Animal Diversity KEY FEATURES OF BODY PLANS ABBOTTS COLLEGE PAGE 73.
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Transcript of Animal Diversity KEY FEATURES OF BODY PLANS ABBOTTS COLLEGE PAGE 73.
Animal DiversityKEY FEATURES OF BODY PLANS
ABBOTTS COLLEGE
PAGE 73
DARWINS THEORY OF EVOLUTION
Organisms are descended from common ancestors
This theory guides scientists in their search for order in the astounding diversity of animal life on earth
The science of taxonomy names and classifies different species to illustrate this order
PHYLA
Animals can be grouped into phyla according to similarities in various features of their basic structure(body plan)
This makes it possible to understand the evolutionary development of the group
Body plan = the general similarities in development, form and function among members of a particular phylum
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The term phylum is one of seven major categories that are used to classify organisms. In order of broad to specific, these seven categories are: Kingdom, Phylum, Class, Order, Family, Genus, and Species. Carolus Linnaeus developed this system of classification in the 18th century
THE FEATURES OF THE BASIC BODY PLAN INCLUDE:
Body Symmetry Number of tissue layers developed from the
embryo The number of openings in the gut The presence or absence of a coelom (body
cavity) and blood systems
BODY SYMMETRY
The body plans of multicellular organisms are either asymmetrical, radially symmetry or bilaterally symmetrical
Asymmetry: Having no symmetry
Sponges
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ASYMMETRY
Having no symmetry
Sponges
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RADIAL SYMMETRY
the body parts are arranged around a central axis
and can be divided into mirror images by an imaginary line through any vertical plane
RADIAL SYMMETRY
Tubular, vase or bowled shaped animals that have a mouth at one end are usually radial symmetrical
Radial symmetry is common in sessile, free-floating or weakly swimming animals.
They need to interact with their surroundings equally well on all sides
BILATERAL SYMMETRY
the body can only be divided into mirror images by an imaginary line through one plane
If cut lengthwise, the y form left and right halves (mirror images)
Also have a top and a bottom And a front and a back This type of symmetry is suited to animals that
move about
BILATERAL SYMMETRY
They show cephalization which allows them to become aware of the environments around them as they move forward
This increases their chance of finding food or predators
Cephalisation = concentration of sense organs, feeding appendages and nervous tissue near the anterior end of the animal
CEPHALIZATION
TISSUE LAYERS
Germ layers formed from developed embryo(zygote)
Upper layer (ectoderm) forms the epithelium of the body surface (skin) and the nervous system
Lower layer (endoderm) forms the wall of the digestive system (gut)
Mesoderm is formed by an interaction between the ectoderm and endoderm
Diploblastic animals only have two layers of tissuesEctoderm and endoderm
Triploblastic animals have three layers of ttissuesEctoderm, mesoderm and endoderm
Why is the development of mesoderm so important?
The development of the mesoderm was a tremendous evolutionary advancement
Mesoderm plays a role in the formation of tissues eg connective tissue, cartilage, bone
and organs eg reproductive organs and systems eg blood and lymph sytems
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NUMBER OF OPENINGS IN THE GUT
Single opening Two openings
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Gut =The alimentary canal or a portion thereof, especially the intestine or stomach.
NUMBER OF OPENINGS IN THE GUT
Single opening Primitive animals Sac like digestive
cavity Take in food and
expel waste out of the same opening
Not an efficient system
Porifera and Cnidarians
NUMBER OF OPENINGS IN THE GUT
Two openings It allows food to be
continually taken through the mouth, digested and the waste released from the anus
This body plan allows specialization of parts along the tube, such as a stomach, intestine, etc.
BODY CAVITIES/COELOM
A coelom is an internal fluid filled body cavity that develops in the mesoderm of triploblastic animals
The coelom separates the digestive tract from the body wall
Diploblastic animals do not have a coelom
In triploblastic animals we distinguish between:
acoelomate, pseudocoelomate and
coelomate animals
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ACOELOMATE ANIMALS
These animals have no coelom (body cavity) in the mesoderm
Can be diploblastic or triploblastic
PSEUDOCOELOMATE
Have a body cavity, Not seen as a true coelom
because it is not completely in the mesoderm
NOT IN TEXTBOOKADD TO WORKBOOK
COELOMATE
Have a body cavity in the mesoderm
They are more advanced than acoelomate animals
ADVANTAGES OF A COELOM
Allows space for larger and more complex organs and systems to develop eg digestive organs, muscular system, blood system and allows animals to reach a considerable size
In soft bodied animals the fluid in the skeleton can act as a hydrostatic skeleton (against which muscles can act)
Allows the digestive system and body wall to move independently
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THE END