Instructional media (ppt) Reproduction and Development

Unit 4 : Reproduction and Development 1

Type of reproduction Reproduction is the multiplication of organisms of the same species. It is considered the most important property in identifying living things and enabling each species to survive (Continuity of species) ; divided into • Asexual reproduction • Sexual reproduction Analogy Asexual reproduction Sexual reproduction Number of progeniting only one parent Both parents organisms have Process of germ cell formation none (except parthenogenesis) have genetic variation Genetic traits of the offspring like all beings that give birth have Fertilization do not have be placed in the environment. Strength The increase in numbers happened that has changed a lot quickly. It takes a lot of energy to Weakness The animal must be in an reproduce. environment with 2 little change By..Teacher.Suklittha Somon

Asexual reproduction) 1. Binary fission - Proliferation from one progenitor cell to two daughter cells of the same size, e.g. dividing into two in Amoeba, Paramecium. 2. Budding - Proliferation by creating daughter cells from the parent. The sprouts (bud) that are formed are smaller, such as gemmule sprouts in sponges, which often occur under inappropriate conditions. Hydra sprouting. 3. Regeneration - The destruction of body parts and the development of new organisms, such as the regeneration of sea star , Planaria. By..Teacher.Suklittha Somon -*Regeneration to replace the damaged or missing parts, such as the regeneration of the lizard's tail. not classified as reproductive because it did not create a new life. It's just to repair the wear and tear only.

4. Parthenogenesis - the maturation of egg cells (egg ;n) into adults without fertilization from males, such as in honey bees. If the egg develops parthenogenesis ,it produces a drone, but if the egg is fertilized with sperm, it develops into a female worker bee. If these female bees are fed with the right hormones, they may develop into a queen bee. next ❑ Hermaphrodite - Many invertebrates have organs of both sexes in the same body called bisexual (Hermaphrodite). These animals are prone to cross fertilization, to increase the genetic diversity of the offspring **except In the group of tapeworms that can occur in self-fertilization By..Teacher.Suklittha Somon

5. Spore formation/Sporulation Cells divide many times until a large number of cells are formed. Each cell is called a spore. Which easily spreads to various places such as fungi, mushrooms, ferns, mosses By..Teacher.Suklittha Somon 5

Life cycle of Rhizopus stolonifer 6. Paedogenesis sporangium • It is reproduction that occurs by the embryo being able to Asexual phase give birth to the embryo together. • Found in fluke larvae in shellfish. The sporocyst embryo Sexual phase gives birth to Redia embryos or Daughter sporocysts. Later, Redia embryos give birth to Cercaria embryos. zygospore By..Teacher.Suklittha Somon 6

7. Fragmentation 8. Duplication of Phage Occurs where parts of the body are disintegrated into parts. Each part can grow into a new organism. tapeworm By..Teacher.Suklittha Somon 7

9. Cloning Animal cloning is performed by removing the nucleus from a somatic cell which contains complete genes and chromosomes. into the oocyte (egg) from which the nucleus has been removed It is believed that egg cells have various factors. to encourage division After that, the resulting cells are placed in the mother's uterus or left to grow. *Animal cloning was first successful in frogs. but very famous is dolly sheep clone By..Teacher.Suklittha Somon 8

Test About Fertilization : What is this? 1 23 4 5 By..Teacher.Suklittha Somon

❑ Sexual reproduction 2. Fertilization 1. conjugation It is the process of merging male gametes and female gametes, which have 2 main forms: The conjugation between the nuclei of two protozoans divides by meiosis. Subsequently, 2.1 External fertilization nuclei are exchanged. After the nuclei have merged , the two protozoa will separate and each - Animals release gametes outside the body. and will continue to divide fertilization takes place outside the body - Found only in aquatic animals. These animals rely on water as a medium for fertilization. By..Teacher.Suklittha Somon 10

2.2 Internal fertilization Platypus - Males generally release their germ cells to fuse with the female germ cells in the body. - found in some cartilaginous fish and most terrestrial vertebrates ▪ Offspring development occurs in internally fertilized animals. It can occur in 3 forms: 1) Oviparity : Animals that produce eggs such as some fish, reptiles, poultry, and some mammals. (platypus) 2) Ovoviviparity : An animal whose embryo develops in an egg inside the body. Acquire food from egg yolks such as Madagascar cockroaches, garter snakes. 3) Viviparity : Animals whose larvae are fed directly from the mother's blood. Does not pass yolk like sharks and all mammals By..Teacher.Suklittha Somon

