Categories
Class 10th Science

Sexual Reproduction in Human Beings : Study Notes for Class 10th Science

Reproduction in human beings

  • Puberty-it is the period during which adolescents reach sexual maturity and become capable of reproduction
  • During early teenage whole new set of changes occurs, appearance of body and proportions change and new features develop.
  • As the rate of general body growth slows down reproductive tissues begin to mature.
  • If animals are to participate in the process of mating, their state of sexual maturity must be identifiable by other individuals.
Pubertal changes in males Pubertal changes in females
a) deepening of voice(low pitch)
b) broadening of shoulders
c) appearance of beard & moustaches
d) Growth of axillary & pubic hairs
a) high pitch voice
b) widening of hips
c) Growth of axillary & pubic hairs
d) Initiation of menstruation
e) Growth of mammary glands.

Male reproductive system

Male reproductive system
Male reproductive system

1. Testis:

  • Testis is a galndular organ made up of fine tubules.
  • The formation of germ cells take place in testes, located outside the abdominal cavity in scrotum because sperm formation requires a lower body temperature.
  • testis also produces certain hormones, like tetosterone which are responsible for secondary sexual characters in humans.
  • These are deep male voice, hair growth in pubic area and under armpits, and facial hair.

2. Seminal Vesicle: Once sperm is produced it is stored in seminal vesicle.

3. Vas Deferens:

  • Vas deference is the tube through which semen containing sperm is transferred out.
  • The sperms produced are transferred by vas deferens which unites with a tube coming from urinary bladder.
  • Urethra forms a common passage for both sperm and urine.
  • To make the transportation of sperms easier prostate and seminal vesicles add their seceretions along the path of vas deferens, that makes the sperms to be transported in fluid which provides nutrition.
  • Cowper‘s gland – Produces white viscous & alkaline secretion
  • Semen = sperm& secretion of accessory glands

Female Reproductive system

1. Ovary:

  • Ovaries are situated on left and right side of the uterus.
  • The female germ-cells are produced in ovary, which is also responsible for production of oestrogen.
  • On reaching puberty some of the immature eggs present in the ovary of a girl start maturing.

2. Fallopian Tubes:

  • Fallopian tubes extends on both sides of the uterus in transverse direction.
  • Fallopian tubes have finger like structures which catch the eggs to transfer them to the uterus.

3. Uterus:

  • Uterus is a bag like structure, with an opening in the vagina.
  • Uterus opens into the vagina through cervix.

Fertilization In Human Beings 

  • Sperms enter through the vaginal passage during sexual intercourse and encounters egg in fallopian tube.
  • Once eggs reach uterus, a layer of soft tissues develops to support the embryo.
  • This layer is called corpus luteum.
  • If fertilization takes place, then the embryo develops into a foetus and ultimately to a fully developed child over a period of about 9 months
  • The zygote gets implanted into the lining of the uterus and starts dividing.
  • The uterus prepares itself every month to receive and nurture the the embryo, the lining thickens and is richly supplied with blood to nourish the growing embryo.
  • The embryo gets nutrition from the mother’s blood with the help of a tissue called placenta, a disc embedded in uterine wall.
  • The child is born as a result of rhythmic contractions of the muscles of uterus.
Female reproductive system
Female reproductive system
  • Implantation : Attachment of embryo to the lining of uterus.
  • Placenta : A connection between the mother & the foetus
  • The foetus meets all its developmental needs such as nutrition, respiration and excretion through the placenta.
  • Gestation period :The period between fertilisation & birth

Menstrual Cycle in Females:

  • If no fertilization takes place then after about two weeks the dead eggs and corpus luteum gets expelled out of the uterus through vagina.
  • This process takes place over a period of about three to four days.
  • This clears the way for new batch of eggs to come in the uterus.
  • The whole cycle from egg production to the expulsion of eggs takes about four weeks.
  • This cycle is known as Menstrual Cycle.
  • Apart from humans, some primates like Chimpanzee and Gorilla also show same
    phenomenon.
  • Ovary secretes one of the important hormones estrogen, which is responsible for secondary sexual characters in female, like thin voice and breast enlargement.

Menarche – commencement of menstrual cycle at puberty which marks the beginning of reproductive life of the human female.

Menopause – cessation of menstrual cycle which marks the end of the  reproductive life of a human female.

Reproductive Health and Birth Control Methods 

  • Creation of a mechanical barrier is a method of contraceptive so that the sperm does not reach the egg is called condoms.
  • Oral pills change the hormonal balance of the body
  • Loops and copper-T is placed in the uterus to prevent pregnancy
  • Surgical method can be used to block vas deferens in male and fallopian tube in female.

