Classification of living organisms

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수업 노트

What is Classification?

There are millions of species on Earth, so we group them to make sense of the diversity.
Classification is the process of grouping organisms based on shared features.
A species is a group of organisms that can reproduce to produce fertile offspring.
Organisms that share features often do so because they evolved from a common ancestor.
Classification systems aim to reflect evolutionary relationships between organisms.

The Linnaean System

Developed by Carl Linnaeus, a Swedish naturalist, in the 18th century.
Organisms are classified into a hierarchy of groups: Kingdom, Phylum, Class, Order, Family, Genus, Species.
The more subdivided the group, the more features the organisms in it share.
The order can be remembered with the mnemonic: King Philip Came Over For Gran's Spaghetti.
Linnaeus also introduced the binomial naming system for species.

Binomial Naming System

Each species has a two-part scientific name: Genus (capitalised) followed by species (lower case).
When typed, binomial names are always in italics (e.g.×Homo sapiens×).
When handwritten, they are underlined.
The binomial system is internationally agreed, so scientists worldwide use the same name.
Example: The Emperor Penguin's binomial name is×Aptenodytes forsteri×.

Development of Classification

Originally, organisms were classified using morphology (overall form and shape) and anatomy (internal structure from dissection).
Improvements in microscopes allowed scientists to study internal structures in more detail.
Advances in biochemistry revealed similarities in proteins and other molecules.
DNA sequencing now provides a more scientific approach to classification.
The more similar the DNA base sequences of two species, the more closely related they are.
Similarities in amino acid sequences in proteins can also show relatedness.

Three-Domain System

Proposed by Carl Woese in 1990, based on chemical analysis evidence.
Organisms are divided into three large groups called domains: Archaea, Bacteria, and Eukaryota.
Archaea are primitive bacteria usually living in extreme environments (e.g. hot springs, salt lakes).
Bacteria are true bacteria (e.g.×E. coli×,×Staphylococcus×).
Eukaryota include protists, fungi, plants, and animals.
Each domain is further subdivided into kingdom, phylum, class, order, family, genus, species.

Evolutionary Trees

Evolutionary trees are diagrams showing relationships between species over evolutionary time.
A new branch shows where speciation has occurred (a new species evolved).
Species that share a recent common ancestor are more closely related.
Example: Chimpanzees are most closely related to bonobos; humans are more closely related to gorillas than to orangutans.
Evolutionary trees are built using current classification data (e.g. DNA analysis, structural similarities) and fossil data for extinct organisms.
They are considered a hypothesis of evolutionary past because new evidence can lead to revisions.

Using DNA to Determine Relationships

DNA base sequences can show how closely related different species are.
The more similar the base sequences, the more closely related the species.
Example:×Brachinus armiger×and×Brachinus hirsutus×have nearly identical DNA sequences, so they are closely related.
DNA codes for amino acid sequences in proteins, so protein similarities also indicate relatedness.
DNA analysis is used to build evolutionary trees and refine classification.

Common Misconceptions

Binomial names must have the genus capitalised and be in italics (or underlined when handwritten).
Classification is not fixed; it is revised as new evidence emerges.
Do not confuse the three domains with the five kingdoms.
Physical similarity does not always mean close evolutionary relationship; DNA evidence is more reliable.

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연습 문제

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1.Which two classification groups are in the wrong sequence in the list: Kingdom, Phylum, Class, Family, Order, Genus, Species?
Easy
- AKingdom and Phylum
- BClass and Family
- COrder and Family
- DFamily and Order
2.Which scientist first devised and set up the three-domain system of classification of organisms?
Easy
- ACarl Woese
- BCarl Linnaeus
- CCharles Darwin
- DGregor Mendel
3.Which of the following statements about the three-domain system are correct? (select all that apply)
Medium
- AArchaea are primitive bacteria usually living in extreme environments.
- BBacteria include true bacteria such as E. coli and Staphylococcus.
- CEukaryota includes protists, fungi, plants and animals.
- DThe three domains are Kingdom, Phylum and Class.
- EThe three-domain system was developed by Carl Linnaeus.
4.All eukaryotes are multicellular organisms.
Easy
True or false?
5.All multicellular organisms are eukaryotes.
Easy
True or false?
6.In an evolutionary tree, which two species are most closely related?
Medium
- ASpecies that share the most recent common ancestor
- BSpecies that look the most similar
- CSpecies that live in the same habitat
- DSpecies that have the same number of chromosomes
7.Which of the following are used by scientists to build evolutionary trees? (select all that apply)
Medium
- ADNA analysis
- BStructural similarities
- CFossil data
- DThe colour of the organism's fur
- EThe size of the organism
8.The more similar the base sequences in the DNA of two species, the more closely related they are.
Easy
True or false?

