BIO 202 Flashcards
What are the three basic kinds of body plans in Bilateria?
Acoelomates, Pseudocoelomates, Coelomates
Acoelomates have no body cavity, Pseudocoelomates have a body cavity between mesoderm and endoderm, and Coelomates have a body cavity entirely within the mesoderm.
Define Acoelomates.
Animals with no body cavity.
Acoelomates are characterized by the absence of a coelom.
What is a Pseudocoelom?
A body cavity between mesoderm and endoderm.
Pseudocoelomates possess a pseudocoelom that is not completely lined with mesoderm.
What is a Coelom?
A body cavity entirely within the mesoderm.
Coelomates have a true coelom that allows for the development of complex organ systems.
What are the three germ layers in bilateral animals?
- Ectoderm
- Mesoderm
- Endoderm
These layers differentiate into various tissues and organs during development.
What are the advantages of bilateral symmetry over radial symmetry?
- Cephalization
- Greater mobility
Bilateral symmetry allows for the evolution of a defined brain area and enhanced movement capabilities.
What is radial symmetry?
Body parts arranged around a central axis.
Radially symmetrical animals can be bisected into equal halves in any 2-D plane.
What is bilateral symmetry?
Body has right and left halves that are mirror images.
Only the sagittal plane bisects the animal into two equal halves.
Do sponges exhibit symmetry?
No definite symmetry.
Sponges (Parazoa) lack any form of symmetry.
What are the two main types of symmetry in animals?
- Radial symmetry
- Bilateral symmetry
These types define how the body structure is organized around axes.
What are the advantages of segmentation in animals?
- Allows redundant organ systems
- Allows for more efficient and flexible movement
Segmentation has appeared multiple times in the evolution of various animal groups.
How do protostomes differ from deuterostomes?
- Protostomes develop mouth first
- Deuterostomes develop anus first
This distinction is fundamental in the embryonic development of these groups.
What is the cleavage pattern of protostomes?
Spiral cleavage.
This type of cleavage leads to determinate development.
What is the cleavage pattern of deuterostomes?
Radial cleavage.
This type of cleavage leads to indeterminate development.
Define determinate development.
Development where the fate of embryonic cells is fixed early.
This occurs in protostomes.
Define indeterminate development.
Development where the fate of embryonic cells is not fixed early.
This occurs in deuterostomes and allows for the potential of identical twins.
What is the basic pattern of Bilaterian development?
Mitotic cell divisions form a hollow ball of cells (blastula).
The blastula undergoes gastrulation to form a two-layer-thick ball.
What are the five key transitions in animal evolution?
- Evolution of tissues
- Evolution of symmetry
- Evolution of body cavity
- Patterns of development
- Segmentation
These transitions highlight significant changes in complexity and organization in animal evolution.
What is heterotrophy?
Obtaining energy and organic molecules by ingesting other organisms.
Heterotrophy is a defining characteristic of animals.
What are the general features of animals?
- Heterotrophy
- Multicellularity
- No cell walls
- Active movement
- Diversity of form
- Diversity of habitat
- Sexual reproduction
- Embryonic development
- Tissues
These features encompass the broad characteristics that define the animal kingdom.
