Mix Examples - How do Organisms Reproduce? Questions in English

(N/A) Pollination is the process of transfer of pollen grains from the anther to the stigma of a flower.
Fertilisation is the process of fusion of the male gamete with the female gamete (egg) to form a zygote.
The site of fertilisation in a flower is the ovule.
The product of fertilisation is the zygote.

(N/A) $gamete$ is a specialized sex cell or germ cell involved in sexual reproduction. There are two types of gametes: male and female.
$A$ $zygote$ is the diploid cell formed as a result of fertilization, where a male gamete and a female gamete fuse together.
The two fusing gametes carry genetic information from their respective parents in their $DNA$. Fertilization combines the genetic material of both parents into a single $zygote$ cell.
The $zygote$ serves as the first cell of the next generation. It undergoes repeated mitotic divisions to form an embryo, which subsequently develops into a new individual.

(N/A) The four whorls of a flower are:
$1$. Calyx (Sepals)
$2$. Corolla (Petals)
$3$. Androecium (Stamens)
$4$. Gynoecium (Pistil/Carpel)
Gamete-producing organs:
- Male gamete-producing organ: The stamen (specifically the anther,which produces pollen grains containing male gametes).
- Female gamete-producing organ: The pistil (specifically the ovary,which contains ovules that produce the egg cell/female gamete).

(N/A) The placenta is a special disc-like tissue embedded in the uterine wall that connects the developing embryo to the mother.
Its roles during pregnancy are:
$1$. It possesses villi on the embryo's side of the tissue,which increases the surface area for glucose and oxygen transfer from the mother to the embryo.
$2$. It facilitates the passage of essential nutrients and oxygen from the mother's blood to the embryo.
$3$. It acts as an excretory organ by removing waste substances and carbon dioxide produced by the embryo into the mother's blood for excretion.

(N/A) The various methods to avoid pregnancy (contraception) include:
$(i)$ Barrier methods (e.g.,condoms) to prevent physical contact between sperm and egg.
$(ii)$ Chemical methods (e.g.,oral pills) which change the hormonal balance of the body to prevent the release of an egg (ovulation).
$(iii)$ Intrauterine devices (e.g.,copper $T$ or loop) which are placed in the uterus to prevent implantation.
$(iv)$ Surgical methods (e.g.,vasectomy in males or tubectomy in females) which block the vas deferens or fallopian tubes respectively.
Elaboration of Chemical Method (Oral Pills):
Oral contraceptive pills contain specific hormones that inhibit the release of eggs from the ovaries. By preventing ovulation,the sperm has no egg to fertilize,thereby effectively preventing pregnancy.

(N/A) During sexual intercourse,sperm enters through the vaginal passage and moves upwards into the fallopian tube (oviduct).
$(b)$ An egg is released from the ovary and reaches the oviduct.
$(c)$ The sperm encounters the egg in the oviduct,where fusion occurs,resulting in fertilization.
$(d)$ Fertilization occurs once a month because the ovary releases only one egg every month during the menstrual cycle.

(N/A) Organisms require energy for survival,which they obtain through life processes such as nutrition and respiration.
$(b)$ Reproduction is an energy-intensive process that does not contribute to the survival of the individual organism.
$(c)$ The primary purpose of reproduction is the transfer of genetic material from one generation to the next through $DNA$ copying.
$(d)$ $DNA$ copying occurs with high fidelity but also introduces variations,which provide advantages to the species,ensuring its stability and survival in a changing environment.

(N/A) $1$. Sexually Transmitted Diseases (STDs) are infections that are primarily spread through sexual contact with an infected person.
$2$. These diseases can be caused by various pathogens,including bacteria (e.g.,syphilis,gonorrhea),viruses (e.g.,$HIV$,genital herpes),or parasites.
$3$. Prevention methods include:
- Practicing safe sex by using mechanical barriers like condoms,which significantly reduce the risk of transmission.
- Maintaining personal hygiene and avoiding sexual contact with multiple or unknown partners.
- Seeking early medical diagnosis and treatment if symptoms appear to prevent further spread.

(N/A) $(i)$ Production of female gametes (ova).
$(ii)$ Secretion of female sex hormones (estrogen and progesterone).

(N/A) Organisms that possess both male and female sex organs in the same individual are called bisexual or hermaphrodite organisms.
Example: $Hydra$,Earthworm,Mustard,or Hibiscus.

(C) Reproduction is the biological process by which an organism produces new individual organisms (offspring). It is essential for the survival of a species and directly contributes to the growth and maintenance of a population over time.

(B) $DNA$ (Deoxyribonucleic acid) is primarily found within the nucleus of a eukaryotic cell,where it is organized into structures called chromosomes. It contains the genetic information necessary for the development and function of living organisms.

