Body Plans of Animals in the Animal Kingdom
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KNOWLEDGE AREA: Diversity,
change and continuity
TOPIC 1: Biodiversity of
Animals
Key features of
Body Plans of Animals
Do you remember the
5 kingdoms
that all living
organisms are classified into?
They are:
1.
Monera
2.
Protista
3.
Fungi
4.
Plantae
5.
Animalia
Organisms
are
classified
according to certain
common characteristics
, for example all the
prokaryotes belong to the Kingdom Monera
.
However we find that
all the organisms
in the
kingdom are not identical
.
They do have
some differences
.
Therefore within
each kingdom
there are
many
large groups
.
These
large
groups
are called
phyla
. (singular
phylum)
The organisms that belong to a
single phylum
share some common characteristics
.
But the
organisms
that
belong to each phylum
are
not identical as well
.
The next slide shows you all the phyla of the
animal kingdom.
This year we will only look at the body plan of 6
phyla.
These are:
1.
Porifera
2.
Cnidara
3.
Platyhelminthes
4.
Annelida
5.
Arthropoda
6.
Chordata.
Morphology and development
are the features
that are often used to
classify organisms
into
groups
.
Morphology
refers to the
external and internal
structural characteristics
.
The
morphological and developmental
characteristics
that are used for
classification
are
as follows:
1.
Symmetry and cephalisation.
2.
Number of tissue layers.
3.
Coelom and blood systems.
4.
Number of openings in the gut.
The
combination
of a
set of morphological and
developmental characteristics
into a
functioning organisms
is referred to an
organism’s
body plan
.
The
body plan of organisms
can be used to
determine its level
of
complexity
.
Or we can say to determine its level of
organization
.
Symmetry
is when
an
organism
can be
divided into 2 identical
halves
.
Some organisms
do not
have a regular shape
.
Therefore these
organisms
do not have
any symmetry
.
We call them
asymmetrical
,
like the sponges shown
alongside.
Animals that have a
circular or radial body
plan show radial
symmetry
.
Radial
symmetry
is when
the
animal
can be
cut
along any vertical plane
through the centre to
form two identical halves
,
for example the sea
anemone shown
alongside.
Animals that show
radial symmetry
have
no
heads or tails
.
In other words they
do not
have
posterior or
anterior ends
.
Remember we mentioned earlier that their
body
parts have a circular arrangement
, this means
that all their
body parts even the sense organs
are evenly distributed through out the body
.
This allows the animal to
sense danger and food
from any direction
.
This means that they will be able to
react to
danger coming from any direction
.
Radial symmetry
is very
important to
animals that do not move
.
Since it
allows the organism to sense food
and danger from any direction
and
to react
to food or danger from any direction
.
These animals that
do not move
are called
sessile
.
Radial symmetry
is also important to the
planktonic animals
that
drift or swim
weakly in the water
.
Some
animals can be cut into
2 identical halves in the
central longitudinal plane.
This is called
bi-lateral
symmetry
.
This means that the
animal
can be cut from the top of
the ventral surface to the
bottom of the dorsal surface
into 2 identical halves
.
Animals in the phylum
Platyhelminthes, Annelida,
Arthropoda and Chordata
show bi-lateral symmetry.
Animals that show bi-lateral symmetry
have 2
important developments
over other organisms.
The
sense organs
are
accumulated at one end of
the body
.
The end that has the
sense organs
is called the
anterior end
and the opposite end is called the
posterior end
.
This means that the
anterior end is different from
the posterior end
.
So the animal now has a
definite anterior and
posterior end
.
The
accumulation of sense organs
at
one end
of
the body is referred to as
cephalisation
.
Cephalisation
lead to the
development
of a
central nervous system
.
The second development that led to bi-lateral is
the
differentiation of the upper and lower
surfaces
.
The
upper surface
is the
ventral surface
.
The
lower surface
is called the
dorsal surface
.
Different dorsal and ventral surfaces
is known as
dorso-ventral differentiation
.
The presence of
dorso-ventral differentiation
and
cephalisation
meant that these organisms have
definite left and right sides
.
Organisms
with
bi-lateral symmetry
are able to
crawl, burrow, swim and fly.
This type of movement needs to be
co-ordinated
by a complex nervous system.
Name and explain the development that lead to
bi-lateral symmetry.
The two developments that led to bi-lateral
symmetry were:
1.
The accumulation of sense organs at one end of
the body. This is known as as cephalisation.
