Classification (aka Taxonomy) Living Environment
Why must we classify? There are SO MANY critters out there! How do we know who s who and what s what? Biologists use a classification system to name organisms and group them in a logical manner. This is known as TAXONOMY!
Taxonomy The discipline in which scientists classify organisms and assign each organism a universally accepted name. Why do they need a special name?
Mountain Lion
Puma
Cougar
Catamount
Panther
Ghost Cat
Indian Devil
Ok you get the point The mountain lion is known to people all over the world by different names In the English language alone, it has 40 different names That s why we need a standardized naming system! So everyone knows what you re talking about!
How do they do it? When taxonomists classify organisms, they organize them into groups that have biological significance This requires smaller as well as larger categories Organisms are placed into a particular group with organisms that are more similar to each other than they are to organisms in other groups
18 th Century Back in to good old days European scientists recognized that referring to organisms by common name was way too confusing! Common names are different everywhere you go! Ex.) In the UK buzzard means hawk, but in the US a buzzard is a vulture
18 th Century Scientists used Latin and Greek during the 18 th century They agreed to come up with a single name for a species and they used Greek or Latin to assign those names We still use Greek or Latin for new organisms that are discovered today
First Attempt at Naming The earliest names tried to describe physical characteristics of a species in great detail This lead to names being up to 20 words long NOT PRACTICAL Ex.) An oak tree Oak with deeply divided leaves that have no hairs on their undersides and no teeth around their edges.
Binomial Nomenclature A two-word naming system developed by Carolus Linnaeus This system is still used today The name is two words First word is CAPITALIZED and is the GENUS Second word is LOWERCASE and is the SPECIES Italicized when typed and underlined when handwritten
Ex.) Ursus arctos AKA Grizzly Bear The first word is the genus A genus is a group of closely related species What s the genus in the example? The second word is the species A species is unique within the genus What s the species in the example?
More Bears All have the same first word Ursus Ursus arctos grizzly bear Ursus maritimus polar bear Ursus americanus american black bear Ursus thibetanus asian black bear
Levels of Organization Each level is referred to as a taxon or taxonomic category From largest to smallest: Kingdom Phylum Class Order Family Genus Species
Kingdom Largest and most inclusive category
Phylum Several different classes make up a phylum
Class Composed of similar orders
Order A broad taxonomic category composed of similar families
Family Genera that share many characteristics
Genus & Species The lowest two levels that help to identify an organism
How the heck will I remember this? Simple! King Phillip Came Over For Good Spaghetti Kingdom, Phylum, Class, Order, Family, Genus, Species
Biomagnification The increasing concentration of pesticides or other toxic materials in living organisms via the food chain.
Ecological Efficiency and Biomagnificiation Pesticides and toxic materials that accumulate via biomagnification CANNOT be metabolized. Individuals cannot use them as a source of energy.
Biomag. Cont d As the organism takes in food and uses its energy, CO2 and H2O are returned to the atmosphere but the pesticides remain. The pesticides accumulate in the organism s tissue over its lifetime.
Increases by Trophic Level Amplified by the flow of energy b/t trophic positions Each organism that eats a toxic organism from a lower trophic position will have a toxic concentration greater than the organism that it ate.
Example: Osprey Eats large bluefish that have concentrations of pesticides up to 10x greater than Atlantic silversides (smaller fish).
Modern Evolutionary Classification Scientists used to classify organisms based on similarities in appearance We know that doesn t work! Ex.) A shark and dolphin look alike, but they are not closely related
Study of Phylogeny Phylogeny is the study of evolutionary relationships among organisms Biologists now group organisms into categories that represent lines of evolutionary descent, or phylogeny, not just physical similarities
Phylogenetic Trees Family trees that hypothesizes about the evolutionary relationships thought to exist between different organisms
Evidence used for Phylogentic Trees 1. DNA 2. Embryology 3. Fossil Record 4. Morphology (Comparative Anatomy)
To aid in making phylogenetic trees, a combination of these lines of evidence are used:
DNA
Embryology
Fossil Record
Morphology
Hyraxes and elephants share similar morphology: 1. Tusks that develop from incisors rather than canines 2. Similar foot and skull structure. 3. 4 toes on forelimbs, 3 toes on hind limbs. 4. Rounded hoof-like nails. 5. Internal testicles in males. 6. Mammary glands on females between forelimbs.
