Biology 2201Unit 2- Biodiversity

Classifying Living ThingsCh. 4 – Patterns of Life

Ms. K. Morris – 2010-2011

Section 4.1 -Characteristics of Life

Characteristics of Living Things (p.104)

Living Things:• Organized systems made up of one or more cells• Carry out chemical reactions to get energy

(metabolize matter and energy)• Interact with the environment and maintain

homeostasis• Grow and develop • Reproduce themselves (biogenesis)• Adapt to their surroundings

• How have scientific classification systems developed? (p. 104-105)

• The first attempt to group organisms was made by Aristotle. He only recognized 1000 different kinds of organisms. He divided them into two groups which he named kingdoms: Kingdom Plantae and Kingdom Animalia. He subdivided each kingdom into smaller groups based on characteristics such as type of movement.

• With the invention of the microscope, microscopic organisms posed problems for classification. Ernst Haeckel was forced to develop a third kingdom which he named Protista.

• Soon biologists identified two more kingdoms: Fungi, which included mushrooms and moulds, and Bacteria, which lack a nucleus.

• During the 1990's, more interest was focused on a special group of bacteria that have been found in extreme environments. These have a unique structure and have been given their own kingdom grouping called the Archaea.

• Presently, biologists are working with a six kingdom classification: Animalia, Plantae, Protista, Fungi, Bacteria, and Archaea.

• Refer to page 105 in the textbook for sample organisms from each kingdom.

Section 4.2 -Naming & Classifying

Organisms

• Taxonomy - the practice of classifying organisms. It is the branch of biology that deals with the classification and naming of living things.

• The system used today was developed by Carolus Linnaeus who used simple physical characteristics to organize organisms into groups.

• This method involves using two Latin or Greek names which are chosen from a characteristic of the organism or to honor a scientist.

• Binomial Nomenclature - a classification system, a standard naming method used by scientists when referring to organisms.

• 'Binomial' means that the scientific name of each organism is actually the combination of two names: – the genus name and the species name.

• The genus name is capitalized, while the species name is not; both are type set in italics. – For example: Homo sapiens. (humans).

• The scientific name can be abbreviated by using the first letter of the genus name followed by the species name. This is usually done when the genus name is being repeated in a written document.

– Example: Homo sapiens becomes H. sapiens

• Common names are used in everyday language but can pose problems for biologists. A cat for people in Newfoundland may not be the same as a cat for people in Africa. Why not?

The Value of the classification system (p. 112)Scientific names: Advantages of binomial nomenclature

• Avoids confusion- Many plants and animals have common, local names that differ from area to area. Even if an organism is named differently in different languages ( or even provinces), the scientific name will always be the same.

• e.g. In Newfoundland we have a tree that some people call the Larch, others call it the Juniper, while other people call it Tamarack. All scientists call this tree Larix decidua. The common groundhog is also called the marmot and woodchuck but all biologists call it Marmota monax.

• It indicates evolutionary relationships between organisms. Classification tries to show how organisms evolved and which species are most closely related to each other.

The Limitations of a Classification System• Anomaly - something that does not fit a pattern or

system. • The kingdom classification system is not perfect.

The classification system was recently changed from a 5 kingdom system to a 6 kingdom system to reflect new discoveries concerning bacteria.

• The discovery of halophiles, methanogens, and thermophiles made it necessary to create a 6th kingdom, the Archaebacteria.

• These bacteria have such unique structures that they differ significantly from other bacteria.

• New biochemical evidence now tells us that it is more closely related to spiders than to crabs.

• In the kingdom protista, there are many anomalies. Indeed, Kingdom protista is often called the garbage bucket kingdom. The protist Euglena is an example. It can move (like animals) - it has flagella, but it also has chloroplasts like a plant cell. ( see p. 147)

• The new six kingdom classification system still has its limits and there are anomalies that don t fit nicely into it.

• Viruses are not classified as a living organism and therefore they are not put into any Kingdom. (see previous note for reason why)

• Another anomaly is the horseshoe crab. It is really a living fossil . We classify it in with arthropods (animals with an shelled exoskeleton) but really, there are no living arthropods like it.

• It is older than most species on the planet. Their design has basically endured for upwards of 300 million years.

The Levels of the Classification System (p. 108-113)

• A scientist named Linnaeus invented this classification system.

• The classification system divides organisms of each kingdom into smaller groups, based on their similarities. Such a system is called hierarchal.

• Hierarchal- a system of classification where groups at each level are subdivided into smaller groups below it.

• The seven major levels of the classification system are, from largest group to most specific are:

• Kingdom• Phylum• Class• Order• Family• Genus• Species

• A memory device for memorizing the order of the levels is remembering the sentence:

• King Phillip Cried Out, For Goodness Sake !

• Each group is smaller than the last. Organisms placed into the lower groups together are very closely related while organisms placed into groups at the higher levels share some common characteristics but are not necessarily similar.– e.g. Both humans and worms are placed into the same

Animalia kingdom. They are both heterotrophic, eukaryotic, and multicellular but after that, they are numerous differences!

• Animals placed into the same genus would be very closely related. – e.g. Dogs and wolves belong to the same genus - not

only are they animals but they have very similar features.

• Kingdoms are divided into smaller groups called taxon.

• A species is a natural group or population of similar organisms that interbreed in nature. It is the basic identifying level and would include a single type of organism.

