Topic 6d - Classification of Living Organisms Flashcards
What is a species?
A species is defined as a group of organisms that can reproduce to produce fertile offspring.
How are living things traditionally classified?
Traditionally living things have been classified into groups depending on their structure and characteristics in a system developed by Carl Linnaeus.
How did Linnaeus classify living things?
In a way that allows the subdivision of living organisms into smaller and more specialised groups. The species in these groups have more and more features in common the more subdivided they get.
What is Linnaeus’ sequence of classification?
- kingdom
- phylum
- class
- order
- family
- genus
- species
What is a mnemonic to remember Linnaeus’ sequence of classification?
Keep Playing Cricket Or Face Getting Squashed.
How did Linnaeus name species?
Organisms are named by the binomial system of genus and species.
Why do organisms share features?
Organisms share features because they originally descend from a common ancestor.
How were organisms originally classified?
Originally, organisms were classified using morphology and anatomy.
What is morphology?
The overall form and shape of an organism, e.g. whether it had wings or legs.
What is anatomy?
The detailed body structure of an organism as determined by dissection.
Why were new models of classification proposed? (2)
- As evidence of internal structures became more developed due to improvements in microscopes.
- The understanding of biochemical processes progressed.
What method of classification can now be used due to technological advances?
As technology advanced, DNA sequencing allowed us to classify organisms using a more scientific approach.
What do DNA sequencing studies show us?
Studies of DNA sequences of different species show that the more similar the base sequences in the DNA of two species, the more closely related those two species are (and the more recent in time their common ancestor is).
What can be used other than bases to determine how closely related species are? Why?
As DNA base sequences are used to code for amino acid sequences in proteins, the similarities in amino acid sequences can also be used to determine how closely related organisms are.
What method of classification be used now due to evidence available from chemical analysis?
The three-domain system where organisms are divided into three large groups called domains.
Who developed the three-domain system? When?
Carl Woese in 1990
What are the three domains in the three-domain system?
- Archaea
- Bacteria
- Eukaryota
What are archaea in terms of the three-domain system?
Primitive bacteria usually living in extreme environments such as hot springs and salt lakes.
What are bacteria in terms of the three-domain system?
True bacteria such as coli and Staphylococcus.
What are eukaryota in terms of the three-domain system?
Includes protists, fungi, plants and animals.
How are the three domains then divided?
These domains are then subdivided into the smaller groups: kingdom, phylum, class, order, family, genus, species.
What are evolutionary trees?
Evolutionary trees are diagrams that show the relationship between species over evolutionary time.
What does a new branch in an evolutionary tree show?
A new branch in the tree shows where speciation has occurred.
How are evolutionary trees created?
Evolutionary trees are created using current classification data for living organisms (such as DNA analysis and structural similarities) and fossil data for extinct organisms.
