BIO153 Lecture 4 notes

Taxonomy: the science of naming, describing, and classifying organisms into groups based on their relatedness.
- Nomenclature: the system of naming organisms.
- Classification: grouping organisms into categories based on shared characteristics.
Phylogeny: the study of evolutionary relationships among biological entities.
- Deduces how organisms are related based on their classification.

Organisms such as:
- Elephant
- White-tailed deer
- Canada lynx
- Sycamore maple
- Cactus
- Fern
Plants (e.g., Sycamore maple, Fern, Cactus) fall under Kingdom Plantae.
- Characterized as photo-autotrophs and vascular plants (which transport water through tube-like structures).
Animals (e.g., White-tailed deer, Canada lynx, Elephant) belong to Kingdom Animalia.
- Defined as chemo-heterotrophs and mammals (which nurture their young with milk).
Is cheetah a cat?
- Yes, the cheetah is classified as a member of the Felidae family, commonly known as the cat family, and it demonstrates unique adaptations for speed and hunting.
- Organisms in the family felidae (cats) have retractable claws that allow them to keep their claws sharp for hunting while also providing traction for climbing and sprinting.
- Cheetah is the fastest terrestrial animal (up to 105 km/h), does not have retract claws, and claws used as spikes whilst running.

Cladistics focuses on classifying organisms based on their ancestral relationships.
- Organisms in the same clade share a common ancestor.
Example: Cheetah (Acinonyx jubatus) is classified in the family Felidae due to its shared traits with other cats, it is a cat first.
- Cheetahs can run fast using semi-retractable claws, differing from other cats with retractable claws.
- cheetah fits the best with other cats when it is classified based on cladistics.

Definition: A phylogenetic tree represents the relationships among various biological species based on their evolutionary history.
- It serves as a hypothesis about how different organisms are related.
THIS RELATIONSHIP IS NOT CONCRETE!!
- classification may change based whatever trait is used/prioritized for building a phylogenetic tree, highlighting the importance of selecting the right characteristics when making evolutionary comparisons.
Basic Features:
- Branch Point: a point where a common ancestor diverges into different species.
- Dichotomy: a specific branch point diverging into exactly two lineages.
- Sister Taxa: groups that share an immediate common ancestor, but not with any other groups.
Root of the Tree: represents the last common ancestor of all taxa presented in the tree.

Example of a basic phylogenetic tree shows relationships among organisms:
- Chimpanzee and Human are considered sister taxa.
- Choosing different common ancestors can redefine sister groups.
- Understanding sister taxa is crucial in determining evolutionary relationships.

Property 1: Phylogenetic trees illustrate how organisms are connected but do not represent similarity.
Property 2: They show patterns of descent, which may differ from physical appearance. E.g., whales are more closely related to hippos than to seals despite similar environments.
Property 3: A phylogenetic tree does not imply that one taxon evolved from a neighboring taxon but indicates their divergence from a common ancestor.

Cladograms: Basic trees showing relationships without additional information.
Phylograms: Trees where branch lengths correspond to evolutionary time or genetic change.
Polytomy: A branch point with more than two descendant species when not enough data is available to resolve all relationships.

Phylogenetic trees provide a foundational understanding of evolutionary relationships, helping scientists to study the history of life on Earth and the connections between different organisms. These classifications are subject to change as new data becomes available, emphasizing the dynamic nature of biological research.