• Demonstrate how to use a taxonomic key to group and identify an organism.– Core Lab #3: “Creating a Dichotomous Key”• p. 110-111

When classifying organisms, taxonomists use a combination of information, including: (p. 113-116)

1. Fossil Information (radioactive dating)2. Structural Information (anatomy)3. Embryological Information4. Biochemical Information5. Evidence from DNA

1. Radioactive Dating (Fossils)• Many fossils contain radioactive isotopes

which can be tested to give the approximate age of a fossil.

• Many radioactive isotopes decay at known rates. Scientists use the decay of carbon-14 in a process called radiocarbon dating to find the ages of some objects up to about 50 000 years old.

2. Structural Information• comparisons of the physical structures are

made between species to determine if they are similar or not.

• The more physical similarities they have, the more closely related they probably are. e.g. a bats wing, a whales flipper and a humans arm don’t appear alike but the bone structure and arrangement are very similar under the skin – this indicates a common ancestor.

• see p. 114 diagram

3. Embryological Information • Comparing the earliest stages of embryonic

development can show who may be related to who.

• e.g. Sea squirts don’t look like vertebrates or even have a backbone but their larvae have a very simple backbone so they are classified into the vertebrates.

• Only a very skilled scientist can tell the early embryos of apes and humans apart.

4. Biochemical Information• DNA/protein comparisons. New technology

allows us to compare the structure of protein molecules between organisms.

• Since proteins are made from the instructions on DNA (genes), the closer the biochemical similarity between proteins in animals means the more closely they are related.

• e.g. although a mouse and a guinea pig look similar, comparison of the structure of their insulin, a protein, tells us that they are not closely related.

Continued…• Proteins are important molecules in organisms• they are made by their cells by following instructions

on genes • Protein structures can vary greatly in different

species. • If two organisms have very similar or identical

protein structure such as the protein insulin, then they are very closely related.

• e.g. guinea pigs and mice look very much alike but a comparison of their insulin reveals that their insulin protein is 35% different which means they are not that closely related.

5. Evidence from DNA

• This is the most modern, powerful and precise classification tool available.

• DNA analysis can easily tell who is related to who.

• Matching the structure of DNA and comparing the differences tells us who is related to who.

• For example, DNA analysis has shown that we are very closely related to chimpanzees - 98% of our genes match those of a chimpanzee!

• Classification systems improved as a result of the development of modern techniques.

• Through the use of these techniques, organisms once thought to be closely related were found to be unrelated and vice versa.

• For example: Echinodermata (sea stars and sea urchins) are more closely related to the chordates than to any invertebrate.

• Note: The use of common or local names for species can be confusing.

Section 4.3 -Virusesp. 122-125

• There is one group of organisms that are not considered to be living things and that is the viruses.

• Viruses have no cellular structure, no cytoplasm, organelles or cell membrane. They carry out no life processes. They are made up of strands of DNA or RNA surrounded by a protein coat called a capsid.

- Refer to page 122 in textbook for examples. • Viruses are usually classified by the size and shape of

their capsid or by the types of disease they cause. They are not able to be classified into a Kingdom.

Virus Reproduction (ref. p. 122) see fig 4.20 p. 122• Viruses classified as non-living because they lack many of the

cell structures and do not carry out basic life processes.– don’t feed, excrete wastes, do cellular respiration, etc. Have no

cytoplasm, organelles, etc. All they seem to do is reproduce, so they are not classified into any kingdom of living things.

Have only two things in common with living things:– 1. ability to reproduce– 2. genetic material ( nucleic acid - DNA or RNA)

• Lifestyle is parasitic. It uses host cells to reproduce, often destroying them in the process.

• 1st identified in 1935 (more than 160 major groups are now known - 21 of these groups infect humans).

Virus Structure: Two sections:

1. Capsid - outer protein capsule which protects the genetic material. It helps to anchor the virus to the host cell during reproduction. Capsids vary in shape with the type of virus: (see fig 4.20, p. 122) – e.g. ( 1) polyhedral - polio virus ( 2 ) spherical - HIV

virus ( 3) cylindrical - tobacco mosaic virus)

2. Genetic material (nucleic acid DNA or RNA - the genes of the virus)

Life cycleGenerally:

1. attach to a host cell2. get inside of the host cell3. use the energy and organelles of the host cell

to reproduce new viruses. The viral genetic material attaches to the cells genetic material, then commands the cells organelles to start manufacturing viruses.

Entry into the host cellTwo methods to enter:

1. Attach and inject its nucleic acid (genetic material) into the host cell.2. Attach and let the host cell form a vesicle around it. The cell takes it in by phagocytosis.

• Once inside, the virus breaks out of the vacuole and injects its DNA into the nucleus of the host cell.

Specificity of Viruses:Viruses often only infect certain species they are adapted to. Viruses may infect

(a) only a particular species(b) only plants and animals(c) only plants and fungi(d) only certain cell types in an organism

(e.g. the polio virus only infects nerve cells and intestinal cells)

T4 Viruses• infects only bacterial cells• also called a bacteriophage• life cycle is called the Lytic Cycle• See figure 4.21 p. 123

T4 Virus Reproduction - Lytic Cycle - see diagram p. 123.A. Virus attaches to host cell.B. Injects it nucleic acid into the host.C. Viral genes take over the cells nucleus, forcing the cell

to replicate virus genetic material. The host cells energy and organelles complete the task.

D. Assembly of new viruses. The cells organelles form protein capsids around viral nucleic acid.

E. Lysis and release. The cell eventually bursts, releasing new viruses. (Lysis = burst)

• the lytic cycle takes about 30 minutes to complete• each host cell usually produces about 200

bacteriophages per cell

• End of Ch. 4 Notes–Test #3 on Monday Dec. 13th