Revision: 12th Std >> Reproduction in Lower and Higher Animals MAH-MHT CET (PCM/PCB) Reproduction in Lower and Higher Animals

All freshwater sponges like Spongilla and some marine sponges reproduce asexually by the formation of specialised endogenous buds, known as gemmules (internal buds).

A mode of reproduction involving the fusion of male and female gametes (sperm and egg) to form a zygote that develops into a new organism.

The period of growth and development before an organism becomes sexually mature is called the juvenile phase.

The secretion of glands with spermatozoa is a whitish viscous fluid known as seminal fluid or semen.

Spermatogenesis is the process of formation and development of sperm cells (spermatozoa) in the testes from spermatogonial stem cells through mitosis and meiosis.

Hernia is an abnormal condition that is caused when the intestine, due to the pressure in the abdomen, bulges into the scrotum through the inguinal canal.

The process of expulsion of semen from the urethra is called ejaculation.

The opening of the vagina in young females is partially closed by a thin membrane called the hymen (or virgin knot).

It is the stage when a girl menstruates for the first time.

The rhythmic series of changes in the sex organs throughout the reproductive life of a female primate (e.g., monkeys, apes, and human beings) from puberty to menopause is called the menstrual cycle (L. mensis = month, lunar month).

The release of the ovum from the ovary is called ovulation.

Spermiation is the process of releasing mature spermatozoa. In this, spermatozoa are shed into the lumen of the seminiferous tubule for transport.

After spermiogenesis, sperm heads become embeded in sertoli cells from which they obtain their nutrition and finally get released into the lumen of seminiferous tubules. This process of release of mature sperms from sertoli cells is called spermiation.

Spermiogenesis is the process of transforming spermatids into mature, flagellated spermatozoa (sperms).

The process of transformation of a circular spermatid to a spermatozoon is called spermiogenesis.

Gametogenesis is the process of formation of gametes i.e., sperms and ovary from the primary sex organs in all sexually reproducing organisms. Meiosis plays the most significant role in the process of gametogenesis.

Gametogenesis is the process by which male and female primary sex organs produce gametes (sperms and ova).

Gametogenesis is the process by which male and female gametes are formed from germinal cells in the gonads through a series of developmental stages.

Formation of haploid sperms (male gametes) from diploid spermatogonia (sperm mother cells) is called spermatogenesis.

The formation of ova in the ovary from primordial germinal cells is said to be oogenesis.

The fusion of the male gamete (sperm) and female gamete (ovum) to form a zygote is called fertilisation.

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Formation of zygote by union of sperm and ovum is called as fertilization.

The formation of a zygote by the union of male and female gametes is known as fertilization.

An extra-embryonic sac involved in waste storage and placental development is called allantois.

Cleavage is the process of early mitotic division of the zygote to generate a multicellular morula stage.

A study of the development of an organism from fertilization to the formation of young one is known as embryogeny.

A solid, mulberry-like ball of cells formed after cleavage is called morula.

The process of formation of blastula from morula is called blastulation.

A hollow embryonic stage formed after morula; in humans it is called blastocyst.

A series of rapid mitotic divisions of the zygote without increase in size is called cleavage.

A disc-like structure attached to the uterine wall that supplies food and oxygen to the foetus and removes waste is called placenta.

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The intimate connection established between the foetal membrane and the uterine wall is known as placenta.

After nine months of pregnancy, the fully developed foetus is ready for delivery. The process of childbirth is called parturition.

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Parturition is the act of expelling the full term foetus from the mother's uterus at the end of gestation.

The term lactation refers to the secretion and ejection of milk by the mammary glands.

It is a technique in which amniotic fluid is withdrawn from the uterus of a pregnant lady and the amniotic cells are cultured and studied for cytological observations to determine any chromosomal abnormalities.

Birth Control refers to the regulation of conception by preventive methods or devices to limit the number of offspring.

Intentional or voluntary termination of pregnancy before full term is called medical termination of pregnancy (MTP) or induced abortion.

