answer in 15 minutes

1

Answer in 15 minutes Answer in 15 minutes Write true or false Write true or false (with correct) (with correct)

1- Metazoa Included Parazoa and metazoa .1- Metazoa Included Parazoa and metazoa .2- Metazoa the animals have unicellular body.2- Metazoa the animals have unicellular body.3- Eumetazoa have bilateral symmetry only .3- Eumetazoa have bilateral symmetry only .4- Parazoa cellular organization .4- Parazoa cellular organization .5- Parazoa are not differentiated cells in layers.5- Parazoa are not differentiated cells in layers.6- Parazoa have true tissues .6- Parazoa have true tissues .7- As example of parazoa are clams .7- As example of parazoa are clams .8- Triploblastic have 2 layers .8- Triploblastic have 2 layers .9- Eumetazoa divided to triploblastica and uniblastica .9- Eumetazoa divided to triploblastica and uniblastica .10- Diploblastica have ectoderm , endoderm & mesoderm tissues.10- Diploblastica have ectoderm , endoderm & mesoderm tissues.11- Diploblastic have three tissues .11- Diploblastic have three tissues .12- Triploblastic is important for movement .12- Triploblastic is important for movement .13- Body cavity lying between the body wall and the internal organs .13- Body cavity lying between the body wall and the internal organs .14- Body cavity may be rich of Mesenchyme cells .14- Body cavity may be rich of Mesenchyme cells .15- Bilateral animals having distinct body cavity .15- Bilateral animals having distinct body cavity .16- for example of pseudocoelomates 16- for example of pseudocoelomates AcanthochitonAcanthochiton . .17- Mesenchyme cells are occupying the space between the body wall and the 17- Mesenchyme cells are occupying the space between the body wall and the anus of the animals .anus of the animals .18- The body cavity derived from the gut of the embryo .18- The body cavity derived from the gut of the embryo .19- This cavity is lined by mesodermal epithelium .19- This cavity is lined by mesodermal epithelium .

2

Answer in 15 minutes Answer in 15 minutes Write true or false Write true or false (with correct) (with correct)

20- Ceolom is Internal fluid-filled cavity .20- Ceolom is Internal fluid-filled cavity .21- Ceolomates have body cavity lined with mesoderm .21- Ceolomates have body cavity lined with mesoderm .22- pseudocoelomates have body cavity partially lined with mesoderm .22- pseudocoelomates have body cavity partially lined with mesoderm .23- Schizocoelous are liquid masses of mesoderm split to form the coelomic 23- Schizocoelous are liquid masses of mesoderm split to form the coelomic cavities As the archenteron . cavities As the archenteron . 24- Enterocoelous are not mesoderm buds off from the wall of the 24- Enterocoelous are not mesoderm buds off from the wall of the archenteron and hollows to become the coelomic cavities .archenteron and hollows to become the coelomic cavities .

Lecture 2Lecture 2

4

SyllabusSyllabus•Introduction

•Phylum: Annelida (General charactes)

•Nereis

•Allolobophra caliginosa

•Hirudo medicinalis

•Phylum: Arthropoda (General charactes)

•Astacus fluviatulis & Neptunus pelagious

•Daphnia, Cyclops, Balanus

•Scolopendra morsitans, Lycosa ferox

•Phylum: Mollusca (General characters)

•Acanthochiton spinigira, Helix pomatia

•Loligo peadlii, Anodonta sp.

•Phylum: Echinodermata (General characters)

•Astropecten sp.

5

AimAim What do know about Segmented worms Segmented worms ?? What do know about SegmentationSegmentation ?? What do know about SymmetrySymmetry ?? What do know about Organ Systems Organ Systems ?? What do know about Mechanism/ModeMechanism/Mode of Locomotion of Locomotion ??

What do know about TyphlosoleTyphlosole ? ? What do know about PolychaetaPolychaeta ? ? What do know about Body wall in Polychaeta Body wall in Polychaeta ??

What do know about habitat in Polychaeta habitat in Polychaeta ?? What do know about Organ Systems in Polychaeta Organ Systems in Polychaeta ??

