Invertebrate Zoology

Lecture 1: Introduction & Bauplans (begin)

Lecture outline Introduction to course Animal Bauplans

Bauplan Overview DefinedDefined Key functions of animal bodiesKey functions of animal bodies Limited optionsLimited options Bauplan as mix of ancestral and derived featuresBauplan as mix of ancestral and derived features

Key aspects of body plans (begin) SymmetrySymmetry Cellularity, body size, germ layers, body cavityCellularity, body size, germ layers, body cavity

Introduction to Course See handouts!

Animal Bauplans

Bauplan overview Definition: “A structural plan or design”

Organ systems and whole animalsHow does structure relate to function?

Bauplan, overview

Key functions of animal bodiesMake a list—audience participation!

Bauplan overview

Limited optionsRecurring themes in

body plans Types of symmetry Types of symmetry

Some aspects vary more freely Reproductive structuresReproductive structures

Bauplan overview What limits options?

Structural constraints Head and bilateral symmetryHead and bilateral symmetry Exoskeleton and size limitsExoskeleton and size limits

Genetic constraints The mutation must arise for The mutation must arise for

the character to existthe character to existSeveral other

constraints… Examples?Examples?

Bauplan overview Bauplan is a mix of

ancestral and derived characters

Example: chambered nautilus Ancestral molluscan Ancestral molluscan

features (such as…?)features (such as…?) Derived cephalopod Derived cephalopod

features (such as…?)features (such as…?)

Bauplans: key features Symmetry

AsymmetryRadial symmetry

Many variationsMany variations

Bilateral symmetry

Bauplans: key features Cellularity, size, germ layers, body cavity

Advantages to >1 cell? S/V ratios (understand this!)S/V ratios (understand this!) Specialized cell types (=multicellularity)Specialized cell types (=multicellularity)

Size constraints even with >1 cell. Why? How overcome in the most “simple” animals?How overcome in the most “simple” animals?

Bauplans: key features Cellularity, size, germ

layers, body cavity Development of internal

systems Such as…?Such as…?

Same principles apply: elongation, folding etc… to maximize surface area Example 1: CtenidiumExample 1: Ctenidium Example 2: KidneyExample 2: Kidney

Littorina (a snail), partial internal view

Bauplans: key features Cellularity, size, germ

layers, body cavity Which derived characters

promote complexity? Embryonic germ layersEmbryonic germ layers

Porifera: none! Cnidaria & Ctenophora:

diploblastic All others: triploblastic NAME THOSE LAYERS!

Bauplans: key features Cellularity, size, germ layers, body cavity

Which derived characters promote complexity? Body cavitiesBody cavities

Additional space with gases and nutrients Additional surface area (exchange) Allows for larger body/ larger organs Cushions organs Can serve as hydrostatic skeleton

Bauplans: key features Cellularity, size, germ

layers, body cavity Which derived characters

promote complexity? Body cavityBody cavity

None if not triploblastic!

Acoelomate = triploblastic but no body cavity

Blastocoelomate (Pseudocoelomate) =body cavity from blastocoel

Eucoelomate = body cavity from mesoderm