Marine Invert

Asymmetry

A body plan with no axis or plane of symmetry.

Radial symmetry

A body plan where structures are arranged around a central axis.

Bilateral symmetry

A body plan with distinct left and right sides separated by one plane.

Cephalization

The evolution of a specialized head containing sensory organs and nervous tissue.

Metazoa

Multicellular animals.

Non-bilaterians

Animals outside Bilateria including Porifera, Placozoa, Cnidaria, and Ctenophora.

Bilateria

Animals with bilateral symmetry and three germ layers.

Germ layers

Embryonic layers that develop into tissues and organs.

Diploblast

An organism with two germ layers: ectoderm and endoderm.

Triploblast

An organism with three germ layers: ectoderm, mesoderm, and endoderm.

Ectoderm

The outer embryonic layer.

Endoderm

The inner embryonic layer.

Mesoderm

The middle embryonic layer found in triploblastic animals.

Cleavage

The first cell divisions of a fertilized egg.

Blastula

The early embryo stage formed after cleavage.

Gastrulation

The process where embryonic germ layers form.

Morphogenesis

The process where cells specialize and form tissues and organs.

Archenteron

The embryonic gut.

Blastopore

The opening formed during gastrulation.

Surface area to volume ratio

The relationship between an organism’s surface area and volume that affects exchange of materials.

Why do large organisms need specialized structures?

As organisms increase in size, surface area to volume ratio decreases, making exchange less efficient.

How do sponges overcome surface area limitations?

Sponges increase internal folding to increase surface area while maintaining efficient exchange.

SA:V ratio

Surface area to volume ratio; organisms need a high ratio to efficiently exchange materials with the environment.

Why does SA:V decrease as animals get larger?

Volume increases faster than surface area, making diffusion and exchange less efficient.

Why do animals evolve specialized systems?

To overcome limitations caused by decreasing surface area to volume ratios.

Sessile

An organism that remains attached to a surface and does not move freely.

Motile

An organism capable of movement.

Planktonic

An organism that drifts with tides and currents.

Benthos

Organisms that live on or near the bottom of aquatic environments.

Porifera

Phylum containing sponges; simple aquatic animals that are primarily suspension feeders.

Cnidaria

Phylum containing jellyfish, corals, and anemones; characterized by cnidocytes.

Ctenophora

Phylum containing comb jellies; gelatinous marine animals with comb rows used for movement.

Placozoa

A simple marine non-bilaterian group with few cells, no organs, and no symmetry.

Body cavity

A space inside an animal body that can allow development of organs and support larger body size.

Coelom

A fluid-filled body cavity completely lined by mesoderm.

Acoelomate

An animal lacking a body cavity.

Pseudocoelomate

An animal with a body cavity not completely lined by mesoderm.

Parazoan grade

A level of body organization historically associated with sponges because they lack true tissues and organs.

Eumetazoa

Animals with true tissues.

Tissue

A group of similar cells working together for a specific function.

Gastrulation

The embryonic process where cells rearrange and form germ layers.

Embryogenesis

The process of development from fertilized egg to mature organism.

Cleavage

The rapid cell division of a zygote into smaller cells.

Zygote

The fertilized egg cell formed after reproduction.

Ectoderm

Embryonic layer that develops into outer body structures and nervous tissue.

Mesoderm

Embryonic layer that develops into muscles, connective tissues, and internal structures.

Endoderm

Embryonic layer that develops into internal digestive-related tissues.

Diploblastic

An organism with ectoderm and endoderm only.

Triploblastic

An organism with ectoderm, mesoderm, and endoderm.

Why are all Bilateria triploblastic?

They contain three germ layers including mesoderm.

Radial symmetry example

Jellyfish; body parts arranged around a central axis.

Bilateral symmetry example

Crabs; body has distinct left and right sides.

Asymmetry example

Sponges; no consistent body axis.

Phylogenetic tree purpose

To show evolutionary relationships and common ancestry.

Clade

A group containing an ancestor and all descendants.

Derived trait

A trait that evolved more recently compared to an ancestral condition.

Ancestral trait

A trait present in an earlier ancestor.

Homology vs analogy

Homology is similarity from common ancestry; analogy is similarity from similar function or convergence.

Homologous structures

Structures with shared evolutionary origin even if functions differ.

Analogous structures

Structures with similar functions but different evolutionary origins.

Divergent evolution

When related organisms become increasingly different over time.

Convergent evolution

When unrelated organisms evolve similar traits.

Porifera

A phylum of simple aquatic animals known as sponges; they lack true tissues and organs and are mostly suspension feeders.

Aquiferous system

The water-circulation system of sponges that moves water through the body for feeding, gas exchange, and waste removal.

Water flow in sponges

Water enters through ostia, moves through canals/chambers with choanocytes, and exits through the osculum.

Ostia

Small pores on a sponge where water enters the body.

Osculum

The large opening where filtered water exits the sponge.

Choanocyte

A flagellated sponge cell that creates water currents and captures food particles using a collar.

Pinacoderm

The outer layer of a sponge made of flattened cells called pinacocytes.

Pinacocyte

A flattened outer sponge cell that forms the protective covering of the sponge.

Choanoderm

The inner layer of a sponge lined with choanocytes.

Mesohyl

The jelly-like internal layer between the pinacoderm and choanoderm containing cells and skeletal elements.

Spicule

A small skeletal structure made of silica or calcium carbonate that supports and protects a sponge.

Sclerocyte

A sponge cell responsible for producing spicules.

Spongocyte

A sponge cell that produces spongin fibers.

Myocyte

A contractile sponge cell that helps regulate water flow.

Sponge suspension feeding

The process where sponges filter small food particles from water using choanocytes.

Asconoid sponge

The simplest sponge body form where water flows directly into a central cavity lined with choanocytes.

Syconoid sponge

A sponge body form with folded walls that increase surface area and contain choanocyte chambers.

Leuconoid sponge

The most complex sponge body form with many chambers and the greatest filtering efficiency.

what is number 1 on this diagram

ectoderm

What is number 2 on this diagram

Blastocoel

What is number 3 on this diagram?

Presumptive mesoderm

What is number 4 on this diagram?

Archenteron

What is number 5 on this diagram?

Endoderm

What is number 6 on this diagram?

Mesoderm

What is number 7 on the diagram?

Blastopore

What is number 1 on the diagram?

Gastrovascular canal: series of radially extending canals acts as the stomach

What is number 2 on the diagram?

tentacle: threads of ectodermal tissue arising from the bell margin/subumbrella surface laden with nematocysts and used for prey capture

What is number 3 on the diagram?

Radial Canal: circulation systems that from central gastro cavity to outer edge of the bell

What is number 4 on the diagram?

Mouth: Opening in the center of the body for eating & expelling waste

What is number 5 on the diagram?

Gonad: reproductive organs

What is number 6 on the diagram?

oral arm: extension of the mouth tube or manubrium; effectively long, thin and often coiled-lips bearing cnidae

What is number 7 on the diagram?

Rhopalium: collection of sense organs into a single body, generally at or close to the bell margin

What is number 8 on the diagram?

Circular Canals: distribute partially digested food, oxygen, and nutrients, throughout their gelatinous bodies

Number 1 on this diagram is what?

the mouth

Number 2 on this diagram is what?

Ctenes of comb rows

Number 3 on this diagram is what?

Tentilla

Number 4 on this diagram is what?

Tentacle sheath

Number 5 on this diagram is what?

Interradial canal