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In this topic of IBDP Biology, we will learn about Classification (Part 2).
How are organisms grouped together?
- Organisms grouped together according to similarities listed above.
- Natural classification:
- Based on homologous structures.
- These have shared evolutionary origin.
- They have similar structure and position, regardless of function.
- Eg pentadactyl limb – arrangement of 5 digits in limbs of terrestrial vertebrates.
- Should not be based on analogous structures.
- These have similar function but do not have a common origin.
- Eg. wings in birds and bats.
- This is an artificial classification.
Taxonomy
- Taxon = a group within a natural classification
- When it comes to IBDP Biology, Taxonomy = the study of these groups.
- This involves:
- Arranging all organisms into a system of hierarchical groups
- Deciding what groups newly discovered species should occupy.
- These species may be alive today or extinct fossils.
Taxonomic ranks
- A series of rank names.
- Allows larger groups to be differentiated from larger groups.
- When it comes to IBDP Biology, It is hierarchical – large groups are subdivided into smaller groups.
- There is no overlap between each group.
- The smaller the group that two organisms can be placed into, the closer they are related through evolution.
- Eg humans and jelly fish are animals.
- Humans and fish are vertebrates (chordata).
- Humans and mice are mammals.
- Humans and monkeys are primates.
- However, It does not demonstrate how closely related 2 groups are within a larger group.
Phylogeny
- A phylogenetic classification system shows the evolutionary lnks between each taxonomic group with respect to time.
- When it comes to IBDP Biology, It can be represented a s a phylogentic tree.
- Eg Reptiles, birds and mammals are all chordates.
- Reptiles and birds have a common ancestor.
- Mammals diverged from reptiles before birds evolved.
- This is not indicated by the taxonomic ranks.
That's the end of this topic.