7

RememberRemember

8

Phylum Annelida Phylum Annelida General charactersGeneral characters

9

Segmented wormsSegmented worms 15,000 species15,000 species TriploblasticTriploblastic ProtostomeProtostome Bilateral symmetry with cephalisation obscured in Bilateral symmetry with cephalisation obscured in

some speciessome species Internal body space is partitioned ( Internal body space is partitioned ( - فصل بحاجز - فصل بحاجز

by septaeby septae قسمقسم Marine, freshwater and terrestrial (in moist Marine, freshwater and terrestrial (in moist

soil/humus) speciessoil/humus) species Cutaneous respirationCutaneous respiration

Skin is highly vascularised and must stay moistSkin is highly vascularised and must stay moist


10

is the subdivision of is the subdivision of the body into the body into segmentssegments

Two advantages result from embryonic segmentationTwo advantages result from embryonic segmentation

1- Each segment Each segment may develop a may develop a more or less more or less

complete set of complete set of adult organ adult organ systems .systems .

2-Locomotion is far Locomotion is far more effective more effective

because of because of increased flexibility increased flexibility

of movement of movement ..


SegmentationSegmentation

11



12

body space is partitioned by septaebody space is partitioned by septae



13


SymmetrySymmetry

14

radial symmetryradial symmetry bilateral symmetrybilateral symmetry

the parts of the body are the parts of the body are arranged around a central arranged around a central axisaxis

the body has a right and left the body has a right and left half that are mirror images of half that are mirror images of each othereach other

1-1-Allows different organs to be located in different parts of the Allows different organs to be located in different parts of the body.body.

2-2-Ultimately led to cephalization.Ultimately led to cephalization.

3-3-Evolution of a definite head and brain area.Evolution of a definite head and brain area.


SymmetrySymmetry

15


systemssystems

16

1-Both longitudinal and circular muscle fibers Allows for coordination of propulsive muscular waves in body wall; peristalsis ( حركات تقلصية متتابعة

فى قناة أو انبوب ) فى الجسم لدفع الغذاء أو الفضالت

2-Special muscles attached to setae to move setae

3- In polychaetes, oblique muscle groups run into the parapodia for movement

Phylum Annelida Phylum Annelida General charactersGeneral characters1-1- Muscular System Muscular System

Note

Mechanism/Mode of Mechanism/Mode of LocomotionLocomotion

peristalsis involving the peristalsis involving the alternating contractions of alternating contractions of longitudinal and circular longitudinal and circular

musclemuscle* layers to change the shape * layers to change the shape

of individual segmentsof individual segments* Burrowing and creeping * Burrowing and creeping using peristalsis and/or using peristalsis and/or

parapodiaparapodia

17

Integumentary System (skin) 1- Cellular epidermis that secretes a mucus 2-Thickened, non-living transparent cuticle 3-Cilia present in many forms chitinous setae often present; setae absent

in leeches; greater number of setae in 4-As compared to oligochaetes

Allows for coordination of propulsive muscular wavesAllows for coordination of propulsive muscular waves

Coelom is fluid-filled spaceCoelom is fluid-filled space


18


Integumentary System Integumentary System (skin((skin(

19


Note Not all organ systems Not all organ systems are metameric (are metameric ( ينقسم ينقسم

أجزاء إلىإلى أو أجزاء مفصصات أو مفصصاتمتتابعة متتابعة متماثلة متماثلة

الجسم الجسم علىامتداد علىامتداداألرض دودة األرض كجسم دودة ((كجسم

For example: the For example: the digestive system digestive system

extends the length of extends the length of the organism and is the organism and is

differentiated along its differentiated along its length .length .

20


21


Nervous SystemNervous System

1-1- Consists of a brain .Consists of a brain . 2-2- cerebral ganglia with two cerebral ganglia with two

fused ventral nerve cords .fused ventral nerve cords . 3-3- various ganglia similar to various ganglia similar to

arthropods .arthropods . ((ganglion in each segment ganglion in each segment

(metameric))(metameric)) 4-4- leeches have an anterior leeches have an anterior

brain of six pairs of fused brain of six pairs of fused ganglia and a posterior brain ganglia and a posterior brain of seven pairs of fused of seven pairs of fused

ganglia ganglia ..