2.
The differentiation between the dorsal and
ventral surfaces. This is called dorso-ventral
differentiation.
Here we are talking about the
number of tissue
layers
that develop in the
embryonic stage
.
Remember that the
zygote
that is formed during
sexual reproduction
is made up of
1 cell only
.
The
zygote
needs to
develop
into a
multicellular
organism
.
Once it becomes
multicellular
then the
cells need
to differentiate
so that the
different organs and
the tissues
needed by the body can
develop
.
But
before differentiation
occurs
the
cells
need to
become
arranged into layers
.
These layers are called the
germ
layers
.
Sometimes in some organisms the
cells arrange themselves into
two
layers.
These
2 layers
are an
outer layer
called the
ectoderm
and an
inner
layer
called the
endoderm
.
Animals that have only
2 germ
layers
are called
diploblastic.
Can you name some diploblastic
animals?
gut
Diploblastic
organism
They are sea anemones, blue bottles and jelly fish.
In some animals there
are
3 germ layers
.
The ectoderm and
endoderm are
separated by a
middle
layer called the
mesoderm
.
Animals who have
3
germ layers
are called
triploblastic.
All
bi-laterally
symmetrical animals
are
triploblastic
.
Triploblastic animal
Ectoderm
gives rise to the
outer covering of the
organism
.
In some cases it
also gives rise
to the
central
nervous system
.
The
endoderm
gives rise to the
gut lining and all
the organs that arise from the gut
.
The
mesoderm
gives rise to the
muscles and most
of the organs
that are found
between
the
digestive tract and the outer body covering
.
Diploblastic animals
do
not have body cavities
.
They
only have a gut
as
shown in the picture
alongside.
The
gut
is
not a body
cavity
.
A
body cavity
is a
fluid
space
found
between
the digestive tract and
the ectoderm
.
This
body cavity
is called
a
coelom
.
GUT
There are
2 types
of
coeloms
.
These are
true coeloms
and
pseudocoeloms
.
A
true coelom
is a
body
cavity
that is
surrounded
by mesoderm
as shown in
the diagram alongside
.
Some triploblastic animals
such as vertebrates,
annelids and arthropods
have coeloms.
Animals that have
true
coeloms
are called
coelomates
.
However some
triploblastic animals
do not have true
coeloms
.
These animals have
body cavities
that are
lined by mesoderm
on one side only
.
This type of body
cavity is called a
pseudocoelom
.
Animals that
do not
have either type of
coelom are called
acoelomates
.
The animals found in
the phylum
Platyhelminthes
are
examples of
acoelmates
.
FUNCTIONS OF A BODY CAVITY
:
The
body cavity creates space
for the
development of internal organs
.
It
separates
the
gut wall from the body wall
so
that each wall can
function independently
.
The
fluid
found within the
body cavity
acts as a
skeleton
. This type of skeleton where the
muscles
contract and relax against a fluid
is called a
hydrostatic skeleton
.
The fluid also act as a
cushion for the organs
,
preventing injury
.
The
separation of the gut wall from the body wall
also means that the
distance between the two
walls has increased
.
This means that
diffusion is no longer
an
effective
means of transport
.
It also means that
excretory waste can no longer
simply diffuse out of the body
.
These problems were solved in the following way:
1.
A
transport system
was developed to
transport gases
from the
body wall to the gut
wall
because some animals (earthworm) used
the
skin as a gas exchange surface
. The
transport system is also used to
transport food
from the gut wall to the body wall
.
2.
An
excretory system
was developed to
get
rid of nitrogenous waste
.
BLIND GUT: What is it?
Some animals have a
gut with only
1
opening
.
This
opening
is usually called the
mouth
.
Food enters and undigested food leaves
the body
through the same opening
.
This type of gut is called a
blind gut
.
Cnidarians and some free living Platyhelminthes
are some examples of animals with a blind gut.
BLIND GUT: Disadvantages:
Since the
digested and undigested food enters
and leaves through the same opening
, there is a
mixing of the digested and undigested food
.
This occurs because the
digested and undigested
food moves in 2 directions
.
This means that the
gut cannot become
specialized
.
That is the
gut cannot have separate regions for
separate functions
.
THROUGH GUT: What is it?
Some animals have a
gut with
2
openings
.
These
2 openings
are called a
mouth and anus
.
The
food enters
the animal through the
mouth
and
undigested food leaves
the body through the
anus
.
