NCERT Solutions for Class 12 Biology Chapter 1 Reproduction in Organism: It’s true that whatever has come to this earth it has to die after a certain time of period without any fail. So, have you ever assumed that how the species of any organism survive years to years? So in the solutions of NCERT class 12 biology chapter 1 reproduction in organism you will study that the answer to this question is reproduction. It becomes a vital process and without this process, species cannot survive for long. Each individual leaves its progeny by asexual or sexual means. Through the NCERT solutions for class 12 biology chapter 1 reproduction in organism you will be able to solve all the doubts and questions of this chapter. Inside the chapter, you will get to know that it's reproduction through which species continue to live through millions of years unless threatened by natural or anthropogenic extinction. If you are looking for the answers of any other class from 6-12 then NCERT solutions are there for you as it's the easiest way to get all the solutions of NCERT.
In the solutions of NCERT class 12 biology chapter 1 reproduction in organism, you will get to know all the answers of each and every question like if it is related to different types of reproduction that are:
- Asexual reproduction
- Sexual reproduction
Asexual reproduction does not involve the fusion of gametes. You will study that it is common in organisms that have a relatively simple organization such as the fungi, algae and some invertebrate animals. And sexual reproduction involves the formation and fusion of gametes. In CBSE NCERT solutions for class 12 biology chapter 1 reproduction in organism you will get answers related to such topics. In solutions for NCERT class 12 biology chapter 1 reproduction in organism, you will get interesting answers like it is also a complex and slow process as compared to asexual reproduction. Most of the higher animals reproduce almost entirely by the sexual method. CBSE NCERT solutions for class 12 biology chapter 1 reproduction in organism will give you all the answers with explanation and it will help you to score good marks in the exam as well as with this you can also prepare for your NEET exam. NCERT solutions for class 12 biology chapter 1 reproduction in organism will help you to understand the chapter and all its concepts very well.
This figure represents the asexual reproduction in different organisms through budding, fusion, etc.
Here are the important topics of class 12 biology chapter 1 reproduction in organism which will be covered in NCERT solutions for class 12 biology chapter 1 reproduction in organism:
1.1 Asexual Reproduction
1.2 Sexual Reproduction
1.2.1 Pre-fertilisation Events
18.104.22.168 Gamete Transfer
1.2.3 Post-fertilisation Events
22.214.171.124 The Zygote
In NCERT solutions for class 12 biology chapter 1 reproduction in organism you will also get question and answers from the topic like eukaryotes and prokaryotes, where you will learn that prokaryotes and unicellular organisms reproduce asexually by cell division or binary fission of the parent cell. Reproduction in organism will tell you about so many important terms related to reproduction like clones, gametes, syngamy, embryogenesis, etc.
After going through the CBSE NCERT solutions for class 12 biology chapter 1 reproduction in organism you can easily answer most of the questions from the exercise of this chapter. And if still confused then solutions for NCERT class 12 biology chapter 1 reproduction in organism is there for you. Try to attempt all the given questions in NCERT, and in case, if you have any doubt then refer to CBSE NCERT solutions for class 12 biology chapter 1 reproduction in organism.
Reproduction in Organisms Excercise:
Q1. Why is reproduction essential for organisms?
Reproduction refers to the process of production of offsprings by living organisms. The offsprings produced are similar to their parents. These offsprings grow and become reproductively mature to leave their progenies. Therefore, this process repeats itself and a continuity of species is maintained generation after generation. If reproduction would not have been there, species would not be able to leave their progenies and sooner or later they might extinct. Thus, reproduction is essential for living organisms.
Among sexual and asexual reproduction, sexual reproduction is considered to be a better mode of reproduction. It is mainly because sexual reproduction tends to create more amount of variations among the organisms. It involves two parents which contribute the 50% of their genomes each to the zygote. As a result of this, offsprings have father's characters, mother's characters and some other unique characters also. The variations caused by sexual reproduction are essential as they help organisms in adjusting to dynamic environmental condition and responsible for survival and gradual evolution of species. On the contrary, in asexual reproduction, single parent produces the offspring and thus, these offsprings are similar to their parent. Due to this, they have no advantage over organisms produced by sexual reproduction. Thus, sexual reproduction is a better mode of reproduction then asexual reproduction.
