for a species.
3. State which presentation of the scientific name for
the domesticated dog is correct. Then explain why it
is correct and why the other three are incorrect.
a. Canis familiaris
c. Canis familiaris
b. Canis familiaris
d. Canis Familiaris
4. Explain the advantages of using binomial
nomenclature rather than common names to refer
to organisms.
5. Use a graphic organizer to compare and contrast the
types, advantages, and disadvantages of the species
concepts described in Table 1.1.
6. The offspring of a horse and a donkey is a mule.
Mules are unable to reproduce. Are horses and
donkeys members of the same species? Why or why
not? Use the biological species concept to explain
why or why not.
Classifying Species
Species concepts allow scientists to determine what groups of organisms make up a
species. Binomial nomenclature allows scientists to apply a formal name for each of
those species. But millions of species currently live on Earth, and many other extinct
species have been identified from fossils. However, to understand, demonstrate, and
communicate the relationships in life’s diversity, scientists need a set of agreed-upon
rules or criteria to help them classify species. Again, it was Linnaeus who developed
the basis of the system of classification we use today.
Activity
1.1
classification the
grouping of organisms
based on a set of
criteria that helps
to organize and
indicate evolutionary
relationships
You Decide: Snake or Lizard?
Suppose that you observe a reptile like the one shown
in the photograph below. The reptile has no legs. However,
that does not mean that it is a snake, because legless lizards
also exist. How could you determine whether this reptile is
a snake or a lizard?
Procedure
1. Use the information in the table on the right to
determine whether your specimen is a snake or a lizard.
Questions
1. What type of reptile do you think the organism is?
Explain your reasoning.
2. Which species concept did you use to help classify your
specimen? Explain your reasoning.
3. What other data could you collect or analyze to provide
additional evidence to help you confirm your decision?
Morphological Characteristics of Snakes and Lizards
Ear
Openings
Tail Tip
Breaks
Off When
Handled
Legs
Organisms
Eyelids
Snakes
Cannot
move
No
No
No
Lizards
Movable
Yes
Yes
Yes
Your
specimen
Movable
Yes
Yes
No
This legless reptile is known as Ophisaurus attenuatus.
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hierarchical
classification the
method of classifying
organisms in which
species are arranged in
categories from most
general to most specific
Hierarchical Classification
Imagine a world in which there are just four sports: golf, tennis, hockey, and soccer.
Any sports competition could then be classified in one of four categories—a very
simple, un-nested system, such as the first one in Figure 1.3. Notice, however, that
this simple system can be modified by rearranging the sports into categories based on
the characteristic of team sports versus non-team sports. The resulting classification
scheme is known as a nested system, because there is a hierarchy of categories. That
is, the four specific sports are clustered into two more general categories. A hierarchy
is an arrangement of items in which the items are identified as being above, below,
or at the same level compared to other items. Because nested classification systems
have categories arranged in hierarchies, this method of organization is called
hierarchical classification.
Un-nested Classification
Sports
Hockey
Soccer
Tennis
Golf
Nested Classification
Sports
Team Sports
Hockey
Non-team Sports
Soccer
Tennis
Golf
Figure 1.3 Both of the classification systems shown here recognize the four activities as sports, but
the nested classification provides more information. As more items (in this case, sports) are added,
nesting becomes increasingly important for making classification as clear and detailed as possible.
rank a level in a
classification scheme,
such as phylum or order
taxon (plural taxa)
a named group of
organisms such as
phylum Chordata or
order Rodentia
Taxonomic Categories Used To Classify Organisms
Taxonomic categories are the groupings, arranged in a hierarchy, that are used to
classify organisms that have been named and identified. In most cases, a species is
classified by assigning it membership in eight nested categories. Each of the eight
taxonomic categories is known as a rank. The name of each rank is called a taxon.
Table 1.2 shows how the species Canis lupus, the grey wolf, is classified using
taxonomic categories. To start, based on the morphology and complexity of its cells,
the grey wolf is placed in the domain Eukarya. A domain is the broadest of the ranks
(categories). All large organisms have similar cells, so the grey wolf shares that domain
with millions of other species, including those that do not have obviously similar
characteristics, such as sugar maples and mushrooms.
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Table 1.2 Taxonomic Classification of the Grey Wolf (Canis lupus)
Rank
(Taxonomic
Category)
Grey Wolf
Taxon
Number of
Species
in Taxon
Domain
Eukarya
Kingdom
Animalia
2 million
Phylum
Chordata
50 000
Class
Mammalia
5 000
Order
Carnivora
270
Family
Canidae
Genus
Canis
7
Species
Canis lupus
1
Examples of Species in Taxon
4–10 million
34
The Grey Wolf: Kingdom to Species
Within the domain Eukarya are four kingdoms, and the grey wolf is placed in the animal
kingdom. The kingdom has fewer species in it than a domain. However, because the
animal kingdom includes insects and all other animals, it still contains more than a
million species. As you can see from Table 1.2, within the animal kingdom is the chordate
phylum. A phylum further narrows an organism’s classification. Wolves are classified in
the chordate phylum. The chordate phylum does not include animals such as insects and
worms, but it still includes other groups, such as fish and birds.
As classification of the grey wolf continues to be narrowed down, the ranks become
more specific and the number of members in each taxon becomes fewer. A major chordate
class is the mammals—warm-blooded animals that have fur or hair and that nurse their
young. Within the mammals is the order Carnivora, a group adapted for meat-eating,
which includes weasels, cats, dogs, and seals. Within that order is the family Canidae, the
dogs, including foxes, jackals, and the domestic dog. The Canis genus includes the grey
wolf, shown in Figure 1.4, as well as the coyote and five other species. Finally, the only kind
of animal that remains at the species level is the grey wolf—Canis lupus.
SuggestedInvestigation
ThoughtLab Investigation
1-A, Classifying Aquatic
Species
Figure 1.4 Wolves are
carnivores, a characteristic
that distinguishes them
from other types of
mammals.
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Section 1.1
RE V IE W
Section Summary
• Biologists use the morphological species concept,
the biological species concept, and the phylogenetic
species concept to define species.
• Species often have common names. However, they are
formally known by two-part scientific names.
• All species are classified by being placed in eight nested
ranks. The broadest category is the domain, continuing to
narrow to kingdom, phylum, class, order, family, genus,
and finally species, which is the narrowest category.
• Each named rank is known as a taxon.
Review Questions
1.
C
Make a Venn diagram to compare and contrast
the morphological species concept and the
phylogenetic species concept.
2.
In northwestern Ontario, there are two similarlooking garter snakes: the red-sided garter snake
and the eastern garter snake. The two interbreed
successfully in nature in that part of Ontario,
producing offspring that have a mix of the physical
traits of the two. The eastern garter snake also co-exists
in southern Ontario with another very similar snake,
the eastern ribbon snake. However, these two snakes
are not known to interbreed successfully. Infer whether
these three snakes are the same species or not. Explain
your reasoning.
3.
4.
A
K/U
Category
Domain
Two terms can be used to describe the
organization of organisms into hierarchies that help
scientists understand the relationships among living
things: classification and taxonomy. Explain why both
terms can be used correctly for this purpose.
K/U
Design a different nested classification for the
four sports in Figure 1.3.
6.
C
A mnemonic is something to help people
remember things. Help yourself remember the eight
taxonomic ranks by making an eight-word mnemonic
sentence using the first letter of each rank as the first
letter of each word in the sentence. An example is Does
Kim Play Chess Or Fix Great Sandwiches?
7.
Distinguish between the terms rank and taxon.
Include an example in your answer.
8.
Two organisms belong to the same family in the
modern classification system. List the other ranks in
which these two organisms would also be placed
within this system.
A
The table below shows the classification of a
praying mantis, an insect that preys on smaller insects.
a. What is the scientific name for the praying mantis?
b. Which is the broadest category of classification for
the praying mantis?
c. What is the narrowest rank and taxon that the
praying mantis and the grey wolf have in common?
Do you think these two organisms are closely
related? Why or why not?
Classification of the Praying Mantis
What is binomial nomenclature?
5.
9.
10.
Praying Mantis
Eukarya
Kingdom
Animalia
Phylum
Arthropoda
Class
Insecta
Order
Mantodea
Family
Mantidae
Genus
Stagmomantis
Species
Stagmomantis carolina
A
C
A praying mantis feeds on ants, bees, and spiders.
K/U
Compare the number and variety of organisms
placed in a kingdom taxon to the number and variety
of organisms found in a species taxon.
K/U
11.
In one naming system used before Linnaeus
developed his, the European honeybee had a name
with 11 descriptive words, all in Latin (Apis pubescens,
thorace subriseo, abdomine fusco, pedibus posticis
glabris untrinque margine ciliatis). In the system
developed by Linnaeus, this bee’s scientific name
became Apis mellifera. Evaluate the advantages of the
current naming system compared to the earlier system.
T/I
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SECTION
1.2
Determining How Species Are Related
The goal of modern classification is to assign species to taxa so that the classification
reflects both morphological similarities among organisms as well as hypotheses about
their phylogeny (evolutionary history). To do this, biologists use the concept of shared
evolutionary history. If two species share much of the same evolutionary history, it means
they have a fairly recent common ancestor. In other words, the more a species shares
its evolutionary history with another, the more closely related they are thought to be.
Consider the example of the animals in the family Canidae, which includes wolves,
coyotes, jackals, foxes, and domestic dogs. Members of this family have morphological
characteristics in common, including having five toes on the front feet and four toes on
the back feet. They are not able to retract, or pull closer to the body, their claws, unlike
other carnivores such as cats. They also have elongated snouts. Aside from morphology,
what other types of evidence do scientists examine to determine relationships among
species? In terms of phylogeny, it is hypothesized that organisms in family Canidae
share a common ancestor. In particular, based on DNA evidence, scientists believe that
the grey wolf is the ancestor of the domestic dog.
Key Terms
ancestor
anatomy
physiology
phylogenetic tree
ancestor an organism
(or organisms) from
which other groups
of organisms are
descended
Evidence of Relationships Among Species
Do you think that the giant panda in Figure 1.5 is more closely related to bears or
raccoons? Giant pandas have characteristics of both groups, and scientists debated the
puzzle of how to classify them for more than 100 years. How do scientists determine
how much of the evolutionary histories of two species is shared? In modern taxonomy,
three main types of evidence that are used include anatomical, physiological, and DNA.
The information is then interpreted to make hypotheses about evolutionary history
and how closely related different species are. In the case of the giant panda, both
physiological and DNA evidence placed this species closer to bears than raccoons.
giant panda
raccoon
other bears
red panda
common ancestor
Figure 1.5 This branching tree diagram shows the relationships among giant pandas, bears, and raccoons.
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anatomy the branch
of biology that deals
with structure and
form, including internal
systems
Anatomical Evidence of Relationships
Recall that morphology refers to the body size, shape, and other physical features of
organisms. Studying morphology helps scientists learn more about how an organism
develops and functions structurally. Studying morphology also helps scientists
determine evolutionary relationships among species. Anatomy, which is the study of
the structure of organisms, is a branch of morphology. Study the oviraptor and the
New Guinean cassowary shown in Figure 1.6.
