Aaron J. Powner, M.Ed.
High School Science Teacher
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Traditions in Species Concepts
Typological - sorting species by physical traits. Examples of physical trait comparisons:
Biological - sorting species by ability to interbreed and produce viable offspring. Examples:
Snake x Spider = nothing
Fish x Bird = nothing
Human x Monkey = nothing
Lion x Tiger = Liger, but sterile
Horse x Zebra = Zorse, but sterile
Plum x Apricot = Plumcot
Phylogenetic - sorting species by evolutionary history. This requires mapping the genome.
Phylogenetic Tree of Life
This sytem has only been in use since the 1970s. Organisms are classified into domains according to cell type and structure, and into kingdoms according to cell type, structure, and nutrition. Further reading: http://en.wikipedia.org/wiki/Kingdom_(biology)
Bacteria
Prokaryotes. Bacteria cell walls contain peptidoglycan (a polymer chain of two alternating sugars), which creates a netlike structure that is simple, porous, yet strong.
Archaea
Prokaryotes. Archaean cell walls do not contain peptidoglycan, but they do have some of the same cell wall proteins as more advanced eukaryotes.
Eukarya
All eukaryotes have cells with a membrane-bound nucleus and other membrane-bound organelles. Domain Eukarya contains Kingdom Protista, Kingdom Fungi, Kingdom Plantae, and Kingdom Animalia.
Bacteria
A diverse group of prokaryotes that can survive in many environments. Some are aerobic (needing oxygen) and others are anaerobic (do not need oxygen). Some are autotrophic (produce their own food), but most are heterotrophic. Image.
The most abundant form of life on Earth. There are more bacteria cells living in your body than the number of your own cells that form your body.
Archaea
Thought to be more ancient than bacteria, archaeans are also prokaryotes. Because of their cell wall similarity with eukaryotes, Archaeans may be the ancestors to higher life forms.
Diverse in shape and nutrition requirements. Some are autotrophic, but most are heterotriphic.
These are extremophiles, which means they can live in extreme environments such as boiling hot springs, salty lakes, thermal vents on ocean floors, and in deep mud of marshes where there is no oxygen. Image.
Protista
Eukaryotes. Simplest of the eukaryotes. Protists can be unicellular, colonial, or multicellular. Though protists are not always similar to each other, they lack bodily organs (as opposed to plants and animals). Three Main Groups: Image.
Algae
Plantlike protists, which are autotrophic (photosynthesis). Video: Kelp forest.
Protozoans
Animal-like protists, which are heterotrophic. Video: Amoebas.
Funguslike Protists
Decomposers - Video: Slime Molds | Image: Mildews.
Weird Protists
Some members of this kingdom cross boundaries between the three main categories of protists and are hard to classify. An example is Euglenoids, which have both plantlike and animal-like characteristics. They can perform photosynthesis but can also move quickly and eat other organisms. Image. | Video: Euglena
Fungi
Eukarotes. More complex, possessing distinct organs. Heterotrophs. Sesile. Have cell walls made of chitin - a rigid polymer. Some are parsites. Some are saprobes (decomposers). Fungi digest their food externally via excreted digestive enzymes, then absorb nutrients directly into cell structures. Image.
Plantae
Eukaryotes. Very complex, possessing multiple systems of organs made of tissues. Most are autotrophs and sesile. Have cell walls made of cellulose. Most contain chloroplasts for photosynthesis. Image.
Divisions - the Plant Kingdom is divided into Divisions rather than Phyla. Major Divisions.
Animalia
Eukaryotes. Very complex, possessing organ system made of tissues. Heterotrophs. Most are mobile. No cell walls. Image.
Phyla - Major Phyla | Existing Phyla Proportions