3. Alternating reproduction (Metagenesis) of Jellyfish and Obelia Reproduce sexually by fertilization between sperm and egg. Interspersed with asexual by budding ▪ Sexual reproduction Female medusa lays eggs , The male Medusa releases sperm in the water. When egg and sperm meet fertilization . Fertilized eggs begin to divide. It then grows into an embryo called a planula, about 0.80 mm in size, that moves freely under water. The planula develops into tiny polyps and then find a place to cling to immobile material. then develops into an adult polyp. When the environment is right ,The tip of the polyp will gradually come off to form a small medusa. Swim up above the water and grow up to be able to reproduce again. ▪ Asexual reproduction The mature polyp sprouts into a planula-like larva. but slightly larger (0.95 mm) .The larva that emerges from the sprout, called a frustule, moves below the water surface and develops into another polyp. - Planula It is an embryo obtained 12 by sexual reproduction. - Ephyra It is an embryo obtained from asexual reproduction. By..Teacher.Suklittha Somon

The structure of the male reproductive system consists of the following parts: 1.อณั ฑะ (testis) : It is the main organ in sperm and testosterone production. Organized as part of the sex glands (gonad) of men, the testes are located within the scrotum which help to adjust the temperature within the testicles to maintain a suitable temperature for spermatogenesis. (The temperature in the scrotum is slightly lower than body temperature). 1.1 หลอดสรา้ งอสจุ ิ (seminiferous tubule) : The small tube is coiled. It contains the following cells: - Cells involved in spermatogenesis - เซลลเ์ ซอรโ์ ทไล (sertoli cell) : It is like a mentor cell that brings food, gas and substances necessary for sperm to culture the sperm cells. - เซลล์เลยด์ ิก (Leydig cell) หรือ Interstitial cell : It is a cell that produces the hormone testosterone. 1.2 หลอดเกบ็ อสจุ ิ (epididymis) : Sperm storage area and stimulate the function of sperm cells By..Teacher.Suklittha Somon

2.ทอ่ นาอสจุ ิ (vas deferens) : Tubes that carry sperm to the outside of the body 3.Glands : Within the male reproductive system are as follows. 3.1 ตอ่ มสร้างน้าเลย้ี งอสุจิ (seminal vesicle) : Serves to create and secrete a light yellow liquid. It consists of various mucus, vitamin C, amino acids, fructose sugars, which are the source of energy for sperm cells. 3.2 ตอ่ มลูกหมาก (prostate gland) : Serves to create and secrete a fluid that has a base property. To neutralize the acidic female vagina. When the sperm moves into the vagina, it can be fertilized. 3.3 ตอ่ มคาวเปอร์ (Cowper’s gland) / bulbourethral gland : produce and ejaculate clear fluid before actual ejaculation (pre- ejaculate fluid) This substance acts to reduce the acidity in the urethra of men. urethral lubrication The ejaculate along with the fluid from this gland may also contain sperm cells. 4.องคชาติ หรือลงึ ค์ (penis) : The main organ involved in sexual intercourse, which is used to penetrate the vagina to allow sperm to move in and fertilize. Inside the penis is a conduit between the urethra and the spermatic duct. The penis becomes erect when blood accumulates in the spongy muscle layer. By..Teacher.Suklittha Somon

Hormones and the male reproductive system 15 Hormonal activity in the male reproductive system occurs when entering puberty, about 13 years old. The hypothalamus produces and secretes GnRH, which stimulates the anterior pituitary gland to release FSH (follicle stimulating hormone), which stimulates the spermatogenesis process, and LH (luteinizing hormone). This stimulates Leydig cells to produce testosterone for regulating the functioning of the reproductive system and controls secondary sex characteristics, which are characteristics that represent masculinity in addition to the ability to produce sperm By..Teacher.Suklittha Somon

