This PSEB 10th Class Science Notes Chapter 8 How do Organisms Reproduce? will help you in revision during exams.
PSEB 10th Class Science Notes Chapter 8 How do Organisms Reproduce?
→ The phenomenon of the formation of new individuals by the existing ones is called reproduction.
→ Reproduction is a means of the perpetuation of the species, and also a method of their multiplication.
→ Reproduction, unlike other life processes, is not essential to maintain the life of an individual organism.
→ Reproduction is the formation of similar organisms with the same body design, due to information of inheritance. (DNA or RNA).
→ Reproduction involves the creation of a DNA copy and additional cellular apparatus by the cell involved in the process.
→ DNA copies formed are not identical and have some variations but if variations are drastic then-new DNA copies cannot work.
→ All organisms reproduce. The reproducing organisms create new individuals that look very much like themselves.
→ The chromosomes in the nucleus of a cell contain information for the inheritance of features from parents to the next generation in the form of DNA (Deoxyribose Nucleic Acid) molecules.
→ The DNA in the cell nucleus is the information source for making proteins. Cells use chemical reactions to build copies of their DNA.
→ No biochemical reaction is absolutely reliable. Therefore, the process of copying the DNA will have some variations each time.
→ Some of the variations might be so drastic that the new DNA copy cannot work with the cellular apparatus it inherits. Such a newborn cell will simply die.
→ The inbuilt tendency for variation during reproduction is the basis for evolution.
→ If a population of reproducing organisms were suited to a particular niche and if the niche were drastically altered, the population could be wiped out.
→ If the water temperature increases by global warming, most of the bacteria living in temperate waters would die.
→ In unicellular organisms, cell division or fission leads to the creation of new individuals.
→ Many bacteria and protozoa simply split into two equal halves during cell division.
→ In Leishmania (which causes kala-azar), binary fission occurs in a definite orientation of the body.
→ The malarial parasite, Plasmodium, divides into many daughter cells simultaneously by multiple fission.
→ Yeast can produce small buds that separate and grow into new individuals.
→ Multicellular organisms have more complex ways of reproduction.
→ Hydra and Planaria can be cut into any number of pieces and each piece grows into a complete organism. This is known as regeneration. It is carried out by specialized cells.
→ Organisms such as Hydra use regenerative cells for reproduction in the process of budding.
→ There are many plants in which parts like the roots, stems, and leaves develop into new plants under appropriate conditions.
→ The methods such as layering or grafting to grow many plants like sugarcane, roses, or grapes are used for agricultural purposes.
→ Plants raised by vegetative propagation can bear flowers and fruits earlier than those produced from seeds.
→ Such methods also make possible the propagation of plants such as banana, orange, rose and jasmine that has lost the capacity to produce seeds.
→ In tissue culture, new plants are grown by taking tissue or cells from the growing tip of a plant.
→ This technique is commonly used for ornamental plants.
→ The hyphae of Rhizopus grow on the bread. They have sporangia, which contain cells or spores, which can eventually develop into new Rhizopus individuals.
→ In sexual reproduction, both sexes, males and females, are needed to produce new generations.
→ Combining variations from two or more individuals would create new combinations of variants.
→ As organisms become more complex, the specialization of tissue increases.
→ The motile germ cell is called the male gamete (pollen) and the germ cell containing the stored food is called the female gamete (ovule).
→ The reproductive parts of angiosperms are located in the flowers.
→ The flower may be unisexual (papaya, watermelon) when it contains either stamens or carpels or bisexual (Hibiscus, mustard) when it contains both stamens and carpels.
→ The ovary contains ovules and each ovule has an egg cell.
→ The fusion of the germ cells or fertilization produces the zygote.
→ The transfer of pollen from one flower to another is achieved by agents like wind, water, or animals.
→ After fertilization, the zygote divides several times to form an embryo within the ovule.
→ The seed contains the future plant or embryo which develops into a seedling under appropriate conditions. This process is known as germination.
→ Humans use a sexual mode of reproduction.
→ As adolescence starts, there are some changes taking place that are different among boys and girls. These do not happen all at the same time in one person, nor do they happen at an exact age.
