Revision: Life Processes in Living Organisms Part - 2 Science and Technology 2 SSC (English Medium) 10th Standard Maharashtra State Board

Lifespan is the duration or period from birth to the natural death of an organism.

Reproduction is the process of formation of new individuals by sexual or asexual means, which can repeat the process in their own turn.

or

Formation of new organism of same species by earlier existing organism is called as reproduction.

or

Reproduction is a biological process that results in the formation of new individuals of the same kind, though usually with slight genetic, structural and physiological variations.

A mode of reproduction where a new organism is formed from a part of the parent body without involving gametes.

or

The process of forming a new organism from an organism of the same species without the involvement of gametes is called asexual reproduction.

or

When offspring is produced by a single parent by the formation of specialised asexual reproductive structures by the parent body, the reproduction is asexual.

Binary fission is an asexual reproduction process in single-celled organisms where a parent cell divides into two genetically identical daughter cells through coordinated nuclear and cytoplasmic division.

Simple binary fission is an asexual reproduction process in which a single Amoeba cell divides along a randomly oriented plane to form two genetically identical daughter cells.

or

When a unicellular organism divides into two identical daughter cells in any plane, due to lack of definite shape, it is called simple binary fission.

Example: Amoeba

When a unicellular organism divides across the transverse (horizontal) axis, it is called transverse binary fission.

or

Transverse binary fission is an asexual reproduction process where the plane of division runs along the transverse (horizontal) axis of the individual, splitting it into two parts.

Example: Paramecium

When a unicellular organism divides along the longitudinal (vertical) axis, it is called longitudinal binary fission.

or

Longitudinal binary fission is an asexual reproduction process where the plane of division passes along the longitudinal (vertical) axis of the animal, splitting it into two parts.

Example: Euglena

The end products of multiple fission that are enclosed in a hard, resistant covering are called spores.

The daughter individuals formed as a result of sporogony in Plasmodium are called sporozoites.

The process of multiple fission occurring in the oocyst of Plasmodium inside the mosquito is called sporogony.

The type of multiple fission in which the parent Amoeba forms a cyst and releases many daughter individuals on return of favourable conditions is called sporulation.

The small daughter cells formed when each daughter nucleus produced during multiple fission in Amoeba gets surrounded by a small amount of cytoplasm are called amoebulae or pseudopodiospores.

When a single organism divides into many daughter cells by forming multiple nuclei followed by cytoplasmic division, it is called multiple fission.

or

The mode of asexual reproduction in which a single parent organism divides to produce many daughter organisms at the same time is called multiple fission.

The process by which Amoeba withdraws its pseudopodia and forms a hard, protective, three-layered cyst around its body during unfavourable conditions is called encystation.

When an Amoeba forms a protective covering around itself during adverse conditions and stops movement, it is called a cyst.

In unicellular organisms like yeast, when a small bud forms on the parent cell, gets a nucleus, grows, and separates to become a new cell, it is called budding.

When the body of a multicellular organism breaks into two or more fragments, and each fragment grows into a new individual, it is called fragmentation.

or

The mode of asexual reproduction in which the body of an organism breaks into fragments, each capable of developing into a complete new organism, is called fragmentation.

Example: Ulothrix, Spirogyra, etc

The process in which an organism develops a new individual from its body parts using specialised cells that multiply and differentiate into various tissues is called regeneration.

or

When an organism regrows its lost or damaged body part, or forms a new organism from a body part, it is called regeneration.

In multicellular organisms like Hydra, when a bud grows on the parent body through cell division and later becomes a new individual, this is called budding.

Reproduction in plants, in which a new plant can arise from a vegetative part such as a root, stem, or leaf without the help of any reproductive organ, is called vegetative propagation.

A special reproductive structure formed by simple plants and fungi that germinates directly to form a new individual is called a spore.

Non-motile asexual spores produced externally and not inside a sporangium in many fungi are called conidia or conidiospores.

Spores that lack flagella and are incapable of movement are called non-motile spores.

Non-motile spores with a typical cell wall and without flagella are called aplanospores.

Asexual spores produced inside a sporangium are called sporangiospores.

Spores that possess flagella and are capable of movement in water are called motile spores or zoospores.

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.

A flower that has only one reproductive whorl (either androecium or gynoecium) is called a unisexual flower.

• If it has only androecium: male flower
• If it has only gynoecium: female flower
  Example: Papaya

A specialised axis or branch over which flowers are produced or borne in definite manner is known as inflorescence.

A flower that has both androecium (male part) and gynoecium (female part) in the same flower is called a bisexual flower.
Example: Hibiscus

A flower that has a stalk called pedicel for support is called a pedicellate flower.