• Lower organisms like Spongilla and Hydra reproduce asexually by gemmule formation and budding, respectively.
• A gemmule is an internal bud formed only in sponges — it is an asexually produced mass of dormant cells called archaeocytes, capable of developing into a new organism.
• Archaeocytes get coated by a thick, resistant layer secreted by amoebocytes. Gemmules are formed to survive unfavourable conditions.
• On return of favourable conditions (water and temperature), gemmules hatch and develop into a new individual. e.g., Spongilla.

• Sexual reproduction involves the formation and fusion of male and female gametes (amphimixis) to form a zygote, with gamete formation by meiosis.
• It occurs in two phases: juvenile phase (no reproduction) and reproductive phase (sex organs active), regulated by hormones.
• It includes three main events: pre-fertilisation (gamete formation and transfer), fertilisation (fusion of gametes), and post-fertilisation (zygote and embryogenesis).
• Sexual reproduction produces genetic variation due to meiosis, recombination, and fertilisation, which is important for evolution.
• Primary sex organs (testes, ovaries) produce gametes, and organisms may be seasonal or continuous breeders depending on the reproduction pattern.

• The male reproductive system is located in the pelvic region and includes testes, accessory ducts, accessory glands, and external genitalia (penis and scrotum).
• Testes are the primary sex organs present in the scrotum; they contain seminiferous tubules where sperm are produced, while Leydig cells secrete testosterone, and Sertoli cells provide nourishment.
• Accessory ducts—rete testis → vasa efferentia → epididymis → vas deferens → ejaculatory duct → urethra—help in storage, maturation, and transport of sperm.
• Accessory glands—seminal vesicles, prostate gland, and bulbourethral glands—add secretions like fructose, enzymes, and mucus, which nourish sperms and aid in their movement.
• The penis acts as the external genital organ, containing the urethra, and helps in the transfer of sperm during ejaculation.

• Includes — Ovaries, Fallopian tubes, Uterus, Cervix, Vagina, External genitalia, Bartholin's glands, Mammary glands — all in the pelvic region.
• Ovaries — outer cortex (follicles) + inner medulla; produce ova and ovarian hormones; release one ovum monthly after puberty.
• Fallopian tube — 3 parts: Infundibulum (fimbriae collect ovum) → Ampulla (site of fertilisation) → Isthmus (connects to uterus); cilia push egg towards uterus.
• Uterus — 3 layers: Perimetrium (outer), Myometrium (muscular), Endometrium (inner, menstrual changes); opens into vagina via cervix (birth canal).
• Zygote implants in the endometrium; the placenta connects the embryo to the mother for nutrient and waste exchange till birth.
• External genitalia — Mons pubis, Labia majora, Labia minora, Hymen, Clitoris. Bartholin's glands provide lubrication.
• Mammary glands — produce milk for newborn. Puberty begins at 10–14 years in females.

• The menstrual cycle is a series of monthly changes in females of reproductive age.
• The beginning of the cycle is called menarche, and its permanent stop is called menopause (around 45–50 years).
• It occurs mainly in primates, including humans, and involves changes in the ovaries and uterus.
• The cycle is controlled by hormones (gonadotropins and ovarian hormones) and repeats every ~28 days.
• In the middle of the cycle, ovulation occurs, where an egg is released from one of the ovaries.

• Fertilisation in humans is the fusion of male and female gametes (sperm and ovum) and is an internal process occurring in the oviduct, leading to the formation of a diploid zygote.
• During copulation, millions of sperms are released into the vagina, but only one sperm reaches the ovum due to selection and protective barriers around the egg.
• Before fertilisation, sperm undergo capacitation and move towards the ovum; interaction between sperm and egg involves recognition molecules like fertilizin (ovum) and antifertilizin (sperm).
• The sperm’s acrosome releases enzymes that help digest the egg coverings (corona radiata and zona pellucida), allowing sperm entry through the membrane.
• After entry, the sperm nucleus and the ovum nucleus fuse (syngamy), forming a zygote (2n); this process restores the diploid chromosome number (46 in humans).
• Fertilisation triggers completion of meiosis II in the oocyte, formation of the second polar body, and formation of the female pronucleus and male pronucleus.
• In humans, sperm carry 22+X or 22+Y chromosomes, while ova carry 22+X only, determining the genetic sex of the offspring.