Read Here on Sexual Reproduction In Plants(Second Part of the Lesson) 

Previously Asked Questions on Reproduction in Human beings 

  1. How does the male gamete reach the egg present in the ovary?
    The pollen tube releases the male gametes in the embryo sac .
  2. What are gonads?
    Gonads are the primary sex organs which produce gametes & secrete sex
    hormones.
  3.  Define syngamy.
    The process of fusion of male gamete with the female gamete is known as syngamy.
  4.  At what age human males attain puberty?
    At the age of 12-14 years
  5.  At what age human females attain puberty?
    At the age of 10-12 years.
  6.  What are the functions of gonads?
    i) production of gametes
    ii) secretion of sex hormones.
  7. Why are testes located outside the abdominal cavity ?
    Sperm formation requires a temperature lower than that of the normal body temperature.
  8.  Where are ovaries located in human females?
    Ovaries are present in the abdominal cavity near the kidneys.
  9. What is placenta?
    A connection between the mother & the foetus.The foetus meets it all its developmental needs such as nutrition, respiration and excretion through the placenta.
  10. What is menstruation?
    If fertilization does not occur the uterine wall slowly breaks & comes out through vagina as blood and mucous.
  11. What is ovulation?
    It is the process of release of a mature ovum from the ovary.
Categories
Class 10th Science

Sexual Reproduction in Plants : Science Notes for Class 10 Biology

SEXUAL REPRODUCTION

  • In a population variations are useful for survival of a population.
  • Sexual mode of reproduction allows individuals to have more variations to be generated.
  • Generation of variations in DNA copying mechanism of asexual mode is fairly slow
  • Each new variation is made in a DNA copy that already has variations accumulated from previous generations.
  • Combining variations from two or more individuals would thus create new combinations of variants.
  • Each combination would be novel, since it would involve two different individuals.
  • For each new cell to not have twice the amount of DNA that previous generation have, special lineages of cells in specialised organs have only half the number of chromosomes and DNA as compared to other cells.
  • Two individuals combining during sexual reproduction, result in re-establishment of the number of chromosomes and DNA content in new generation.
  • Motile germ cell is called male gamete and germ-cell containing food is called female-gamete

Sexual reproduction in flowers

  • Flower can be termed as the sexual organ of a plant.
  • All the parts of a flower are arranged around an axis.
    1. Sepals: Green leaf like structure.
    2. Petals: Colourful structures, which add attraction to a flower. This attraction is not only having ornamental value, but a more important role in facilitating reproduction. Insects and birds, attracted by the colour, help transfer pollen grains or male gametes from male flower to female flower. This helps in pollination.
    3. Male Reproductive Organ of Plant: Androecium
  • The flower of a plant contains tube like structures called stamen.
  • At the top of stamen is a chambered structure called Androecium.
  • Androecium is responsible for the production of male gamete also called pollen grains.
    4. Female Reproductive Organ of Plant:
  • GynoeciumUsually at the centre of a flower you can notice Gynoecium.
  • Gynoecium is pitcher shaped structure with a long tube protruding out of it.
  • The gynoecium produces female gamete also called eggs.

Difference between Unisexual and Bisexual Plants

Unisexual Bisexual
  • A flower containing either stamen or carpel is unisexual e.g.watermelon
  • Flower containing both stamen and carpel are bisexual e.g hibiscus
  • Stamen is the male-reproductive part producing pollen which is yellowish in color.

 

  • Stamens and carpels are the reproductive parts of a flower.
  • Carpel is present in the centre of the flower and is the female reproductive part.
  • Carpel is made up of three parts , the swollen part is ovary , the middle elongated part is style and the terminal part is sticky and called stigma.
  • The ovary contains ovule which has an egg cell, the male gamete fuses with the female gamete present in ovule.

Pollination In flower

  • Pollination is the transfer of pollen from a male part of a plant to a female part of a plant, later enabling fertilisation and the production of seeds.
  • The pollen needs to be transferred from stamen to the stigma.
  • If the transfer of pollen occurs in the same flower it is self-pollination, if the transfers occurs in a different flower it is called cross-pollination
  •  Cross pollination can be facilitated by insects, birds, animals, air or water.
  • A tube growing out of the pollen grain and travels through the style to reach the ovary helps the landed pollen grain to reach female-germ cell.