At first glance, it may not seem that these two organisms—one a dinosaur, the other
a bird—are closely related. In fact, biologists used to think that modern reptiles shared a
much closer evolutionary relationship with dinosaurs than birds did. However, detailed
studies over the past several decades provide convincing evidence that dinosaurs and
birds share a surprising number of anatomical features. For example, both have bones
with large hollow spaces, whereas living reptiles have dense bones. Also, the arrangement
of dinosaur bones in the hip, leg, wrist, and shoulder structures show stronger similarities
to birds than to living reptiles. Some small dinosaur fossils, calculated to be about
150 million years old, have feathers, as you can see in Figure 1.6 (C). These are some
of the kinds of anatomical evidence that biologists have used to hypothesize a close
evolutionary relationship between modern birds and dinosaurs.
A
B
C
Figure 1.6 (A) This artist’s conception of Oviraptor philoceratops might not appear to be related
to the cassowary (B), a bird from New Guinea, but these animals have many similar characteristics
that indicate a shared evolutionary history. (C) This fossil shows the remains of Archaeopoteryx,
an animal from about 150 million years ago that had many dinosaur features as well as feathers.
Infer Which similarities might prompt you to think that the oviraptor and the cassowary are
more closely related than was commonly thought?
Another example of using anatomical evidence to determine relationships among
organisms comes not from fossils, but from living species. Compare the bones in
Figure 1.7 from a whale flipper, a bat wing, a horse leg, and a human arm. Even though
these species look different on the outside, they have similar bone structures on the
inside. Over millions of years, the size and the proportions of the bones have been
modified for different purposes (swimming, flying, running, and grasping). However,
the overall arrangement and similarities indicate a shared evolutionary history.
Figure 1.7 The same
bones are found in the
forelimbs of these four
mammals. The matching
sets of bones are colourcoded in this illustration.
Whale
Bat
Horse
Human
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Physiological Evidence of Relationships
Physiology is the study of the functioning of organisms—how they work. Physiology
includes studying the biochemistry of organisms, including the proteins they make.
Whether as enzymes or as parts of cells and tissues, an organism’s proteins are
determined by the organism’s genes, since genes are coded instructions for making
proteins. By comparing proteins among different species, the degree of genetic
similarity or difference can be determined. Modern technology has provided new tools
for comparing species at this level, which has led to some organisms being reclassified.
A
physiology the branch
of biology dealing
with the physical and
chemical functions of
organisms, including
internal processes
B
Figure 1.8 Guinea pigs (Cavia porcellus) (A) were once considered to be in the rodent order,
like mice (B). Studies of protein structure suggest that guinea pigs are sufficiently different from
other rodents that they should be placed in a separate order.
For example, do you think the guinea pig and the mouse in Figure 1.8 are closely
related? In the past, both mammals were classified in the order Rodentia, the rodents.
However, an analysis of several proteins, including insulin, caused scientists to rethink
this classification. Guinea pig insulin is so different from that of typical rodents that
guinea pigs were reclassified into a taxon of their own. What about the horseshoe crab
in Figure 1.9? Although it has the word crab in its common name, studies of blood
proteins in the horseshoe crab have shown that this animal is more closely related to
modern spiders than to crabs.
Figure 1.9 Horseshoe
crabs have pincher-like
appendages and lack jaws.
Learning Check
7. What is the main goal of modern classification?
8. Use a graphic organizer, such as a flowchart or a
main idea web, to show clearly how the following
words are related: morphology, anatomy,
and physiology.
9. Scientists often reclassify organisms as new
information is discovered. Why is it important
for scientists to continue to classify and
reclassify organisms?
10. Sharks and dolphins have similar morphological
characteristics. They both have fins and bodies
shaped for swimming. How could examining their
anatomy and physiology help to further classify
these two organisms?
11. Refer to Figure 1.5. Which pair of organisms in
the diagram do you think is more closely related—
Pair A: a giant panda and a red panda or Pair B: a
red panda and a raccoon? Explain your reasoning.
12. Many animal species have red blood cells that
contain the oxygen-carrying protein hemoglobin.
Chickens (45), dogs (15), gorillas (1), frogs (57),
and humans are included in this list. The numbers
in brackets represent the number of amino acid
differences between human hemoglobin and the
hemoglobin of the other species. Based on this
information, rank these animals from most closely
to least closely related to humans.
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Figure 1.10 Based on
analysis of DNA, scientists
hypothesize that animals
and fungi are more closely
related to each other than
plants and fungi.
Plants
Fungi
Time
Animals
Common Ancestor
DNA Evidence of Relationships
Study the diagram in Figure 1.10. Are you surprised that it shows that fungi are more
closely related to animals than to plants? Genetic analysis suggests that this is the case.
Genes are DNA made of long chains of molecules called nucleotides. (You will learn more
about genes, their composition, and their function in Unit 3.) Technological advances
over the past few decades have made it increasingly possible to determine the sequence
of the nucleotides of specific genes. Just as anatomical and physiological evidence can be
compared among species, so too can these DNA sequences. This research has been a great
benefit to our understanding of evolutionary history and its application to classification.
In some cases, new DNA evidence has meant that prior classifications based on
morphological, physiological, or other evidence have to be dramatically restructured.
Sometimes DNA evidence indicates unexpected relationships. For example, fungi
and plants are superficially similar in that they do not move and they grow out of the
ground. However, DNA evidence suggests that fungi are more closely related to animals
than to plants. The diagram in Figure 1.10 reflects this evidence. Similarly, Canada’s
only vulture, the turkey vulture shown in Figure 1.11, appears similar to vultures from
Asia and Africa. However, DNA indicates the turkey vultures may be more closely
related to the storks, which are large wading birds.
Figure 1.11 DNA evidence
suggests that the turkey
vulture (A) is really more
closely related to the
wading stork (B) than it is
to the vultures of Asia and
Africa. Both turkey vultures
and storks are the only
birds known to urinate on
their legs, which they do to
help keep their bodies cool
during hot weather as well
as to kill bacteria and other
pathogens that cling to
their legs.
A
B
Phylogenetic Trees
phylogenetic tree
a branching diagram
used to show
the evolutionary
relationships among
species
Once scientists have studied the features of organisms and learned more about their
evolutionary histories, they often use a tool called a phylogenetic tree to represent a
hypothesis about the evolutionary relationships among groups of organisms. You saw
an example of a phylogenetic tree in Figure 1.5, when you considered the relationships
among giant pandas, bears, and raccoons.
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Order Artiodactyla
Figure 1.12 shows another example of a phylogenetic tree—this time, one that
illustrates the phylogeny of hooved mammals. Like a family tree, the roots or the base
of the phylogenetic tree represents the oldest ancestral species. The upper ends of the
branches represent present-day species that are related to the ancestral species. Forks
in each branch represent the points in the past at which an ancestral species split—
evolved, or changed over time—to become two new species.
In Figure 1.12, these four species have a common ancestor, and this common
ancestor has general characteristics that it shares with all the species that evolved from
it. All members of the order Artiodactyla have an even number of hooved toes on each
hind foot and have specialized teeth and digestive systems adapted to eat plants. There
are about 150 members of this order worldwide, including goats, deer, cattle, antelopes,
and pigs.
Family Bovidae
New species that evolve from a common ancestor have some characteristics in common
with the common ancestor, as well as new features. Biologists use these new features to
define each family level of classification on this tree. For example, members of the family
Bovidae (cows and antelopes) are artiodactyls that have the anatomical feature of horns.
Members of the family Cervidae (deer) are artiodactyls that have the anatomical features
of antlers. There are about 110 species of Bovidae and 40 species of Cervidae.
With continuing evolution, further new characteristics are developed. On the time
scale of the tree, members of different genera have split apart from one another more
recently than members of different families. Smaller differences help distinguish one
genus from another. For example, the family Cervidae includes 16 genera. The genus
Cervus includes deer with highly branched antlers, while animals in the genus Rangifer
are deer with broad, palmate antlers (having the shape of a hand).
Aepyceros melampus
(impala)
Oryx gazella
(oryx)
Cervus elaphus
(red deer)
Rangifer tarandus
(reindeer)
Aepyceros
Oryx
Cervus
Rangifer
Species
Genus
Family
Bovidae
Cervidae
Order
Artiodactyla
Figure 1.12 This phylogenetic tree shows the evolutionary relationships among various species
of plant-eating hooved mammals.
Interpret To which other organism shown in the phylogenetic tree is Cervus elaphus most
closely related?
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The Importance of Classification to Technology,
Society, and the Environment
Understanding the evolutionary relationships among species and groups of organisms
can have important consequences in the medical field, as well as in agriculture and in
the conservation of biodiversity. Consider the following examples:
• When scientists are looking for sources of pharmaceutical drugs, hormones, and
other important medical products, they can narrow their search to species closely
related to organisms already known to produce valuable proteins or chemicals.
• Understanding phylogeny can help scientists trace the transmission of disease and
develop and test possible treatments. Diseases can spread more rapidly between
species that share certain genetic characteristics. For example, Creutzfeldt-Jakob
disease, a disease that affects the nervous system, may be transmitted from cows
to people.
• In agriculture, ways to increase crop yields and disease resistance have already been
developed by cross-breeding closely related species. Biological control through the
use of natural predators, parasites, and diseases also depends on a knowledge of
different taxa and their particular characteristics.
• Sometimes, finding a new species or reclassifying an organism as a separate species
has implications for environmental conservation. For example, in 2001, based
on morphological and DNA analysis, scientists reclassified the forest-dwelling
elephants in Africa as a new species, Loxodonta cyclotis. These elephants, shown in
Figure 1.13, had previously been considered the same species as the African bush
elephant, Loxodonta africana. Conservationists worried about the status of the new
species. Loxodonta africana is classified as threatened and protected by anti-poaching
and anti-trading laws. Now that Loxodonta cyclotis was a separate species, it was
potentially no longer protected. However, an international agreement that helps
protect species from illegal trading gives Loxodonta cyclotis the highest category
of protection.
A
B
Figure 1.13 The forest-dwelling elephant (Loxodonta cyclotis) (A) have smaller bodies, smaller ears,
and longer tusks than the African bush elephant (Loxodonta africana) (B).
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Section 1.2
RE V IE W
Section Summary
• Modern classification organizes diversity according to
evolutionary relationships.
• Taxonomists rely on morphological, physiological, and
DNA evidence to identify and classify species.
• Anatomical evidence includes comparing the structure
and form of organisms, including bones.
• Physiological evidence includes comparing the
biochemistry of organisms, including proteins. DNA
evidence includes comparing organisms’ DNA sequences.
• Understanding phylogeny can help scientists trace the
transmission of disease and develop and test possible
treatments.
Review Questions
1.
C
Construct a chart that differentiates the three
main types of evidence scientists use to determine
relationships among species. Include an example of
each type of evidence.
2.
K/U Explain why knowing the shared evolutionary
history of organisms is useful to each of the following:
a. a biologist
b. a biology student
c. a pharmaceutical laboratory assistant
d. a conservation ecologist
3.
K/U List three anatomical features scientists have
used to hypothesize the relationship between modern
birds and dinosaurs.
4.
What do the nucleotide sequences in the genes
of turkey vultures suggest about their relatedness to
vultures of Asia and Africa?
5.
