C7: Animal Taxonomy, Phylogeny, and Organization

What is taxonomy?

Taxonomy is the science of identifying, naming, and classifying species into a structured system.

What is phylogeny?

Phylogeny describes the evolutionary history and relationships of species, often depicted as a tree diagram. It adds an evolutionary dimension by showing how species are related through common ancestry.

What are the levels of the taxonomic hierarchy, from most broad to most specific?

The taxonomic hierarchy, originally developed by Carolus Linnaeus, is: domain, kingdom, phylum, class, order, family, genus, and species.

What are the three main types of animal symmetry?

The three main types of animal symmetry are asymmetry, radial symmetry, and bilateral symmetry.

How is an animal with asymmetry characterized?

An asymmetrical animal has no central point or axis and its body parts are irregularly arranged. Many sponges are examples of asymmetrical animals.

How is an animal with radial symmetry characterized?

An animal with radial symmetry has body parts arranged around a central axis. Any plane that passes through this axis divides the animal into mirror images. Cnidarians and echinoderms are examples of radially symmetrical animals.

What is the adaptive significance of radial symmetry?

Radial symmetry is adaptive for animals that are sessile or slow-moving and interact with their environment from all directions. However, it limits the development of complex sensory and nervous systems.

How is an animal with bilateral symmetry characterized?

An animal with bilateral symmetry has a single plane that divides the body into right and left mirror images. A fox is an example of a bilaterally symmetrical animal.

What is the adaptive significance of bilateral symmetry?

Bilateral symmetry facilitates active, directional movement and the concentration of sensory structures at the anterior end (cephalization), which enhances interaction with the environment.

What is cephalization?

Cephalization is the evolution of a distinct head region with concentrated sensory and nervous structures, which is supported by bilateral symmetry and enables efficient forward movement and environmental sensing.

What are the levels of cellular organization in animals?

The levels of cellular organization are unicellular (single cells, e.g., protists), cellular aggregates (loosely associated cells without true tissues, e.g., sponges), tissues (organized groups of cells), and organs (multiple tissue types working together).

What are the three types of body cavities and how are they defined?

The three types of body cavities are: Acoelomate (no body cavity between the digestive tract and body wall), Pseudocoelomate (a body cavity not completely lined by mesoderm), and Coelomate (a true coelom completely lined by mesodermal tissue).

In what way does the coelom facilitate an animal's body?

The coelom provides space for organ development, allows organs to move independently of the body wall, and can act as a hydrostatic skeleton for support and movement.

What is the difference between homologous and analogous features?

Homologous features arise from a common ancestry and reflect evolutionary relationships. Analogous features result from convergent evolution and do not indicate a close evolutionary relationship.

What is the difference between cladistics and evolutionary systematics?

Cladistics focuses on shared derived characters (synapomorphies) to group organisms into monophyletic groups. Evolutionary systematics considers both common descent and the amount of evolutionary change, and may include paraphyletic groups as valid taxa.

What is a cladogram?

A cladogram is a tree diagram that represents a hypothesis of evolutionary relationships based on shared derived characters. It shows branching points (nodes) where groups diverged from a common ancestor, but it does not show time scales or abundance.

What is a monophyletic group?

A monophyletic group consists of a common ancestor and all of its descendants, defined by shared derived characters (synapomorphies).

What is a paraphyletic group?

A paraphyletic group includes a common ancestor but excludes some of its descendants.

What is a polyphyletic group?

A polyphyletic group is formed from unrelated lineages that do not share a recent common ancestor.

What is a synapomorphy?

A synapomorphy is a shared, derived character that evolved in the most recent common ancestor of a group and is present in all of its descendants. These traits are essential for identifying monophyletic groups and reconstructing accurate evolutionary relationships.

How are outgroups used in phylogenetic analysis?

An outgroup is a taxon outside the group of interest that is used to infer the ancestral state of a character, helping to determine which traits are derived versus ancestral.

What are some examples of molecular markers and what are they used for?

Molecular markers such as microsatellites and Amplified Fragment Length Polymorphisms (AFLP) analyze variation in extragenic (non-coding) DNA to provide data for recent evolutionary relationships and population genetics.

Why is extragenic (non-coding) DNA useful for studying recent evolutionary events?

Extragenic DNA does not code for proteins and is not subject to strong natural selection, allowing it to accumulate mutations relatively rapidly. This makes it valuable for studying recent evolutionary relationships among closely related species.