This means that
food travels
in
1 direction only
, it
enters through the mouth and leaves through the
anus.
This type of gut is called a
through gut
.
THROUGH GUT: Advantages:
Since the
food moves in only 1 direction
specialization of the gut can occur
.
The
different regions become adapted
(specialized)
for
different functions
.
This allows for
digestion to occur all the time
,
even when ingestion and egesting occurs
.
This lead to
greater efficiency
.
Phyla
: Large groups of organisms with similar
characteristics within the kingdom.
Morphology
: refers to the external and internal
structural characteristics.
Body plan
: refers to the combination of a set of
morphological and developmental characteristics into
a functioning whole.
Symmetry
: is when an organism can be divided into 2
identical halves.
Asymmetrical
: refers to an organism with no
symmetry.
Radial symmetry
: is when the animal can be cut along
any vertical plane through the centre to form two
identical halves.
Sessile: these are animals that do not move.
Bi-lateral symmetry
: refers to animals can be cut into
2 identical halves in the central longitudinal plane.
Cephalisation
: refers to the accumulation of sense
organs at one end of the body.
Dorso-ventral differentiation
: is when the dorsal and
ventral surfaces of the organism are different from
each other.
Diploblastic animals
: are animals that have only 2
germ layers.
Triploblastic animals
: are those who have 3 germ
layers.
True coelom
:
is a body cavity that is surrounded by
mesoderm
Pseudo-coelom
: refers to body cavities that are lined
by mesoderm on one side only.
Acoelomate
: are animals that do not have coelom.
Hydrostatic skeleton
: is a type of skeleton where the
muscles contract and relax against a fluid.
Blind gut
: is a gut with only 1 opening
Through gut
: is a gut with 2 openings
Animals that have an irregular shape are …
A. Symmetrical
B. Radially symmetrical
C. Bi-laterally symmetrical
D. Asymmetrical
That animals that have a regular shape maybe…
A. Symmetrical
B. Asymmetrical
C. Both A and B
D. None of the above
Accumulation of sense organs at one end of the body is called…
A. Dorso-ventral differentiation
B. Cephalisation
C. Radial symmetry
D. None of the above
A gut that has 2 openings is called…
A. Stomach
B. Intestine
C. Blind gut
D. Through gut
_________ leads to bi-lateral symmetry…
A. Through gut and blind gut
B. Acoelomate and coelom
C. Cephalisation and dorso-ventral differentiation
D. A and B only
Dorso-ventral differentiation refers to…
A. Cells that have been differentiated
B. Cells that are still meristematic
C. A dorsal surface that is different from the
ventral surface
D. Organisms that show bi-lateral symmetry.
A through gut allows for…
1. mixing of food
2. differentiation to occur
3. food to move in one direction
A. 1 & 3
B. 3 & 2
C. 1 & 2
D. 1 only
The disadvantage of presence of a coelom is…
A. The animal becomes larger
B. Diffusion can no longer be used as a
transport
system
C. Food travels in 1 direction only
D. None of the above
The fluid space that lies between the digestive tract and the
outer wall and is lined by the mesoderm on one side only is
the…
A. Coelom
B. True coelom
C. Pseudocoelom
D. gut
A fluid filled space that lies between the gut wall and the outer wall
and is surrounded by the mesoderm on one side only is the…
A. Coelom
B. True coelom
C. Pseudocoelom
D. Gut
Animals which arise from 2 germ layers are…
A. Acoelomate
B. Diploblastic
C. Triploblastic
D. A and B
Animals that arise from 3 germ layers are…
A. Acoelomate
B. Diploblastic
C. Triploblastic
D. A and B
The germ layer that gives rise to muscles and internal
organs other than those of the digestive tract is…
A. Ectoderm
B. Mesoderm
C. Endoderm
D. Both B and C
The germ layer that gives rise to outer coverings of the animal
is…
A. Ectoderm
B. Mesoderm
C. Endoderm
D. Both B and C
The germ layer that gives rise to the lining of the
digestive tract is…
A. Ectoderm
B. Mesoderm
C. Endoderm
D. Both B and C
1.
D
2.
A
3.
B
4.
D
5.
C
6.
C
7.
B
8.
B
9.
B
10.
C
11.
D
12.
C
13.
B
14.
A
15.