22

Phylum Annelida Phylum Annelida General characters General characters

Sensory OrgansSensory Organs sensory tentacles Palps Eyespots in polychaetes (Especially on prostomium)

23

Phylum Annelida Phylum Annelida General characters General characters Circulatory System

1- 1- closed circulatory closed circulatory system that is system that is segmentally arranged segmentally arranged with aortic arches with aortic arches (“hearts”)(“hearts”)

2-2- and ventral and dorsal and ventral and dorsal blood vesselsblood vessels surrounding pharynxsurrounding pharynx for for circulating bloodcirculating blood

3-3- blood contains blood contains respiratory pigments respiratory pigments including hemoglobinincluding hemoglobin

4-4- Blood with haemoglobin Blood with haemoglobin as Oas O22-carrying molecule-carrying molecule

24


Respiratory System (gas exchange)Respiratory System (gas exchange)

25

gas exchange by simplesimple diffusiondiffusion = cutaneouscutaneous respirationrespiration and/or

Gills in some polychaetes and/or

parapodia in polychaetes act as gills = example of convergent evolution to appendages

and specializedspecialized gillsgills seen inin arthropodsarthropods

Phylum Annelida Phylum Annelida General characters General characters Digestive System Digestive System

(food/water supply((food/water supply( Complete digestive system

with mouth and anus, not segmentally arranged

well muscularized pharynx in oligochaetes

Crop for storage, Gizzard for grinding and TyphlosoleTyphlosole with increase surface area for absorption in oligochaetes

In oligochaetes, ingested soil may contain high levels of calcium; calciferous glands along esophagus secrete calcium ions into gut to reduce calcium ion concentration and maintain acid-base balance in blood

26

In tube worm polychaetes, specialized feathery arms or radioles use ciliary actionهدبي

Mucous to trap food particles of a digestible size

leeches are parasitic, but also predaceous and scavenging on fluids and tissuesتنظيف

terrestrial leeches feed on insect larvae, earthworms and slugs

27

Phylum Annelida Phylum Annelida General characters General characters Digestive System Digestive System

(food/water supply((food/water supply(


Digestive System (food/water supply)Digestive System (food/water supply)

TyphlosoleTyphlosole

28


Immune SystemImmune System

Ameobocytes found in blood

29

Phylum Annelida Phylum Annelida General characters General characters Excretory SystemExcretory System

Well developed metanephridia in most segments that involves removal of wastes from the blood and the coelom .

Generally have metanephridia; some have protonephridia each metanephridium has a ciliated funnel or nephrostome that leads by a small ciliated tubule through the septum in to the segment behind to a nephric tubule that empties into a bladder and waste is excreted out a nephridiopore (opening) .

Aquatic annelids secrete ammonia . Terrestrial oligochaetes secrete less

toxic urea . Osmoregulation occurs via the body

surface and the nephridia .

30


Reproductive SystemReproductive System -Monoecious in oligochaetes and leeches

(Hirudinae) with internal fertilization and direct development (no larval stage = juvenile worms look like mini adults)

-Dioecious ( ثنائي البيت اي ان اعضاءالتذكير التناسلية في فرد واعضاء التأنيث in polychaetes (التناسلية في فرد اخرwith external fertilization and formation of a trochophore larva .

-Asexual = most highly organized animals capable of complete regeneration.

- This ability varies considerably within the phylum.

- Evolutionarily, regenerative capability has been lost in many species.

-Both anterior (tail to head) and posterior (head to tail)

-Segment regeneration has been shown in some species.

31


Reproductive SystemReproductive System Hermaphrodites - with Hermaphrodites - with

cross fertilizationcross fertilization Clitellum is a special Clitellum is a special

region at the anterior end region at the anterior end of the worm that of the worm that

1-1-secretes a mucus secretes a mucus cocoon, cocoon,

2-2-both during mating (to both during mating (to hold the worms together) hold the worms together)

3-3-protective coat around protective coat around eggs eggs

Trochophore is typical Trochophore is typical larval stagelarval stage

32


Major ClassesMajor Classes

33


PolychaetaPolychaeta

1- (pol'e-ke'ta) (Gr. polys, many, + chaiti?, long hair).

2- About 5300 species. 3- Segmented inside and out; parapodia used in used in

locomotionlocomotion with many large number of chitinous bristles setae

4- Distinct head with eyes 5- palps, and tentacles 6- No clitellum 7- Separate sexes 8- Trochophore larva usually present 9- Mostly marine. 10- Examples: Nereis

34


PolychaetaPolychaeta

Well - developed head .Well - developed head . **ProstomiumProstomium is well equipped is well equipped

with sensory and feeding with sensory and feeding structures .structures .