The structure of the female reproductive system It consists of the following parts: 1.รงั ไข่ (ovary) : Main structures involved in ovulation and female hormone production (comparable to testicles) 2.มดลกู (uterus) : Main structures in embryo implantation The embryo will implant in the inner uterine wall. (endometrium). If fertilization does not occur, the inner uterine wall will fall off in menstruation. 3.ทอ่ นาไข่ (oviduct) หรือปีกมดลกู (uterine tube) : The area where fertilization takes place and the egg/embryo is implanted in the uterus. There will be cells with cilia waiting to wave. 4.ปากมดลกู (cervix) : the lower uterine area adjacent to the vagina looks like a narrow mouth converging 5.ชอ่ งคลอด (vagina) : the tip of the female reproductive system It is the area that supports the penetration of the penis and used to give birth. By..Teacher.Suklittha Somon

Hormones and the female reproductive system The function of hormones in the female reproductive system is more complex than that in males. Because in females there will be a menstrual cycle (menstruation) which is caused by the interaction of 5 types of hormones, GnRH, FSH, LH, estrogen and progesterone in a correlated pattern. A woman begins having her first menstrual period (menarche) at about 11-12 years of age. After that, her periods continue until she is about 50 years old and the menstrual periods stop and the menopause begins. A woman's menstrual cycle begins when the hypothalamus secretes GnRH, which stimulates the anterior pituitary gland to produce and release FSH, which FSH stimulates follicular cells. follicle surrounding the egg cell to develop. As follicle cells proliferate These follicle cells produce more estrogen until it is high enough to stimulate the anterior pituitary gland to release LH. This causes the secondary oocyte to escape from the ovary, causing ovulation. By..Teacher.Suklittha Somon

Ovulation Ovulation is when an egg matures and leaves the ovary into the fallopian tube. Ovulation occurs 13-15 days after the first day of your menstrual cycle. The first ovulation of a person's puberty begins 2-3 years after menstruation, with ovulation occurring from the age of 14-15 until about 44-45 years. up to 400 eggs (It is estimated that approximately 2 million oocytes are present during infancy, which are already present from infancy until birth. Subsequently, the initial oocyte gradually decreases. Until the age before menstruation or about 12-14 years old, there are approximately 400,000 oocytes left in the early stages of the 2 sides of the ovary). first day of 13-15 days later decomposed menstruation Menstrual cycle 26-28 days eggs (menstrual Ovulation (13-15 (24 hours later) phase 2-5 days later) 18 days) By..Teacher.Suklittha Somon

Process of reproduction of higher animals (Gametogenesis) 1. Spermatogenesis 2. Oogenesis By..Teacher.Suklittha Somon • The sperm-producing organ is the testis and the egg cell-producing organ is the ovary. • Within the testicles there are cells called spermatogonium and within the ovary there is a group of cells called the oogonium. • Both cell groups originate from primordial germ cell .These are cells from the abdominal cavity that move into the gonads during gonad formation. 19

1. The process of producing male gametes (spermatogenesis) Occurs within the seminiferous tubule in the testes, inside which there are cells. spermatogonium (2n) is numerous and mitotic cell division To increase the number all the time from when the baby was in the womb. - At puberty, spermatogonium cells Some will develop into larger cells called primary spermatocyte (2n), which when the body receives FSH hormone to stimulate this type of cell, it will divide by meiosis I to become secondary spermatocyte (n) 2 cells before meiosis II cell division produces 4 spermatids (n). - After that, the spermatid changes shape through the process. spermatogenesis to continue to create sperm cells By..Teacher.Suklittha Somon

- Approximately 180-500 million sperm/2-7 cm3 live in the female body for no more than 2 days (48 hours). - 75-80% of all semen is obtained from the spermatic glands, 15-20% from prostate gland and least from sperm collection tube By..Teacher.Suklittha Somon

2. The process of producing female reproductive cells (Oogenesis) - Occurs within the ovaries It has a starting cell, the oogonium (2n), which undergoes mitotic cell division to multiply. Some of the oogonium develop into a primary oocyte (2n) in the womb. and stop dividing at prophase I - until entering adolescence which will have sex hormones to stimulate the primary oocyte to divide by meiosis I , into one secondary oocyte (n) and one small cell called the first polar body (n) - Cell division is then stopped again in metaphase II and ovulation occurs each menstrual cycle. Until the secondary oocyte is fertilized. After fertilization, the cell continues to divide into ootid (n) and secondary polar bodies, in which these polar bodies eventually decay. By..Teacher.Suklittha Somon