C
Introduction to the diverse phyla within the Animal Kingdom, highlighting key features of body plans such as symmetry, cephalization, tissue layers, coeloms, and gut types. Exploring the classification system through common characteristics shared within phyla and the significance of morphology in grouping organisms.
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Presentation Transcript
LIFE SCIENCES GRADE 11 CAPS STRUCTURED, CLEAR, PRACTICAL - HELPING TEACHERS UNLOCK THE POWER OF NCS KNOWLEDGE AREA: Diversity, change and continuity TOPIC 1: Biodiversity of Animals Key features of Body Plans of Animals
SUMMARY OF PRESENTATION The term phylum Introduction to the Animal Kingdom Key features of the body plans of animals Symmetry and Cephalisation Number of Tissue Layers in Embryo Coeloms and blood systems Type of Gut based on Number of Openings
PHYLUM: Do you remember the 5 kingdoms that all living organisms are classified into? They are: Monera Protista Fungi Plantae Animalia Organisms are classified according to certain common characteristics, for example all the prokaryotes belong to the Kingdom Monera. 1. 2. 3. 4. 5.
PHYLUM: However we find that all the organisms in the kingdom are not identical. They do have some differences. Therefore within each kingdom there are many large groups. These large groups are called phyla. (singular phylum) The organisms that belong to a single phylum share some common characteristics. But the organisms that belong to each phylum are not identical as well.
INTRODUCTION TO THE ANIMAL KINGDOM The next slide shows you all the phyla of the animal kingdom.
INTRODUCTION TO THE ANIMAL KINGDOM Phylum Porifera Phylum Cnidara Phylum Invertebrates Platyhelminthes Phylum Nematoda Kingdom Animalia Phylum Annelida Phylum Mollsuca Phylum Arthropoda Phylum Echinoderma Phylum Chordata Vertebrate
INTRODUCTION TO THE ANIMAL KINGDOM This year we will only look at the body plan of 6 phyla. These are: Porifera Cnidara Platyhelminthes Annelida Arthropoda Chordata. 1. 2. 3. 4. 5. 6.
KEY FEATURES IN RESPECT OF BODY PLANS OF ANIMALS. Morphology and development are the features that are often used to classify organisms into groups. Morphology refers to the external and internal structural characteristics. The morphological and developmental characteristics that are used for classification are as follows: Symmetry and cephalisation. Number of tissue layers. Coelom and blood systems. 1. 2. 3.
KEY FEATURES IN RESPECT OF BODY PLANS OF ANIMALS. Number of openings in the gut. The combination of a set of morphological and developmental characteristics into a functioning organisms is referred to an organism s body plan. The body plan of organisms can be used to determine its level of complexity. Or we can say to determine its level of organization. 4.
SYMMETRY AND CEPHALISATION Symmetry is when an organism can be divided into 2 identical halves. Some organisms do not have a regular shape. Therefore these organisms do not have any symmetry. We call them asymmetrical, like the sponges shown alongside.
SYMMETRY AND CEPHALISATION Animals that have a circular or radial body plan show radial symmetry. Radial symmetry is when the animal can be cut along any vertical plane through the centre to form two identical halves, for example the sea anemone shown alongside.
SYMMETRY AND CEPHALISATION Animals that show radial symmetry have no heads or tails. In other words they do not have posterior or anterior ends. Remember we mentioned earlier that their body parts have a circular arrangement, this means that all their body parts even the sense organs are evenly distributed through out the body. This allows the animal to sense danger and food from any direction. This means that they will be able to react to danger coming from any direction.
SYMMETRY AND CEPHALISATION Radial symmetry is very important to animals that do not move. Since it allows the organism to sense food and danger from any direction and to react to food or danger from any direction. These animals that do not move are called sessile. Radial symmetry is also important to the planktonic animals that drift or swim weakly in the water.
SYMMETRY AND CEPHALISATION Some animals can be cut into 2 identical halves in the central longitudinal plane. This is called bi-lateral symmetry. This means that the animal can be cut from the top of the ventral surface to the bottom of the dorsal surface into 2 identical halves. Animals in the phylum Platyhelminthes, Annelida, Arthropoda and Chordata show bi-lateral symmetry.
SYMMETRY AND CEPHALISATION Animals that show bi-lateral symmetry have 2 important developments over other organisms. The sense organs are accumulated at one end of the body. The end that has the sense organs is called the anterior end and the opposite end is called the posterior end. This means that the anterior end is different from the posterior end. So the animal now has a definite anterior and posterior end.