A
You are comparing three species (A, B, and C)
and you face a dilemma. Morphologically, species A
and B are very similar, but they are both different from
species C. However, you have sequenced some genes in
all three and the gene sequences indicate a high degree
of similarity between species B and C. How would you
resolve this situation?
6.
Use the phylogenetic tree below to justify the
conclusion that the leopard is more closely related to
the domestic cat than it is to the wolf.
K/U
7.
A
Refer to Figure 1.12. Explain why a reindeer
(Rangifer tarandus) is more closely related to a red deer
(Cervus elaphus) than it is to an oryx (Oryx gazella).
8.
Invasive species can out-compete native
species when they are introduced outside of their
natural environment. This can threaten a region’s
ecosystems, economy, and society. Recently, Canadian
researchers helped identify 15 new bird species
through genetic analysis. Scientists were able to
identify so many new species by analyzing and
comparing the DNA of over 600 North American bird
species. Explain how you think the use of genetic
analysis could help prevent the introduction of new
invasive species into Canada.
9.
C
There is growing concern worldwide about the
number of species that are going extinct. Conservation
organizations work to protect endangered species, but
there may be a disagreement about exactly what a
species is.
a. How can classifying an organism influence our
attitudes about that organism? For example, is a fish
more likely to be protected if it is known to be an
endangered species, or if it is newly discovered and
different from all known species of fish?
b. Suppose you had been working for a conservation
group when the forest-dwelling elephants
(Loxodonta cyclotis) were reclassified as a separate
species. Write a letter urging the Convention on
International Trade of Endangered Species to
consider the new species as endangered.
T/I
Wolf
Leopard
Domestic Cat
10.
A
C
Construct a graphic organizer of your choice to
show the importance of classification to technology,
society, and the environment.
Common Ancestor
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SECTION
1.3
Key Terms
structural diversity
prokaryotic
eukaryotic
dichotomous key
autotroph
Kingdoms and Domains
All of the millions of species on Earth share certain fundamental similarities, such
as being made of cells and having DNA. Despite these similarities, however, the
structural diversity of Earth’s species—diversity that is based on variety of both
external and internal structural forms in living things—is so great that it is almost
impossible to imagine. Examining all of life’s structural diversity at the species level
would be impractical, so biologists look for similarities and differences at a much
higher taxonomic rank, such as kingdoms and even domains.
heterotroph
The Six Kingdoms
structural diversity
a type of biological
diversity that is
exhibited in the variety
of structural forms
in living things, from
internal cell structure to
body morphology
Until the 1800s, the highest category for classifying organisms was the kingdom and
there were only two: Plants and Animals. Table 1.3 summarizes how the number of
kingdoms has changed since that time. In the 1800s, single-celled organisms were
added to the classification system through the creation of the kingdom Protista,
bringing the total to three. In the first half of the 1900s, some single-celled organisms
were found to be extremely small and without a cell nucleus, so a new kingdom,
Bacteria, was created for them, bringing the total to four. By the 1960s, it was known
that fungi were so different that they also needed their own kingdom, bringing the total
to five. During the 1990s, with new genetic information, the bacterial kingdom was
divided in two, giving the current six-kingdom system.
In Chapters 2 and 3, you will examine each of the six kingdoms in more detail.
As you study the remainder of this chapter, keep the following three important ideas
in mind:
• There are two main cell types that are significant for classification at the upper
ranks, such as kingdom.
• The study of cell types and genes has led scientists to add a rank higher than
kingdom—the domain.
• It is important to understand how biologists think the domains and kingdoms
are connected in their evolutionary history.
Table 1.3 Changes in Classification Systems for Life’s Kingdoms
Original
Animals
1860s
Animals
1930s
Animals
1960s
Animals
1990s
Animals
Plants
Plants
Plants
Plants
Fungi
Fungi
Protists
Protists
Protists
Bacteria
Bacteria
Bacteria
Archaea
Plants
Protists
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Two Major Cell Types
If an organism is made up of one cell only, it is described as being single-celled or
unicellular. If an organism is made up of more than one cell, it is multicellular. There
is substantial variation among the cells of unicellular and multicelluar organisms.
However, after centuries of study, biologists agree that there are two major types of
cells: prokaryotic cells and eukaryotic cells.
Prokaryotic cells, such as the bacterial cell shown in Figure 1.14, are the most
ancient cell type, though they remain abundant today. They do not have a membranebound nucleus. The name prokaryotic reflects this important distinction in the two
cell types, because it means “before the nucleus.” Eukaryotic, on the other hand,
means “true nucleus.” Eukaryotic cells do have a membrane-bound nucleus. There
are other differences as well. Eukaryotic cells, also shown in Figure 1.14, have a much
more complex internal structure, and on average they are about 1000 times larger than
prokaryotic cells. Thus, the two cell types represent a major division in the structural
diversity of life. You will read more about differences between prokaryotes and
eukaryotes in Chapter 2.
prokaryotic a smaller,
simple type of cell
that does not have
a membrane-bound
nucleus
eukaryotic a larger,
complex type of cell that
does have a membranebound nucleus
Prokaryotic cell
A
DNA
cell membrane
cell wall
flagellum
capsule
Eukaryotic cell
B
cell membrane
nucleus
chromosomes
ribosomes
Figure 1.14 Species are made of one of two kinds of cells. Compared to eukaryotic cells,
prokaryotic cells are small, less complicated, and without a membrane-bound nucleus.
Describe one other difference between the prokaryotic cell and eukaryotic cell shown above.
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The Three Domains
As scientists continued to analyze organisms in the kingdoms Bacteria and Archaea,
the category of domain was added to the classification system. Scientists found that the
differences between these two groups at the genetic and cellular levels were so great
that each group was elevated to a rank higher than kingdom—domain. So Bacteria and
Archaea are two of the three domains.
As a result of reclassifying these kingdoms as domains, biologists reclassified the
remaining kingdoms in a domain of their own, Eukarya. This makes sense, since the
other four kingdoms represent all the organisms with eukaryotic cells. Organisms in
the two prokaryotic domains are unicellular, whereas both unicellular and multicellular
organisms occur in the Eukarya. Figure 1.15 shows the current classification at the level
of domain and kingdom.
Domains
Figure 1.15 There are
six major categories in
the classification system
for living and extinct
organisms.
Bacteria
Archaea
Eukarya
Protista
Fungi
Plantae
Animalia
Traditional eukaryotic kingdoms
Dichotomous Keys
dichotomous key an
identification tool
consisting of a series of
two-part choices that
lead the user to a correct
identification
Even when taxonomists have put together logical classifications, biologists still face a
practical challenge. Imagine having a specimen whose identity is completely unknown.
How could sorting through all the names and ranks in various classifications assist
in determining what it is? The short answer is: it cannot. As a result, taxonomists use
another tool to identify individuals or species: the dichotomous key.
A dichotomous key [dih-KAW-ta-mus kee] is a system for narrowing down the
identification of a specimen, one step at a time. The word key is used as a solution, and
a dichotomy is a two-pronged fork, where there are two choices. So, a dichotomous
key is an identification solution that uses many two-part choices to narrow down the
solution. An example of a two-part choice could be something as simple as red and
not red.
Learning Check
13. Explain how scientists overcome the impractical
task of studying the structural diversity of life at the
species level.
16. Draw a flowchart or other graphic organizer
illustrating the relationship between the domains
and the kingdoms found in each domain.
14. What led scientists to add the category called
domain to modern classification systems?
17. The following is the first step in a tool used by
taxonomists to classify vertebrate animals. Identify
this tool and describe how it works.
1a. Hair present ......................... Class Mammalia
1b. Hair absent .......................... go to Step 2
15. Make a table to compare and contrast prokaryotic
cells and eukaryotic cells. Include the following
categories in your table: Meaning of Name, Presence
of Nucleus, Size, and Internal Structure.
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Using a Dichotomous Key
The ultimate goal of many taxonomists is to make an identification at the species level.
Table 1.4 shows a small key that could be used to distinguish among just eight species:
the frogs and toads in central Ontario.
Table 1.4 Dichotomous Key—Frogs and Toads of Algonquin Park
1a. Skin dry and warty ............ American toad
1b. Skin not dry and warty ................. go to 2
2a. Toes with “sticky pads” ................. go to 3
2b. Toes without sticky pads ............... go to 4
3a. Brown, < 2 cm, a darker X-shaped mark on
the back ..................... spring peeper
3b. Grey or green, yellow under the legs ..........
eastern grey treefrog
4a. Back without a pair of ridges .......... go to 5
4b. Back with a pair of ridges .............. go to 6
5a. Mottled pattern, with a mammal-like odour
................................. mink frog
5b. Unmottled green pattern; to 15 cm ............
bullfrog
6a. Back with large round or squarish spots
................................. go to 7
6b. Back unspotted (or with a few small spots)
....................................... go to 8
7a. Spots round ......................... leopard frog
7b. Spots squarish ................... pickerel frog
8a. Predominantly green colour .....................
green frog
8b. Brown, with a dark mask through the eye
....................................... wood frog
Assume you are trying to identify the species in Figure 1.16. Before you begin, since
you do not actually have the specimen in your hand, be aware that it has smooth, moist
skin and it does not have “sticky pads” on its toes. To use a dichotomous key, always
begin by choosing from the first pair of descriptions (1a and 1b). In this case, because
the skin is not dry and warty, you proceed to the next description within the first
pair of choices, 1b. If the skin had been dry and warty, you would have concluded the
animal is an American toad, and your use of the key would be complete.
At the second set of choices (2a and 2b), since the toes are not sticky, you are
directed to the fourth pair of choices (4a and 4b). Here, because you can see from
Figure1.16 that the back has a pair of ridges, you move on to the sixth pair of choices
(6a and 6b). Check Figure1.16 again to see if the back is spotted or unspotted. Because
it is unspotted, you then move to the eighth pair of choices (8a and 8b). Finally, here
you decide, based on its brown back and dark mask, that it is a wood frog (8b).
Figure 1.16 Use the dichotomous key in Table 1.4 to identify this species.
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SuggestedInvestigation
Inquiry Investigation 1-C,
Creating a Dichotomous
Key to Identify Species
of Beetles
Activity
1.2
A Dichotomous Key for Kingdoms
To design a key to make identifications at the species level, appropriate choices of
characteristics must be made. For instance, to identify the species of wildflowers
growing on a lawn, it would be logical to focus on things like the number and
arrangement of leaves, flower colour, plant size, and branching pattern.
But keys are not always designed to identify species. If you are instead designing
a key to determine what kingdom an organism is in, the focus has to be different. Here,
it is more useful to consider fundamental differences, such as the following: cell type
and cell structure; whether the organism is multicellular; and methods of reproduction
and obtaining nutrition.
Create a Dichotomous Key
Dichotomous keys are very helpful to identify and classify
organisms. In this activity, you will develop a dichotomous
key as you group familiar objects based on their
characteristics.
Possible Materials
• several different types of an object or material, such as
backpacks, shoes, pens, or notebooks
Procedure
4. Examine the characteristics of the objects in each
subgroup. Write a second question that focuses on a
characteristic that distinguishes the objects in one of the
groups. Divide that group into two smaller groups based
on this distinguishing characteristic.
5. Continue adding questions to your key and dividing
the objects until there is only one object in each group.
Make a branching diagram to identify each object with a
distinct name.