The term clone refers to a group of genetically and morphologically similar individuals. In asexual reproduction, a single organism is able to give rise to offsprings. Due to this, the offsprings thus produced are copies of their parents. These offsprings are exact replicas of each other also. That is why the offsprings produced by asexual reproduction are referred to as a clone.
During sexual reproduction male and female gametes from male and female individuals respectively fuse with each other and form zygote. This zygote contains new combinations of DNA/genes that are a result of recombination and crossing over. Due to the presence of these new combinations of DNA, variations are caused. These variations allow organisms to survive in unfavourable conditions. This is the reason why offsprings formed due to sexual reproduction have better chances of survival over those formed due to asexual reproduction.
The above statement is not always true, because there have been instances when continuous sexual reproduction among species of a given population, causes a reduction in yield and reduces the chances of survival. It mainly occurs because, sometimes due to recombination, less desired combinations of DNA/genes are formed and they make species vulnerable to extreme conditions. Thus, the statement, offspring formed due to sexual reproduction have better chances of survival is not always true.
The progeny formed from asexual reproduction differs from that formed from sexual reproduction in the following ways:
||Progeny formed from asexual reproduction
||Progeny formed from sexual reproduction
||These are formed from single parent
|| Their formation requires the involvement of two parents i.e. a male and female
||The process of formation does not involve meiosis and crossing over
||Formation of gametes involves meiosis and crossing over
||These progenies are copies of their parents and of each other
||These progenies are different from their parents and from each other
||These progenies do not show genetic variations
These progenies show genetic variation due to crossing over and recombination
Differences between sexual and asexual reproduction are as follows:
| Asexual reproduction
|| Sexual reproduction
|It involves a single parent
||It involves two parents
|There is no requirement of sex organs and gametes
||Gamete formation occurs in sex organs
|It involves somatic cells of the body
||it involves germ cells of the body
|Offsprings produced in asexual reproduction are exactly similar to their parent
||offsprings produced in sexual reproduction are different from their parents
|It occurs rapidly
||It is a slow process
|It occurs in unicellular organisms, lower invertebrates, plants etc.
||It occurs in higher organisms
Vegetative reproduction is considered to be a type of asexual reproduction because
1. Vegetative reproduction is uniparental i.e. it involves a single parent.
2. The reproductive propagules of vegetative reproduction are somatic cells as in asexual reproduction.
3. Meiosis and fertilisation are absent in vegetative reproduction.
4. Vegetative reproduction does not cause variations. The offsprings produced are similar to their parent
Vegetative propagation is a method of asexual reproduction in plants. In this method, a vegetative part of a plant gives rise to new plants. This vegetative part which has the ability to produce new plants is called vegetative propagule. Some common vegetative propagules are runner, rhizome, sucker, tuber, offset, bulb etc. Vegetative propagation is of two types i.e. natural vegetative propagation and artificial vegetative propagation. In natural vegetative propagation, a vegetative structure detaches from the parent plant and give rise to new plants. Artificial vegetative propagation includes methods developed by horticulturists to readily develop multiple plants through vegetative propagation.
The examples of vegetative propagation are
1. Vegetative propagation by roots: Roots of some plants can develop adventitious buds to form new plants e.g. Dalbergia, guava, poplar, Albizia, Murraya etc. Fleshy roots such as those of sweet potato, tapioca, Dahlia etc. also develop adventitious buds and form new plants.
2. Vegetative propagation by leaves: The leaves of some plants develop buds over them. From these buds, new plants arise. E.g Bryophyllum.
(a) Juvenile phase,
All organisms have to reach a particular growth stage before they attain reproductive maturity. This pre-reproductive period of growth is called juvenile phase in animals. In plants, this phase is known as the vegetative phase. The duration of the juvenile phase varies in different organisms.
(b) Reproductive phase
Reproductive phase refers to that phase of an organisms' life cycle in which it attains reproductive maturity and become able to produce gametes and mate. This phase is marked by certain hormonal changes.
The senescent phase refers to the post-reproductive phase in which an organism not just loses its reproductive potential but also the rate of metabolism slows down and there is deterioration of vital activities of the body.
Higher organisms have resorted to sexual reproduction because sexual reproduction enables these organisms to survive during unfavorable conditions. It tends to induce genetic variability in these organisms which further becomes a cause of the evolution of better-adapted species.
