Intro to Comparative Anatomy

Comparative Vertebrate Anatomy

The study of descriptive and functional morphology of vertebrates, emphasizing evolution and interrelationship of different animals.

Morphology refers to structural evolution, while anatomy describes the structure as it is.

What is the difference between morphology and anatomy?

Comparative Morphology

It formulates questions regarding structure, such as the differences in tail shapes between homocercal and heterocercal tails.

Homocercal tail

A tail found in teleost fishes (like salmon and tuna) that has a swim bladder for buoyancy, allowing them to maintain position in water.

Heterocercal tail

A tail found in sharks and other fishes lacking swim bladders, where the extended lobe provides lift during swimming.

Evolutionary Morphology

It shows evidence of past evolutionary changes inscribed in animal structures, with modern groups carrying traits from their ancestors.

Carl von Linne

A Swedish naturalist who devised binomial nomenclature and argued that species were unchangeable.

Georges Cuvier

He argued that anatomical parts performed specific functions and that organisms are functional wholes, meaning parts cannot change without risking the organism's survival.

Richard Owen

He believed that major animal groups were constructed from the same body plan (archetype), leading to homologies between parts.

Jean Baptiste de Lamarck

He proposed that species change over time through progressive steps and that evolution occurs via inheritance of acquired traits.

Louis Agassiz

He was the creator of the Museum of Comparative Zoology at Harvard University and wrote about the evidence of divine attributes in nature.

Charles Darwin

He studied the morphology of tortoises and finches in Galapagos Island, leading to his theory of natural selection.

Alfred Russel Wallace

He studied the diversity of plants and animals in the Malay Archipelago and the Amazon jungle, contributing to the theory of evolution.

Similarity

It distinguishes homologous structures, analogous structures, and homoplastic structures.

Radial Symmetry

A body layout that is equally arranged from a central axis, allowing for multiple planes to divide the animal into equal halves, seen in jellyfish and sea anemones.

Bilateral Symmetry

A body layout where only the midsagittal plane divides the body into two mirrored halves, typical in vertebrates.

Segmentation (metamerism)

The division of the body into repeating or duplicated patterns, significant for support and locomotion in organisms like annelids and tapeworms.

It summarizes evolutionary relationships in dendrograms, depicting connections between groups and showing the continuity of life.

What does phylogeny represent in comparative anatomy?

Anatomic Position

The position of a quadruped standing erect on all four limbs, facing left, with the tail slightly raised, used as a reference for anatomical nomenclature.

Median Plane

A plane that divides the body or limb longitudinally into equal right and left halves.

Sagittal Plane

A plane that passes through the right or left side of the body parallel to the median plane.

Tranverse Plane

A plane that passes through the head, body, limb, or organ at right angles to the structure's long axis or the median plane.

Dorsal Plane

A plane that runs at right angles to both the median and transverse planes horizontally, dividing the body into dorsal and ventral positions.

Homologous structures

two or more features that share a common ancestry

Analogous structures

perform similar functions ,but they may or may not have similar ancestry

Homoplastic structures

look alike may not be homologous or analogous

Phylogeny

• summarized in dendrograms that depict treelike, branched connections between groups

• the evolution of life is continuous and connected process from one moment to the next

Dendrograms

• can be used to express relative abundance and diversity

• the balloons represent the relative numbers of vertebrates that existed in each group during various geological times

Anatomic Plane

any surface, real or imaginary, along which any two points can be connected by a straight line