Monday:
Modern Classification
Modern taxonomists have reordered many groups of organisms since Linnaeus. The main categories that biologists use are listed here from the most specific to the least specific category (Figure below).
Least Specific Domain
Kingdom
Phylum
Class
Order
Family
Genus Most Specific Species
Modern Classification
Modern taxonomists have reordered many groups of organisms since Linnaeus. The main categories that biologists use are listed here from the most specific to the least specific category (Figure below).
Least Specific Domain
Kingdom
Phylum
Class
Order
Family
Genus Most Specific Species
Tuesday:
Difficulty Naming Species
Even though naming species is straightforward, deciding if two organisms are the same species can sometimes be difficult. Linnaeus defined each species by the distinctive physical characteristics shared by these organisms. But two members of the same species may look quite different. For example, people from different parts of the world sometimes look very different, but we are all the same species.
So how is a species defined? The term species has its origins in the ancient Latin language. In this language, the word species means kind. A more technical definition of species is a group of interbreeding organisms that do not ordinarily breed with members of other groups. Biologists estimate that about 10 to 40 million different species inhabit the Earth. Of these species, approximately 1.5 million have been classified.
The first individual to propose an orderly system for classifying the variety of organisms found on our planet was Linnaeus (1753). In his system of classification, the finest unit in the organization of life is the species. Linnaeus suggested that every organism should be classified with a unique binomial name. The first term in this classification system is the organism's generic name or Genus. The second term is the organism's specific name or species designation.
Current classification systems have developed from Linnaeus' original work. However, modern classification systems are much more complicated having many levels of hierarchical organization. These systems are also taxonomic (structural and physiological connections between organisms), phylogenic (classification based on genetic connections between organisms), and are structurally based on Darwin's theory of evolution.
Modern classifications of organisms are standardized in a hierarchical system that go from general to specific.
Wednesday:
Domains of Life
Let’s explore the least specific category of classification, called a domain.
All of life can be divided into 3 domains, which tell you the type of cell inside of an organism:
Archaea and Bacteria seem very similar, but they also have significant differences.
Similarities:
Eukarya
All of the cells in the domain Eukarya keep their genetic material, or DNA, inside the nucleus. The domain Eukarya is made up of four kingdoms:
Viruses
We have all heard of viruses. The flu and many other diseases are caused by viruses. But what is a virus? Based on the material presented in this chapter, do you think viruses are living?
The answer is actually “no.” A virus is essentially DNA or RNA surrounded by a coat of protein. It is not a cell and does not maintain homeostasis. Viruses also cannot reproduce on their own – they need to infect a host cell to reproduce. Viruses do, however, change over time, or evolve. So a virus is very different from any of the organisms that fall into the three domains of life.
Difficulty Naming Species
Even though naming species is straightforward, deciding if two organisms are the same species can sometimes be difficult. Linnaeus defined each species by the distinctive physical characteristics shared by these organisms. But two members of the same species may look quite different. For example, people from different parts of the world sometimes look very different, but we are all the same species.
So how is a species defined? The term species has its origins in the ancient Latin language. In this language, the word species means kind. A more technical definition of species is a group of interbreeding organisms that do not ordinarily breed with members of other groups. Biologists estimate that about 10 to 40 million different species inhabit the Earth. Of these species, approximately 1.5 million have been classified.
The first individual to propose an orderly system for classifying the variety of organisms found on our planet was Linnaeus (1753). In his system of classification, the finest unit in the organization of life is the species. Linnaeus suggested that every organism should be classified with a unique binomial name. The first term in this classification system is the organism's generic name or Genus. The second term is the organism's specific name or species designation.
Current classification systems have developed from Linnaeus' original work. However, modern classification systems are much more complicated having many levels of hierarchical organization. These systems are also taxonomic (structural and physiological connections between organisms), phylogenic (classification based on genetic connections between organisms), and are structurally based on Darwin's theory of evolution.
