Ernest Haeckel’s idea was that ontogeny recapitulates phylogeny. His recapitulation theory is considered arcane, but disparate early embryos of vertebrates show remarkable structural similarities, do they not?

BIOL 1880 ~ Lecture #1

Introduction to the Course and Vertebrate Classification I. How to Use the lecture notes

Lecture notes are intended for use as supplement to material covered in lectures and the textbook, and not as replacement for either. Lecture notes will be available on Canvas before each lecture whenever possible, more than 48 hours prior (once we get started). Relevant textbook pages will be listed at the end of the lecture notes. You will also be lab notes, following the same principle. It is important that you read relevant sections in the lab notes before lecture. Bring these notes to class so you can add to them, color code them and label diagrams, but for exam purposes, it will also be a good idea to keep a lecture and a lab notebook. Words in the notes that are underlined will be defined during class and I expect you to be able to remember and use them. II. Layout of the Course We will travel up (and sometimes down) the vertebrate phylogeny (evolutionary tree) to build an understanding of how increasingly complex animal anatomies are derived from an ancestrally simple plan-form (derived from German, bauplan). During the course, you will be able to build an appreciation of how increasing levels of sophistication in organismal “design” are correlated with increased costs of existence, in terms of energy use, but also with greater levels of organization and functional abilities to overcome greater challenges posed by the surroundings. The focus of the course is an understanding of design plan of each level of organization and also the transitions between each level; how these transitions happened as integrated evolutionary events. III. Nature of the Course: Evolutionary approach to comparative anatomy: study of an animal in the context of its environment and in relation to its past history Liem et al. textbook (required) - takes a comparative (systemic) approach Both approaches are applicable to this course. The importance of an evolutionary approach is understanding the animal as a whole. Premise of the course: to understand animal structure and design. An evolutionary approach provides understanding of design constraints. Evolution can only build on the design of the earliest vertebrates: small, sessile marine organisms. All subsequent vertebrate evolution must occur through modifications of this original design. This course emphasizes knowledge of structure and we will use this knowledge to build an integrated approach to understanding vertebrate adaptations at various levels of organization. A solid foundational knowledge of physiology and evolution are essential for this course. Useful Background: Physiology (BIOL 0800), Vertebrate Embryology (BIOL 0320), Developmental Biology (1310), Animal Locomotion (BIOL 1800).

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supinate

Depression

pronate

IV. Anatomical terminology: Vertebrate body plans consist of 3 axes:

- Dorsal –Ventral - Anterior – Posterior - Left – Right

Other directional terms:

- Proximal – Distal - Medial – Lateral - Cranial (Rostral) – Caudal - Axial – Appendicular

- Apical-Basal: often used to refer to epithelial cells, which form epithelial sheets of tissue that

line body cavities and organs of the body. They have a distinct basal side, which is attached to a ‘basement membrane’ and an apical side, the side of the cell oriented towards the lumen, or the cavity. However, organisms such as hydra or tunicates (we will talk about them later) that are anchored on one side to a substrate also have apical-basal polarity.

It is essential you understand these terms as soon as possible as they are used constantly throughout the course. Body Planes:

- Sagittal: separates right and left halves of the body (parasagittal is a plane offset from the dorsoventral midline).

- Transverse: separates anterior and posterior halves of the body

- Frontal/coronal: Separates dorsal and ventral halves of the body

Positional terminology:

- Anatomical reference pose: The way you stand when you prepare to “beam up”. I will demonstrate in class.

- Prone: moving two body parts towards one another - Supine: moving two body parts towards

one another Terminology for motions:

- Flexion: moving two body parts towards one another

- Extension: moving two body parts away from one another

- Protraction: Moving forward relative to previous position

- Retraction: Moving backward relative to previous position

Source: Liem (3rd ed.)

Source: Kardong (6th ed.)

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Padian,  1985

- Abduction: Moving a structure away from the midline

- Adduction: Moving a structure towards the midline

- Supination: Rotation towards the midline

- Pronation: Rotation away from the midline

V. Useful evolutionary-developmental terms Homology: Similar structures of the body or

genes in different species are homologous when they share a common origin. E.g. the wings of bats and the arms of humans have many homologous structures (e.g. humerus, radius, phalanges, etc…) because they both evolved from a single common ancestor with that basic pattern of bones.

Analogy: However, these wings also have analogous

structures; the hand-wings are supported by different phalangeal elements.

- Orthology: Homology produced by a speciation event

- Paralogy: Homology produced by a duplication event (of a genetic sequence).

This is perhaps easier to think of in a genetic contest, but duplications of genes prior to speciation can give rise to homologous structures that would not have arisen without the duplication

Homoplasy: Character shared by species that is missing in their common ancestor. Examples

include eyes, ballistic tongues in salamanders, intramandibular joints in bony fishes. Synapomorphy: Derived features shared by a group of organisms that defines that group (e.g. all

vertebrates have spines, all birds have feathers, all mammals have mammary glands, etc.).

Pedomorphosis: retaining juvenile stage or traits

through development. The form is often referred to as a neotenic form.

VI. Structural Terminology

Understanding how structures of the body, especially muscle, are named will help you recall their function and/or location in the body.

Chimpanzee juvenile Chimpanzee adult

Source: Unknown

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Introduction to the Skeleton:

These are bone names you should already be familiar with. A more detailed understanding will be expected later in the course. The axial skeleton is comprised of the bones of the body and the appendicular skeleton is comprised of the bones of the limbs. Introduction to Muscle Names: Many muscles are named for their origin and insertion points. The origin is the place of attachment to stationary bone and the insertion is the attachment to moving bone. E.g. the Coracobrachialis muscle originates at the coracoid process of the scapula and inserts onto the humerus (brachial = ‘of the arm’) to control flexion of the arm. Muscles also derive their names from anatomical regions of the body. E.g. the Transversus abdominis lies across the abdominal region and the tibialis anterior is named for the location (anterior) on the bone (tibia) it attaches to. Finally, muscles names may refer to their function. E.g. the depressor mandibulae helps to lower (depress) the mandible (lower jaw). VII. What is a Vertebrate? A phylum is a grouping of animals based on a basic type of body plan/organization and characteristics shared by all members of the group (synapomorphies). Phylum Chordata includes all animals that possess a notochord, hollow nerve cord, pharyngeal gill slits, and a post-anal tail during some portion of their lives. Vertebrata is a subphylum of Chordata, and consists of chordates possessing a backbone. Most of the animals we are immediately familiar with are vertebrates including fish, amphibians, reptiles, birds, and mammals.

Skull

Vertebrae

Ribs

Source: Kardong (6th ed.)

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Readings: Liem et al. Chapter 1. This serves as a basic background for many of the approaches and concepts in this course. The more specific details on modes of classification, etc., will be covered in the first lab . Chapter 3 is an introduction to the diversity of vertebrates (= “craniates” in Liem et al., we’ll be explaining this difference in terminology later). Most of this type of diversity information is covered in the labs, but it would be worth while skimming this chapter now to find out “who’s who”, and to know where to refer back for more specific information later.

Source: Unknown