(N/A) Regeneration is the process by which an organism can regrow lost or damaged body parts. Simple organisms like $Planaria$,$Hydra$,and $Earthworm$ possess the ability to regenerate their entire body from a small fragment or piece. Therefore,any two of these,such as $Planaria$ and $Hydra$,are correct examples.

(N/A) $(i)$ The study of the mechanism by which variations are created and inherited is called $Genetics$.
$(ii)$ The development of new types of organisms from existing ones is called $Evolution$.

(D) Vegetative propagation is an asexual method of reproduction in plants. An important advantage of this method is that it can be used to grow plants that do not produce seeds (e.g.,banana,jasmine) or produce non-viable seeds. Additionally,it ensures the production of genetically identical offspring,which helps in maintaining desirable traits of the parent plant.

(C) The cells that undergo regeneration are known as regenerative cells. These are specialized cells that have the ability to proliferate and produce a large number of cells to replace the lost or damaged body parts.

(B) The basic difference in the body design of organisms arises due to variations that occur during the process of $DNA$ replication.
When a cell divides,it must copy its $DNA$ to ensure that each daughter cell receives a complete set of genetic information.
This copying process is not perfectly accurate and introduces small errors or changes,known as variations.
These variations accumulate over generations,leading to the diverse body designs observed in living organisms.

(B) Chromosomes are composed of $DNA$ and proteins. During the interphase of the cell cycle,the genetic material exists as a loose network called chromatin. However,when the cell enters the process of cell division (mitosis or meiosis),the chromatin condenses into highly organized,thread-like structures known as chromosomes. Therefore,chromosomes can be clearly identified and observed under a microscope only during the phase of cell division.

(B) The testes are located outside the abdominal cavity in the scrotal sac because the process of spermatogenesis (the production of sperms) requires a temperature that is approximately $2\,^{\circ}C$ to $2.5\,^{\circ}C$ lower than the normal internal body temperature. This lower temperature is essential for the survival and maturation of sperm cells.

(N/A) Pollen grains are the male reproductive units in flowering plants that contain the male gametes. They are typically produced in the anther.
Ovules are the female reproductive structures in flowering plants that contain the female gamete (egg cell). They are located within the ovary and develop into seeds after fertilization.

(N/A) Germination: It is the process by which an embryo develops into a seedling under favorable conditions. It marks the beginning of the growth of a new plant from a seed.
Fertilization: It is the process of fusion of the male gamete (pollen grain/sperm) with the female gamete (ovum/egg cell) to form a zygote. It is a crucial step in sexual reproduction.

(N/A) $(i)$ Sexually Transmitted Diseases $(STDs)$ are infections that are primarily transmitted from one person to another through sexual contact.
$(ii)$ $AIDS$ (Acquired Immuno Deficiency Syndrome) is an $STD$ caused by the $HIV$ virus,which specifically targets and damages the immune system of the human body.

(N/A) Regeneration is a process that relies on the presence of specialized cells known as stem cells or undifferentiated cells.
These cells have the potential to proliferate and differentiate into various cell types to replace lost or damaged tissues.
In complex organisms,the body organization is highly specialized and differentiated,meaning cells have lost their ability to revert to an undifferentiated state.
Therefore,only organisms with a simple body organization and the presence of these specialized regenerative cells can exhibit the phenomenon of regeneration.

(B) Spores are protected by a thick,resistant cell wall,which allows them to survive in adverse environmental conditions like extreme heat or lack of water.
Additionally,spores are produced in large numbers and are very light in weight,which facilitates their easy dispersal over long distances by wind,water,or animals.

(C) If the egg is not fertilized,the thick and spongy lining of the uterus is no longer needed. Consequently,this lining slowly breaks down and comes out through the vagina as blood and mucus. This process is known as menstruation.

(N/A) The lining of the uterus becomes thick and spongy every month to prepare itself to receive and nurture the growing embryo in case fertilization occurs. This rich,vascularized lining provides the necessary blood supply and nutrients to support the development of the zygote.

(N/A) In $Amoeba$,binary fission occurs,where the parent cell divides into two daughter cells. In $Plasmodium$,multiple fission occurs,where the parent cell divides into many daughter cells simultaneously.
$(b)$ In binary fission,a single-celled organism divides into two daughter cells. In fragmentation,the body of a multicellular organism breaks into two or more pieces,and each piece develops into a new individual.

(N/A) $(i)$ $DNA$ is primarily located within the nucleus of a cell,specifically within the chromosomes.
$(ii)$ Genes are segments of $DNA$ located on the chromosomes.
$(b)$ The expansion of $DNA$ is Deoxyribonucleic Acid.