But
Despite the fact that the dugong looks even nothing like either the elephant or the hyrax, it is a close relative This can be seen in the dugong s skeletal structure (especially its limbs) which is similar to the hyrax and elephant even though its limbs serve very different functions. This is called HOMOLOGY.
Homologous Structures - characteristics in different organisms that carry out different functions and which may appear superficially different but which were inherited from a common ancestor that also had that character share an evolutionary history.
Homology is caused by ADAPTIVE RADIATION Adaptive radiation When an ancestral species diversifies rapidly and gives rise to a variety of new physiological forms that fill different ecological niches.
Sometimes, morphology can be misleading These animals have evolved similar adaptations for obtaining food because they occupy similar niches. What can you infer about their phylogeny from their geographic locations?
Analogous Structures = traits that are superficially similar and which carry out the same function but which have separate evolutionary origins. Analogous Structures are caused by CONVERGENT EVOLUTION the process whereby organisms not closely related, independently evolve similar traits as a result of having to adapt to similar environments or ecological niches.
Structural patterns are clues to the 51 history of a species. Vestigial structures are remnants of organs or structures that had a function in an early ancestor. Examples include ostrich wings, human appendix, and wisdom teeth, whale and snake pelvis/hind legs
Pythons 52 have tiny femurs (leg bone)
Cladistics A relatively new system of phylogenetic classification that uses shared derived characteristics to establish evolutionary relationships
Cladograms Use characteristics that appear in the recent parts of a lineage but not in its older members These are called derived characteristics A feature that only evolved within the group under consideration Derived characteristics can be used to construct a cladogram A diagram that shows the evolutionary relationships among a group of organisms
Help scientists see evolutionary relationships
The last common ancestor is where lines last connected
Three Basic Assumptions of Cladistics 1. Organisms within a group are descended from a common ancestor 2. There is a branching off from common ancestor showing a new species is formed 3. Change in characteristics occurs in lineages over time
Perhaps the first and most important split in the tree of life is what separates the two types of cells that represent life on Earth.
Prokaryotic Cell Unicellular No nuclear membranes (nucleus) Instead there is a nucleoid region No membrane bound organelles Appeared around 4 billion years ago
Eukaryotic Cell Can be unicellular or multicellular More advanced than prokaryotes Nucleus present (nuclear membrane) Membrane bound organelles Appeared about 1 billion years ago
Three Domains Domains are the most inclusive category. Larger than kingdoms There are three domains: 1. Bacteria 2. Archaebacteria 3. Eukarya
Domain Bacteria Unicellular organisms Prokaryotic Thick, rigid cell walls that surround a cell membrane Contain peptidoglycan (made of sugars and amino acids) Very diverse bacteria ranging from harmless to deadly
Domain Archaea Unicellular and prokaryotic Live in some of the most extreme environments imaginable Hot springs, brine pools, mud without oxygen Cell walls lack peptidoglycan Cell membranes are made of lipids that are not found in other organisms
Domain Eukarya Consists of all organisms that have a nucleus Composed of very diverse organisms that make up four kingdoms
Kingdoms Kingdoms are the second highest rank below domain They are composed of smaller groups called phyla There are currently six kingdoms: 1. Eubacteria 2. Archaebacteria 3. Protista 4. Fungi 5. Plantae 6. Animalia
Eubacteria The only kingdom in the domain Bacteria They are very diverse bacteria that may make you sick or help you stay healthy Can be autotrophic or heterotrophic Ex.) Streptococcus or Escherichia coli
Archaebacteria Only kingdom in the domain Archaea Can be autotrophic or heterotrophic Ex.) methanogens & halophiles
Protista Composed of eukaryotic organisms that cannot be classified as animals, plants, of fungi Members display great variety Most are unicellular, but not all Can be photosynthetic or autotrophic Can share characteristics with plants, fungi, or animals Ex.) algae
Fungi Heterotrophs Most feed on dead or decaying organic matter Secrete digestive enzymes into their food source and absorb the smaller food molecules into their bodies Ex.) mushrooms & yeast
Plantae Multicellular organisms Photosynthetic Autotrophs Nonmotile can t move from place to place Cell walls with cellulose
Animalia Multicellular Heterotrophic Lack cell walls Motile (mostly) can move about at least for part of their life cycle
Dichotomous Key Device used to identify an organism based on previous descriptions Follow a series of steps to find the identity of the organism Sequence of choices between two statements that lead you to another choice Sort of like a treasure hunt!
A. one pair of wings 1. B. Two pairs of wings