मराठी

Overview of Reproduction in Lower and Higher Animals

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Maharashtra State Board: Class 12

Definition: Primary Sex Organs

The organs that produce gametes, i.e., testis in males and ovary in females, are called primary sex organs.

Maharashtra State Board: Class 12

Definition: Secondary Sex Organs

Organs other than gonads that assist in reproduction are called secondary sex organs.

Maharashtra State Board: Class 12

Definition: Secondary Sexual Characters

The externally visible features that distinguish males and females are called secondary sexual characters.

Maharashtra State Board: Class 12

Definition: Amphimixis

Sexual reproduction involving fusion of gametes is also called amphimixis.

Maharashtra State Board: Class 12

Definition: Asexual Reproduction

The mode of reproduction in which offspring are produced by a single parent without gamete formation and fertilisation is called asexual reproduction.

Maharashtra State Board: Class 12

Definition: Gemmule Formation

The formation of a resistant internal bud consisting of dormant cells in sponges to survive unfavourable conditions is called gemmule formation.

Maharashtra State Board: Class 12

Definition: Budding

The process in which a new individual develops from a small outgrowth (bud) on the parent body is called budding.

Maharashtra State Board: Class 12

Definition: Clones

The genetically identical offspring produced during asexual reproduction are called clones.

Maharashtra State Board: Class 12

Key Points: Female Reproductive System

  • The female reproductive system includes ovary, oviducts, uterus, vagina, external genitalia and accessory glands, and is responsible for reproduction and continuation of species.
  • The ovary is the primary female sex organ that produces ova and female hormones such as estrogen, progesterone, relaxin, inhibin and activin.
  • Oogenesis starts before birth; many primordial follicles undergo degeneration (atresia), and only a limited number of ova are released during the reproductive life.
  • A mature Graafian follicle releases the ovum during ovulation, and the remaining follicle transforms into corpus luteum, which later becomes corpus albicans if fertilisation does not occur.
  • The fallopian tubes transport the ovum and provide the site for fertilisation, which normally occurs in the ampulla region.
  • The uterus is a muscular organ where implantation, growth and development of the embryo take place; its endometrium shows cyclic changes during menstruation.
  • The vagina serves as a copulatory organ, passage for menstrual flow and birth canal during childbirth.
  • External genitalia (vulva) and vestibular glands protect reproductive openings and secrete lubricating fluid to facilitate copulation.
Maharashtra State Board: Class 12

Key Points: Mammary Glands

  • Mammary glands are accessory organs of the female reproductive system responsible for production and secretion of milk after parturition.
  • Their development begins at puberty under the influence of estrogen and progesterone, while prolactin (LTH) stimulates development of lactiferous tubules during pregnancy.
  • Each mammary gland consists of 15–20 mammary lobes containing alveoli that secrete milk, which passes through mammary tubules, ducts and ampullae.
  • Milk is released through lactiferous ducts opening at the nipple, which is surrounded by a pigmented area called the areola.
 
Maharashtra State Board: Class 12

Key Points: Puberty and Sexual Maturity in Humans

Aspect Males Females
Meaning of puberty Stage when reproductive system becomes functional and starts producing gametes and hormones Stage when reproductive system becomes functional marked by onset of menstrual cycle
Age of onset Usually between 12–15 years Usually between 10–14 years
Key features Appearance of secondary sexual characters under testosterone Onset of menarche and cyclic menstrual changes
Duration Remains functional throughout life Continues from menarche till menopause (45–50 years)
Reproductive phase Lifelong after puberty From menarche to menopause
Hormonal control Mainly testosterone Controlled by gonadotropic hormones
Maharashtra State Board: Class 12

Key Points: Pregnancy

Aspect Duration / Period Major Features
Pregnancy (Gestation) ~266 days from fertilization or ~280 days from LMC Period between fertilization and parturition; divided into three trimesters
First Trimester Fertilization to 12th week Organogenesis occurs; embryo becomes foetus; heart starts beating; limbs form; mother experiences morning sickness
Second Trimester 13th to 26th week Rapid foetal growth; placenta takes over hormone production; foetal movements felt; hair, eyebrows and eyelashes appear
Third Trimester 27th week to birth Foetus gains weight and size; organs mature; eyes open; foetus becomes ready for parturition
Maharashtra State Board: Class 12

Key Points: Reproductive Health

  • Reproductive health refers to complete physical, mental, emotional, social and behavioural well-being related to reproduction, as defined by WHO.
  • India aims to achieve a reproductively healthy society through national programmes like the Reproductive and Child Health Care (RCH) programme.
  • The main goals of RCH include creating awareness about reproduction, providing reproductive health facilities, and reducing infertility, infant mortality rate and maternal mortality rate.
  • Reproductive health can be improved through sex education, awareness of safe and hygienic sexual practices, and information about sexually transmitted diseases.
  • Education about birth control, prenatal and postnatal care, child immunisation, and prevention of social evils related to sex is essential.
  • Controlling rapid population growth by promoting small family norms and use of contraceptive methods is crucial for maintaining reproductive health.
 
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