(N/A) To create copies of $DNA$ or genetic material,cells utilize biochemical reactions.
These biochemical processes result in the replication of $DNA$.
Along with the $DNA$ copies,the cell synthesizes additional cellular apparatus to support the new cell.
Finally,the cell divides,resulting in the formation of two almost identical daughter cells.

(N/A) Variations in organisms are primarily caused by the following factors:
$(1)$ Genetic changes: These occur due to inaccuracies or changes in the $DNA$ copying process during reproduction,leading to new combinations of genes.
$(2)$ Environmental factors: External influences such as light,temperature,nutrition,wind,and water supply can influence the phenotype of an organism.
$(3)$ Mutations: Sudden,permanent changes in the genetic sequence $(DNA)$ can also introduce new variations.

(N/A) Spore formation: It is a method of asexual reproduction where organisms produce tiny,unicellular,reproductive bodies called spores. These spores are covered by thick walls to withstand unfavorable conditions and develop into new individuals upon germination.
$(b)$ Regeneration: It is the ability of an organism to regrow lost or damaged body parts. In some organisms,if the body is cut into pieces,each piece can grow into a complete new organism.
$(c)$ Multiple fission: It is a type of asexual reproduction in which a single parent cell divides into many daughter cells simultaneously,often occurring under unfavorable conditions.

(N/A) $Planaria$ exhibits high regenerative capacity; therefore,each cut piece grows into a complete new organism.
$(b)$ The buds present in the notches of the $Bryophyllum$ leaf develop into new plantlets when they come in contact with moist soil.
$(c)$ The release of testosterone triggers the development of secondary sexual characteristics in boys during puberty,such as voice change,growth of facial hair,and increased muscle mass.

(N/A) The primary difference is that sperms are motile,while eggs are non-motile.
The importance of this difference is that the motility of the sperm allows it to travel through the female reproductive tract to reach the egg for fertilization.
Alternatively,another significant difference is in their chromosomal content:
Sperms contain either an $X$ or a $Y$ chromosome.
Eggs contain only an $X$ chromosome.
The importance of this difference is that it determines the sex of the offspring upon fertilization:
If an $X$-bearing sperm fertilizes the egg,the zygote becomes $XX$ (female).
If a $Y$-bearing sperm fertilizes the egg,the zygote becomes $XY$ (male).

(N/A) Budding is a form of asexual reproduction in $Hydra$.
$1$. In $Hydra$,a small outgrowth called a bud develops on the body wall due to repeated cell division at a specific site.
$2$. This bud gradually grows and develops into a small,complete $Hydra$ with tentacles and a mouth.
$3$. Once fully developed,the new $Hydra$ detaches from the parent body and begins to live as an independent organism.
(Refer to the provided diagram showing the stages of bud development,the formation of tentacles,and the final detachment of the new individual.)

(N/A) $(i)$ In sexual reproduction, the fusion of male and female gametes takes place. These germ cells/gametes contain half the number of chromosomes compared to the somatic (body) cells.
$(ii)$ When male and female gametes fuse during fertilization, the zygote formed receives one set of chromosomes from each parent, which restores the original diploid number of chromosomes, thereby ensuring the stability of the species.

(N/A) $(i)$ $DNA$ copying is essential for the formation of additional cellular apparatus, ensuring that when $DNA$ copies separate, each daughter cell receives its own complete set of cellular machinery.
$(ii)$ The process of $DNA$ copying is not perfectly accurate and results in minor variations each time. Consequently, while the generated $DNA$ copies are similar to the original, they may not be identical, which allows for evolution and adaptation over generations.

(N/A) Variation refers to the differences in the characteristics or traits among individuals of the same species,which arise primarily due to inaccuracies in $DNA$ copying during sexual reproduction.
Variations are beneficial to a species because they provide a survival advantage. If environmental conditions change drastically,individuals with favorable variations are more likely to survive and reproduce,thereby ensuring the continuity of the species.

(N/A)

< strong>Pollination	< strong>Fertilization
$(i)$ It is the transfer of pollen grains from the anther to the stigma of a flower.	$(i)$ It is the fusion of the male gamete with the female gamete (egg).
$(ii)$ It is achieved by agents like wind,water,or animals.	$(ii)$ It is achieved by the growth of the pollen tube so that the male gamete reaches the female germ cells.
$(iii)$ It leads to fertilization.	$(iii)$ It leads to the formation of seeds.
$(iv)$ It is an external process.	$(iv)$ It is an internal process.