Difference between Spermatogenesis vs Oogenesis Spermatogenesis Oogenesis 1. Result: 4 mature spermatozoa 1. The result is a single ovum, the polar body is dissolved. 2. Occurs all the time during the lifetime of an organism 2. Potentail ova (primary oocyte) already in ovary at birth 3. Spermatogenesis continue to be born 3. Oognesis has a break. By..Teacher.Suklittha Somon 23

Animal Development Animal development consists of 4 processes: 1. Cell division It increases the number of cells for the growth of the embryo. 2. Enlargement of cells (Cell growth) 3. To change the shape of a cell to perform a specific function (cell differentiation) 4. The grouping of cells to form tissues and organs. (morphogenesis) stages of development in animals It consists of the following sub-steps: ▪ Fertilization ▪ Cleavage ▪ Blastulation ▪ Gastrulation ▪ Organogenesis By..Teacher.Suklittha Somon

Fertilization and implantation of embryos in the uterine wall 25 Fertilization : It is the union of male and female germ cells. A fertilized egg cell is called a zygote. If the zygote begins to divide, it enters the embryo stage. By..Teacher.Suklittha Somon

❑ การคลเี วจ (cleavage) By..Teacher.Suklittha Somon : It increases the number of cells of the zygote by mitosis resulting in more cells. But the size of the cell is reduced. This results in the overall size of the embryo being the same. Because individual cells do not grow (no cell enlargement) • increase the number of cells→more cells, smaller size→ Each cell is called a blastomere. **In summary, the form of clevage depends on the type of egg yolk, for example: -Yolk-less animals (sea urchins, mammals): Clevage occurs throughout the embryo. - Medium-yolked animals (frogs): Clevage occurs throughout the embryo. The bottom area has a lot of yolk (vegetal pole) and less cell division. The cells are therefore larger than the group of cells at the top of the embryo (animal pole).) - animals that have a lot of yolk (Reptiles, Poultry): Clevage will occur in certain areas. In chickens, it occurs only on the upper surface of the yolk, where the cytoplasm and nucleus are located. It's an area known as the germinal disc. (a), (b) and (c) show exogenous blastula. Clevage is one that divides throughout the egg. but not equally divided. Therefore, the resulting blastomere have different sizes.(d) shows a cross-sectional view of the blastula. The blastocoel chamber formed towards the animal pole, blastoderm is composed of more than one layer of cells. ❑ In humans, when an embryo enters the clevage stage, numerous cell divisions occur. It produces an embryo that looks like an custard apple, called morula

❑ การบลาสทเู ลชนั (blastulation) : It is the process by which embryo cells are layered on the periphery. In the center there is a fluid-filled cavity called the blastocoel that allows cells to move. ❑ In humans or other primates, the blastula is the implantation stage in the inner uterine wall (endometrium) during which the embryo moves to the uterine wall, there will be movement of cell groups divided into 2 groups: 1) Trophoblast – It is a group of cells arranged in a single layer on the outside. which in the next growth will grow together with the tissue of the uterine wall to become the placenta 2) Inner cell mass – grouped inside It is the part that continues to grow into the organs of the embryo and because the embryo baggy Therefore, this stage of the embryo is called a blastocyst. By..Teacher.Suklittha Somon 27

❑ การแกสทรเู ลชนั (gastrulation) : It is the process by which cells in an embryo are organized into three germ layers: ectoderm, mesoderm, and endoderm, respectively. -Movement of cells in the gastrula stage This leads to the development of an internal cavity known as the gastrocoel or archenteron (which then develops into the tube of the digestive tract). The opening of the gastrocoel is known as the blastopore, and the development of the blastopore is one of the main classification criteria for animals in the animal kingdom. • In animals, blastopore develops in the following ways: 1) In Protostomia, the blastopore develops into the oral cavity. The second opening develops into the anus. This group of animals is called Protostomia, including Nematode, Annelid , Mollusk and Arthropods. 2) Deuterosmomia, It means that the mouth comes second. Which means the anus comes before the oral cavity This group is called Deuterostone namely Echynoderm and Chordate. By..Teacher.Suklittha Somon 28