더 많은 문제

9.Which of the following best explains why classification systems have changed over time?
Medium
- ANew evidence from microscopes, biochemistry and DNA sequencing has become available.
- BScientists have disagreed about the names of organisms.
- COlder classification systems were based on DNA analysis.
- DOrganisms have evolved to look different.
10.Match each domain to its correct description.
Medium
- Archaea
- Bacteria
- Eukaryota
- Primitive bacteria usually living in extreme environments
- True bacteria such as E. coli and Staphylococcus
- Includes protists, fungi, plants and animals
11.Place the following classification groups in the correct order from largest to smallest.
Medium
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
12.The domestic dog and the grey wolf share the same binomial name Canis lupus, but the dog is given an additional subspecies name familiaris. What does this suggest?
Medium
- AThey are different species but in the same genus.
- BThey are the same species but different subspecies.
- CThey are different genera but the same species.
- DThey are not closely related.
13.Which classification group comes immediately below kingdom in the Linnaean system?
Easy
- APhylum
- BClass
- COrder
- DFamily
14.Archaea are primitive bacteria that are usually found living in extreme environments such as hot springs and salt lakes.
Easy
True or false?
15.Match each domain to the type of organism it contains.
Medium
- Archaea
- Bacteria
- Eukaryota
- True bacteria such as coli and Staphylococcus
- Protists, fungi, plants and animals
- Primitive bacteria usually living in extreme environments
16.A species is best defined as a group of organisms that:
Easy
- Acan reproduce to produce fertile offspring
- Blook identical to one another
- Clive in the same habitat
- Dbelong to the same genus
17.In an evolutionary tree, species Y and species Z are shown branching from the same point, while species W branches off earlier. Which statement is correct?
Medium
- AY and Z are more closely related to each other than either is to W.
- BY and W are more closely related to each other than either is to Z.
- CZ and W are more closely related to each other than either is to Y.
- DAll three species are equally closely related.
18.The capybara belongs to the classification groups shown, in descending order of size: Eukaryotes, Animals, Chordates, Mammals, Rodents, Caviidae, Hydrochoerus, hydrochaeris. Which are the family and the class of the capybara?
Medium
- AFamily Caviidae and class Mammals
- BFamily Mammals and class Caviidae
- CFamily Rodents and class Mammals
- DFamily Hydrochoerus and class Chordates
19.The King Penguin and Emperor Penguin share the same groups down to genus Aptenodytes, but their species names differ (patagonicus and forsteri). What is the binomial name of the Emperor Penguin?
Medium
- AAptenodytes forsteri
- BAptenodytes patagonicus
- Cforsteri Aptenodytes
- DSpheniscidae forsteri
20.The DNA base sequences of four species were compared. Species P and Q differ by 3 bases out of 100. Species P and R differ by 12 bases out of 100. Species P and S differ by 7 bases out of 100. Which species is most closely related to species P?
Medium
- ASpecies Q
- BSpecies R
- CSpecies S
- DAll are equally related
21.In an evolutionary tree, species A and B share a recent common ancestor, while species C branches off much earlier. Which statement is correct?
Medium
- AA and B are more closely related to each other than either is to C
- BA and C are more closely related because C is older
- CB and C are more closely related because C branched first
- DAll three species are equally related
22.A scientist compares the amino acid sequences of a protein in four mammals. Species 1 and 2 have identical sequences; species 3 differs by two amino acids; species 4 differs by five amino acids. Which conclusion is best supported?
Medium
- ASpecies 1 and 2 are the most closely related pair
- BSpecies 1 and 4 are the most closely related pair
- CSpecies 2 and 3 are the most closely related pair
- DAmino acid sequences cannot be used to judge relatedness
23.A new species of single-celled organism is discovered living in a hot spring. It has a nucleus and no cell wall. Which statements about its classification are correct? (select all that apply)
Medium
- AIt belongs to the domain Eukaryota
- BIt belongs to the domain Archaea
- CIt is a prokaryote
- DIt is a eukaryote
- EIt belongs to the domain Bacteria
24.Which of the following are features of the binomial naming system? (select all that apply)
Medium
- AThe genus is written with a capital letter
- BThe species is written with a lower case letter
- CThe name is always written in italics when typed
- DThe name consists of three parts
- EThe name is written in English
25.In the three-domain system, the domain Archaea contains primitive bacteria that usually live in extreme environments.
Easy
True or false?
26.Physical similarity always shows that two species are closely related.
Easy
True or false?
27.Match each classification group to its position in the Linnaean hierarchy.
Medium
- Kingdom
- Phylum
- Class
- Order
- Largest group
- Second largest group
- Third largest group
- Fourth largest group
28.Place the following classification groups in order from largest to smallest.
Medium
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
29.Of the following pairs of primates, which two species share the most recent common ancestor?
Medium
- AChimpanzees and bonobos
- BHumans and gorillas
- CGorillas and orangutans
- DHumans and orangutans