SYMMETRY AND CEPHALISATION The accumulation of sense organs at one end of the body is referred to as cephalisation. Cephalisation lead to the development of a central nervous system. The second development that led to bi-lateral is the differentiation of the upper and lower surfaces. The upper surface is the ventral surface. The lower surface is called the dorsal surface. Different dorsal and ventral surfaces is known as dorso-ventral differentiation.
SYMMETRY AND CEPHALISATION The presence of dorso-ventral differentiation and cephalisation meant that these organisms have definite left and right sides. Organisms with bi-lateral symmetry are able to crawl, burrow, swim and fly. This type of movement needs to be co-ordinated by a complex nervous system.
SOMETHING FOR YOU TO DO: Name and explain the development that lead to bi-lateral symmetry.
SOLUTION: The two developments that led to bi-lateral symmetry were: The accumulation of sense organs at one end of the body. This is known as as cephalisation. The differentiation between the dorsal and ventral surfaces. This is called dorso-ventral differentiation. 1. 2.
NUMBER OF TISSUE LAYERS: Here we are talking about the number of tissue layers that develop in the embryonic stage. Remember that the zygote that is formed during sexual reproduction is made up of 1 cell only. The zygote needs to develop into a multicellular organism. Once it becomes multicellular then the cells need to differentiate so that the different organs and the tissues needed by the body can develop.
NUMBER OF TISSUE LAYERS: But before differentiation occurs the cells need to become arranged into layers. These layers are called the germ layers. Sometimes in some organisms the cells arrange themselves into two layers. gut These 2 layers are an outer layer called the ectoderm and an inner layer called the endoderm. Diploblastic organism Animals that have only 2 germ layers are called diploblastic. Can you name some diploblastic animals?
SOLUTION: They are sea anemones, blue bottles and jelly fish.
NUMBER OF TISSUE LAYERS: In some animals there are 3 germ layers. The ectoderm and endoderm are separated by a middle layer called the mesoderm. Animals who have 3 germ layers are called triploblastic. All bi-laterally symmetrical animals are triploblastic. Triploblastic animal
NUMBER OF TISSUE LAYERS: Ectoderm gives rise to the outer covering of the organism. In some cases it also gives rise to the central nervous system. The endoderm gives rise to the gut lining and all the organs that arise from the gut. The mesoderm gives rise to the muscles and most of the organs that are found between the digestive tract and the outer body covering.
COELOM AND BLOOD SYSTEMS Diploblastic animals do not have body cavities. They only have a gut as shown in the picture alongside. The gut is not a body cavity. A body cavity is a fluid space found between the digestive tract and the ectoderm. This body cavity is called a coelom. GUT
COELOM AND BLOOD SYSTEMS There are 2 types of coeloms. These are true coeloms and pseudocoeloms. A true coelom is a body cavity that is surrounded by mesoderm as shown in the diagram alongside. Some triploblastic animals such as vertebrates, annelids and arthropods have coeloms. Animals that have true coeloms are called coelomates.
COELOM AND BLOOD SYSTEMS However some triploblastic animals do not have true coeloms. These animals have body cavities that are lined by mesoderm on one side only. This type of body cavity is called a pseudocoelom.
COELOM AND BLOOD SYSTEMS Animals that do not have either type of coelom are called acoelomates. The animals found in the phylum Platyhelminthes are examples of acoelmates.
COELOM AND BLOOD SYSTEMS FUNCTIONS OF A BODY CAVITY: The body cavity creates space for the development of internal organs. It separates the gut wall from the body wall so that each wall can function independently. The fluid found within the body cavity acts as a skeleton. This type of skeleton where the muscles contract and relax against a fluid is called a hydrostatic skeleton. The fluid also act as a cushion for the organs, preventing injury.
COELOM AND BLOOD SYSTEMS The separation of the gut wall from the body wall also means that the distance between the two walls has increased. This means that diffusion is no longer an effective means of transport. It also means that excretory waste can no longer simply diffuse out of the body.
COELOM AND BLOOD SYSTEMS These problems were solved in the following way: A transport system was developed to transport gases from the body wall to the gut wall because some animals (earthworm) used the skin as a gas exchange surface. The transport system is also used to transport food from the gut wall to the body wall. 1. An excretory system was developed to get rid of nitrogenous waste. 2.