1. Choose an object for which you will create a
dichotomous key.
6. Use your diagram to classify the same type of object
from a different source.
2. Place a collection of the object in a pile. For example, you
may have your group members all place their backpacks
or their notebooks in a pile.
Questions
3. Examine the objects and write the first question for
your dichotomous key. The question should focus on a
distinguishing characteristic among the objects. Divide
the objects into two groups based on that distinguishing
characteristic.
1. Relate the groups you used to classify your object to taxa.
How do your groups relate to the groups of kingdom,
phyla, and the remaining six taxa in the modern
classification system?
2. How did you use your dichotomous key to classify the
object from a different source in step 6? For example, did
you have to revise your key? Explain.
3. How could you modify your dichotomous key so that the
user could more effectively identify an object of this type?
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Main Characteristics of Kingdoms
Table 1.5 summarizes some of the main characteristics of kingdoms and, below
it, Figure 1.17 shows some examples of organisms in each kingdom. A distinction
has already been made between prokaryotic and eukaryotic cells based on size,
the presence of a nucleus, and internal complexity. Another cell-level distinction
is the cell wall, a tough structure that surrounds most cells. Cell walls are absent
in animals, but in other organisms the composition of the cell wall varies. With
respect to nutrition, an autotroph is an organism that obtains energy by making
its own food, usually using sunlight. A heterotroph must consume other organisms
to obtain energy-yielding food. Finally, asexual reproduction can be found in all
kingdoms. However, sexual reproduction, in which genetic material from two
parents combines to form offspring with a unique combination of genes, is a trait
that only occurs in the Eukarya. The data in Table 1.5 are all that is needed to make
a dichotomous key that can assign any species to its kingdom.
autotroph an organism
that captures energy
from sunlight (or
sometimes non-living
substances) to produce
its own energy-yielding
food
heterotroph an
organism that cannot
make its own food and
gets its nutrients and
energy from consuming
other organisms
Table 1.5 Characteristics That Differentiate the Six Kingdoms
Domain
Bacteria
Archaea
Eukarya
Kingdom
Bacteria
Archaea
Protista
Plantae
Fungi
Animalia
Example
Staphylococcus
Sulfolobus archaea
Amoeba
Maple tree
Mushroom
Rabbit
Cell type
Prokaryote
Prokaryote
Eukaryote
Eukaryote
Eukaryote
Eukaryote
Number of cells
Unicellular
Unicellular
Unicellular and
multicellular
Multicellular
Mostly
multicellular
Multicellular
Cell wall material
Peptidoglycan
Not peptidoglycan;
occasionally no
cell wall
Cellulose in some; Cellulose
occasionally no
cell wall
Chitin
No cell wall
Nutrition
Autotrophs and
heterotrophs
Autotrophs and
heterotrophs
Autotrophs and
heterotrophs
Autotrophs
Heterotrophs
Heterotrophs
Primary means
of reproduction
Asexual
Asexual
Asexual and
sexual
Sexual
Sexual
Sexual
Staphylococcus 4800×
Sulfolobus archaea
Maple tree
Mushroom
5000×
Amoeba
160×
Rabbit
Figure 1.17 Organisms from each of the six kingdoms represent Earth’s biodiversity.
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Section 1.3
RE V IE W
Section Summary
• The variety of internal and external forms exhibited
by species represents structural diversity.
• There are two cell types: prokaryotic and eukaryotic.
Prokaryotic cells do not have a membrane-bound
nucleus. Eukaryotic cells are more complex and do
have a membrane-bound nucleus.
• Organisms in the domain Eukarya have eukaryotic
cells and are unicellular or multicellular. There are four
kingdoms in the domain Eukarya: Protista, Plantae,
Fungi, and Animalia.
• Taxonomists use dichotomous keys to make choices
between pairs of options to narrow down identifications.
• Organisms in the domains Bacteria and Archaea
are unicellular and prokaryotic.
Review Questions
1.
Make a Venn diagram to compare and contrast
prokaryotic and eukaryotic cells.
2.
K/U Identify the three domains and the kingdoms
within each domain.
3.
K/U Refer to Figure 1.15. Explain, in your own words,
how scientists arrived at the three-domain system.
C
4.
C
K/U Distinguish between autotrophs and
heterotrophs.
6.
Refer to Table 1.5 to answer the following
questions.
a. What form or forms of nutrition do eukaryotes use?
b. What type of reproduction is used primarily by
prokaryotes?
c. Describe the cells of organisms in domain Archaea.
d. What is one characteristic that is unique to all
animals?
8.
Use the dichotomous key in the table below to
identify the organism in the image.
A
Explain how a dichotomous key works.
5.
7.
9.
A
Dichotomous Key—Salamanders of Algonquin Park
Cyanobacteria, commonly called blue-green
algae, are classified in the kingdom Bacteria.
Cyanobacteria make their own food using carbon
dioxide, water, and energy from sunlight. They contain
the pigment chlorophyll and another pigment that is
blue. Explain why scientists in the early days of
taxonomy would likely have classified cyanobacteria in
the kingdom Plantae.
A
T/I Refer to Table 1.5. A student was looking at
some pond water under a microscope and noticed a
single-celled organism in the field of view. This
organism had a nucleus as well as chloroplasts in its
cytoplasm. The organism was enclosed by a cell wall.
After looking through a dichotomous key, the student
determined this organism was a green alga. Predict the
domain and kingdom of this organism. Explain the
basis for your prediction.
10.
1a. Skin without spots
..................... go to 2
1b. Skin with spots
..................... go to 4
2a. Found under cover in or
beside streams ............
two-lined salamander
2b. Found in forests
...............................
go to 3
3a. Red stripe down back
................................
red-backed salamander
3b. Grey-black overall .......
red-backed salamander
(black variant)
4a. Bright red small spots
..................... go to 5
4b. Blue or yellow spots
..................... go to 6
5a. Green overall, found
in aquatic ecosystems
................................
red-spotted newt
5b. Reddish overall, found
in terrestrial ecosystems
........ red-spotted newt
juvenile (“red eft”)
6a. Many irregular blue
spots ........................
blue-spotted salamander
6b. Large yellow spots .......
yellow-spotted
salamander
C
Use a graphic organizer to compare the
characteristics of the kingdom Plantae to those of the
kingdom Animalia.
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SECTION
1.4
Classifying Types of Biodiversity
When you hear or read the word biodiversity, you probably think first about species
diversity. Species diversity is the variety and abundance of species in a given area.
However, there are other ways of thinking about diversity other than species diversity,
and they are just as important. Genetic diversity is evident in the variety of inherited
traits within a species. The patterns on the tails of humpback whales, such as the one
shown in Figure 1.18, are evidence of genetic diversity within this species. Ecosystem
diversity is the rich diversity of ecosystems found on Earth, each of which contains
many species. In this section, you will learn about the importance of all three of these
types of diversity.
A
Key Terms
species diversity
genetic diversity
ecosystem diversity
gene pool
population
resilience
species diversity the
variety and abundance
of species in a given area
B
genetic diversity the
variety of heritable
characteristics (genes)
in a population
of interbreeding
individuals
ecosystem diversity
the variety of
ecosystems in the
biosphere
C
Figure 1.18 Biological diversity exists at different levels. (A) Within species there is genetic
diversity, as evident in the different tail patterns of humpback whales. (B) Within ecosystems,
like this alpine meadow, is species diversity. (C) Finally, a variety of ecosystems, such as this one
in Algonquin Park, make up ecosystem diversity.
Describe one example of genetic diversity and one example of ecosystem diversity.
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Genetic Diversity
Figure 1.19 The Tasmanian
devil is native to Tasmania,
the island that is the
southernmost state of
Australia.
gene pool all the genes
of all the individuals in a
population
population a group of
individuals of the same
species in a specific area
at a specific time
Since 1996, Tasmanian devils (Sarcophilis harrisii), shown in Figure 1.19, have been
suffering from a contagious cancer that causes tumours on the face and mouth of
the animals. The disease, spread from one individual to another by biting, eventually
results in death. The population of Tasmanian devils has been reduced so extensively,
from about 150 000 in 1996 to between 20 000 and 50 000 by 2006, that the species
was classified as endangered. Research has shown that a lack of genetic diversity in the
Tasmanian devil population is a key factor in the impact of the disease.
Genes are the genetic material that controls the expression and inheritance of
traits, such as sugar content in blueberries, pattern arrangement in ladybeetles, and
human height. The variation among individuals in a population is largely a result of
the differences in their genes. Genetic diversity within a population is known as the
gene pool. In other words, the gene pool is the sum of all the versions of all the genes
in a population. The genetic diversity within a species is always greater than that within
a population, because the gene pools of separate populations usually contain different
types or combinations of the different versions of genes.
Genetic Diversity Provides Resistance to Disease
Genetic diversity is especially important in disease resistance. As illustrated by the
Tasmanian devil example, populations that lack genetic diversity are more susceptible to
disease than those that have high diversity. If none of the individuals in a population have
the ability to survive the disease, the entire population could be eliminated. If populations
of the same species continue to be eliminated, it can lead to the extinction of the species.
Resistance to disease is just one example of why genetic diversity is important.
Genetic diversity also allows populations and species to survive changing
environmental conditions, such as a change in resource availability, climate change, a
change in a predator population, or the introduction of a non-native species.
Genetic Diversity Supports Conservation Biology
As scientists have learned more about the importance of genetic diversity and its
relationship to species survival, they have begun to use their knowledge to help struggling
populations. For example, in 1995 the population of Florida panthers, shown in
Figure 1.20, had been reduced to between 30 and 50 individuals, partially due to a lack
of genetic diversity. As part of the recovery plan for this endangered species, scientists
introduced eight female panthers taken from a population of panthers in Texas. The effort
was considered a success, and in 2009 the population had risen to about 100 individuals.
Figure 1.20 The Florida
panther (Felis concolor coryi)
population continues to be
threatened by habitat loss
and collisions with vehicles.
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Learning Check
18. Describe the difference among the three types of
biodiversity.
22. Explain why genetic diversity is important to the
survival of a species.
19. Refer to Figure 1.18 (C). Identify three ecosystems
you might find in Algonquin Park.
23. In the case of the Florida panther, humans
intervened to save the species. Do you agree or
disagree that humans should intervene to save
endangered species? Explain your answer.
20. What is a gene pool?
21. Explain why genetic diversity within a species is
always greater than the genetic diversity within
an individual population.
Ecosystem Diversity
If the smallest scale at which scientists consider biodiversity is genetic diversity, then the
largest scale is ecosystem diversity. Ecosystem diversity refers to the variety of ecosystems
in the biosphere. Recall that ecosystems are made up of two components—biotic factors
and abiotic factors. Biotic factors include interacting populations of species. Examples of
abiotic factors include altitude, latitude, geology, soil nutrients, climate, and light levels.
Because of the diversity of relationships among organisms and the variety of abiotic
factors, Earth’s surface is highly varied physically and chemically, making ecosystem
diversity very rich. Ecosystems can range in size from a small plant that grows on another
plant to an entire biome, such as a tropical rainforest or Canada’s vast boreal forest.
Sustainability and Diversity—Find a Balance?
