3- classification Flashcards
classification
the naming and organising of organisms in groups based on their characteristics
classification system hierarchy
domain, kingdom, phylum, class, order, family, genus, species
binomial naming system
- binomial names are italicised
- first part- genus is capitalised
- second part- species is lowercase
species
a group of organisms with similar characteristics that are all potentially capable of interbreeding to produce fertile offspring
morphological species model
group based on the degree of similarity and difference in their physical characteristics
morphological species model disadvantages
- there can be variation within closely related organisms
- when there is sexual dimorphism, different sexes could be considered different species
reproductive species model/ mate recognition species model
- group based on whether they are capable of producing fertile offspring
- group based on their fertilisation systems, including mating behaviour
reproductive species model/ mate recognition species model disadvantages
- organisms may not interbreed due to geographical isolation
- cross breeding between species can result in fertile offspring
- many species have never been observed mating
- many species do not reproduce sexually
- fossil organisms cannot reproduce but still need to be classified
ecological species model
group based on the ecological niche they occupy
ecological species model disadvantages
- niche definitions vary
- many species occupy more than one niche
genetic species model
grouped based on dna evidence
genetic species model disadvantages
- scientists have not decided on the amount of genetic difference needed to consider organisms to be seperate species
- dna collection is difficult and takes a lot of time and money
- fossil organisms do not in most cases have accessible dna
evolutionary species model
grouped based on shared evolutionary relationships between species
disadvantages of evolutionary species model
there are not always clear evolutionary pathway for organisms
molecular phylogeny
a branch of biology where the genetic differences among organisms are analysed to distinguish between species and determine their evolutionary relationships
gel electrophoresis process
1) make wells in agarose jelly
2) extract the dna, and cut it into fragments with restriction endonuclease enzymes
3) dye the DNA with florescent dye
4) turn on a current to seperate the DNA by electrophoresis- DNA is (-) and moves to the anode
5) different bands represent different amino acids, they can be compared to known fragments
dna sequencing
a technique used to find the exact sequence of nucleotides in a dna molecule, thus highlighting similarities and differences in the genetic data of organisms
bioinformatics
an interdisciplinary field that used computational methods and software tools to analyse and compare genetic data between organisms
analysis of genetic data
- genetic sequences can be used to establish evolutionary relationships among species
- the degree of similarity in sequences can indicate how closely related the species are
role of scientific journals
scientific journals serve as platforms for researchers to publish their findings and contribute to the existing body of knowledge in a field
peer review process
other scientists, experts in the same field, critically evaluate the evidence, methodology and results of a study. this adds credibility and validation to the findings
scientific conferences
these events allow scientists to present their research, debate, and evaluate data. they also provide an opportunity for potential errors to be spotted and rectified
3 domain model of classification
archaea, bacteria and eukaryotes
basis for the three domain model
- Woese sequenced bacterial RNA and DNA, observed that methanogens lacked sequences characteristic of bacteria and proposed they belonged in a new domain; archae
- archae lack peptidoglycan in their cell walls, have different phospholipids in their cell membranes, and show differences in membrane structure, proteins and organelles when compared to other bacteria
differences between the three domain and five kingdom systems
the three domain system gives less importance to eukaryotic groups, reflecting the greater diversity within prokaryotes by separating Archaea from other bacteria
