24 Questions
What is the characteristic of an animal that has radial symmetry?
It can be divided into matching halves with many lines passing down the central axis
Which of the following is a characteristic of animals that are bilaterally symmetrical?
They have a right side that is a mirror image of the left side
What is the process by which the germ layers develop early in embryonic life?
Gastrulation
What is the inner layer of cells in an embryo called?
Endoderm
What is the term for a group of cells in an embryo that interact with each other to form all organs and tissues?
Germ layer
Which of the following is NOT a characteristic of an animal that has asymmetrical body shape?
It has a right side that is a mirror image of the left side
What is the characteristic of a diploblastic organism?
Radial symmetry and two layers of cells in the embryo
What is the function of the mesoderm in triploblastic organisms?
It gives rise to muscles, circulatory, reproductive, excretory system, and skeleton
What is the characteristic of a coelomate organism?
Presence of a fluid-filled body cavity with a complete lining derived from mesoderm
What is the characteristic of an acoelomate organism?
Absence of a body cavity, with organs having direct contact with the epithelium
What type of gut is characterized by having two openings, a mouth and an anus?
Through gut
What is the term for a 'false cavity' that is fully functional?
Pseudocoelom
What is the characteristic of an animal with bilateral symmetry?
Can be divided into 2 matching halves with one line passing down the central axis
What happens during the process of gastrulation?
The blastula reorganizes into 2 primary germ layers
What is the outer layer of cells in an embryo called?
Ectoderm
What is the term for a type of gut that has one opening?
Incomplete gut
How many germ layers do most animals develop?
Three
What is the characteristic of an animal with radial symmetry?
Can be divided into matching halves with many lines passing down the central axis
What is the main difference between a coelomate and a pseudocoelomate?
The presence of a complete lining of the body cavity
What is the characteristic of an organism with a blind gut?
Food enters and leaves through the same opening
Which of the following is a characteristic of a triploblastic organism?
The presence of three tissue layers
What is the main function of the mesoderm in a triploblastic organism?
To form muscles, circulatory, reproductive, excretory systems, and skeleton
What is the characteristic of an organism with a diploblastic body?
The presence of only two tissue layers
What is the characteristic of an acoelomate organism?
The presence of semi-solid mesodermal tissues between the gut and body wall
Study Notes
Animal Diversity
- There are three types of symmetry: radial, bilateral, and asymmetrical.
Symmetry
- Radially symmetrical: can be divided into matching halves with many lines passing down the central axis; oral surface (mouth) and aboral surface (without mouth).
- Bilaterally symmetrical: can be divided into 2 matching halves with one line passing down the central axis; right side is a mirror image of the left side; head and tail region; sense organs and nervous tissue concentrated in the head region.
- Asymmetrical: no body axis and no plane of symmetry.
Germ Layers
- Germ layers are groups of cells in an embryo that interact with each other to form all organs and tissues.
- All animals, except perhaps sponges, form two or three germ layers.
- Germ layers develop early in embryonic life through gastrulation.
- Blastula reorganizes into 2 primary germ layers: endoderm (inner layer) and ectoderm (outer layer).
Tissue Layers
- Diploblastic: 2 layers in embryo; ectoderm becomes epidermis and nervous system; endoderm becomes digestive system.
- Triploblastic: 3 layers of cells in embryo; mesoderm becomes muscles, circulatory, reproductive, excretory system, and skeleton.
Presence of Body Cavity
- Coelomate: fluid-filled body cavity with a complete lining (peritoneum) derived from mesoderm; allows organs to be attached to each other.
- Pseudocoelomate: "false cavity" but fully functional; tissue derived from mesoderm only partly lines the fluid-filled body cavity; organs are held in place loosely.
- Acoelomate: no body cavity at all; organs have direct contact with the epithelium; semi-solid mesodermal tissues between the gut and body wall hold their organs in place.
Type of Gut
- Blind gut: food enters and leaves through the same opening.
- Through gut: two openings, mouth and anus.
This quiz covers the basics of animal diversity, focusing on body symmetry, tissue layers, coelom presence, and gut development. Understand the differences between radial and bilateral symmetry, and their characteristic features.
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