Union of the second male gamete with two polar nuclei to form endosperm, along with fertilization, is called double fertilization.

Transfer of pollen grains from the anther to the stigma of a flower is called pollination.

or

Pollination is the transfer of pollen grains from the anther of a flower to the stigma of the same flower or of another flower of the same species.

Development of a new plant from a seed under favourable conditions is called seed germination.

Reproduction is a process that results in the formation of new individuals of the same kind, though usually with slight genetic, structural and physiological variations.

1. 1. Umbilical cord
   2. Placenta
   3.  Amniotic fluid
2. Functions of placenta: 
   • It allows the diffusion of oxygen, nutrients and immune products from the mother to the foetus.
   • It allows the diffusion of waste material generated by the foetus to the mother for excretion.
3. Functions of amniotic fluid:
   • The amniotic fluid prevents the foetus from injury and shocks.
   • It allows the foetus some amount of movement.
   • It prevents the amnion from sticking to the foetus.
   • It maintains an even pressure all around the foetus.
4. Gestation:
   • The time period required for the development of the foetus inside the uterus is called gestation. 
   • The normal gestation period in humans is 280 days (9 months).
5. Male sex chromosomes:
   • One ‘X’ chromosome and one ‘Y’  chromosome (XY).
   • Female sex chromosomes: Two ‘X’ chromosomes (XX).

Puberty is the process of physical and hormonal changes by which a child’s body matures into an adult body capable of sexual reproduction to enable fertilization.

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

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

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

or

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

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.

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.

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.

Gamete is a male or female reproductive cell that unites with another gamete during sexual reproduction to form zygote.

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

The union of a male gamete with the egg cell to form a zygote is called fertilization.

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

or

The formation of a zygote by the union of a sperm and an ovum is called fertilization.

The process of the blastocyst embedding itself into the endometrial lining of the uterus about 5–7 days after ovulation is called implantation.

or

The process of fixing the blastocyst to the wall of the uterus/endometrium is termed implantation.

Gastrulation is the early developmental process in which the embryo changes from a single-layered blastula into a three-layered structure called the gastrula.

Placenta is a temporary organ formed during pregnancy that connects the foetus to the uterine wall and allows exchange of nutrients, gases and wastes between the mother and the foetus.

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

or

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.

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.

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

A woman in whose uterus an embryo is implanted, and who carries the baby until birth on behalf of another woman, is called a surrogate mother.

When a single embryo divides into two groups of cells within 8 days after zygote formation, and both develop into separate embryos, they are called monozygotic twins.

If the embryo splits into two groups after 8 days of zygote formation, the resulting twins may be born with body parts joined together, and some organs may be common. Such twins are called conjoined twins.

When two embryos develop simultaneously in the same uterus and two offsprings are delivered at the same time, they are called twins.

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.

A population explosion means very rapid growth of the population, much faster than economic growth. In India, this has mostly happened because of a high birth rate and a much lower death rate in recent times.

• Meaning - Reproduction is the production of young ones similar to their parents. It is an essential biological process for the continuation of the species and continuity of life.
• Lifespan = period from birth to natural death; ranges from 1 day (Mayfly) to 3,000–4,000 years (Sequoia).
• Two Types - All methods of reproduction fall into two categories: Asexual Reproduction and Sexual Reproduction.
• Single-celled organisms (Amoeba, Bacteria) do not undergo natural death — they divide by binary fission.
• Four life stages: Juvenile → Reproductive → Senescent → Death.
• In plants, the reproductive phase begins at flowering.
• Monocarpic plants flower once; Polycarpic plants flower every season.
• Asexual reproduction = one parent, clones produced, faster.
• Sexual reproduction = two parents, gametes, zygote formed, genetic variation.
• The three phases of sexual reproduction: Pre-fertilisation → Fertilisation → Post-fertilisation.

• Meaning: Asexual reproduction involves only one parent, produces no fusion of gametes, and results in offspring that are genetically identical to the parent, called clones.
• Modes of Asexual Reproduction: Common methods include Binary Fission (Amoeba, Paramoecium), Fragmentation (Spirogyra), Budding (Yeast, Protosiphon), Spore Formation/Zoospores (Chlamydomonas), Conidia (Penicillium), and Gemmules (Marchantia).
• In Plants: Asexual reproduction in plants is called Vegetative Propagation. It can be Natural or Artificial (e.g., cutting, grafting, tissue culture).
• In Animals: Common in lower animals only. Does not involve meiosis or gamete formation. Lower animals reproduce asexually by budding and gemmule formation.
• Key Feature: Since only one parent is involved and no fusion occurs, all offspring are morphologically and genetically identical (clones) to the parent.