JawsJaws

TeethTeeth

Postomial tentachelsPostomial tentachels

Peristomial palpsPeristomial palps

Peristomial tentachelsPeristomial tentachels

35


Polychaeta Polychaeta Body wall

It consists of an outer cuticle which is secreted by :

The cells of the hypodermis just beneath

it .

several muscular layers under the hypodermis

36


Polychaeta Polychaeta 1- BristleBristle worms worms 2- Mostly Mostly marinemarine 3- Most free-living (living in Most free-living (living in

substrate or free-swimming), substrate or free-swimming), but some live in mucus-but some live in mucus-supported tubes that are supported tubes that are surrounded by substratesurrounded by substrate

4-Many are active Many are active predatorspredators, , while others are while others are filter filter feedersfeeders

37


Polychaeta Polychaeta Habitat Habitat

Many crawl on or burrow Many crawl on or burrow in the seafloor.in the seafloor.

A few drift and swim in A few drift and swim in the plankton.the plankton.

Polychaetes include Polychaetes include carnivorescarnivores, , scavengersscavengers, , and and planktivoresplanktivores..

The brightly colored The brightly colored fanworms trap planktonon fanworms trap planktonon feathery tentacles.feathery tentacles.

38


Polychaeta Polychaeta systems

39


Polychaeta Polychaeta Nervous SystemNervous System

1-dorsal brain (brain is fund above the pharynx in the head whis is consists of a pair of supra

pharynx geal ganglia. - it is connected with a pair of sub pharyngeal ganglia by acircumpharyngeal

commissure on either side which from aring around the pharynx) .

2- ventral, with a pair of ganglia 3-solid nerve cord, with ganglia in each segment. 4- Endocrine- hormones secreted by nervous system. The brain gives off:- A- An optic nerve to each eye B- Palpal nerve to each palpus C- Atentacular nerve to each group of tentacles. 5- Three pairs of nerves arise from each of ganglia of the ventral nerve chain - One pair to 1- the parapodia 2- the anterior segment 3- the muscles of the segment

40


Polychaeta Polychaeta Nervous SystemNervous System

41


Polychaeta Polychaeta Digestive systemDigestive system

42



1- The mouth opens into the pharynx which forms assort of proboscis .

(This is accomplished by protractor and retractor muscles ).

2- The pharynx leads into a slender esophagus which have digestive gland .

3 - Straight stomach following the esophagus

it extending to the anus .

43



Feeding:Feeding:

Clamworms (Clamworms (NereisNereis) crawl ) crawl about on marine surfaces about on marine surfaces hunting for food using hunting for food using well-developed sensory well-developed sensory structures. Once located, structures. Once located, prey are seized with prey are seized with chitinous jaws on a rapidly chitinous jaws on a rapidly everted, muscular pharynxeverted, muscular pharynx

44



Note• Digestive Digestive

system system

• Includes a Includes a muscular muscular pharynx pharynx

that can be that can be everted everted through through

the mouththe mouth

45


Polychaeta Polychaeta Circulatory SystemCirculatory System

Closed system Use hemoglobin as oxygen carrier.

46


Polychaeta Polychaeta Circulatory SystemCirculatory System

1- The blood is contained in contractile tube ( the blood vessels ).

2- There is a dorsal vessel , that lies between the two dorsal longitudinal muscles bands ( which carried blood anteriorly ).

3- A ventral vessel below the intestine which carries blood posteriorly.

4- In each segment , the longitudinal vessels are connected on either by right and left transverse vessels to form

networks of capillaries in parapodia.

47

QuizQuiz

48

AnswerAnswer

1-1- Parapodium Parapodium 11- 11- Ventral blood vesselVentral blood vessel

2-2- Coelom Coelom 12- 12- Circular muscleCircular muscle

3-3- Dorsal blood vessel Dorsal blood vessel 13- 13- Cuticle Cuticle

4-4- Intestine Intestine 14- 14- NephridiumNephridium

5-5- Longitudinal muscle Longitudinal muscle 15- 15- NephridioporeNephridiopore

6-6- Capillary ped in parapodium Capillary ped in parapodium 16- SetaeSetae

7-7- Notopodium Notopodium

8-8- Neuropodium Neuropodium

9- 9- Transverse parapodial muscleTransverse parapodial muscle

10-10-Venteral nerve cordVenteral nerve cord49


Polychaeta Polychaeta Respiratory systemRespiratory system

• Although many of the Although many of the smaller polychaetes lack smaller polychaetes lack respiratory structures, the respiratory structures, the larger one do possess gillslarger one do possess gills

• Gills are usually Gills are usually modifications of the modifications of the parapodiaparapodia

50


PolychaetaPolychaeta Excretory SystemExcretory System

Every segment contains a pair of nephridia except the peristomium and the anal segment .