Meiosis refers to the cell division which causes a reduction in the number of chromosomes by half and gametogenesis is the formation of male and female gametes. These two terms are often interlinked because gamete formation in diploid organisms occurs through meiosis only. The number of chromosomes in diploid organisms must be reduced to half because if this doesn't happen then the zygote after fertilisation would have 4n ploidy. Thus, gametogenesis and meiosis are interlinked.
The anther is the male reproductive part of a flower. It is diploid (2n) i.e. it consists of 2 sets of chromosomes.
The egg is the female gamete and is formed by meiosis so it is haploid (n).
Pollen grains are haploid i.e. they contain one set of chromosomes
(e) Male gamete
Male gametes in plants are formed by mitosis in pollen grain which is a haploid structure. Thus, male gametes are haploid (n).
A zygote is formed after fertilisation of male and female gametes which are haploid (n). Thus, zygote is diploid (2n).
Q12. Define external fertilisation. Mention its disadvantages.
External fertilisation refers to the fusion of male and female gametes outside the body of the organism. The disadvantages of external fertilisation are as follows:
1. External fertilisation requires an aquatic medium
2. Offsprings produced are highly vulnerable to predators
3. Parental care is not provided to offsprings
Q13. Differentiate between a zoospore and a zygote.
The differences between zoospore and zygote are as follows:
| It is an asexual reproductive body
||It is the result of sexual reproduction
Zoospores contain flagella, so they are motile
|The zygote does not contain flagella, so it is non-motile
Zoospores can be haploid in some organisms and diploid in some others
|A zygote is formed as a result of
|Zoospores give rise to new individuals after germination
The zygote undergoes development to form an embryo which gives rise to new individual
|These are formed in lower organisms
||The zygote is formed in higher plants and animals
Q14. Differentiate between gametogenesis from embryogenesis.
Differentiation between gametogenesis and embryogenesis is as follows:
|The process of formation of gametes is called gametogenesis
||The process of formation of the embryo is called embryogenesis
|This process involves meiotic divisions that lead to the formation of gametes
||This process involves mitotic division that leads to the development of a zygote into an embryo
|Gametogenesis leads to fertilisation
||embryogenesis is followed by organogenesis
The post fertilisation changes that occur in a flower are as follows:
1. Formation of zygote occurs in the ovule. zygote further develops into an embryo.
2. The ovary develops into the fruit while the ovary wall develops into pericarp.
3. Ovules develop into seeds
4. Sepals, petals and stamens wither and fall off while pistils remain attached to the plant.
Bisexual flowers are those flowers which possess both male and female reproductive parts i.e. stamen and pistil respectively. Some of the common bisexual flowers that you will be able to collect in your neighbourhood are given below:
Cucurbits bear unisexual flowers. These type of flowers bear either male or female reproductive organs. It means that a staminate flower bears only stamen i.e. male reproductive organ while pistillate flower contains only pistil i.e. female reproductive organ. So you can identify staminate and pistillate flowers on the basis of the presence of male and female parts respectively. Another example of a plant bearing unisexual flowers is maize.
Oviparous organisms are those organisms that lay fertilized or unfertilized eggs whereas viviparous organisms are the ones that give birth to young ones. The offsprings of oviparous animals are considered to be at a greater risk as compared to offsprings of viviparous animals because of the following reasons:
1. In oviparous animals, the development of offsprings occurs outside the body of the organism and they do not get proper protection and nourishment as in viviparous organisms.
2. The offsprings of oviparous organisms develop inside eggs made of calcareous shells. These eggs are prone to attack by predators
Hence, offsprings of oviparous animals are at a greater risk as compared to offsprings of viviparous animals.
NCERT Solutions Class 12 – Biology
NCERT Solutions for Class 12- Subject wise
Benefits of NCERT solutions for class 12 biology chapter 1 reproduction in organism is given below:
- Solutions for NCERT class 12 biology chapter 1 reproduction in organism provides such answers which are easy to understand and to remember them as well.
- It will also help you to prepare for CBSE exams through NCERT solutions for class 12 biology chapter 1 reproduction in organism.
- It also helps you to prepare for the NEET entrance exam along with your 12th board exam.
- CBSE NCERT solutions for class 12 biology chapter 1 reproduction in organism are easy to access (any time, anywhere).