• Simple binary fission is an asexual reproduction method in which a unicellular organism, such as an Amoeba, divides along a random plane to produce two genetically identical daughter cells.
• The process begins with cell growth and DNA replication, ensuring that the parent cell synthesises the necessary proteins and creates an exact duplicate of its genetic material.
• Following replication, the cell undergoes nuclear division (mitosis), during which the nuclear membrane dissolves and the duplicated chromosomes separate into two distinct daughter nuclei.
• The final step is cytokinesis, wherein a cleavage furrow forms randomly, pinching the cell membrane inward to divide the cytoplasm and release two independent, fully functional daughter cells.

• Transverse binary fission is an asexual reproduction process in which an organism divides horizontally along its transverse axis to produce two distinct individuals.
• In Paramecium, the larger macronucleus divides amitotically while the smaller micronucleus divides mitotically, distributing one pair of each to the anterior and posterior ends of the cell.
• Following nuclear division, a horizontal constriction forms in the middle of the Paramecium and deepens until the cell splits completely into two independent daughter paramecia.
• Planaria (flatworms) also utilise this method by developing a constriction behind the pharynx and splitting in two, with each resulting half regenerating its missing segments to form a complete organism.

• A unicellular organism divides along its longitudinal (vertical) axis, splitting into two daughter cells - an asexual reproduction process, as seen in Euglena.
• The cell first suspends locomotion (flagellum sometimes withdrawn), then the blepharoplast splits, followed by eumitotic nuclear division where the nuclear membrane fully dissolves.
• A longitudinal cleavage furrow begins at the reservoir on the anterior end and proceeds down the body, gradually dividing the cell into two.
• The furrow deepens until two independent daughter euglenae are formed, with any lost parts regenerated immediately after division.

• In multiple fission, a single parent divides into many daughter cells at once by first forming multiple nuclei, followed by cytoplasmic division around each.
• In Amoeba, under unfavourable conditions, it withdraws its pseudopodia and secretes a three-layered chitinous cyst around itself - a process called encystation.
• Inside the cyst, the nucleus divides repeatedly into many daughter nuclei, each gathering a little cytoplasm to form tiny daughter cells called amoebulae (pseudopodiospores), which are released as adults when favourable conditions return.
• In Plasmodium, schizogony occurs in the human liver and red blood cells, producing many merozoites by multiple fission.
• In Plasmodium, sporogony occurs in the oocyst inside the female Anopheles mosquito, where multiple fission produces sporozoites.

• In unicellular organisms like yeast, a small bud forms on the parent cell, receives a nucleus, grows, and separates to become a new cell.
• A small projection appears on the parent cell's surface and enlarges into a bud, while the nucleus divides and one nucleus moves into the bud.
• The bud continues to grow while attached to the parent, then the mature bud separates to become an independent new yeast cell.

• When the body of a multicellular organism breaks into two or more fragments, each fragment grows into a new individual - a common, efficient method of asexual reproduction.
• In filamentous algae like Ulothrix and Spirogyra, the thallus breaks into small fragments, and each grows independently into a new thallus.
• In fungi, a small fragment of the hypha detaches from the parent mycelium and develops into a new individual.

• Regeneration is the process by which an organism regrows lost or damaged body parts - or forms a complete new individual from a body fragment - using specialised cells that multiply repeatedly and differentiate into various tissues.
• In Hydra and Planaria, a cut body fragment can regenerate the missing parts and grow into a complete organism (genetically similar clones), making it a form of asexual reproduction.
• Starfish also show strong regenerative ability, where a body fragment can, in some cases, grow into a complete new starfish, reflecting the high regenerative capacity of lower animals.

• In multicellular organisms like Hydra, a bud grows on the parent body through cell division and later detaches to become a new individual.
• The bud arises from repeated multiplication of epidermal interstitial cells, contains both epidermis and gastrodermis, and its cavity stays continuous with the parent's gastrovascular cavity.
• As it grows, the bud develops a mouth and tentacles, then separates and attaches to a surface by its basal disc to live independently as a new Hydra.

• Vegetative propagation is an asexual method where a new plant regenerates from root, stem, leaf, or bud, forming offspring genetically identical to the parent (a clone).
• It is rapid, easy, and inexpensive, useful for plants with poor seed viability or that cannot form seeds, like banana, seedless grapes, and rose.
• It preserves the parent's characters (mango, citrus, litchi) and aids grafting and disease-free micropropagation.
• Drawbacks: propagules decay easily, are prone to disease, show no variation, and cause overcrowding due to poor dispersal.