Each nephridium opens into the coelomic cavity by means of a ciliated funnel.

Each nephridium passes posteriorly through the septum into the following segment. Where it forms coiled tube .

It opens at the base of aparapoium on the ventral surface through nephridiopore.

51


Polychaeta Polychaeta ReproductionReproduction

1- Sexes are separate. 2- No well _ defined gonads are present but

during breeding season ova or spermatozoa arise from the wall of the coelom in each segment except near the anterior end.

3- At this time the worm is differentiated into 2 regions:

An anterior atoke. A posterior epitoke which contains the gonads. 4- The specialized worm is called aheteronereid. 5- Fertilization occurs (external external ) in the open

water. 6- Trochophore larvae develop from the

fertilized eggs.

52



53



EpitokyEpitoky Morphological changes Morphological changes that take place in many that take place in many polychaetes associated polychaetes associated with the reproductive activity with the reproductive activity in tube-dwelling speciesin tube-dwelling species At breeding time, many At breeding time, many

morphological changes morphological changes associated with swimming associated with swimming allow the worms to leave their allow the worms to leave their tubes and swarm to the tubes and swarm to the surface of sea for matingsurface of sea for mating

54

General viewGeneral view

55

1-1- Annelida are Annelida are ……………. , ………….. , ………… ……………. , ………….. , ………… andand ……… ……… wormsworms . 2-2- What the meaning of cutaneous respiration ? 3-3- What the meaning of Segmentation ? 4-4- What the advantages result from embryonic segmentation ? 5-5- Body space is partitioned by Body space is partitioned by ………………………… . 6-6- What the meaning of Symmetry ? 7-7- Compare between two type of Symmetry ? 8-8- Symmetry are Symmetry are …………………………………… and and …………..………….. . 9- 9- What the important of Symmetry ? 1010- What are the systems of Annelida ? 11-11- Both longitudinal and Both longitudinal and …………………………………………………………..allows for coordinationallows for coordination of propulsive muscular waves in of propulsive muscular waves in ………………………….…………………………. . Special muscles attached to Special muscles attached to ……………………. to move it to move it . 1212- What are the mechanism of locomotion of Annelida ? 13-13- Illustrate Integumentary System ? 14- 14- ……………… epidermis that secretes a epidermis that secretes a ……..…….. .

56

QuizQuiz

QuizQuiz 15- 15- ………………..……………….. transparent cuticle transparent cuticle . 16-16- setae absent in setae absent in …………… …………… . 17-17- Coelom is Coelom is ……………….. ……………….. SpaceSpace . 18-18- Not all organ systems are Not all organ systems are ……………..…………….. . 19-19- Illustrate the nervous system with drawing ? 20-20- leeches have an …....... brain of leeches have an …....... brain of ……………… pairs of fused pairs of fused

ganglia and a ganglia and a …… …… brainbrain ofof …… …… pairs of fused ganglia pairs of fused ganglia . 21-21- What are the sensory organs of Annelida ? 22- 22- Circulatory System in Annelida is Circulatory System in Annelida is ………………………… . 23-23- ventral and dorsal blood vessels surrounding ventral and dorsal blood vessels surrounding

……….……….. for circulatingfor circulating …………………… . 24-24- Blood contains Blood contains

……………………………………………………………………..including hemoglobinincluding hemoglobin . 25-25- Blood with hemoglobin as O2-carrying Blood with hemoglobin as O2-carrying ……….……….. .