Zygote Formation in Plant Reproduction

  • Once pollen grains enter the androecium, one of them enters the egg to fertilize it to form a zygote.
  • Seeds are the zygote or embryo of the plant.
  • To survive and to germinate,  seeds need source of food.
  • In all seeds there is abundance of food.
  • That is why for our daily need we depend on so many seeds like rice, wheat, groundnut for food.
  • During germination the food in the cotyledon is used to grow a new plant.
  • Once green leaves come out, they take care of further food production
  • After fertilization the zygote develops several times to form an embryo within the ovule.
  • The ovule develops a tough coat and is gradually converted into a seed
  • The seeds contain the embryo which develops into a seedling under proper conditions, this is known as germination

 

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Categories
Class 10th Science

How do Organism Reproduce:Class 10th Science Notes on Biology

Reproduction 

  • Reproduction is defined as a biological process in which an organism gives rise to young ones (offspring) similar to itself.
  • Reproduction at its basic level involves creation of the copy of DNA
  • DNA present in the chromosome of the cell is the information source for making proteins.
  • If the information is changed, different proteins will be made, and would lead to altered body designs.
  • The two DNA’s need to be separated, for the copy of DNA to have an organised cellular structure, DNA copying is accompanied by creation of additional cell apparatus.
  • Since no bio-chemical reaction is absolutely reliable, therefore the copying of DNA will have some variations each time.
  • DNA copies generated will be similar to each other and not identical.
  • Some of the variations may even be drastic enough for the new DNA generated not would not be able to work with the cellular apparatus and would eventually lead to death of the new cell.
  • The consistency of DNA copying during reproduction is important for maintenance of body design features that allow the organism to use a particular niche .
  • Reproduction is linked to stability of population of species.

IMPORTANCE OF VARIATION in Reproduction 

  • Population of organisms fill well-defined places or niches in the ecosystem, using their ability to reproduce.
  • Variation in DNA copying can ensure the survival of some individuals among a population, in case of changes in a particular niche in which the population is suited to survive in.
  • Variation is useful for survival of species over time.

ASEXUAL REPRODUCTION

  • Asexual reproduction:A sexual reproduction involves production of Offsprings by single parents.
  • There is no involvement of specialized gamete cell .
  • Offspring are genetically identical to their parents

Types of  Asexual Reproduction 

FISSION

  • In unicellular organisms, fission is the mode of reproduction used to create new individuals.
  • In simple unicellular organisms fission can take place in any plane, such as in amoeba.
  • In organisms showing somewhat more organisation of body, it occurs in a definite orientation in relation to the structure, for example leishmania having a whip-like structure present in one end.
  • Some single-celled organisms simply divide into many daughter cells simultaneously using multiple fission, for example plasmodium.
  • Yeast can put out small buds that separate and grow further

FRAGMENTATION

  • Multicellular organisms with simpler body design use fragmentation as a method of reproduction, for example in spirogyra, which breaks up into smaller pieces upon maturation.
  • These fragments grow into new individuals.
  • Not all multicellular organisms can use cell by cell division for reproduction as they are not simply a random collection of cells, and have organised body designs and structures,
  • In multicellular organisms reproduction via a single cell-type which is capable of growing, proliferating and making other cell types under right circumstances.

REGENERATION

  • Many fully differentiated organisms have the ability to give rise to new individuals from their body parts.
  • For example , if hydra or planaria is cut or broken into any number of pieces each piece grows into a complete organism this is known as regeneration
  • It is not the same as reproduction, since organisms would not depend on being cut up to be able to reproduce.

Budding

  • Organisms such as hydra use regenerative cells for reproduction in process of budding.
  • In hydra a bud develops as an outgrowth due to repeated cell division at one specific site
  • These buds develop into tiny individuals and detach themselves from parent body when fully mature.
Budding In Hydra
Budding In Hydra

Vegetative propagation

  • There are many plants in which parts like roots, stems and leaves can develop into new plants in appropriate conditions, this property is used in vegetative propagation method such as layering or grafting
  • Plants raised by vegetative propagation can bear fruits and flowers earlier than those reproduced by seeds.
  • Plants raised by vegetative propagation are genetically similar enough to the parent plant to have all its characteristics.

Spore formation

  • In rhizopus tiny blob-on-a-stick structures called sporangia containing spores that can develop into new rhizopus are involved in reproduction.
  • The spores have thick walls that protect them until they come into contact of another moist surface and being to grow.
Spore formation in rhizopus
Spore formation in rhizopus

Read the NCERT Solution On Reproduction here