Overview of Animal Diversity II Lecture 26 (Chapter 32)
Date: 19 July 2022
Location: Viking Bay Ko, Phi Phi Le, Thailand
Featured Species:
Ocellaris Anemonefish (Amphiprion ocellaris)
Magnificent Sea Anemone (Radianthus magnifica)
Biblical Perspective on Animal Creation
Genesis 1:24 (NIV): "And God said, “Let the land produce living creatures according to their kinds: the livestock, the creatures that move along the ground, and the wild animals, each according to its kind.”"
Date: 7 September 2018
Location: Maasai Mara National Reserve, Kenya
Featured Species:
Common Wildebeest (Connochaetes taurinus)
Plains Zebra (Equus quagga)
Body Plans: Symmetry
Asymmetrical
Characteristics:
Irregularly shaped
Example:
Stylissa massa (Sponges known for their lack of regular shape)
Date: 17 December 2017
Location: Mana Island, Fiji
Radial Symmetry
Definition:
Symmetrical around a central point; any line through the central point yields mirror image halves.
Features:
No central nervous system or cephalization (contrast to bilateral symmetry)
Many species are sessile (attached) or planktonic (drifting).
Example:
Pacific Stubby Rose Anemone (Urticina clandestina)
Date: 4 July 2024
Location: Mendocino Headlands, California
Bilateral Symmetry
Definition:
Symmetrical around one line with mirror images on each side. Distinction between anterior (front) and posterior (back) ends.
Features:
Usually have a central nervous system and exhibit cephalization (formation of a head).
Most species are motile (capable of locomotion).
Example:
European Peacock Butterfly (Aglais io)
Date: 8 August 2021
Location: Nyzhnya Rozhanka, Ukraine
Comparison of Symmetries
Radial Symmetry
Oral and Aboral surfaces defined; often found in stationary or drifting organisms.
Bilateral Symmetry
Anterior, Dorsal, Ventral, and Posterior surfaces defined; aligns with active movement and predation.
Body Plans: Germ Layers
Absence in Sponges
Sponges (phylum Porifera) do not possess true germ layers.
Example:
Large Tube Sponge (Haliclona fascigera)
Date: 13 July 2023
Location: Changuu Island, Zanzibar, Tanzania
Diploblastic Organisms
Structure:
Composed of two germ layers: Endoderm (inner) and Ectoderm (outer).
Note: Some definitions reference a non-living layer (Mesoderm) but may vary.
Triploblastic Organisms
Structure:
Composed of three germ layers: Endoderm, Ectoderm, and Mesoderm.
Body Plans: Body Cavity
Acoelomate
Definition:
Animals lacking a body cavity; their body is a solid mass of cells.
Example: General flatworms
Germ Layer Composition:
Ectoderm
Mesoderm
Endoderm
Digestive cavity present within the mass.
Pseudocoelomate
Definition:
Body cavity lies between the digestive tract and the outer body wall, originating from the blastopore.
Germ Layer Composition:
Ectoderm
Mesoderm
Endoderm
Characteristics:
Pseudocoelom is not completely surrounded by mesoderm.
Coelomate
Definition:
True body cavity located between the digestive tract and the outer body wall, lined with mesoderm.
Functions:
Mesodermal structures serve to suspend and cushion internal organs.
Germ Layer Composition:
Ectoderm
Mesentery (Tissue supporting organs)
Endoderm
Mesoderm (forming the coelom)
Hemocoel
Definition
An open circulatory system found in some phyla where blood-like fluid (hemolymph) transports nutrients, gases, and wastes throughout the organism.
Body Plans: Embryonic Development
Protostome Development
Characteristics:
Determinate cleavage is evident; the fate of cells is fixed at the 4-cell stage meaning they cannot form a complete organism if separated.
Spiral cleavage occurs where cells align obliquely.
Mouth formation arises from the blastopore; the anus is formed later from a separate opening.
Coelom develops by schizocoely where a solid mass of mesoderm splits.
Visuals of Development Stages:
Anus and mouth formation details illustrated with stages of gastrulation and coelom formation.
Deuterostome Development
Characteristics:
Indeterminate cleavage allows for the possibility of separating cells at the 4-cell stage to develop into separate organisms (e.g., twins).
Radial cleavage occurs where cells layer directly on top of one another.
Mouth is formed from another opening, with the anus originating from the blastopore.
Coelom is formed via enterocoely from pouches made in the wall of the primitive gut.
Development Stages:
Similar diagrammatic representation as in protostomes, highlighting stages of development, cleavage types, and formation processes.
Body Plans of Major Animal Phyla
Comparative Table
Highlights the body symmetry, germ layers, body cavity types, and embryonic development stages for several phyla including:
Porifera: Asymmetrical, Two layers but no germ layers, Acoelom, Neither.
Cnidaria: Radial, Diploblastic, Acoelom, Neither.
Ctenophora: Biradial or bilateral, Diploblastic or triploblastic?, Acoelom, Neither.
Key clades and timelines represent the evolutionary history of animals with significant markers such as:
770 million years ago: Origin of Metazoa.
680 million years ago: Emergence of Eumetazoa.
670 million years ago: Formation of Bilateria.
Major clades include Ecdysozoa, Lophotrochozoa, and Deuterostomia with each defined by unique characteristics such as ecdysis in Ecdysozoa and lophophore in Lophotrochozoa.
Clade Overview
Metazoa: All animals, sponges (phylum Porifera) are basal animals.
Eumetazoa: Animals with true tissues, includes basal phyla Ctenophora and Cnidaria.
Bilateria: Animals with bilateral symmetry, inclusive of three main clades.
Deuterostomia: Clade includes vertebrates and defined by deuterostome development.
Lophotrochozoa: Characterized by a lophophore feeding structure or trochophore larva.
Study Reference
Study recommendation for preparations over lectures 25-26 (Chapter 32).