57

QuizQuiz 26-26- Gas exchange by simple Gas exchange by simple …………… …………… . 27- 27- …………….……………. in some polychaetes in some polychaetes . 28- 28- parapodia in polychaetes act parapodia in polychaetes act asas ……………. ……………. . 29-29- ………………………………………………seen in arthropods seen in arthropods . 30-30- A meobocytes found in A meobocytes found in ……………………………… . 31-31- A meobocytes act as A meobocytes act as ……………. ……………. SystemSystem . 32-32- ……………………………… digestive system with mouth and anus, not digestive system with mouth and anus, not

………………………… arranged arranged . 33-33- well muscularized pharynx well muscularized pharynx inin …………… ……………. . 34-34- Crop for Crop for ………………, Gizzard for Gizzard for …….……. and Typhlosole with and Typhlosole with

increase surface area forincrease surface area for ……………….………………. in oligochaetesin oligochaetes 35-35- In oligochaetes what is the function of calciferous glands ? 36-36- leeches are leeches are ……………………. 37-37- Terrestrial leeches feed on Terrestrial leeches feed on …………….. , ………………….. …………….. , …………………..

andand ……………..…………….. .

58

ASASRespiratory Respiratory

System System

38-38- Aquatic annelids secrete Aquatic annelids secrete …………..………….. . 39-39- Write short notes on excretory system ?excretory system ? 40-40- Type of sex in oligochaetes Type of sex in oligochaetes ………….. ………….. 41-41- Type of sex in polychaetes Type of sex in polychaetes ……….. ……….. with external fertilization and with external fertilization and

formation of a formation of a ………….………….. larva . larva . 42-42- Annelids are Annelids are ……………………………… with cross fertilization with cross fertilization . 43-43- …………….…………….. is a special region at the anterior end of the worm .. is a special region at the anterior end of the worm . 44-44- What is the function of clitellumclitellum ? 45-45- …………………….……………………. is typical larval stage is typical larval stage 46-46- What are the major classes in Annelids? 47-47- Write short notes on the three major classes in Annelids (what are

you know about them ) ? 48-48- What the meaning of monoecious , dioecious monoecious , dioecious ? 49-49- In polychaetes In polychaetes …………………………………………. used in locomotion with many . used in locomotion with many

large number oflarge number of ……………………… ………………………setaesetae 50-50- Write five characters of polychaetes ?

59

QuizQuiz

51-51- What do you mean when you say ProstomiumProstomium and what the function ? 52-52- Write short notes on habitat of polychaetes ? 53-53- What are the components of nervous system in polychaetes and can

you illustrate how the syrians of nervous is flow ? 54-54- Draw the nervous system ? 55-55- …………..………….. is located just below the prostomium, but in front of the is located just below the prostomium, but in front of the

modified segments – peristomium .modified segments – peristomium . 56-56- ………….…………. is surrounded by digestive glands is surrounded by digestive glands . 57- 57- ………………………………is equipped with pincer-like jaws is equipped with pincer-like jaws 58-58- …………………………………… is straight , finally opens with anus in the anal segment is straight , finally opens with anus in the anal segment 59-59- In polychaetes can you illustrate the way which any particles tack it to

arrange to anus ? ( with draw and the type of this particle ) 6060- - Muscular pharynx exist in Muscular pharynx exist in ……………..…………….. and can be everted through the and can be everted through the

…………………………………… . 61-61- Draw the circulatory system in polychaetes and illustrate each function

of vessels ?

60

QuizQuiz

62-62- Every segment contains a pair ofEvery segment contains a pair of…………………….except the .except the peristomium and the anal segment peristomium and the anal segment .

63-63- Each nephridium opens into the coelomic cavity by means of Each nephridium opens into the coelomic cavity by means of ………………..………………..

64-64- Each nephridium passes posteriorly through the Each nephridium passes posteriorly through the ……….………. into the into the following segment. Where it forms following segment. Where it forms ……………….……………….

65-65- Reproduction tack place in Reproduction tack place in ……………….………………. 66- 66- Give notes about epitoky and the function of it ?

Can you give another example Can you give another example of polychaetes with it systems? of polychaetes with it systems?

(search)(search)61

QuizQuiz

What do you benefit in this lecture ?What do you benefit in this lecture ?

(write in short point and we (write in short point and we

will see it in the next lecture ) will see it in the next lecture )

Prepare the next lecture pleasePrepare the next lecture please

62

QuizQuiz

answer in 15 minutes

Documents

body wall

distinct body cavity

unicellular body

speciesinternal body

example of parazoa

endoderm mesoderm tissues

true tissues

bilateral animals