30.Which statement about the evolutionary relationships between humans, gorillas and orangutans is correct?
Medium
- AHumans are more closely related to gorillas than to orangutans
- BHumans are more closely related to orangutans than to gorillas
- CAll five species are equally closely related
- DOrangutans are more closely related to chimpanzees than to gorillas
31.Humans, chimpanzees, bonobos, gorillas and orangutans all share a common ancestor from the distant past.
Easy
True or false?
32.A student is comparing the DNA base sequences of two species of beetle. They find the sequences are identical except for one base at position 42. What does this result suggest about the two species?
Medium
- AThey are closely related and share a recent common ancestor.
- BThey are not related at all because their DNA is different.
- CThey belong to different domains.
- DThey are the same species because only one base is different.
33.A scientist wants to classify a newly discovered organism. They find it has a nucleus, is multicellular, and obtains its food by photosynthesis. Which domain should it be placed in?
Medium
- AArchaea
- BBacteria
- CEukaryota
- DIt cannot be classified into a domain.
34.Two species of fish, A and B, have DNA that differs by 15 bases out of 1000 compared. Species A and C differ by 45 bases out of 1000. Which statement is correct?
Hard
- AA is more closely related to C than to B.
- BA is more closely related to B than to C.
- CA is equally related to B and C.
- DThe number of base differences does not indicate relatedness.
35.Which of the following are reasons why the classification of organisms has changed over time? (select all that apply)
Medium
- AImprovements in microscopes allowed internal structures to be studied.
- BDNA sequencing provided a more scientific approach.
- CScientists decided to use common names instead of Latin names.
- DUnderstanding of biochemical processes progressed.
- EThe three-domain system was developed by Carl Woese.
36.The three-domain system was developed by Carl Linnaeus.
Easy
True or false?
37.In the three-domain system, the domain Bacteria contains true bacteria such as E. coli and Staphylococcus.
Medium
True or false?
38.Match each domain to the description that is unique to it.
Medium
- Archaea
- Bacteria
- Eukaryota
- Primitive bacteria usually living in extreme environments such as hot springs and salt lakes
- True bacteria such as E. coli and Staphylococcus
- Includes protists, fungi, plants and animals
39.Which scientist gave his name to the system of classification that groups organisms into kingdom, phylum, class, order, family, genus and species?
Easy
- ACarl Woese
- BCarl Linnaeus
- CCharles Darwin
- DGregor Mendel
40.A group of students are studying fruit flies, which belong to the kingdom Animalia. What type of cells are found in a fruit fly?
Medium
- AProkaryotic cells with no nucleus
- BEukaryotic cells with a nucleus
- CPrimitive bacterial cells found only in extreme environments
- DCells without a cell membrane
41.Complete the sentence about species using the correct words.
Easy
A species is a group of similar ____ that can ____ naturally with one another and produce ____ offspring.
42.Name the biologist who gave his name to the system of classification that uses genus and species.
Easy
43.Name the three domains of the three-domain system of biological classification.
Easy
The three domains are ____, ____, and ____.
44.What term describes the group of organisms that can reproduce to produce fertile offspring?
Easy
45.Complete the sentence about the binomial naming system.
Medium
The binomial naming system is useful because it is an ____ agreed system, so scientists worldwide can ____ organisms.
46.Complete the sentence about the binomial naming system using the correct words.
Easy
In the binomial system, the first part of the name is the ____ and the second part is the ____.
47.Name the scientist who developed the three-domain system of classification.
Medium
48.In a DNA sequence comparison, species P and species Q differ by 3 bases out of 100. What percentage of bases are different?
Medium
49.Two species of beetle have DNA sequences that differ by 4 bases out of a total of 200 bases compared. What percentage of the bases are different?
Medium
50.Complete the sentence about the binomial system.
Easy
The scientific name of an organism is made up of two parts: the genus and the ____.
51.Complete the sentence about evolutionary trees.
Medium
In an evolutionary tree, a new branch shows where ____ has occurred.
52.Complete the sentence using the correct words.
Easy
A species is a group of organisms that can ____ to produce ____ offspring.
53.Describe how the process of classifying organisms has changed over time.
Medium
54.Explain how DNA sequencing of an enzyme involved in aerobic respiration could be used to determine the relationship between the domestic dog, grey wolf and coyote.
Hard
55.Explain why the classification of organisms has changed over time.
Hard
56.Which of these two statements is correct: (1) All eukaryotes are multicellular organisms, or (2) All multicellular organisms are eukaryotes? Explain your answer.
Medium
57.Suggest a reason why the binomial naming system is a useful way of helping scientists classify organisms.
Hard
58.In a DNA sequence comparison, species P and species Q differ by 3 bases out of 100. What percentage of bases are different?
Medium
- A5 %
- B4 %
- C2 %
- D3 %
59.Two species of beetle have DNA sequences that differ by 4 bases out of a total of 200 bases compared. What percentage of the bases are different?
Medium
- A4 %
- B1 %
- C3 %
- D2 %

