Animal Architecture: Levels of Organization, Tissue Types, and Body Plans

Flashcards covering the levels of organization, tissue types, organ systems, extracellular components, and internal and external body plans in animals as discussed in the lecture.

What are the two main classifications of organisms based on cellularity discussed?

Unicellular organisms (Protozoa) and Multicellular organisms (Metazoans).

How are Protozoa characterized?

They are unicellular animal-like organisms and unicellular eukaryotes.

What defines a Metazoan?

An ingestive, heterotrophic, sexual, multicellular eukaryote that undergoes embryonic tissue formation.

What is the difference between a Unicellular eukaryote 'cell' and a Metazoan cell?

A unicellular eukaryote 'cell' is autonomous and lives independently, while a Metazoan cell is part of a whole organism and cannot live independently.

What are Mesozoans and Parazoans?

Multicellular animals without true tissues, representing a transitional group between protozoan and metazoan traits.

What are Eumetazoans?

Multicellular animals that possess true tissues.

Describe the Cytoplasmic level of organization.

All life functions occur within a single 'cell' which possesses specialized organelles.

Describe the Cellular level of organization.

Multicellular organisms with a division of labor, but cells are not organized into true tissues.

Describe the Cell-tissue level of organization.

Aggregation of cells into tissues (definite patterns/layers), where cells produce an extracellular matrix.

Describe the Tissue-organ level of organization.

Aggregation of tissues into organs, where organs are made up of more than one kind of tissue (parenchyma and stroma).

Describe the Organ-system level of organization.

Organs work together as a system to perform a specific function, typically associated with basic body functions.

What is a tissue?

An organization of like cells; the fundamental structure of which animal organs are composed.

What are the four primary types of tissues found in animals?

Epithelial, Muscular, Nervous, and Connective tissue.

What is the function of epithelial tissue?

Sheets of cells that cover an external or internal surface.

What is the function of muscular tissue?

Specialized for voluntary and involuntary movement, making it the most common tissue in most animals.

What is the function of nervous tissue?

Specialized for reception and conduction of stimuli and impulses, composed of neurons and neuroglia.

What is the function of connective tissue?

A diverse group of tissues specialized to bind and support other tissues.

Which type of epithelial tissue is flattened and facilitates gas and molecule movement?

Simple squamous epithelium.

Which type of epithelial tissue is made of tall, elongated cells often associated with absorptive surfaces?

Simple columnar epithelium.

Which type of epithelial tissue is layered to withstand mild mechanical abrasion?

Stratified (squamous) epithelium.

Name some of the organ systems observed within metazoans.

Digestive, Circulatory, Respiratory, Immune, Skeletal, Endocrine, Excretory, Nervous, Integumentary, Reproductive, and Muscular systems.

What are the two fluid compartments found in Eumetazoans?

Interstitial fluid (surrounding cells) and blood plasma (fluid portion of blood).

What are 'extracellular structural elements'?

Non-cellular components like bone, cartilage, cuticle (e.g., exoskeleton), and loose connective 'tissue' that provide mechanical stability and/or protection.

What is asymmetry in body plans?

No body axis and no plane of symmetry, as seen in Poriferans (sponges) and some unicellular eukaryotes.

What is spherical symmetry?

Body parts arranged concentrically around a central point with an infinite number of planes of symmetry, typically lacking polarity (no differentiation along an axis). It is rare, found in unicellular eukaryotes like Radiolarians.

What is radial symmetry?

The body has the general form of a cylinder with one main axis, around which body parts are radially arranged, and it can be divided equally by two or more planes passing through the longitudinal axis.

Why is radial symmetry common in sessile or drifting species?

It allows them to confront the environment from all directions for feeding, defense, etc.

What is bilateral symmetry?

Division along the midsagittal plane results in two equal halves, with body parts oriented about a single anterior-to-posterior axis.

What is bilateral symmetry associated with?

Controlled mobility/unidirectional movement and cephalization (development of a head region).

What are the three embryonic germ layers in Metazoans?

Ectoderm, Endoderm, and Mesoderm.

What does 'diploblastic' mean?

Having two primary germ layers (ectoderm and endoderm), like Cnidarians.

What does 'triploblastic' mean?

Having three primary germ layers (ectoderm, endoderm, and mesoderm), characteristic of most metazoans.

What is a coelom?

A fluid-filled cavity between the outer body wall and the gut found in bilateral animals.

What are the advantages of having a coelom?

It enables internal organs to grow larger and become more sophisticated, fluid cushions internal organs preventing injury, and it can act as a hydrostatic skeleton for soft-bodied animals.

Describe an acoelomate animal.

An animal with no true coelom; the region between the ectoderm and gut is occupied by mesoderm.

Describe a pseudocoelomate (blastocoelomate) animal.

An animal that possesses a pseudocoel (a persistent blastocoel) where the mesoderm lines only the outer edge of the blastocoel, not surrounding the internal organs entirely.

Describe a coelomate animal.

An animal where the blastocoel fills with mesoderm, and a new cavity (the coelom) forms inside this mesoderm, fully enclosing the organs.