Sustainable agriculture must balance the risks of technology
with the benefits. For example, atrazine is a herbicide used
in agriculture to prevent the growth of weeds. Crops that
have atrazine applied early in the growing season show a
25 percent increase in weed control, an 8 percent increase in
corn yield, and an increase in profit of $20 per hectare.
On the other hand, the herbicide is applied to crops early
in the spring and can run off into nearby lakes and rivers.
Studies have shown that atrazine and other chemicals can
reduce reproductive success in many freshwater organisms.
The timing of atrazine contamination of water sources
directly coincides with amphibian breeding activities, since
many amphibians reproduce during early spring rains.
In several European nations, atrazine has been banned
because of environmental concerns. However, atrazine
is approved for use in Canada. Alternative forms of weed
control in corn crops are being investigated and include
the use of bacteria and low-growing plants that block
weeds from growing. Should the use of atrazine be banned
completely worldwide?
Procedure
1. Read the introductory text and make a T-chart to list the
benefits and risks of using atrazine on corn crops.
2. Examine the graph on the right and add information to
your chart.
3. Discuss the benefits and risks of using atrazine on corn
crops with classmates.
Questions
1. Why is the timing of atrazine application such an
important factor?
2. Draw an illustration that shows the steps involved in how
atrazine reaches aquatic ecosystems.
3. What is the direct impact of atrazine use on the leopard
frog? Why is this something to be concerned about?
4. Name five other species that would be affected by
reduced frog reproduction. Sketch a food web to show the
effects of atrazine on the biodiversity in ponds.
5. Analyze your T-chart. Do the benefits of using atrazine
outweigh the risks? Explain your reasoning.
Testosterone Levels in
Northern Leopard Frogs
(Rana pipiens)
Testosterone (Ng/mL)
1.3
5
4
3
2
1
0
No
ntre
a
At
ra Ma ted
zin le
e- s
tre
M ate
a d
No les
nt
Fe rea
m te
al d
es
Activity
The graph shows the
results of an experiment
in which male northern
leopard frogs were
exposed to atrazine
during development.
The levels of
testosterone in the
atrazine-treated frogs
were then compared to
testosterone levels in
non-treated male and
female frogs.
Treatment Group
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SuggestedInvestigation
ThoughtLab Investigation
1-B, Resilience of a
Grassland Ecosystem
Ecosystem Services
Ecosystem services are the benefits experienced by organisms, including humans,
which are provided by sustainable ecosystems. Without ecosystem diversity, Earth
would lose most of the services that ecosystems provide, which are shown in
Table 1.6. Forests, for instance, take up carbon dioxide and maintain soil fertility.
Ecosystems also maintain populations of organisms that are necessary for pest control,
pollination, waste management, and other processes beneficial to people.
In particular, wetlands provide several important ecosystem services, including
storing water, which reduces the risk of floods; filtering water, which removes pollutants;
and providing habitat for commercially important species of fish and shellfish. Because
wetlands are so valuable, government agencies and non-governmental organizations
often work together to preserve and protect them. For example, between 2000 and
2005, acting under the Great Lakes Wetlands Conservation Action Plan, more than
12 000 hectares of wetlands around the Great Lakes region were preserved. During that
same time period government agencies worked with private organizations to restore
another 4400 hectares of wetlands that had been disrupted by human activities such as
agriculture and development.
Table 1.6 Examples of the World’s Ecosystem Services
Ecosystem Service
Example
Atmospheric gas supply
Regulation of carbon dioxide, ozone, and oxygen levels
Climate regulation
Regulation of carbon dioxide, nitrogen dioxide, and methane levels
Water supply
Irrigation, water for industry
Pollination
Pollination of crops such as apples, blueberries, and clover
Ecological control
Pest population regulation
Wilderness
Habitat for wildlife
Food production
Crops, livestock
Raw materials
Fossil fuels, timber
Genetic resources
Medicines, genes for disease resistance in plants
Recreation
Ecotourism
Cultural benefits
Aesthetic and educational value
Waste treatment
Sewage purification
Soil erosion control
Retention of topsoil
Nutrient recycling
Nitrogen, phosphorus, carbon, and sulfur cycles
Ecosystem Function and Species Diversity
resilience the ability
of an ecosystem to
remain functional and
stable in the presence of
disturbances to its parts
Ecologists have long had the sense that ecosystems with greater species diversity
were more likely to provide important services reliably. As well, there has also been a
belief that such ecosystems exhibit resilience, the ability of an ecosystem to maintain
an equilibrium, or balance, even in the face of significant outside disturbances. Field
research conducted by scientists from the University of Minnesota in the 1980s and
1990s has provided convincing evidence that this is the case.
Experiments came from a long-term project using many growing plots, each with
a specific number of native plant species, ranging from 1 to 24. In all cases, the more
species present in the plot, the more efficient the ecosystem. The plots with more native
species produced more biomass, which means they trapped more carbon dioxide. They
also consumed more nitrate, which can be toxic in high quantities. The more diverse
plots were better able to resist the invasion of non-native species and exhibited reduced
disease. The results of these experiments are shown in the graphs in Figure 1.21.
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Plant Species Diversity and
Percentage of Plant Coverage
Plant Species Diversity and
Disease Severity
Plant Species Diversity and
Number of Invasive Species
65
4
60
8
50
45
40
35
30
3
Disease Severity Index
Number of Invasive Species (%)
Total Plant Cover (%)
55
6
4
2
1
2
25
0
5
10
15
20
25
0
Plant Species Diversity
5
10
15
20
25
0
Plant Species Diversity
4
8
12
16
20
Plant Species Diversity
Figure 1.21 In experiments conducted at the University of Minnesota from 1982 to 1993,
researchers concluded that greater biodiversity in an ecosystem results in at least three beneficial
patterns: increased plant cover, more resistance to invasive species, and more disease resistance.
Ecosystem Services and Human Actions
Sometimes humans make changes to an ecosystem to enhance the services of the
ecosystem. For example, wildlife officials may stock a lake with fish to provide
recreation for fishing enthusiasts. But what effects could this action have on the natural
ecosystem of the lake? The results of a four-year study conducted by wildlife biologists
in California showed that the introduction of non-native trout to mountain lakes in the
western United States led to reduced population numbers of several amphibian species
and changes in the number and variety of aquatic insect species. In particular, trout
consume aquatic insects in the larval stage. Other organisms, including amphibians
and other fish, also rely on insect larvae as a food source. As well, birds and bats that
live near the lakes eat adult insects. All of these species must now compete with the
non-native trout for food. The presence of trout has been linked with a decrease in the
number of birds and in the activity of some types of bats.
In Ontario, the most successfully stocked fish is the smallmouth bass, shown
in Figure 1.22. Introductions to previously bass-free lakes have greatly increased its
Ontario range northward. This has enhanced recreational fishing, but ecologists have
documented resulting changes to lake ecology. One consequence is the loss of some
native fish species such as stickleback and dace. This leads to a decline in species
diversity and affects ecosystem diversity because the system loses complexity.
Where the bass are introduced into lakes with lake trout, the situation is worse.
Trout are commonly top predators, but the reduced numbers of small fish caused by the
introduced bass affect trout populations. With fewer small fish, trout must then consume
less nourishing food, resulting in slower growth, smaller ultimate size, and decreased
population numbers. This is a further impact on ecosystem diversity because of the food
web alteration. Research documenting the negative effects of bass introductions has
greatly reduced the practice. In Chapter 3, you will read more about how human actions
affect biodiversity, particularly species diversity and ecosystem diversity.
Figure 1.22 Widespread
introductions of the
smallmouth bass in
thousands of Ontario lakes
have increased recreational
fishing opportunities, but
there have been negative
consequences for species
and ecosystem diversity.
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STSE
BIOLOGY Connections
DNA Bar Codes
Most people would find it odd if their friend collected vials
containing muscles from 940 different species of fish—but
then again most people haven’t undertaken a project as
ambitious as this one.
Paul Hebert, a geneticist at the University of
Guelph, in Ontario, is trying to gather cell samples from all
of the world’s organisms. With small pieces of tissue no larger
than the head of a pin, Hebert and his colleagues are working
to assign DNA bar codes to every living species.
Hebert has shown that the segment of mitochondrial
DNA, called cytochrome c oxidase I, or COI, can be used as
a diagnostic tool to tell animal species apart. The COI gene
is easy to isolate and allows for identification of an animal.
A different gene would need to be used for plants. Just like
the Universal Product Codes (UPC) that appear on product
packaging, the DNA segment sequence could be stored in
a master database that would allow for easy access to the
material. A hand scanner, when supplied with a small piece
of tissue, such as a scale, a hair, or a feather, could identify
the species almost instantly.
DNA UPC
Honeybee
Bumble bee
This representation of DNA bar codes shows that the more closely
related two species are, the more similar their bar codes are.
POTENTIAL BENEFITS This technology has several potential
benefits. A doctor might use it to pinpoint disease-causing
organisms quickly to prevent epidemics or to determine what
antidote to give a victim of a snake bite. Health inspectors
could scan foods for plant and animal contaminants. People
who are curious about their surroundings could learn what
lives around them. Farmers would be able to identify pests
and use species-specific methods for their removal.
Using bioinformatics—a field of
science in which biology, computer science, and information
technology merge—to create a database of DNA bar codes
allows taxonomists to classify more organisms quickly.
Currently, taxonomists have identified approximately two
million species. Scientists estimate that anywhere between
5 and 20 million species exist. Historically, species have been
classified using morphology, genetics, phylogeny, habitat,
and behaviour. While the bar codes would not replace classic
taxonomic methods, they could supplement them by giving
scientists another tool to use.
A NEW WAY TO CLASSIFY
American robin
Hermit thrush
Connect to the Environment
One benefit of DNA bar code technology might be that
farmers could identify pests and use species-specific methods
for their removal. Do some research to find out what is
meant by “species-specific methods” and assess whether
they are less harmful to the environment than other methods
of pest removal.
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Section 1.4
RE V IE W
Section Summary
• Too little genetic diversity reduces a population’s ability
to resist disease or other changing environmental
conditions.
• Ecosystems are diverse due to variations in abiotic and
biotic factors.
• Ecosystems provide services, such as recycling nutrients
and regulating gases in the atmosphere.
• Ecosystems with greater species diversity have higher
resilience.
Review Questions
1.
C
Use a graphic organizer to show the relationship
between the terms biodiversity, species diversity, genetic
diversity, and ecosystem diversity.
2.
A pitcher plant (Sarracenia
purpurea), shown on the right, is
an Ontario bog plant with leaves
that hold water in which various
organisms live. Is a pitcher plant a
species or an ecosystem? Explain
your answer.
3.
K/U Identify which of the following are ecosystems
and explain what your answers tell you about
ecosystem diversity.
a. flower basket
b. surface of your skin
c. schoolyard
d. Lake Ontario
e. the tundra
9.
A
A
Attempts to calculate the cash value of diverse
ecosystems have been made. One 1997 estimate placed
Earth’s ecosystem services at more than 33 trillion
dollars per year. Use the table below to answer the
following questions.
a. Which ecosystem has the greatest global economic
value? Why do you think this is?
b. Which ecosystem has the least global economic
value? What is different about this ecosystem
compared to the others?
c. In your opinion, which ecosystem provides the
most important ecosystem service? Why?
