CLASSIFICATION SYSTEMS ESSAY
- Phylogenic - reflected revolutionary relatedness
- A phylogenic classification system is where organisms that are closely related are placed into groups. Organisms of the same group have a more recent common ancestor with each other than with those in another group.
- Classification is hierarchial: larger groups divide into smaller groups.
- In classification any group is called a taxon.
- Taxa are discrete: at any level of classification organisms can belong to one taxon only.
- A classification system is universal and so helps us to communicate.
- It allows us to infere the relatedness of two species, and if a new species is discovered, we can predict some of its features.
- It is also beneficial when determining the health of an ecosystem, as we count the families rather than individual species.
- Classification is tentative: it is not fixed or certain.
3 DOMAINS: EUBACTERIA, ARCHAEA AND EUKARYOTA
5 KINGDOMS: ANIMALIA, PLANTAE, FUNGI, PROTOCTISTA, PROKARYOTA
Characteristics of the five kingdoms:
- Cell wall comprised of murein
- No membrane-bound organelles
- Membrane-bound organelles
- No tissue differentiation
- They have hyphae
- They are saprotrophs
- Cell walls made of chitin
- Reproduce by spores
- They have membrane-bound organelles, such as chloroplasts
- Cell walls made of cellulose
- They are photoautotrophic: they undergo photosynthesis
- Show nervous coordination
- Lack cell walls
Assessing the relatedness of organisms
1. Using physical features
You must look for a homologous structure - these are structures that have a similar structure and same developmental origin but a different function.
For example, the pentadactyl limb of the vertebrate. Its common structure is present in all four terrestrial organisms: birds, reptiles, mammals and amphibians. However, they all have different functions. Therefore, this provides an example of divergent evolution: a common ancestrial feature has evovled.
Analogous structures - structures of the same shape and function but a different developmental origin.
For example, a bird, a butterfly and a bat. These all have wings, except one is an insect, one is a bird and the other is a mammal. Therefore, they do not share a common ancestor, but instead their ancestors have adapted to a similar environment and so evolved wings. This is an example of convergent evolution: a structure of similar function has evolved from different developmental origins.
2. Using genetic evidence
When a species evolves over time to form a new one, the new species will have slight differences in its DNA base sequences. Over time, this species would accumulate…