→ The period of adolescence is called puberty.
→ The male reproductive system consists of portions that produce the germ cells and other portions that deliver the germ cells to the site of fertilization.
→ The formation of germ cells or sperms takes place in the testes.
→ In addition to regulating the formation of sperms, testosterone brings about changes in appearance seen in boys at the time of puberty.
→ The female germ cells or eggs are made in the ovaries.
→ The fertilized egg, the zygote, gets implanted in the lining of the uterus and starts dividing.
→ The embryo gets nutrition from the mother’s blood with the help of a special tissue called the placenta.
→ Since the ovary releases one egg every month, the uterus also prepares itself every month to receive a fertilized egg.
→ If the egg is not fertilized, the uterus lining slowly breaks and comes out through the vagina as blood and mucus. This cycle takes place roughly every month and is known as menstruation. It usually lasts for about two to eight days.
→ The process of sexual maturation is gradual.
→ Gonorrhea and syphilis and viral infections such as warts and HIV-AIDS are sexually transmitted diseases.
→ The sexual act always has the potential to lead to pregnancy.
→ Many mechanical, hormonal, and surgical methods are used to avoid pregnancy.
→ Pre-natal sex determination has been prohibited by law.
→ Because of reckless female foeticides, the child sex ratio is declining at an alarming rate.
→ Population explosion is raising problem in our country.
→ Birth control is an attempt to control the number of births in a family so that a couple may not have more children than required.
→ Physical barriers include the use of condoms, diaphragm, and cervical caps.
→ Chemical methods include the use of specific drugs by females i.e. oral pill and vaginal pill.
→ The use of IUCD (Copper-T) is very effective.
→ Surgical methods include vasectomy and tubectomy.
→ The communicable diseases occurring due to sexual contact are called sexually transmitted diseases such as gonorrhea, syphilis, and AIDS.
→ Reproduction: It is the process of producing new organisms by existing organisms of a species.
→ Sexual reproduction: The production of offspring by the fusion of male and female gametes is called sexual reproduction. It is biparental.
→ Asexual reproduction: The production of progeny without the fusion of male and female gametes is called asexual reproduction. It is uniparental.
→ Fission: The division of an organism into two or more individuals is called fission.
→ Budding: The process of development of an outgrowth due to repeated cell division at one specific site which grows into a tiny individual is called budding.
→ Vegetative propagation: The process of development of the new individual from any part of the body is called vegetative propagation.
→ Grafting: The technique of joining the different parts of two different plants to grow into one plant.
→ Unisexual: When the male and female are separate individuals, they are called unisexual.
→ Bisexual/Hermaphrodite: The organisms having male and female in a single individual are called bisexual/hermaphrodite.
→ Scion: A stem piece of good quality plant is grafted to grow into a new plant is called the scion.
→ Layering: The production of a new plant by covering the leaned branches of a plant under the soil.
→ Pollination: The transfer of pollen from another to stigma.
→ Fertilization: The fusion of male and female gametes is called fertilization.
→ Syngamy: The fusion of male gamete with female gamete is called syngamy.
→ Double fertilization: When the fertilization occurs two times (with ovum and polar cell) in angiosperms the process is called double fertilization.
→ DNA Replication: Duplication of DNA molecule by copying from a molecular template of DNA.
→ Regeneration: The formation of the lost part is called regeneration.
→ Gamete: Haploid sex cell is called gamete.
→ Zygote: Diploid fertilized egg is called a zygote. If undergoes cleavage (non-motile division) to form a complete organism.
→ Sperm: Haploid male gamete is called sperm.
→ Ovum: Haploid female gamete is ailed ovum.
→ Ovule: A structure in the ovary of a seed plant that develops into a seed after fertilization.
→ Puberty: The process of becoming sexually mature.
→ Ovulation: The release of the ovum from the ovary.
→ Implantation: The fixation of the embryo in the uterus is called implantation.
→ Placenta: It is the connection between mother and embryo.
→ Parturition: The process of giving birth to foetus is called parturition.