UNIT 1: Diversity of Living Things

Chapter 1: Classifying Life’s Diversity

How do scientists classify life on Earth?

Chapter 2: Diversity: From Simple to Complex

Chapter 3: Multicellular Diversity

Chapter One: Classifying Life’s Diversity

The yeti crab (Kiwa hirsuta) is a species discovered during the Census of Marine Life.

• Why was such a project created?

• Why might it be important?

UNIT 1 Chapter 1: Classifying Life’s Diversity Section 1.1

1.1 Identifying, Naming, and Classifying Species

• Farmers and gardeners need to separate weeds from crops.

• Doctors must correctly identify infectious organisms before treatment.

• Edible and medicinal plants must be correctly identified before use.

• What other examples can you think of?

How could scientists determine if this pink iguana is a different species from others on the island?

UNIT 1 Chapter 1: Classifying Life’s Diversity Section 1.1

Scientists identify, define, and name species of organisms. Why is this important?

Identifying Species: Using Species Concepts

Scientists require a working definition of the concept of a species. Three are commonly used:

• Biological Species Concept

• Morphological Species Concept

• Phylogenetic Species Concept

morphology: the branch of biology that deals with the structure or form of organisms]

phylogeny: the evolutionary history of a species

UNIT 1 Chapter 1: Classifying Life’s Diversity Section 1.1

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Identifying Species: Using Species Concepts

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Identifying Species: Using Species Concepts

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Identifying Species: Using Species Concepts

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Standard Names for Species: Binomial Nomenclature

Taxonomy is the identification, classification, and naming of species.

Binomial nomenclature refers to a two-part naming system. An organism’s scientific or species name has two parts:

UNIT 1 Chapter 1: Classifying Life’s Diversity Section 1.1

• The first part, the genus name, identifies the group of closely related species to which the species belongs.

• The second part is the species name.Continued…

 

 

Standard Names for Species: Binomial Nomenclature

The Binomial nomenclature system was first developed by Carolus Linnaeus.

Scientists around the world refer to this animal as Marmota (genus) monax (species).

What are some of its local (common) names?

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Classifying Species Scientists use the three species concepts to determine

which organisms make up a species. Then they arrange the different species in related groups.

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Classification is the grouping of organisms based on a set of criteria that helps to organize and indicate evolutionary relationships.

Hierarchical Classification A hierarchy arranges items above, below, or at the same

level as other items in the group.

Hierarchical classification classifies organisms by arranging species based on categories from most general to most specific. This is known as a nested system.

UNIT 1 Chapter 1: Classifying Life’s Diversity Section 1.1

Taxonomic Categories Used To Classify Organisms

Taxonomic categories are used to classify organisms that have been identified. The categories or groupings are arranged in a hierarchy.

Each level or category is known as the rank. The particular classification of an organism at each rank level is called the taxon (pl. taxa).

UNIT 1 Chapter 1: Classifying Life’s Diversity Section 1.1

There are eight ranks. Domain is the most general, containing the most species. The species rank is specific to one species.

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Taxonomic Categories Used To Classify Organisms

UNIT 1 Chapter 1: Classifying Life’s Diversity Section 1.1

Write the rank levels in order from most general to most specific.  Write the full taxonomic classification of the grey wolf.

Section 1.1 Review

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1.2 Determining How Species Are Related Modern classification uses morphological similarities and evolutionary

history to assign a species to taxa.

Hypotheses about the evolutionary history and relationships among different species are made based on three types of evidence:

UNIT 1 Chapter 1: Classifying Life’s Diversity Section 1.2

• anatomical• physiological• DNA

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Determining How Species Are Related

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Species that have many anatomical, physiological, and molecular (DNA) characteristics in common are thought to share a common evolutionary ancestor.

Anatomical Evidence of Relationships

Anatomy is the study of the structure and form of organisms (including internal systems). It is a branch of morphology and further helps scientists determine evolutionary relationships among species.

These bone structures are similar even though the limbs look different. Over millions of years, the limbs have changed to better suit swimming, flying, running, or grasping, but the overall arrangement of bones and similarities indicate a shared evolutionary history.

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Physiological Evidence of Relationships Physiology deals with the physical and chemical

functions of organisms, including their biochemistry and internal processes. Taxonomists use the data on the physical and chemical functions of an organism to classify it.

Guinea pigs and mice were once both classified in the order Rodentia. An analysis of proteins, including insulin, showed that guinea pig insulin is very different from that of typical rodents. Guinea pigs were reclassified into a taxon of their own.

UNIT 1 Chapter 1: Classifying Life’s Diversity Section 1.2

DNA Evidence of Relationships New technology has made it possible to conduct genetic

analysis and de-code the sequences of nucleotides in DNA. DNA from different species can be compared to determine relationships. 