Value of the World’s Ecosystem Services
Ecosystem
Coastal shelf
Total Global
Value (trillions
of dollars)
4283
Ecosystem
Service
Nutrient cycling
Coral reef
375
Recreation
Explain how the relationship between genetic
diversity and disease resistance is similar to the
relationship between species diversity within an
ecosystem and disease resistance.
Cropland
128
Food production
Estuaries
4100
Nutrient cycling
906
Waste treatment/
food production
5.
K/U Using examples from Table 1.6, explain why it is
important to conserve ecosystem diversity.
Lakes and rivers
1700
Water regulation
Open ocean
8381
Nutrient cycling
6.
Why is it important to protect species diversity
within an ecosystem?
Swamps
3231
Water supply
7.
Summarize the information shown in the
graphs in Figure 1.21.
8.
A microhabitat is an identifiably different
portion of a larger discrete habitat such as a forest.
Microhabitats offer a variety of microclimates, food,
camouflage, and shelter. The northern flicker is a
woodpecker that finds shelter in a hole in a tree, while
a millipede finds food and shelter in the leaf litter at
the base of the tree. Based on this information, predict
the relationship between structural diversity and
species diversity of an ecosystem.
4.
K/U
Grasslands
K/U
Temperate forest
894
C
Tropical forest
T/I
3813
Climate regulation/
timber
Nutrient cycling/
raw materials
10.
Explain the statement, “Maintaining the
diversity of Earth’s ecosystems is important for
species diversity.”
11.
C
Make a concept map that organizes the results
of the study by biologists in which non-native trout
were introduced to mountain lakes in the western
United States.
K/U
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ThoughtLab
INVESTIGATION
1-A
Skill Check
Initiating and Planning
✓
Performing and Recording
✓
Analyzing and Interpreting
✓
Communicating
Materials
• reference books
• computer with Internet access
Classifying Aquatic Species
In the same way that marine organisms are mixed up in seafood stew, the names
of the taxa that identify five species are mixed up in the table below. In this lab,
you will place each organism in its proper taxon at each level of the hierarchy.
Organisms in Seafood Stew
Common name
Market squid, American lobster, blue mussel,
Virginia oyster, European oyster
Phylum
Arthropoda, Mollusca, Mollusca, Mollusca, Mollusca
Class
Malacostraca, Bivalvia, Bivalvia, Bivalvia, Cephalopoda
Order
Decapoda, Decapoda, Mytiloida, Pterioida, Pterioida
Family
Ostreidae, Ostreidae, Nephropidae, Mytilidae, Loliginidae
Genus
Homarus, Mytilus, Ostrea, Loligo, Crassostrea
Species
americanus, virginica, edulis, edulis, opalescens
Pre-Lab Questions
1. What is the order of classification for organisms?
2. Why is it useful to have a classification system for organisms?
Question
Which organisms are closely related to each other? Which are not?
Organize the Data
1. Draw a table with six columns and seven rows. At the top of the first
column, write “Taxon.” At the top of each of the other columns, write the
common name of each organism. Label the rows Phylum, Class, Order,
Family, Genus, and Species.
2. Use reference books or the Internet to classify each organism at each
taxon level.
The American lobster and the blue
mussels shown here are both members
of the animal kingdom.
Analyze and Interpret
1. Which order name is found in both the Arthropoda and Mollusca phyla
(plural of phylum)? What does this name mean?
2. Which two genera (plural of genus) have species with names containing the
same word? What does this word mean?
Conclude and Communicate
3. Which two organisms are most closely related to each other? Explain why.
4. Which organism is least closely related to the other four? Explain why.
Extend Further
Go to Organizing Data in a Table in
Appendix A for help with making
your table.
5. INQUIRY Place five organisms from your neighbourhood in the proper
taxon at each level of the hierarchy.
6. RESEARCH How are names for the levels in the hierarchy determined?
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ThoughtLab
1-B
INVESTIGATION
Skill Check
Initiating and Planning
✓
Performing and Recording
✓
Analyzing and Interpreting
✓
Communicating
Materials
• graph paper
• ruler
Resilience of a Plant Community
During a Drought
Number of
Plant Species
Resistance to
Drought (change
in biomass/yr)
0
0.00
2
-1.10
4
-0.80
6
-0.75
8
-0.65
10
-0.50
12
-0.42
14
-0.40
16
-0.40
18
-0.40
20
-0.38
22
-0.38
24
-0.38
Resilience of a Grassland Ecosystem
Resilience is the ability of an ecosystem to maintain an equilibrium, or
balance, despite significant outside disturbances. Results of studies conducted
using experimental plots of plants showed that increased biodiversity in the
experimental plots led to increased resistance to the invasion of non-native
species and decreased incidence of disease. The scientists who reported these
results also recorded data about the ability of grassland plants to resist drought
conditions in relation to species diversity. They measured the change in biomass
of the plants from 1986, the year before the drought began, to 1988, the peak of
the drought. The data collected are shown in the table below. Resistance values
closer to zero imply greater resistance to the drought.
Pre-Lab Questions
1. What is resilience?
2. How is resilience related to species diversity within an ecosystem?
3. Why is it important to maintain biodiversity in ecosystems?
Question
How does species diversity affect the resilience of an ecosystem?
Organize the Data
1. Make a line graph of the data in the table. Note that the values on the
y-axis begin with zero and decrease to negative values.
2. Label the axes of your graph and give your graph a title.
Analyze and Interpret
1. Explain the relationship between resilience and species diversity in the
grassland plots used in this experiment.
2. Another factor that scientists analyze when determining the stability of an
ecosystem is the amount of time it takes for the ecosystem to return to the
conditions that existed before the disturbance. Predict which plots returned
to the pre-drought conditions more quickly—those with high species
diversity or those with low species diversity. Explain your reasoning.
Conclude and Communicate
3. How does species diversity affect the resilience of an ecosystem?
Extend Further
Go to Constructing Graphs in Appendix A
for help with making your graph.
4. INQUIRY Describe another experiment to gather more evidence about the
relationship between the resilience of an ecosystem and its biodiversity.
5. RESEARCH Find out more about how planting native species in a disturbed
area can help improve the ecosystem. Use the Internet or library to find an
example of how the resilience of a disturbed ecosystem was improved after
native plants were planted.
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Inquiry
INVESTIGATION
1-C
Skill Check
Initiating and Planning
✓
Performing and Recording
✓
Analyzing and Interpreting
✓
Communicating
Materials
• illustration of 18 beetles
• sample dichotomous keys
Creating a Dichotomous Key
To Identify Species of Beetles
If you find an insect you have never seen before, how could you discover
its identity? Many field guides help you match up the characteristics of your
specimen with those of similar organisms using a dichotomous key. This
identification key uses a series of paired comparisons to sort organisms into
smaller and smaller groups. In this investigation, you will learn how to make
your own keys to identification.
Pre-Lab Questions
1. What characteristics do all insects have in common?
2. Name two characteristics that scientists use to tell different insects apart.
3. How can you use the characteristics of beetles to classify them?
Question
How do you make a dichotomous key?
Prediction
Predict which characteristics of insects will be most useful in creating an
identification key.
Procedure
1. Copy the diagram of a dichotomous tree shown here onto a separate
piece of paper.
group 7
A dichotomous key can help you
identify beetles such as these.
group 3
group 8
group 1
group 9
group 4
group 10
All
beetles
group 11
group 5
group 12
group 2
group 13
group 6
group 14
2. Study the illustration of 18 beetles shown on the next page.
3. Select one characteristic and sort the beetles into two groups based on
whether they have the characteristic or not.
4. List each beetle’s number under either group 1 or group 2 on your diagram.
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5. Record the characteristic that identifies each group.
6. Select another characteristic of each subgroup, and
repeat steps 4 and 5 for the next level down on your
diagram.
7. Continue to subdivide the groups until you have 18
groups with one beetle in each.
8. Using the characteristics shown on your diagram,
construct a dichotomous key that someone could use
to identify any beetle from the original large group.
a. To do this, create a series of numbered steps with
the first step showing the first characteristic you
used.
b. At each step, offer two choices for classifying the
beetle based on a single characteristic. For example,
you may have used the characteristic “antennae
longer than front legs” as your first dividing
characteristic. The first numbered step in your key
would be (1a) antennae longer than front legs or
(1b) antennae not longer than front legs.
c. Use the sample keys provided by your teacher to
help you.
9. Exchange your key with a partner. Use your
partner’s key to classify a beetle, and record all the
characteristics of the species you chose.
1
2
Variegated
mud-loving beetle
7
3
13
Red flour beetle
9
14
4. In your own words, define dichotomous key.
Extend Further
5. INQUIRY Your teacher will provide you with several
different “mystery” beetles. Use your dichotomous
key to see if you can identify what species they are.
You may be unable to completely identify your beetles
using your key. If this is the case, how far could you
go with your key?
6. RESEARCH Visit the library or the Internet and get a
field guide to beetles. Use this to identify the mystery
beetles. What characteristics would you have needed
in your key in order to fully identify them?
5
Cucumber
snout beetle
False wireworm
beetle
6
Predaceous
diving beetle
Water tiger
10
15
Blind
ant-beetle
Conclude and Communicate
3. Why does a key offer two choices at each step and not
more than two?
Apricot borer
Red-necked
cane borer
Flathead apple borer
2. Which beetle characteristics were not useful for
creating your key? Explain why.
4
Mycetaeid beetle
8
Analyze and Interpret
1. Did your partner produce a dichotomous key identical
to yours? Explain why or why not.
11
Whirligig beetle
16
12
Broad-horned
flour beetle
Ironclad beetle
17
White-marked
spider beetle
Crawling
water beetle
18
Monterey
cyprus beetle
Drug store
beetle
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STSE
Case Study
Tree Plantations
The root of the problem or the solution to deforestation?
You have joined the International Youth Delegation (IYD),
an international coalition of youth working on urgent
ecological issues, such as deforestation. The Food and
Agriculture Organization of the United Nations (FAO) reports
that approximately 13 million hectares of forests worldwide
are cut down every year. Much of that land, particularly in
the tropics, is cleared to increase arable land so people can
grow food. A possible solution is to encourage the planting
of fast-growing and economically important tree species,
such as eucalyptus, as crops to be harvested. These managed
tree plantations would provide income to local landowners
and, at the same time, discourage ongoing deforestation.
Your IYD group has been asked to assess the viability of
monoculture tree plantations as a solution to deforestation.
Many large organizations, including the United Nations
and the World Bank, support the practice of monoculture
tree plantations. Members of the IYD are divided on the
issue. The members who agree with the UN and the World
Bank have summarized their position on the issue. The key
points of this summary include the following:
• Tree plantations can be planted on cleared and deforested
land. These “re-created” forest areas provide habitats for
many plant and animal species, some of which are at risk
of extinction due to habitat loss.
• Forests reduce the potential for damage from drought
and floods. As well, forests reduce soil erosion, which
dramatically benefits local water quality in streams
and rivers.
• Tree plantations bring many social and economic
benefits to local farmers, including providing income
and opportunities for other agricultural activities in the
plantation, such as livestock grazing.
• Aside from providing the raw materials for the lumber
industry, tree plantations also provide the waste wood
that remains after harvesting. The waste wood can
be used to produce renewable energy in the
form of biofuels.
