Biology 2 Chapter 23 Flashcards

Phylogeny and Systematics

• Phylogeny represents a hypothesis about relationships among species, illustrated with a cladogram or phylogenetic tree.
• Systematics is the reconstruction and study of evolutionary relationships among organisms.

Phenotypic Similarity

• Phenotypic similarity does not always indicate close evolutionary relationships due to varying rates of evolution and non-divergent evolution patterns.

Ancestral vs. Derived Characteristics

• Derived characteristics are inherited from the most recent common ancestor of a group, while ancestral characteristics predate that common ancestor.
• Only shared derived characters indicate close evolutionary relationships, determined through comparisons with a closely related outgroup.

Cladograms

• Cladograms are constructed to minimize the amount of character evolution required, reflecting evolutionary relationships accurately.

Taxonomic Groups

• Monophyletic groups (clades) include the most recent common ancestor and all its descendants.
• Paraphyletic groups include the common ancestor but not all descendants.
• Polyphyletic groups do not include the common ancestor of all members.

Phylogenetic Species Concept (PSC)

• PSC emphasizes shared derived characters and is controversial as it considers historical separation for character development; applicable to both sexual and asexual species.

Homoplasy

• Homoplasy refers to traits that may have similar functions but did not arise from a common ancestral source, impacting the interpretation of evolutionary change.

Evolutionary Trees

• Phylogenetic trees can reveal homoplasy by examining trait distribution among species within their evolutionary context.
• Timing of species diversification can be inferred by correlating phylogenetic branching with known evolutionary events.

Disease Transmission

• Phylogenetic analysis can track the evolution of disease strains, aiding in identifying sources and transmission patterns, exemplified by HIV studies.

Key Concepts and Terms

• Convergent evolution results in similar traits not derived from a common ancestor.
• Synapomorphy refers to a derived character shared by members of a clade.
• The principle of parsimony favors cladograms with the fewest evolutionary changes.
• Biological species concept (BSC) highlights reproductive isolation as a key factor in defining species.
• Homologous structures arise from a common ancestral source, such as a dolphin's flipper and a horse's leg, while analogous structures serve similar functions due to similar selection pressures.
• Homoplastic convergence describes traits evolving separately due to environmental adaptations, like plant conducting tubes.

Classification and Evolution

• Classification involves placing species into a taxonomic hierarchy based on evolutionary history.
• All organisms share traits such as cellular composition, metabolic activity, energy transfer via ATP, and hereditary information encoded in DNA.
• Darwin's concept of "descent with modification" holds that all species have a common ancestor and experience evolutionary change.

Cladogram Features

• In cladograms, derived features are shared by only part of the group while ancestral features are shared by the whole group.
• Outgroup comparison involves studying species closely related to but not part of the main group to determine ancestral traits.

Simian Immunodeficiency Virus (SIV)

• SIV is found in 36 species of primates and generally does not cause illness.