In some cases, new DNA evidence has meant that classifications based on morphological, physiological, or other evidence have to be restructured.

Fungi and plants are superficially similar—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.

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Phylogenetic Trees

The animals shown here are all part of the order Artiodactyla.

UNIT 1 Chapter 1: Classifying Life’s Diversity Section 1.2

A phylogenetic tree is a branching diagram used to show the evolutionary relationships among species.

Study the phylogenetic tree. To which other organism is Cervus elaphus most closely related? At what rank and taxon are they related?

The Importance of Classification

Classification can assist in:

• the discovery of new drugs, hormones, and other medical products

• tracing the transmission of disease and the development and testing of possible treatments

• increasing crop yields and disease and pest resistance

• environmental conservation of organisms

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Section 1.2 Review

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1.3 Kingdoms and Domains The second most general rank, kingdom, includes six different taxa. There is incredible structural diversity (internal and external

forms) within the kingdoms even though species are grouped.

Advances in microscopy and molecular biology have increased the number of kingdoms from two in the 1800s to six in 2010. Classification at the kingdom level is based on general internal and external similarities, but it begins with the two basic cell types on Earth.

UNIT 1 Chapter 1: Classifying Life’s Diversity Section 1.3

Two Major Cell Types There are two major cell types: prokaryotic and eukaryotic.

Which type of cell might have originated first, prokaryotic or eukaryotic? Explain your answer.

What other differences can you observe?

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The Three Domains and Dichotomous Keys There are three domains:

• Bacteria

• Archaea

• Eukarya

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Eukarya includes all species made up of eukaryotic cells (four kingdoms). Both Bacteria and Archaea are prokaryotic domains but are not grouped due to great cellular and genetic (DNA) differences.

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The Three Domains and Dichotomous Keys

UNIT 1 Chapter 1: Classifying Life’s Diversity Section 1.3

To classify an organism, scientists begin at the domain level and work through many sequential questions with only two possible answer choices to reach a genus/species level of identification. This system is called a dichotomous key. Most questions involve anatomical and structural analysis. In some cases, only the kingdom taxon is required.

Main Characteristics of Kingdoms

• number of cells (unicellular or multicellular)• cell wall material (if present)• nutrition (autotroph or heterotroph)• primary means of reproduction (asexual or sexual)

 

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When classifying only to the kingdom rank, the following characteristics can be used:

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Main Characteristics of Kingdoms UNIT 1 Chapter 1: Classifying Life’s Diversity Section 1.3

An autotroph captures energy from sunlight/abiotic substances. A heterotroph obtains energy by consuming other organisms.

 

Try to use the characteristics above to identify the kingdom for each organism. Infer where necessary.

Section 1.3 Review

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1.4 Classifying Types of BiodiversityUNIT 1 Chapter 1: Classifying Life’s Diversity Section 1.4

There are three important ways of studying biodiversity.

 

Genetic diversity

 

Species diversity

 

Ecosystem diversity

 

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Classifying Types of Biodiversity

• Genetic diversity is the variety of heritable characteristics (genes) in a population of interbreeding individuals.

• Species diversity is the variety and abundance of species in a given area.

• Ecosystem diversity is the variety of ecosystems in the biosphere.

 

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Genetic and Ecosystem Diversity

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A gene pool is the sum of all the versions of all the genes in a population. The larger the gene pool and genetic diversity, the better the chances of species survival despite environmental pressures or changes (diseases, for example).  On a much larger scale, ecosystem diversity refers to the variety of ecosystems in all sizes from a plant to an entire biome. The health and sustainability of the biosphere can be measured by the richness of ecosystem diversity.

The population of Tasmanian devils (Sarcophilis harrisii) has been severely reduced by cancer. A lack of genetic diversity made the animals vulnerable to disease.

Ecosystem Services

• atmospheric gas supply• climate regulation• water supply• food production

 

UNIT 1 Chapter 1: Classifying Life’s Diversity Section 1.4

Ecosystem services are the benefits experienced by species (including humans) that are provided by sustainable ecosystems. Examples of services include:

• raw materials

• waste treatment

• soil erosion control

• nutrient recycling

 

Ecosystem Services and Human Activity

 • non-native species invasion• disease• changes in abiotic factor concentrations

 

UNIT 1 Chapter 1: Classifying Life’s Diversity Section 1.4

Ecosystems with greater species diversity are more likely to provide important services reliably and are also more resilient despite disturbances. Disturbances can include:

Human activity must not lower the species diversity of an ecosystem and consequently lower its sustainability and services.

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Ecosystem Services and Human Activity

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Section 1.4 Review

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DNA Bar Codes

UNIT 1 STSE Feature

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 sequences 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.