❑ ออร์แกนโนเจเนซสี (Organogenesis) : It is a process in which all 3 layers of embryo tissue are transformed into organs. The first system developed was the nervous system. - Each layer of tissue will develop into different organs. in the body as follows tissue layer organs and tissues that develop as Ectoderm adults Mesoderm Epidermis of the skin, epithelial cells in the mouth and anus, nervous system, parts of Endoderm the cornea and lens of the eye. , sensory cells in the skin By..Teacher.Suklittha Somon Skeletal system and muscles, circulatory system, excretory system, reproductive system (except cells involved in gametogenesis), mucous membranes Epithelial cells in the gastrointestinal tract and respiratory tract, liver, pancreas, thyroid and parathyroid glands, thymus, urethra, bladder and reproductive system 29

Types of eggs are classified according to the amount of yolk. 30 1.Homolecithal egg : It is an egg with little yolk. distributed in the cytoplasm, such as sea star eggs 2.Mesolecithal egg : It is an egg with medium yolk. The eggs are gathered on either side of the egg, like a frog egg. 3.Polylecithal egg : It is an egg with a lot of yolk, like the eggs of a chicken or bird. By..Teacher.Suklittha Somon

❑ development of frog embryo Frog eggs have two sides: 1. The upper half (Animal pole) is dark because melanin pigment is the side where the sperm will fertilize. 2. The lower half (Vegetal pole) is faded, with food or egg yolk accumulating at the bottom. There are 2 phases of growth: 1. Embryo stage (2 days) has 4 sub-stages: cleavage , blastulation, gastrulation, morphogenesis and organogenesis. 2. Late embryos have Metamorphosis. By..Teacher.Suklittha Somon 31

By..Teacher.Suklittha Somon สัตวก์ ลมุ่ แอมนโิ อต (amniotes) Amniotes are a group of vertebrates that have specialized structures for the embryo. (extraembryonic membrane), including reptiles, birds, mammals which has many structures developed can be summarized as follows 1.ถุงไขแ่ ดง (yolk sac) - Inside contains egg yolks, which is used as food for the embryo while developing inside the egg 2.ถุงน้าครา (amnion) - Inside there is a fluid called amniotic fluid that acts to prevent shock and prevent the embryo from drying out and dehydration. 3.ถงุ แอลแลนทอยส์ (allantois) - is the part adjacent to the chorion along with surrounding capillaries Serves to store uric acid waste type out. until the embryo hatches from the egg including gas exchange 4.คอเรยี น (chorion) - It is the outermost membrane and is adjacent to the eggshell. serves in gas exchange 5.เปลอื กไข่ (shell) - Helps to prevent harm and prevent water loss of the egg cell. 32

Summary of structure and solution of chicken embryo • ถุงแอลแลนทอยส์ (Allantois) acts as a gas exchanger O2 and CO2 Including the accumulation of uric acid waste. Or act as excretion itself. • ถงุ นา้ ครา (Amnion) around the embryo Contain a fluid called amniotic fluid that is responsible for preventing impact to the embryo. • เปลือกไข่ (Shell) Has a duty to prevent danger and reduce water loss • ไข่แดง (Yolk) as a food source for the embryo ❑ chicken embryo development • The egg cell is a specialized region known as the yolk, consisting of the nucleus and cytoplasm.  chicken embryo development: Meroblastic cleavage (the yolk is plentiful, so cells divide only in small areas near the cell surface that are free from the yolk. →Blastulation →Gastrulation →Organogenesis and Morphogenesis Brahma chicken breed By..Teacher.Suklittha Somon 33

By..Teacher.Suklittha Somon supplement knowledge!! 34

❑ development of human embryo By..Teacher.Suklittha Somon Fertilization process; - Human fertilization takes place in the ampulla of the oviduct or fallopian tube. The fertilized egg continues to divide and implants in the uterus within 7 days. Sperm (n)+ Ovum (n) Fertilization occurs at the beginning 1/3 of the fallopian tubes or the late 2/3 of the fallopian tubes on the 14th day of the menstrual cycle.→zygote (2n)→Blastocyst embryo (7 days old, implanted in the inner uterine wall (day 21 of the menstrual cycle)→pregnant →The embryo is 8-10 weeks old (about 2 months), which is the end of the embryo stage due to the completion of all organs → fetus →give birth - When fertilization takes place, the clevage increases the number of cells into morula and blastula, respectively. -Around day 7, a blastocyst embryo forms a cortical sac around it. and implantation in the inner uterine wall where the trophoblast will continue to grow into the placenta. If the embryo implants somewhere other than the uterus, it is considered an ectopic pregnancy. Which may be dangerous to the mother -When an embryo is about 8 weeks old, it undergoes complete development of various organs, an embryo from 8 weeks onwards is called a fetus. ▪ รก (placenta) : It is a structure formed by the chorion of the fetus and the tissue of the inner uterine wall of the 35 mother. It is involved in the exchange of gases, nutrients, and waste products. The placenta also produces HCG (human chorionic gonadotropin), which maintains the corpus luteum for the production of progesterone and estrogen, preventing The inner wall of the uterus is dislodged once the embryo has implanted.

