Animals Diversity Flashcards
What are the important features of a body plans
- Symmetry
- Cephalisation
- Embryonic tissue layers
- Development of a coelom
- Number of gut openings
- Blood systems
What is symmetry
The way in which body parts are arranged in the body plan is referred to as its symmetry.
List the three types of symmetry
Asymmetry
Radial symmetry
Bilateral symmetry
Explain what asymmetry is
• No symmetry in the body shape.
• No pattern to body parts; unicellular animals are irregular.
• Cannot divide animal into halves that are mirror images.
• Animals usually sessile (attached to substrate).
Explain what radial symmetry is
• Body parts are arranged around a central axis.
• Mirror images will be seen along a number of planes if sliced longitudinally.
• Radial animals have no front or back end.
• Radial animals are mostly sessile.
Explain bilateral symmetry
• Body parts are arranged on either side of a central axis.
• Can be cut in two mirror images in only ONE plane to give a right and a left half.
• Bilateral animals are motile.
• They have a front (anterior) and a back (posterior) end.
• There are definite dorsal (top) and ventral (bottom) surfaces.
Cephalisation
Define
• Cephalisation is a characteristic of bilaterally symmetrical organisms.
• The head forms the anterior end in which there is a concentration of nerve cells. This concentration of nerve cells is a simple brain in primitive animals. In highly advanced animals, the mass of nerve cells in the head form a more complex brain, which receives and interprets stimuli from sensory cells.
• Sense organs are housed in the head region, which places them near the concentration of nervous tissue or ‘brain’. Animals move forward with their heads entering their environment head first.
• The organism is able to detect food, danger and other stimuli and respond quickly.
What is laid out during embryological stages
An animals body plan
An embryo develops layers of cells called what
Germ layers
What do the germ layers do
.These germ layers give rise to specific tissues and organs that make up the body of a fully developed animal.
There are three living germ layers
Name them
ectoderm - (outer layer that forms the skin)
endoderm - (inner layer which lines the gut)
mesoderm - (middle layer that gives rise to internal organs
How many layers do primitive animals have and what do u call them
More primitive animals had only two germ layers in their embryos, the ectoderm and the endoderm an termed diploblastic.
How many layers do advanced animals have and what do u call them
The more advanced animals have all three germ layers and thus triploblastic.
Describe diplomatic animals
Diploblastic animals
• Organisms have cells arranged in two layers during embryonic development.
• Outer layer is called the ectoderm.
• Inner layer is called the endoderm.
Describe triploblastic anima
Triploblastic animals
• Organisms have their cells arranged in three layers during embryonic development.
• Ectoderm, endoderm and mesoderm.
Development of a coelom
In certain triploblastic animals, a fluid filled cavity called the coelom develops in the mesoderm. The coelom separates the gut from the body wall. This allows the outer parts of the body to move independently from the inner parts of the body.
Tissues in the outer part of the mesoderm form muscle layers of the body and tissues on the inner layer of the mesoderm form muscles of the gut. Separating these two muscle layers with a coelom allows muscles of the gut, which aid digestion, to contract without affecting the rest of the body.
Triploblastic animals without a coelom are called acoelomate.
They have a solid mass of tissue in the mesoderm which surrounds the digestive cavity and contains the organs
what are the advantages of a coelom
A coelom provides a number of advantages:
* It allows materials to diffuse rapidly through the fluid in the coelom to body cells.
* Redistribution of body fluid can help an animal alter its body shape and aid in locomotion.
* Organs are not restricted by a mass of tissue and are able to grow larger and move more freely
* The fluid in the coelom serves as a hydrostatic skeleton. to allow muscle movement
acts as a shock absorber to protect internal organs
What is a blind gut
Blind gut - having only one body opening through which ingestion (eating) as well as egestion (defecation) takes plac
What are the disadvantages of a blind gut
Disadvantages of a blind gut:
• The animal cannot ingest and egest at the same time
• The ingestion, digestion and egestion are not systematic
• There is a mixing of digested and undigested food
• Digested food is also expelled during egestion
What is a through gut
Through gut - having two body openings, a mouth at one end and an anus/ cloaca (common opening for the digestive system and the reproductive system) at the other end.
What are the advantages of a through gut
Advantages of a through gut:
• Allows specialisation - mouth ingests food; stomach and intestines digest foo intestines absorb food; anus egests undigested food
• Ingestion, digestion and egestion are systematic processes
• There is no mixing of digested and undigested food
What are the advantages and disadvantages of asymmetry
Advantages:
Food and oxygen can be absorbed through the whole body
Disadvantages:
Animals are often sessile (stays in one place)
Movement is absent or ineffective
Cephalisation does not
What are the advantages and disadvantages of radial symmetry
Advantages:
The body can obtain food from all directions
Stimuli can be observed in all directions for protection and catching of prey
Disadvantages:
Movement is slow and ineffective
No concentrated nervous system
Cephalisation does not
occur
What are the advantages and disadvantages of bilateral symmetry
Advantages:
Cephalisation causes the sensory organs to be concentrated in the front of the body
Movement is very fast and effective
Disadvantages:
Due to cephalisation the organisms may have blind spots (cannot see behind themselves)