• A spore is a reproductive structure in simple plants and fungi that germinates directly into a new individual; it may be motile (zoospores) or non-motile (aplanospores).
• In algae like Chlamydomonas, the protoplast divides into 4–8 parts, each forming a zoospore that grows into a new individual.
• Fungi reproduce asexually by two spore types - sporangiospores and conidia.
• Sporangiospores form inside a sporangium: motile zoospores (e.g., Pythium) and non-motile aplanospores (e.g., Rhizopus).
• Conidia are non-motile spores formed externally on conidiophores, as in Aspergillus and Penicillium.

• Sexual reproduction involves the formation and fusion of male and female gametes (amphimixis) through meiotic division to create a diploid zygote.
• Life cycles progress from an initial juvenile phase focused purely on vegetative growth and development to a mature reproductive phase in which sex organs become functional.
• The reproductive process is strictly regulated by hormones and sequence-driven, consisting of three sequential stages: pre-fertilisation, fertilisation, and post-fertilisation.
• Pre-fertilisation focuses on gamete production and transfer, while post-fertilisation events track zygote development and the formation of embryonic structures.
• Meiotic cell division and cross-fertilisation blend parental genetic material, generating the vital variations needed to drive species adaptation and organic evolution.

• Sexual reproduction involves the fusion of male and female gametes from two parents to form a diploid zygote.
• A flower is the reproductive structure in plants that produces gametes and enables fertilisation.
• A flower has four whorls: calyx, corolla, androecium (male), and gynoecium (female).
• It includes meiosis for gamete formation and fertilisation, producing genetically different offspring.
• Sexual reproduction occurs in three stages: pre-fertilisation, fertilisation, and post-fertilisation.

• Humans are sexually reproducing and viviparous (giving birth to young ones, not eggs).
• 6 stages of reproduction in order: Gametogenesis → Insemination → Fertilisation → Implantation → Gestation → Parturition.
• Gametogenesis (gamete formation), Insemination (sperm transfer), Fertilisation (fusion → zygote), Implantation (blastocyst attaches to uterine wall), Gestation (embryo development), Parturition (delivery of baby).
• Sperm formation continues throughout a man's life; ovum formation ceases at around age fifty (menopause) in women.
• Testes (males) produce sperm; Ovaries (females) produce eggs; these are the primary reproductive organs (gonads).
• Features like beards (males) and breasts (females) are secondary sexual characteristics; they do not directly participate in reproduction.

• 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 the vagina via the 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 newborns. Puberty begins at 10–14 years in females.

• Gametogenesis is the process of formation of male and female gametes in the reproductive organs.
• It occurs in the testes of males and ovaries of females.
• Spermatogenesis produces sperms, while oogenesis produces ova (eggs).
• In this process, diploid germ cells form haploid gametes for sexual reproduction.

• Fertilization 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 fertilization, 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).
• Fertilization 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.

• The zygote divides by mitosis (cleavage) while moving towards the uterus.
• It forms blastomeres, and the 8–16 cell stage is called morula.
• A morula develops into a blastocyst with a trophoblast (outer layer) and an inner cell mass.
• Trophoblast attaches to the uterine lining (endometrium), and the inner cell mass forms the embryo.
• Implantation is the embedding of the blastocyst into the endometrium, leading to pregnancy.

• Placenta is formed after implantation and helps in exchange of nutrients, oxygen and wastes between mother and foetus.
• Three germ layers (ectoderm, mesoderm and endoderm) are formed, which develop into all body organs.
• Hormones like hCG, progesterone and estrogen increase to support pregnancy and foetal growth.
• Foetal development occurs gradually, and by nine months the foetus is fully developed and ready for birth.

• 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 neuroendocrine 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 afterbirth (placenta removal).

• Lactation involves the mammary glands secreting and ejecting milk to nourish and protect the newborn, initiated after childbirth.
• Prolactin, released by the anterior pituitary, stimulates alveolar cells to produce milk, a process called lactogenesis.
• Oxytocin, from the posterior pituitary, triggers the let-down reflex by causing myoepithelial cells to contract and eject milk when the baby suckles.
• Colostrum, the initial yellowish milk produced for a few days post-birth, is low in fat but highly concentrated in proteins, lactose, and essential antibodies.
• The abundant IgA antibodies present in colostrum transfer crucial natural passive immunity to the infant, protecting them while their own immune system develops.

• 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.

• Test-tube baby technique (IVF) involves fertilisation of the ovum by sperm outside the female body under laboratory conditions.
• The fertilised egg (embryo) is allowed to divide up to the 8–16 cell stage and is then transferred into the uterus for implantation.
• IVF is especially useful in cases of infertility caused by blocked fallopian tubes, low sperm count, or failure of natural fertilisation.
• Embryo freezing and surrogacy are advanced extensions of IVF, allowing storage of embryos and use of a surrogate mother in special cases.

• 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.