Human fetal development By..Teacher.Suklittha Somon 36

เยอื หมุ้ ทารก (Fetal membrane) 3. คอเกรยี น (Chorion) -prosper as part of the placenta 4. แอลแลนทอยส์ (Allantois) -prosper as part of the placenta 1. ถุงห้มุ ไขแ่ ดง (Yolk sac) - Give food in the 5. รก (Placenta) -serves to feed the baby, exchange gases , beginning later did not perform any duties excrete waste and produce hormones HCG and 2. ถงุ น้าครา (Amnion) - Prevent impact to the baby. Progesterone, so the placenta is comparable to the small helps regulate temperature It will break before birth, intestine (source of food absorption), lungs (gas exchange) called Nam Tun Hua, like a liquid wedge and kidneys (excretion of waste). (hydrostatic wedge), helping to facilitate delivery. 6. สายสะดอื (Umbilical cord) -It is a contiguous structure comparable to the yolk sac (feeding) and allantois between the baby and the placenta. There are 3 blood (gas exchange and waste excretion) in chicken vessels inside: 2 Artery which carries blood from the fetus embryos and 1 Vein which carries healthy blood from the placenta to the fetus. By..Teacher.Suklittha Somon 37

❑ Metamorphosis Metamorphosis refers to the growth after the embryonic stage of animals that have greatly changed their appearance, behavior, and lifestyle. The morphological changes during post-embryonic maturation of animals are varied. : Animals with metamorphosis include crustaceans, Growth after the larval stage of insects crabs, most insects, and amphibians. 1. อะเมตาโบลสั (Ametabolus) หรอื อะเมทามอรโ์ ฟซสิ (Ametamorphosis) no metamorphosis For example, bi-pronged, silver-pronged, fly-tailed insects. By..Teacher.Suklittha Somon 38

2. เมตามอร์โฟซสิ แบบคอ่ ยเป็นคอ่ ยไป (Gradual 3. เมตามอรโ์ ฟซสิ แบบไมส่ มบูรณ์ (Incomplete Metamorphosis) Metamorphosis) egg – Nymph - Adult egg – Naiad - Adult such as grasshoppers, cockroaches, such as dragonfly, needle dragonfly, white sheep, stonefly crickets, termites, cicadas -The larval stage is different from the adult stage in -The larval stage is different from the adult in many ways and the some stages. And during the growth period from the growth period from the larval stage to the adult stage does not have larval stage to the adult stage, there will be no pupa. a pupa. ▪ Nymph : Lives on land, uses breathing tubes, has no wings ▪ Naiad : Lives in water, uses gills to ▪ Adult : lives on land, uses breathing tubes, has wings breathe, has no wings By..Teacher.Suklittha Somon ▪ Adult : lives on land, uses breathing tubes, has wings 39

4. เมตามอร์โฟซสิ แบบสมบรู ณ์ (Complete Metamorphosis) 40 egg – Larva – Pupa – Adult such as mosquitoes, ants, flies, bees, wasps, butterflies By..Teacher.Suklittha Somon

Graph showing the growth of living organisms. 1. S-shaped graph • It is found in all animals (except arthropods) and in herbaceous plants. Divided into 3 stages of growth: 1) Stage I has a low growth rate. 2) Stage II has the highest growth rate. 3) Stage III has the lowest growth rate. 2. Continuous S-shaped graph 3. Step graph (Intermittent growth) • Found in perennial woody plants that grow in • Found in all arthropods such as insects, 41 different seasons. shrimp, crayfish, crabs, centipedes and millipedes, which molt to grow. • In the watery season, there will be a high growth rate. In the dry season, the growth rate is low. By..Teacher.Suklittha Somon