• The tree plantations act as a carbon
sink, storing carbon in the wood of the
trees and helping to keep it out of the
atmosphere. Forests are known to store
more carbon than they emit, so increasing
forest cover means reducing net emissions
of greenhouse gases.
Other members of the IYD have a different
opinion. They do not agree that planting trees
as part of monoculture tree plantations is a
solution to the problem of deforestation. Rather,
they believe these plantations will increase
the problems associated with loss of forest
biodiversity, particularly in tropical countries.
IYD members who oppose monoculture tree
plantations have compiled a list of their concerns
about tree plantations in a memo to the FAO, shown
in the next page.
This large monoculture operation shows regularly spaced
eucalyptus trees in Brazil. The regular, unobstructed
spacing makes planting and harvesting easier than in a
natural eucalyptus forest, but monocultures are at risk
if a pest or disease attacks the crops.
42 MHR • Unit
Unit 11 Diversity
Diversityof
ofLiving
LivingThings
Things
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Research and Analyze
1. There are tree plantations in
Canada, and one of the key
species planted is red pine.
The purpose of these tree
plantations varies from helping
the recovery of accidentally
destroyed forests, such as those
affected by forest fire, to replacing
the stock of wood harvested by
pulp and paper companies. Research and
analyze the similarities and differences between
tree plantations in Canada and tree plantations in
tropical countries as described in the scenario.
Delegation
From: International Youth
tion
and Agriculture Organiza
To: United Nations Food
ns
Practice of Tree Plantatio
RE: Concerns About the
irable tree
ng landowners to plant des
We believe that encouragi
harvesting is
s and mahogany, for later
species, such as eucalyptu
The economic
fight against deforestation.
counterproductive in the
mers to clear
actually encourage local far
benefits of tree plantations
e tracts of
forests in order to plant larg
existing stands of natural
monoculture trees.
to make up for
g tree plantations in order
The practice of developin
tree plantations
s does not recognize that
the loss of natural ecosystem
ity between
ilar
ural forests—the only sim
have no relationship to nat
tain many
con
s
tain trees. Natural forest
them is that they both con
is
bas
the
other plants that form
different species of trees and
ing
lud
inc
ersity of other organisms,
for supporting a huge div
port some
als. Monocultures may sup
insects, reptiles, and mamm
s compared
itat
hab
vide a limited number of
biodiversity, but they pro
systems
eco
t
por
ests, which are able to sup
to naturally occurring for
in
tem
sys
eco
mple, a natural forest
rich in biodiversity. For exa
vides
pro
h
eac
55 species of trees, and
als.
Nigeria has between 40 and
mm
ma
and
ds
other species, such as bir
habitat and resources for
a single species of tree.
A tree plantation has only
ny ecosystem
ests include providing ma
The benefits of natural for
ng soil
g water supply and reduci
services, such as regulatin
by planting
ed
lac
rep
be
services cannot
erosion. These ecosystem
s destined for harvest.
monocultures of tree specie
e, and natural
vulnerable to pests, diseas
Monocultures are highly
l be wiped
ps
eats occurs, entire cro wil
disasters. If any of these thr
to support
p
cro
ated and have no other
out. Farmers will be devast
e.
tur
wait for new crops to ma
them as they replant and
2. Tree plantations are considered to be a key factor
in the fight against climate change because forests
capture carbon. The United Nations Framework
Convention on Climate Change (UNFCCC) is
promoting a program to subsidize tree plantations
in order to trap carbon and create “carbon credits”
for the plantation owners. These credits can then
be sold in international carbon markets, such as the
European Union Emission Trading Systems (EU ETS).
Research these programs and consider whether
you agree that tree plantations are an important
part of fighting climate change.
3. Make a Venn diagram to compare and contrast
monoculture tree plantations and natural
forests. What is your opinion of monoculture tree
plantations? What questions do you have regarding
tree plantations?
Take Action
1. Plan In a group, discuss the concerns related to
the issue of monoculture tree plantations. Based on
research and the information in the scenario, what
are the differing points of view in your group with
respect to the practice? What are the differences, if
any, between tree plantations in Canada and tree
plantations in other, less developed countries?
Share the results of the research and analysis you
conducted in questions 1 to 3 above.
2. Act Prepare a letter to be submitted to the FOA
outlining your recommendations about the
viability of monoculture tree plantations as a
solution to deforestation. Support your position
with information from credible sources.
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Chapter 1
Section 1.1
SUMMARY
Classifying and Naming Species
Taxonomists classify species by using two-part scientific
names and by using hierarchical classification based on
eight ranks.
KEY TERMS
binomial nomenclature
classification
genus
hierarchical classification
morphology
phylogeny
rank
species
taxon
taxonomy
KEY CONCEPTS
• Biologists use the morphological species concept, the
biological species concept, and the phylogenetic species
concept to define species.
• Species often have common names. However, they are
formally known by two-part scientific names.
• All species are classified by being placed in eight nested
ranks. The broadest category is the domain, continuing to
narrow to kingdom, phylum, class, order, family, genus, and
finally species, which is the narrowest category.
• Each named rank is known as a taxon.
Section 1.2
Determining How Species Are Related
Modern classification uses a variety of types of evidence
to classify and determine relationships among species,
but genetic information is currently a strong influence
in our understanding of how to classify.
• Taxonomists rely on morphological, physiological, and DNA
evidence to identify and classify species.
KEY TERMS
anatomy
ancestor
• Physiological evidence includes comparing the
biochemistry of organisms, including proteins. DNA
evidence includes comparing organisms’ DNA sequences.
phylogenetic tree
physiology
KEY CONCEPTS
• Modern classification organizes diversity according to
evolutionary relationships.
Section 1.3
• Understanding phylogeny can help scientists trace the
transmission of disease and develop and test possible
treatments.
Kingdoms and Domains
All species are placed in three domains that contain six
kingdoms, and taxonomists use dichotomous keys to
identify species.
KEY TERMS
autotroph
dichotomous key
eukaryotic
heterotroph
prokaryotic
structural diversity
KEY CONCEPTS
• The variety of internal and external forms exhibited by
species represents structural diversity.
Section 1.4
• Anatomical evidence includes comparing the structure and
form of organisms, including bones.
• There are two cell types: prokaryotic and eukaryotic.
Prokaryotic cells do not have a membrane-bound
nucleus. Eukaryotic cells are more complex and do have a
membrane-bound nucleus.
• Organisms in the domains Bacteria and Archaea are
unicellular and prokaryotic.
• Organisms in the domain Eukarya have eukaryotic cells and
are unicellular or multicellular. There are four kingdoms in
the domain Eukarya: Protista, Plantae, Fungi, and Animalia.
• Taxonomists use dichotomous keys to make choices
between pairs of options to narrow down identifications.
Classifying Types of Biodiversity
Species diversity, genetic diversity, and ecosystem
diversity are three types of biodiversity. Each is
important to the health of a population, a species,
and an ecosystem.
KEY TERMS
ecosystem diversity
gene pool
genetic diversity
population
resilience
species diversity
KEY CONCEPTS
• Too little genetic diversity reduces a population’s ability to
resist disease or other changing environmental conditions.
• Ecosystems are diverse due to variations in abiotic and
biotic factors.
• Ecosystems provide services, such as recycling nutrients
and regulating gases in the atmosphere.
• Ecosystems with greater species diversity have higher
resilience.
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Chapter 1
REVIEW
Knowledge and Understanding
Select the letter of the best answer below.
1. Which kingdom has species whose cells do not have
cell walls?
a. Animalia
d. Plantae
b. Archaea
e. Protista
c. Bacteria
Use this table to answer questions 2 and 3.
Classification of Selected Mammals
Kingdom Animalia
Animalia
Animalia
Animalia
Phylum
Chordata
Chordata
Chordata
Chordata
Class
Mammalia
Mammalia
Mammalia
Mammalia
Order
Carnivora
Perissodactyla
Perissodactyla Perissodactyla
Family
Phocidae
Rhinocerotidae Equidae
Genus
Halichoerus Diceros
Equus
Equus
Species
Halichoerus Diceros
grypus
bicornis
Equus
caballus
Equus
grevyi
Horse
Zebra
Common Grey seal
Name
Rhinoceros
Equidae
2. Which animal is the most distant relative to the others?
a. E. grevyi
d. rhinoceros
b. grey seal
e. zebra
c. horse
3. At which level does the rhinoceros split from the
zebra?
a. class
d. order
b. genus
e. species
c. family
4. Which term describes an identification tool that uses
a series of two-part choices?
a. binomial nomenclature
b. dichotomous key
c. phylogenetic tree
d. phylogenetic key
e. taxonomic key
5. Which type of diversity describes the variety
of heritable characteristics in a population of
interbreeding individuals?
a. biodiversity
b. ecosystem diversity
c. evolutionary diversity
d. genetic diversity
e. species diversity
6. Which species concept focuses on the evolutionary
relationships among organisms?
a. morphological species concept
b. biological species concept
c. phylogenetic species concept
d. taxonomic species concept
e. hierarchical species concept
7. In which kingdom would you place an organism that
is multicellular, has a cell wall made of cellulose, and is
autotrophic?
a. Bacteria
b. Archaea
c. Protista
d. Plantae
e. Fungi
8. Which structure that makes up genes is of most
interest to modern taxonomists?
a. glucose
b. chitin
c. cellulose
d. eukaryote
e. DNA
Answer the questions below.
9. What is the main benefit of scientists using the same
system to classify living things?
10. Explain the meaning of the term binomial
nomenclature.
11. What is a domain? Give an example of a domain.
12. Which organisms are more closely related, those in the
same genus or those in the same family?
13. In your notebook, state whether each of the following
statements is true or false. If the statement is false,
rewrite it so that it is true.
a. Some species of bacterium are eukaryotes.
b. Species in the same family are more closely related
to one another than species in the same class.
c. The morphological species concept classifies
organisms based on their evolutionary histories.
14. The little brown bat (Myotis lucifugus) is common
throughout northwestern Ontario. The northern
long-eared bat (Myotis septentrionalis) is
also found in many regions of Canada. Explain the
taxonomic relationship between these two mammals.
15. Identify five ecosystem services that sustainable
ecosystems provide.
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Chapter 1
REVIEW
16. Describe how anatomical evidence can be used to
indicate the shared evolutionary history of whales,
bats, horses, and humans.
22. Infer the relatedness of the vertebrate animals shown in
this phylogenetic tree. Explain your reasoning.
Snakes
Lizards
Crocodiles
Thinking and Investigation
17. You have discovered an unknown organism while on a
field trip. You think it is a new species of protist. How
could you test to identify this species as a protist? What
data would you need to classify it in kingdom Protista?
18. You have found a heterotrophic species with cell walls
made of chitin. What resources could you use from
this chapter to determine in which kingdom it belongs?
Identify the kingdom to which it belongs.
19. Many agricultural crops are known as monocultures,
in which a single species is cultivated in a large
field. Identify some problems that might occur in
monocultures, given experiments that show the
relationship between species diversity and ecosystem
efficiency.
20.
All living things can be classified according
to their anatomical and physiological
characteristics. Study the organisms shown below.
Create a dichotomous key to identify them. Give the
key to another person to use to identify the organisms.
