4.2.2 Classification Flashcards
Define classification
Placing living organisms into groups based on similarities or differences
Define taxonomy
The system of classifying organisms according to their observable features or genetic characteristics
Why do we classify things?
- for convenience
- to make the study of living things more manageable
- to make it easier to identify organisms
- to predict characteristics of other species in a group
- to help see evolutionary relationships (phylogeny) between species
Explain how organisms were classified originally
Morphology/anatomy/observable features
What modern evidence is used to classify organisms?
- DNA base sequences of genes
- amino acid sequences of proteins (e.g. cytochrome c)
- embryonic similarities
- behaviour + physiology
- shared evolutionary past
Who first classified organisms?
Carl Linnaeus (1701-1778)
- 250 years ago
- classified by visible features
- put organisms into series of ranked categories
List the taxanomic groups in order from broadest to most specific
Kingdom
Phylum
Class
Order
Family
Genus
Species
How do you know organisms are the same species?
- they can interbreed to produce fertile offspring
- have similar shape, physiology, biochemistry + behaviour
How do you organisms aren’t the same species?
- genetically incompatible - DNA sufficiently different
- may have a different number of chromosomes
- physical or behavioral reason for reproductive incompatibility
Explain the binomial system of naming
- one internationally accepted scientific name in Latin that has two parts
- just the Genus and species name
- always in italics
- Genus capital FIRST letter
- species lower case FIRST letter
Why is the binomial system used?
- some organisms have different common names which can be confusing
- universal and recognised worldwide
- the binomial name tells us the Genus and the species of an organism
- allow to see related species
Define autotrophic
Organisms that use light energy or chemical energy along with inorganic molecules to synthesise complex organic molecules
Define heterotrophic
Organisms that ingest and digest complex organic molecules, releasing the chemical potential energy stored in them
Define Saprotrophic/saprophytic
Organisms that gain nutrients by absorption, mainly of decaying material
What are the five kingdoms?
Prokaryotae
Protoctista
Fungi
Plantae
Animalia
Give information about Prokaryotes
- mostly unicellular
- no nucleus, nucleolus, nuclear membrane
- no histone proteins or chromosomes
- no other membrane bound organelles
- 70s ribosomes
- respiration carried out on special membrane systems(mesosomes)
- smaller cells than eukaryotes
- cell wall always presemt (peptidoglycan)
- free living or parasitic
- heterotrophic and autotrophic
- some have flagella
- no nervous co-ordination
Give information about Protoctista
- eukaryotic - nucleus + nuclear envelope
- mostly single-celled
- wide variety of forms
- shows various plant or animal like features
- mostly free-living
- heterotrophic or autotrophic nutrition
- some have cell walls
- some have flagella or cilia
- no nervous co-ordination
Give information about fungi
- eukaryotes
- unicellular (yeast) or multicellular (bread mould)
- multicellular have a body made of mycelium - network of numerous strands called hyphae + form spores
- polysaccharide chitin cell wall
- multinucleate cytoplasm
- large permanent vacuoles
- mostly free living
- heterotrophic + saprophytic
- no nervous co-ordination
Give information about plantae
- eukaryotic
- multicellular
- cellulose cell walls
- large permanent vacuole
- produces multicellular embryos from fertilised eggs
- photoautotrophic
- gametes of some plants have flagella
- no nervous co-ordination
Give information about Animalia
- eukaryotes
- multicellular
- heterotrophs
- have fertilised eggs that develop into balls of cells
- able to move around (presence of muscle tissue
- no cell walls
- small temporary vacuoles
- most have nervous co-ordination
What molecular evidence used to classify organisms?
- differences will reflect evolutionary relationships
What biochemicals are used in classification?
- cytochrome c
- haemoglobin
- DNA + RNA
How is DNA + proteins used to classify organisms?
- amino acid sequences compared in proteins
- DNA base sequence of specific genes compared in DNA
- If amino acid sequences/nucleotide base sequences in DNA are the same = two species are not related
What is the 3 domain system?
- proposed by Carl Woese in 1977
- prokaryotae divided into bacteria + archaea
- based upon study of ribosomal RNA
What is the evidence for the 3 domain system?
- based on the fact bacteria is very different from archeae + eukaryote
- bacteria have different cell membrane structure, different flagella structure, different RNA polymerase + peptidoglycan cell wall
- archea + eukaryotae share similar membrane structure, similar RNA polymerase, similar mechanisms for building DNA + RNA, similar proteins at bind to DNA
Compare Archaebacteria and Eubacteria
Archae
- known as ‘ancient bacteria’
- live in extreme environment
Bacteria
- known as ‘true bacteria’
- most bacteria in this group
Summarise the 3 domain system
- more accurately reflects origin of prokaryotes + eukaryotes
- divides prokaryotes
- reflects differences of bacteria + archaea
groups eukaryotes together - reflects that fact there are similarities between eukaryotic kingdoms
What is the six kingdom system?
Combines the three-domain + five-kingdom classification system together.
- seperates Prokaryotes into Eubacteria and Archaebacteria
- keeps eukaryotic kingdoms seperate
- having domain as a further level of classification at the top of the hierarchy
What are the five kingdoms?
Eubacteria
Archaebacteria
Protoctista
Fungi
Plantae
Animalia
Define phylogeny
The study of the evolutionary relationships between organisms and the closeness of these relationships
Give key facts about phylogeny
- explains who is related to who + how closely related
- all organisms have evolved from shared common ancestors (relatives) - not alive today
- evolutionary relationships and closeness of these relationships show in a phylogenetic tree
- basis of modern classification
Give key aspects of phylogenetic trees
- represent the evolutionary relationships between organisms
- shows how different species have evolved from a common ancestor
Summarise phylogeny + phylogenetic trees
- phylogeny produces a continuous tree
- can be done without reference to Linnaean classification
-phylogeny confirms classification groups are correct