플래시카드

Define the term 'species'.

A species is a group of organisms that can reproduce naturally with one another to produce fertile offspring.

Who devised the traditional classification system based on structure and characteristics?

Carl Linnaeus, a Swedish naturalist.

List the seven levels of the Linnaean classification system in descending order of size.

Kingdom, Phylum, Class, Order, Family, Genus, Species.

What is the binomial naming system?

A system where the scientific name of an organism has two parts: the genus (capital letter) followed by the species (lower case letter).

How should a typed binomial name be written?

The genus starts with a capital letter, the species with a lower case letter, and the whole name is in italics, e.g. Homo sapiens.

Give the correct way to write the binomial name of the bald eagle.

Haliaeetus leucocephalus — genus capitalised, species lower case, written in italics.

In the binomial name Homo sapiens, which part is the genus and which is the species?

Homo is the genus and sapiens is the species.

Why is the binomial naming system useful to scientists?

It is an internationally agreed system, so scientists worldwide use the same name for the same organism, avoiding confusion from local common names.

What features do all mammals share?

Bodies covered in hair, young fed from mammary glands, and external ears (pinnas).

What two things were originally used to classify organisms?

Morphology (overall form and shape) and anatomy (detailed body structure determined by dissection).

How did improvements in microscopes change classification?

They allowed internal structures to be studied in more detail, leading to new models of classification being proposed.

How is DNA sequencing used to classify organisms?

The more similar the base sequences in the DNA of two species, the more closely related they are and the more recent their common ancestor.

Why can amino acid sequences be used to determine how closely related organisms are?

DNA base sequences code for amino acid sequences in proteins, so similarities in amino acid sequences also show relatedness.

Who developed the three-domain system and when?

Carl Woese developed it in 1990, based on evidence from chemical analysis.

Name the three domains of the three-domain system.

Archaea, Bacteria and Eukaryota.

Describe the domain Archaea.

Primitive bacteria that usually live in extreme environments such as hot springs and salt lakes.

What does the domain Bacteria contain?

True bacteria, such as E. coli and Staphylococcus.

Which organisms are included in the domain Eukaryota?

Protists, fungi, plants and animals.

How are the three domains further subdivided?

Into the smaller groups: kingdom, phylum, class, order, family, genus and species.

What is an evolutionary tree?

A diagram showing the relationship between species over evolutionary time.

What does a new branch on an evolutionary tree represent?

A point where speciation has occurred — when a new species has evolved.

On an evolutionary tree, what does a recent common ancestor tell you about two species?

The more recent their shared common ancestor, the more closely related and more similar the two species are.

What data are used to build evolutionary trees?

Current classification data for living organisms (such as DNA analysis and structural similarities) and fossil data for extinct organisms.

Why are evolutionary trees described as a hypothesis of the evolutionary past?

They are based on evidence and interpretation, so they represent scientists' best explanation and may be revised as new evidence emerges.

Why has the way scientists classify organisms changed over time?

As evidence from improved microscopes, biochemistry and DNA sequencing developed, new models of classification were proposed.

What is the mnemonic to remember the order of classification?

King Philip Came Over For Gran's Spaghetti — Kingdom, Phylum, Class, Order, Family, Genus, Species.

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