Classification Of Organisms Flashcards
Why have scientists designed classification systems
As a way to organize biodiversity.
Living organisms are divided into groups and subgroups according to similarities and shared characteristics
Taxa
The groups into which organisms are classified
The formal scientific classification of organisms is known as
Taxonomy
What made classification systems complex for scientists
The structure of cells, microorganisms, evolution, genetics and molecular biology
Two kingdom system
In 1758,a Swedish botanist, Carl Linnaeus classified living organisms into two kingdoms:Plantae(plants) and Animalia(animals)
Linnaeus developed a hierarchical system of classification where 7 categories (taxa) under each kingdom where used.
Kingdom>phylum/division >class>family> genus >species
The above categories are based on shared physical properties within each group. Each level becomes even more specific. Organisms within the same family have more in common than organisms within the same order.
A kingdom is subdivided into phyla for…. But in….. The term division is used
Animal, plants
Biological classification
System used to sort out living things based on their similarities
Carl Linnaeus used this system to separate
Plants that can make their own food, can’t move and are auto trophic and animals that can make their own food, can move and are hetero trophic
Kingdom plantae characteristics
Can’t move
During daytime they are involved in photosynthesis as they need sunlight and obtain carbon dioxide and liberate oxygen
Unlimited growth for certain plants
Excretory and nervous system aren’t present
They reserve food material(starch)
Reproduce asexually(not direct contact) and Fertilization takes place with the help of agents like wind, water etc..
Plant cells don’t have Centrosomes so they may have inorganic crystals
Kingdom Animalia characteristics
Definite body shape and no branches
Move place to place but can’t make their own food.
Release carbon dioxide and take in oxygen from plants
Can’t partake in photosynthesis
Grow a certain length, size and width
Excretory and nervous system are advanced
Reserve food materual(glycogene)
Centrosomes are present and have organic crystals
Disadvantages of the two kingdom system
Unicellular organisms do not fit in either of the kingdoms. This system does not provide a separate distinction for such organisms.
It grouped the photosynthetic organisms (plants) and the non-photosynthetic organisms (fungi) in the same kingdom, Plantae.
No distinction between the eukaryotes and prokaryotes.
Five kingdom system
The two kingdom was expanded into a five kingdom system as more scientific information about organisms was obtained. In 1969,Robert Whitaker proposed the five kingdom system
5 kingdoms
Monera(bacteria)
Protista
Fungi
Animalia
Plantae
What criteria was used to classify organisms into the five kingdoms
Body structure - unicellular/multicellular/colonies
Cell structure - presence/absence of a nucleus:organelles(chloroplasts)
Composition of cell wall– cellulose/chitin/no cell wall
Motility - mobile /immobile
Mode of nutrition - autotroph/heterotroph
Method of reproduction - binary fission/asexual/sexual
Prokaryotes
Organisms that don’t have a true nuclei
Their DNA is not enclosed by a nuclear membrane and therefore occurs free in the cytoplasm
No true organelles in the cytoplasm
Monera are prokaryotes
Eukaryotes
Organisms with cells that have true nuclei.
Their DNA is enclosed by a nuclear membrane and therefore occurs inside the nucleus
True organelles occur in the cytoplasm. All Protista, fungi, Plantae and Animalia are all eukaryotes
Characteristics of kingdom monera
Unicellular have no true nuclei and therefore prokaryote
Bacterium cell is surrounded by cell wall
Some bacteria are autotroph ice and produce their own organic substances by photosynthesis
Majority of the bacteria are heterotrophic and cannot produce their own organic substances. Heterotrophic bacteria are either parasites or saprophytes, or they live Mutualistically with other organisms.
Reproduction occurs asexually by binary fission whee a single cell divides into two cells of identical DNA composition
Parasitic
Dependent on living organic matter for food where organisms live together (symbiosis) and one benefits and the other is harmed.
Saprophytic
Dependent on dead organic matter for food
Mutualistic
Living together with other organisms so that both can benefit from the relationship (a type of symbiosis)
Characteristics of kingdom Protista
Distinguished into 3 groups :
Protozoa-animal like, unicellular and heterotrophic organisms
Algae - plant like. Autotrophic (have chlorophyll and can photosynthesise)
Slime moulds and water moulds fungus like organisms
Subgroups :
Chrysophytes:Chrysophytes are agroup of algae with yellowish green to golden brown pigments.They are usually found in freshwater and marine habitats with low calcium(desmids)
Dinoflagellates-Dinoflagellates aresingle-celled aquatic organisms with two flagella found in fresh and saltwater. Usually photosynthesise and the color they appear is dependent on the key pigments in their cell: red,, brown, green.
Euglenoids:Euglenoids aresingle-celled protists
Instead of the cell wall, a protein-rich cell membrane known as pellicle is present.
They bear two flagella on the anterior end of the body.
A small light-sensitive eye spot is present.
Magnification of cells
The formula to calculate magnification is: magnification = size of image / real size of object12. This equation can be rearranged to calculate the actual length of the cell and the magnification used as well as the length of the image3. To calculate magnification using the formula in micrometres, convert the measurement of the cell from mm into micrometres4
Types of monera
Coccus(circles)
Vibro(pea shaped)
Bacillus (oval)
Spirillum(, spirals)
