Classification

Biologists want to better understand organisms so they organize them.

One tool that they use to do this is classification- the grouping of objects or information based on similarities.

Taxonomy is the branch of biology that groups and names organisms based on studies of their different characteristics.

Biologists who study taxonomy are called taxonomists.

Taxonomy

Taxonomists group similar organisms, both living and extinct. Classification provides a framework in which to study the relationships among living and extinct species.

Are dinosaurs more closely related to birds or to reptiles?

The bones of some dinosaurs have large internal spaces like those in birds. In addition, dinosaur skeletons share many other remarkable similarities with birds. Because of such evidence, dinosaurs are more closely related to ostriches (birds) then to lizards, which are reptiles.

Taxonomic rankings

Organisms are ranked in taxa that range from having very broad characteristics to very specific ones.

The broader a taxon, the more general its characteristics, and the more species it contains.

The smallest taxon is species. Organisms that look alike and successfully interbreed belong to the same species.

Taxonomic rankings

Appearance of a lynx (Lynx canadenis), bobcat (Lynx rufus), mountain lion (Felis concolor).

The lynx and the bobcat belong to the same genius Lynx. All the species in the genus Lynx share characteristic of having a jaw that contains 28 teeth.

Mountain lions and other lions, which are similar to bobcats and lynxes, are not classified in the Lynx genus because their jaws contain 30 teeth.

Taxonomic rankings

Bobcats, lynxes, lions, and mountain lion belong to the same family called Felidae.

Domesticated cats, bobcats, lynxes, and lions belong to the family Felidae. All members of the cat family share certain characteristics.

They have short faces, small ears, forelimbs with five toes, and hindlimbs with four toes. Most can retract their claws.

Taxonomic Rankings from largest to smallest

Kingdom Animalia

Phylum Chordata

Class Mammalia

Order Carivora

Family Felidae

Genus Lynx

Species rufus (bobcat) canadenis (lynx)

The Six kingdoms

1. Eubacteria – prokaryote-unicellular

2. Archaebacteria- prokaryote-unicellular

3. Protists- eukaryote - decomposers, producers,

consumers

4. Fungi- eukaryote - decomposers

5. Plants- eukaryote - producers

6. Animals- eukaryote- consumers

Archaebacteria: The Extremists

Archaebacteria live mainly in extreme habitats where there is usually no free oxygen available.

Three types of archaebacteria:

1. Live in oxygen-free environments and produce methane gas.

• Found in marshes, lake sediments, digestive tracts of some animals, sewage disposal plants where they breakdown sewage

Archaebacteria2. Lives only in water with high concentrations of salt.

• Utah’s Great Salt Lake and the Middle East’s Dead Sea.

3. Lives in the hot, acidic waters of sulfur springs.

• Cracks deep in the ocean floor, where it tis the autotrophic producer for a unique animal community’s food chain

Eubacteria

Eubacteria: the heterotrophs

Live almost everywhere and use organic molecules as their food source.

Some are parasites, obtaining their nutrients from living organisms.

Others are saprophytes- organisms that feed on dead organisms or organic waste.

Eubacteria

Eubacteria: photosynthetic autotrophs

Live in places with sunlight because they need light to make the organic molecules that are their food.

Cyanobacteria are photosynthetic autotrophs that contain the pigment chlorophyll that traps the sun’s energy.

Cyanobacteria commonly live in ponds, streams, and moist area lands.

Eubacteria

Eubacteria: chemosynthetic autotrophs

They do not obtain energy from sunlight, instead they break down and release the energy of inorganic compounds containing sulfur and nitrogen in the process called chemosynthesis.

The fix nitrogen from the atmosphere into a form plants can use.

The structure of bacteria

Prokaryotic cells have ribosomes that are smaller than ribosomes of eukaryotes.

A single DNA molecule arranged as a circular chromosome and not enclosed in a nucleus.

They have a cell membrane

Cell wall supports and protects the bacteria.

Some bacteria have flagellum

Some have a capsule around the cell wall (bacteria with capsule are more likely to cause disease than those without)

Reproduction of bacteria

1. Asexually by a process known of binary fission. A copy of the chromosome is made. The bacteria gets larger and the chromosome move opposite ends of the cell. Then the cytoplasm split.

2. Sexual reproduction called conjugation. One bacteria transfers all or part of its chromosome to another bacteria cell through or on a bridgelike structure called pilus that connects the two cells. Then the bacteria goes through binary fission.

ConjugationBinary fission

The importance of bacteria

Nitrogen fixation- nitrogen fixing bacteria convert nitrogen in the atmosphere into a form plants can use.

Recycling of nutrients- decomposing bacteria breakdown the organic materials in dead organisms and wasted, returning nutrients, both organic materials and inorganic materials, to the environment

Importance of bacteria

Food and medicines- swiss cheese, tangy yogurt, vinegar, cheeses. Bacteria also inhabit your intestines and produce vitamins and enzymes that help digest food. Some bacteria produce important antibiotics that destroy other types of bacteria.