(N/A)

Binary Fission	Multiple Fission
$(i)$ The nucleus divides into two parts.	$(i)$ The nucleus divides into many parts.
$(ii)$ It occurs during normal conditions.	$(ii)$ It takes place during unfavourable conditions (Encysted stage).
$(iii)$ It gives rise to two individuals.	$(iii)$ It forms many individuals.
$(iv)$ Cytoplasm divides after each nuclear division. Example: $Amoeba$.	$(iv)$ Cytoplasm does not divide after every nuclear division. Example: $Plasmodium$.

(N/A) In humans,the female produces eggs that always contain the $X$ sex chromosome. However,the male produces sperms that contain either an $X$ or a $Y$ sex chromosome.
This chromosomal difference is crucial for sex determination in the offspring.
When a sperm carrying an $X$ chromosome fertilizes an egg (which always has an $X$ chromosome),the resulting zygote has an $XX$ genotype,leading to the birth of a female child.
Conversely,when a sperm carrying a $Y$ chromosome fertilizes an egg,the resulting zygote has an $XY$ genotype,leading to the birth of a male child.
Thus,the sperm determines the sex of the child.

(N/A) Vegetative propagation is a type of asexual reproduction in plants where new plants are produced from vegetative parts such as roots,stems,and leaves,rather than from seeds or spores,under appropriate environmental conditions.
$(b)$ Two advantages of vegetative propagation are:
$(i)$ It allows for the propagation of plants that do not produce viable seeds,such as bananas,oranges,and grapes.
$(ii)$ Plants produced through this method are genetically identical to the parent plant,ensuring that desirable traits are preserved and the offspring reach maturity and bear fruit/flowers faster than those grown from seeds.

(N/A)

< strong>Plumule	< strong>Radicle
$(i)$ The part of the growing embryo which later forms the shoot of the young plant.	$(i)$ The part of the growing embryo which later forms the root of the young plant.
$(ii)$ It is positively phototrophic and negatively geotrophic.	$(ii)$ It is positively geotrophic and negatively phototrophic.

(A) Planaria reproduces by Regeneration,where the organism can regrow lost body parts or develop into a new individual from a body fragment.
$(b)$ Rhizopus reproduces by Spore formation,where specialized structures called sporangia produce numerous spores that develop into new individuals.
$(c)$ Spirogyra reproduces by Fragmentation,where the filament simply breaks into smaller pieces upon maturation,and each piece grows into a new filament.
$(d)$ Hydra reproduces by Budding,where a small outgrowth or bud develops on the parent body,which eventually detaches to form a new individual.

(N/A) $(i)$ The ovum (egg cell) fuses with the male gamete to form a zygote.
$(ii)$ The ovary ripens and develops into the fruit.
$(iii)$ The ovule develops into the seed.
$(iv)$ The sepals and petals usually wither,shrivel,and fall off.

(B) Copper-$T$ is an intrauterine device $(IUD)$ used for contraception.
Its primary function is to prevent pregnancy by inhibiting the implantation of the fertilized egg in the uterus.
It also releases copper ions which are toxic to sperm,thereby reducing their motility and preventing fertilization.
The common side effect of using Copper-$T$ is uterine irritation or discomfort,which may lead to increased bleeding or cramping in some women.

(N/A)

Self-pollination	Cross-pollination
$(i)$ It is the transfer of pollen grains from the anther to the stigma of the same flower or another flower on the same plant.	$(i)$ It is the transfer of pollen grains from the anther of one flower to the stigma of another flower on a different plant of the same species.
$(ii)$ It does not require external agents like insects, wind, or water.	$(ii)$ It requires external agents like insects, wind, or water for pollination.
$(iii)$ It results in less genetic variation in the offspring.	$(iii)$ It results in greater genetic variation in the offspring.

(B) The leaves of $Bryophyllum$ possess adventitious buds in the notches along the leaf margins.
When these leaves fall on moist soil,the adventitious buds develop into new plantlets under favourable conditions.
This is a form of vegetative propagation.

(D) $(i)$ To prevent unwanted pregnancies.
$(ii)$ To prevent sexually transmitted diseases (STDs).
$(iii)$ To maintain a healthy spacing between children.
$(iv)$ To ensure overall reproductive health and well-being.

(N/A)

< strong>Male gamete	< strong>Female gamete
$(i)$ It is smaller in size compared to the female gamete.	$(i)$ It is larger in size.
$(ii)$ It is generally motile.	$(ii)$ It is generally non-motile.

(A) The contraceptive method that prevents $STDs$ (Sexually Transmitted Diseases) is the $(a)$ Barrier method.
This method is effective because it creates a physical barrier between the genital organs of the male and the female.
By preventing direct contact between the genital fluids and tissues,it effectively blocks the transmission of pathogens that cause $STDs$.