• Meaning - Placenta is a temporary structural and functional connection between foetal and maternal circulation, formed by chorionic villi (finger-like projections of trophoblast) interdigitating with uterine tissue and maternal blood.
• Attachment - The placenta is attached to the wall of the uterus on one side and connected to the baby via the umbilical cord on the other side.
• Umbilical cord - Contains two small arteries (carry blood towards the placenta) and one large vein (returns blood to the foetus).
• Functions - Supplies oxygen and nutrients to the foetus; removes CO₂ and excretory wastes from foetal blood to maternal blood.
• Hormones produced - Placenta produces hCG (human Chorionic Gonadotropin), hPL (human Placental Lactogen), Oestrogen, and Progesterone. By the end of the 1st trimester, progesterone production shifts to the placenta.

• Parturition is the process of childbirth, i.e., the delivery of the foetus at the end of the gestation period.
• It is controlled by a neuro-endocrine mechanism involving signals from the fully developed foetus and placenta.
• Foetal signals trigger uterine contractions known as the foetal-ejection reflex (labour pain).
• Hormones like ACTH and corticosteroids from the foetus stimulate the release of oxytocin from the mother’s pituitary gland.
• Parturition occurs in three stages: dilation, expulsion of the baby, and after birth (placenta removal).

• Lactation is the process by which mammary glands produce milk at the end of pregnancy, under the influence of the hormone Prolactin.
• The first milk secreted soon after childbirth is called Colostrum — it is sticky, yellowish and rich in proteins, lactose and antibodies (IgA); fat content is low.
• Antibodies (especially IgA) in colostrum provide passive immunity to the newborn when its own immune system is not yet fully developed.
• Lactation helps the mother in feeding and nourishing the newborn baby, providing all essential nutrients required in early life.

• Reproductive health, as defined by WHO, refers to complete physical, emotional, behavioural, and social well-being in all aspects related to reproduction.
• India’s Reproductive and Child Health (RCH) programmes aim to promote reproductive health through family planning, maternal and child care, awareness creation, and access to medical facilities.
• Education and awareness, including sex education for adolescents, help prevent myths, sexually transmitted diseases (STDs), unsafe practices, and promote hygienic and responsible sexual behaviour.
• Preventive measures such as menstrual hygiene, genital cleanliness, planned parenthood, immunisation, and statutory bans on sex determination are essential for a healthy society.
• Sexually transmitted diseases like syphilis and gonorrhoea adversely affect reproductive health, highlighting the need for early diagnosis, treatment, and improved medical infrastructure.

• Medical Termination of Pregnancy (MTP) is the voluntary termination of pregnancy before full term, also called induced abortion.
• MTP is done in cases of unwanted pregnancy or when fetal abnormalities are detected, often using amniocentesis.
• Amniocentesis is a diagnostic test that collects amniotic fluid to study fetal chromosomes and detect genetic defects.
• MTP is legally allowed in India under the MTP Act (1971, amended 2017), with conditions and is generally safe in the first 12 weeks.
• It requires the woman’s consent and a doctor’s approval, and is allowed only when pregnancy risks the mother’s life or involves serious fetal abnormalities.

• Infertility is the inability to conceive after 12 months or more of regular unprotected intercourse and may be due to male, female, or both partners.
• Male infertility includes low sperm count, no sperm production, poor sperm motility, or abnormal sperm structure.
• Female infertility may result from hormonal imbalance, poor egg production, or defects in reproductive organs like the ovaries, fallopian tubes, uterus, or cervix.
• Mechanical or physiological problems, such as blocked reproductive tracts or thick cervical mucus, can prevent fertilisation.
• Infertility is diagnosed and treated by identifying the cause and using methods like hormonal therapy, surgery, or lifestyle changes.
• Assisted Reproductive Technologies (ART) help infertile couples and include IVF, ICSI, GIFT, ZIFT, AI, and IUI, which assist in fertilisation and conception.