Make revisions to your key as needed.
Birds
Common
Ancestor
Communication
23. Create a graphic organizer such as a main idea web to
show the different domains and kingdoms.
For each grouping, include a list of the characteristics
that define the grouping.
24. Create a handout to compare and contrast prokaryotic
and eukaryotic cells. If you were to teach this material
to students in a lower grade, what information
would be the most important to teach them the basic
differences between the two cell types?
25.
Human activities affect the diversity of
living things in ecosystems. There are many
examples of plants that are harvested for medicinal use,
such as the Pacific yew, which is used to make
medication used in the treatment of certain cancers.
In some areas, native plants used for medicinal
purposes have been overharvested. Think about the
possible effects that overharvesting of medicinal plants
could have on biodiversity within an ecosystem. Make
an argument for regulating the number of plants that
can be harvested from a particular ecosystem.
26. Over 100 billion Cavendish bananas are consumed
worldwide annually. As a result of agricultural
practices, each Cavendish is genetically identical to
all others. Write an e-mail to the owner of a banana
plantation outlining your concerns about the lack of
genetic diversity found in this important food source.
21. The scientific name of a Bengal tiger is Panthera
tigris tigris, and the Siberian tiger’s scientific name is
Panthera tigris altaica. The third term in each name
identifies the subspecies of these animals. Why do
you think taxonomists added the third term to the
scientific names of these animals?
27. Biological diversity exists at different levels. Draw a
pyramid diagram showing the relationship between the
three widely accepted levels of biodiversity.
28. Summarize your learning in this chapter using a
graphic organizer. To help you, the Chapter 1 Summary
lists the Key Terms and Key Concepts. Go to Using
Graphic Organizers in Appendix A to help you decide
which graphic organizer to use.
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Application
29. Taxonomists rely on more than anatomical,
physiological, and DNA evidence to classify. With
animals, they also compare behaviour patterns
between different species to determine the degree of
relatedness.
a. How valuable do you think this type of evidence is?
Explain.
b. Provide an example of a type of behaviour that
may be helpful to a taxonomist, and give reasons to
support your answer.
30. Use the information in the table below to answer the
following questions.
32. In 2005, a hunter shot what he thought was a polar
bear in the Canadian Arctic. The bear was brownish
white and had some other features not typical of
polar bears. Genetic tests proved it was a hybrid, the
offspring of a grizzly bear and a polar bear mating.
Your friend says that this is evidence that polar bears
and grizzly bears are the same species. Do you agree?
What other information might you want to know
before you agree or disagree? Explain your reasoning.
33. Use the dichotomous key below to answer the
following questions.
A
Ontario Reptiles
Scientific Name
Family
Eastern garter snake Thamnophis sirtalis
Common Name
Colubridae
Painted turtle
Chrysemys picta
Emydidae
Eastern massasauga
rattlesnake
Sistrurus catenatus
Viperidae
Snapping turtle
Chelydra serpentine
Chelydridae
Spotted turtle
Clemmys guttata
Emydidae
Five-lined skink
Eumeces fasciatus
Scincidae
Smooth green snake Opheodrys vernalis
Colubridae
Musk turtle
Sternotherus
odoratus
Kinosternidae
Ringneck snake
Diadophis
punctatus
Colubridae
Thamnophis
sauritus
Colubridae
Eastern ribbon
snake
a. Which pair of species is the most closely related
pair? Explain.
b. How many families are represented by the four
turtle species? Explain.
c. How many families are represented by the five snake
species? Explain.
d. Is the spotted turtle more closely related to the
painted turtle or the musk turtle? Why?
31. Canadian researchers have helped uncover 15 new
bird species through a process of genetic testing that
they say will pave the way for cataloguing the world’s
organisms. The discovery of so many new species was
made possible by analyzing and comparing the DNA
genetic bar codes of 643 North American bird species.
Predict what the use of DNA genetic bar codes will
have on the current taxonomic systems.
B
1a. Front and hind wings similar in size and shape,
and folded parallel to the body when at rest
. . . . . . . . . . . . . . . . damselfly
1b. Hind wings wider than front wings near base,
and extend on either side of the body when
at rest. . . . . . . . . . . . . . . . dragonfly
a. Identify the organisms shown in the diagrams.
Explain how you came to your decision.
b. From the key and the diagrams above, explain why
you could conclude that dragonflies and damselflies
evolved from a common ancestor.
34. Use the Internet or the print resources in your school’s
library to research the common names of the animal
Puma concolor. Based on your research, explain why
scientists prefer to use binomial nomenclature rather
than the common names of organisms.
35. Scientists are racing to discover new species that live
just below the ice in the Arctic Ocean. However, the
sea ice is disappearing and many of these unique
organisms may become extinct. Use the Internet or
print resources to research the services provided by
this ecosystem. Based on this information, predict
how the loss of sea ice will affect these services.
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Chapter 1
SELF-ASSESSMENT
Select the letter of the best answer below.
1.
2.
3.
4.
K/U Which is the correct order of the categories of
classification, from most diverse to most specific?
a. Kingdom, Domain, Phylum, Family, Class, Order,
Species, Genus
b. Species, Genus, Family, Order, Class, Phylum,
Kingdom, Domain
c. Kingdom, Family, Domain, Species, Genus, Phylum,
Class, Order
d. Domain, Kingdom, Phylum, Class, Order, Family,
Genus, Species
e. Domain, Kingdom, Phylum, Family, Class, Order,
Species, Genus
K/U Of the organisms listed below, which is the
closest relative of the snowy owl (Bubo scandiacus)?
a. barn owl (Tyto alba)
b. great horned owl (Bubo virginianus)
c. saw-whet owl (Aegolius acadicus)
d. eastern screech owl (Megascops asio)
e. burrowing owl (Athene cunicularia)
K/U Which species concept focuses on the ability of
organisms to interbreed in nature and produce viable,
fertile offspring?
a. morphological species concept
b. biological species concept
c. phylogenetic species concept
d. taxonomic species concept
e. hierarchical species concept
7.
K/U Which statement about binomial nomenclature
is false?
a. An organism’s scientific name is made up of two
words.
b. The first word of an organism’s scientific name is
its genus, and the second word is its species.
c. The scientific name is italicized if typed.
d. The scientific name is underlined if handwritten.
e. Both the genus and species names are capitalized.
8.
K/U The following is an example of a tool used by
taxonomists to divide Order Cetacea (whales,
dolphins, and porpoises) into two suborders.
K/U Which two kingdoms are not classified in
Domain Eukarya?
a. Protista and Fungi
b. Plantae and Animalia
c. Bacteria and Fungi
d. Archaea and Protista
e. Bacteria and Archaea
The monarch butterfly (Danaus plexippus) and
viceroy butterfly (Limenitis archippus) look almost
identical. Which species concept might have led
taxonomists to classify them as the same species?
1a. have baleen plates for filtering food from water ......
Suborder Mysticeti: baleen whales
1b. have teeth ........... Suborder Odontoceti: toothed
whales
What is the name of this taxonomic tool?
a. scientific name
b. binomial nomenclature
c. phylogenetic species concept
d. dichotomous key
e. hierarchical classification
K/U
a.
b.
c.
d.
e.
5.
6.
phylogenetic species concept
Linnaean species concept
biological species concept
morphological species concept
binomial species concept
K/U An autotrophic prokaryote with no cell wall
would be found in which kingdom?
a. Archaea
d. Fungi
b. Bacteria
e. Plantae
c. Protista
9.
10.
Identify the level of diversity that is evident in
the variety of inherited traits within a species.
a. species diversity
b. genetic diversity
c. ecosystem diversity
d. taxonomic diversity
e. phylogenetic diversity
K/U
K/U Which is not a benefit of understanding the
evolutionary relationships among species?
a. discovering the source of new medicines
b. discovering new proteins or chemicals
c. identifying biological controls through use of
natural predators
d. protecting and conserving existing species
e. determining the number of wolves in an area
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Use sentences and diagrams as appropriate to answer the
questions below.
11.
17.
A
The clouded leopard is a medium-sized wildcat
found in the forests of Asia. In a study comparing
differences in clouded leopard coat patterns and
coloration throughout the cat’s range, researchers
concluded that individuals found on the islands of
Borneo and Sumatra are markedly different from
animals found on the Southeast Asian mainland.
These observations have been supported by genetic
testing. Based on this information, are the clouded
leopards of Borneo and Sumatra the same species as
those on the mainland, or are the two groups different
species? Explain your reasoning.
18.
A
In the 1800s, Irish farmers planted a large
number of potatoes that were genetically identical to
one another. When a potato disease swept through the
country in the 1840s, the potatoes, and the people who
depended on them for food, were devastated. Explain
how the lack of genetic diversity of the potatoes grown
in Ireland could have contributed to a period of low or
no crop yield and widespread starvation.
19.
Rhizopus stolonifer can be found growing on an
old loaf of bread or a piece of fruit that has been sitting
on the counter for several days. Members of this
species cannot make their own food, and they have a
cell wall. Is there enough information provided above
to definitively place this species in one of the six
kingdoms? Explain why or why not.
20.
K/U List the characteristics of eukaryotic cells and
prokaryotic cells.
21.
K/U Define the term ecosystem services and list five
examples of the world’s ecosystem services.
22.
While hiking in the Hudson Bay Lowlands, you
find a multicellular organism growing on the bark of
a dying black spruce tree. Under a microscope, you
observe that its cells are eukaryotic, have cells walls,
and do not contain chloroplasts. Into what kingdom
would you classify this organism? Explain why.
23.
C
Suppose you had to explain the phylogenetic
tree shown in Figure 1.5 to a class of Grade 6 students.
Write a short paragraph explaining what the diagram
shows and how scientists use other diagrams like it to
help classify organisms.
K/U Identify the kingdom in which you would place
a single-celled, eukaryotic organism that makes it
own food.
Use the table below to answer questions 12 and 13.
Classification of a Coyote and a Dog
Rank
Domain
Coyote
Eukarya
Dog
Eukarya
Kingdom
Animalia
Animalia
Phylum
Chordata
Chordata
Class
Mammalia
Mammalia
Order
Carnivora
Carnivora
Family
Canidae
Canidae
Genus
Canis
Canis
Species
Canis latrans
Canis familiaris
12.
Use the scientific name of the coyote to explain
binomial nomenclature.
13.
T/I Predict the family into which the red wolf
(Canis rufus) would be classified. Explain, in terms of
the hierarchical classification system, your prediction.
14.
C
Construct a dichotomous key you could use to
classify the music of 10 performers on a personal
digital audio player.
15.
C
A group of concerned students is developing a
plan to increase the biodiversity of their school’s
grounds. Currently, the school ground is primarily a
large open grass field with a handful of trees planted
near the chain-link fence that surrounds the grounds.
Make a list of at least five actions the students could
include in their plan to increase the biodiversity of
their school’s grounds.
16.
A
Two scientists, working independently, produce
the phylogenetic trees shown below for the same group
of organisms. Explain why the two scientists could
come up with the two different phylogenetic trees.
T/I
L
M
N
N
L
M
Common Ancestor
Common Ancestor
Phylogenetic Tree A
Phylogenetic Tree B
T/I
T/I
Self-Check
If you missed
question ...
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4
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8
9
10
11
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