NUMBER OF OPENINGS IN THE GUT BLIND GUT: What is it? Some animals have a gut with only 1 opening. This opening is usually called the mouth. Food enters and undigested food leaves the body through the same opening. This type of gut is called a blind gut. Cnidarians and some free living Platyhelminthes are some examples of animals with a blind gut.
NUMBER OF OPENINGS IN THE GUT BLIND GUT: Disadvantages: Since the digested and undigested food enters and leaves through the same opening, there is a mixing of the digested and undigested food. This occurs because the digested and undigested food moves in 2 directions. This means that the gut cannot become specialized. That is the gut cannot have separate regions for separate functions.
NUMBER OF OPENINGS IN THE GUT THROUGH GUT: What is it? Some animals have a gut with 2 openings. These 2 openings are called a mouth and anus. The food enters the animal through the mouth and undigested food leaves the body through the anus. This means that food travels in 1 direction only, it enters through the mouth and leaves through the anus. This type of gut is called a through gut.
NUMBER OF OPENINGS IN THE GUT THROUGH GUT: Advantages: Since the food moves in only 1 direction specialization of the gut can occur. The different regions become adapted (specialized) for different functions. This allows for digestion to occur all the time, even when ingestion and egesting occurs. This lead to greater efficiency.
TERMINOLOGY: Phyla: Large groups of organisms with similar characteristics within the kingdom. Morphology: refers to the external and internal structural characteristics. Body plan: refers to the combination of a set of morphological and developmental characteristics into a functioning whole. Symmetry: is when an organism can be divided into 2 identical halves. Asymmetrical: refers to an organism with no symmetry.
TERMINOLOGY: Radial symmetry: is when the animal can be cut along any vertical plane through the centre to form two identical halves. Sessile: these are animals that do not move. Bi-lateral symmetry : refers to animals can be cut into 2 identical halves in the central longitudinal plane. Cephalisation: refers to the accumulation of sense organs at one end of the body. Dorso-ventral differentiation: is when the dorsal and ventral surfaces of the organism are different from each other. Diploblastic animals: are animals that have only 2 germ layers.
TERMINOLOGY: Triploblastic animals : are those who have 3 germ layers. True coelom: is a body cavity that is surrounded by mesoderm Pseudo-coelom: refers to body cavities that are lined by mesoderm on one side only. Acoelomate: are animals that do not have coelom. Hydrostatic skeleton: is a type of skeleton where the muscles contract and relax against a fluid. Blind gut: is a gut with only 1 opening Through gut: is a gut with 2 openings
QUESTION 1 Animals that have an irregular shape are A. Symmetrical B. Radially symmetrical C. Bi-laterally symmetrical D. Asymmetrical
QUESTION 2 That animals that have a regular shape maybe A. Symmetrical B. Asymmetrical C. Both A and B D. None of the above
QUESTION 3 Accumulation of sense organs at one end of the body is called A. Dorso-ventral differentiation B. Cephalisation C. Radial symmetry D. None of the above
QUESTION 4 A gut that has 2 openings is called A. Stomach B. Intestine C. Blind gut D. Through gut
QUESTION 5 _________ leads to bi-lateral symmetry A. Through gut and blind gut B. Acoelomate and coelom C. Cephalisation and dorso-ventral differentiation D. A and B only
QUESTION 6 Dorso-ventral differentiation refers to A. Cells that have been differentiated B. Cells that are still meristematic C. A dorsal surface that is different from the ventral surface D. Organisms that show bi-lateral symmetry.
QUESTION 7 A through gut allows for 1. mixing of food 2. differentiation to occur 3. food to move in one direction A. 1 & 3 B. 3 & 2 C. 1 & 2 D. 1 only
QUESTION 8 The disadvantage of presence of a coelom is A. The animal becomes larger B. Diffusion can no longer be used as a transport system C. Food travels in 1 direction only D. None of the above
QUESTION 9 The fluid space that lies between the digestive tract and the outer wall and is lined by the mesoderm on one side only is the A. Coelom B. True coelom C. Pseudocoelom D. gut
QUESTION 10 A fluid filled space that lies between the gut wall and the outer wall and is surrounded by the mesoderm on one side only is the A. Coelom B. True coelom C. Pseudocoelom D. Gut
QUESTION 11 Animals which arise from 2 germ layers are A. Acoelomate B. Diploblastic C. Triploblastic D. A and B
QUESTION 12 Animals that arise from 3 germ layers are A. Acoelomate B. Diploblastic C. Triploblastic D. A and B