Modern classifications of organisms are standardized in a hierarchical system that go from general to specific.
Wednesday:
Domains of Life
Let’s explore the least specific category of classification, called a domain.
All of life can be divided into 3 domains, which tell you the type of cell inside of an organism:
- Bacteria: Single-celled organisms that do not contain a nucleus
- Archaea: Single-celled organisms that do not contain a nucleus; have a different cell wall from bacteria
- Eukarya: Organisms with cells that contain a nucleus.
Archaea and Bacteria seem very similar, but they also have significant differences.
Similarities:
- Do not have a nucleus
- Small cells
- One-celled
- Can reproduce without sex by dividing in two
- Cell walls made of different material
- Archaea often live in extreme environments like hot springs, geysers, and salt flats while bacteria can live almost everywhere.
Eukarya
All of the cells in the domain Eukarya keep their genetic material, or DNA, inside the nucleus. The domain Eukarya is made up of four kingdoms:
- Plantae: Plants, such as trees and grasses, survive by capturing energy from the sun, a process called photosynthesis.
- Fungi: Fungi, such as mushrooms and molds, survive by "eating" other organisms or the remains of other organisms.
- Animalia: Animals survive by eating other organisms or the remains of other organisms. Animals range from tiny ants to the largest dinosaurs (reptiles) and whales (mammals), including all sizes in between. (Figure below).
- Protista: Protists are not all descended from a single common ancestor in the way that plants, animals, and fungi are. Protists are all the eukaryotic organisms that do not fit into one of the other three kingdoms. They include many kinds of microscopic one-celled organisms, such as algae and plankton, but also giant seaweeds that can grow to be 200 feet long
Viruses
We have all heard of viruses. The flu and many other diseases are caused by viruses. But what is a virus? Based on the material presented in this chapter, do you think viruses are living?
The answer is actually “no.” A virus is essentially DNA or RNA surrounded by a coat of protein. It is not a cell and does not maintain homeostasis. Viruses also cannot reproduce on their own – they need to infect a host cell to reproduce. Viruses do, however, change over time, or evolve. So a virus is very different from any of the organisms that fall into the three domains of life.
Friday:
1. Who designed modern classification and invented the two-part species name?
2. Define a species.
3. What kingdoms make up the domain Eukarya?
4. What is the name for the scientific study of naming and classifying organisms?
5. How are organisms given a scientific name?
6. In what domain are humans?
7. Quercus rubra is the scientific name for the red oak tree. What is the red oak’s genus?
8. In what domain are mushrooms?
9. What information do scientists use to classify organisms?
10. Is it possible for organisms in two different classes to be in the same genus?
11. If molecular data suggests that two organisms have very similar DNA, what does that say about their evolutionary relatedness?
12. Can two different species ever share the same scientific name?
13. If two organisms are in the same genus, would you expect them to look much alike?
- Scientists have defined several major categories for classifying organisms: domain, kingdom, phylum, class, order, family, genus, and species.
- The scientific name of an organism consists of its genus and species.
- Scientists classify organisms according to their evolutionary histories and how related they are to one another - by looking at their physical features, the fossil record, and DNA sequences.
- All life can be classified into three domains: Bacteria, Archaea, and Eukarya.
1. Who designed modern classification and invented the two-part species name?
2. Define a species.
3. What kingdoms make up the domain Eukarya?
4. What is the name for the scientific study of naming and classifying organisms?
5. How are organisms given a scientific name?
6. In what domain are humans?
7. Quercus rubra is the scientific name for the red oak tree. What is the red oak’s genus?
8. In what domain are mushrooms?
9. What information do scientists use to classify organisms?
10. Is it possible for organisms in two different classes to be in the same genus?
11. If molecular data suggests that two organisms have very similar DNA, what does that say about their evolutionary relatedness?
12. Can two different species ever share the same scientific name?
13. If two organisms are in the same genus, would you expect them to look much alike?