Biology Reproduction in Organisms Chapter 1 – Exercise

Q-1  Why is reproduction essential for organisms?
Ans. Reproduction is essential for organisms because the continuity of the species generation after generation.
Q-2 Which is a better mode of reproduction sexual or asexual ? Why ?
Ans. Sexual reproduction is a better mode of reproduction because is needs meiosis and fusion of male
and female gametes. Such as a fusion involving two parents result in the offspring that are not
identical to the parents. It also cause variation which is essential for evolution and survival of
species under diverse change in environmental factors.
Q-3 Why is the offspring formed by asexual reproduction referred to as clone?
Ans. Asexual reproduction results in the production of Offspring  which are morphological and
genetically similar. Such individuals are called clones.
Q-4 Offspring formed due to sexual reproduction have better chances of survival , why ? Is this
statement always true?
Ans. Offspring formed due to sexual reproduction have better chance of survival because they possess
the genetic material of two parents and that too shows variation. This is important for survival of
the species. The variation is usually advantageous and helps the offspring to survival under
changing environmental conditions. Sometimes the variation are not fit for the survival of the
species. Therefore, we can not say that this statement is always true.
Q-5 How does the progeny formed from asexual reproduction differ from those formed by sexual
reproduction?
Ans.  Since asexual reproduction does not involve meiosis and fusion of gametes, the progeny formed
from asexual reproduction are genetically similar to parents and they  do not show variation. The
individuals product as a  result of meiosis and gametic fusion exhibit genetic variation and
difference from either of the two parents as well as among themselves.
Q-6 Distinguish  between asexual reproduction. Why is vegetative reproduction also considered as a type of asexual reproduction ?
Ans. Refer to table 1.2. Since vegetative reproduction does not involve meiosis and fusion of gametes, it is considered as a type of asexual reproduction.
Q-7 What is vegetative propagation ? Give two suitable examples.
Ans. The vegetative propagation involves production of new individuals from some vegetative plant
propagules such as buds, tubers, rhizomes , etc . Examples – (1) Potato tubers possess buds which
grow into new plants ; (2) Adventitious  buds of Bryophyllum leaves grow to from new plants.
Q-8 Define : (i) Juvenile phase , (ii) Reproductive phase, (iii) Senescent phase
Ans. (i)  Juvenile phase is the period of growth between the birth of an individual  up to reproductive
maturity.(ii) Reproductive phase starts after juvenile phase and remains upto the stage when an organism
is capable of reproduction.(iii) Senescent phase  is the phage of ageing when an organism loses its capacity of reproduction. In plants, it is characterized by yellowing and leaf fall.
Q-9 Higher organisms have resorted to sexual reproduction in spite of its complexity, why ?
Ans.  In spite of its complexity , higher organisms have resorted to sexual reproduction because it enables these organisms to survive during unfavorable  conditions. It contributes to evolution of
the species by introducing variation in a population much more rapidly than asexual reproduction.
Q-10 Explain why meiosis and  gametogenesis are always interlinked ?
Ans. Gametogenesis is the process of the formation of haploid gametes inside gametangia. The normal body if organisms is usually diploid but the gametes are haploid. Thus, gametes are formed as a
result of meiosis so that their chromosome number becomes haploid.
Q – 11 Identify each part and write whether it is haploid (n) in diploid  (2n), in a flowering plant.
(a) Ovary   (b)  Anther  (c) egg  (d) pollen  (e) male gamete  (f) zygote
Ans. (a) Ovary – Diploid (2n) (b) Anther – diploid (2n) (c) Egg – haploid (n) (d) pollen – haploid (n)
(e)  male gamete – haploid (n) (f) zygote – diploid (2n)
Q – 12 Define external fertilization. Mention its disadvantages.
Ans. External fertilization occurs outside the body of the organisms. During this process, the parents
release sperms and eggs into surrounding water ( example, frog) where fertilization occurs. The
major disadvantages of this type of fertilization are : (i) the fertilization of egg is not always sure,
(ii) the offspring are not protected from the predators, and (iii) a large number of gametes are
wasted.
Q – 13 Differentiate between a zoospore and a zygote.
Ans. A zoospore is usually flagellated, haploid or diploid spore formed inside a zoosporangium. The
zygote, on the other hand, is always diploid and formed as a result of fusion of gametes. The
zygote is usually no flagellated.
Q – 14 Differentiate between gametogenesis and embryogenesis.
Ans. Gametogenesis occurs inside the gametangia where meiosis occurs resulting in the formation of
gametes. Embryogenesis is the development of zygote into an embryo. During this process, the
zygote divides by mitotic division.
Q – 15 Describe the post fertilization change in a flower.
Ans. After fertilization, the sepals, petals and stamen wither and fall off. In some cases , the sepals
remain persistent. The ovules are transformed into seeds, zygote becomes embryo and ovary
becomes a fruit.
Q – 16 What is the bisexual flower ? Collect five bisexual flowers from your neighborhood   and with the help of your teacher find out their common and scientific names .
Ans. A bisexual flower possesses both stamens as well as carpels.
Q – 17  Examine a few flower of any cucurbit plant and try to identify the staminate and distillate flower. DO you know any other plant that bears unisexual flower ?
Ans. The staminate flower bear bright colored petals and stamens. They do not develop fruits. The
distillate flowers develop fruits. The other unisexual plant is Papaya . date palm is also unisexual
and bear unisexual flowers.
Q – 18 Why offspring of oviparous animals are at a greater risk as compared to offspring of
viviparous animals ?
Ans. Oviparous animals lay eggs in a safe place in the environment. In an open area, the eggs are not always safe and the offspring are always at a risk.  The viviparous animals give birth of young ones.
The fertilized eggs of oviparous animals ( examples – birds , reptiles, etc.) undergo a period of
incubation and then their young ones hatch out . This period has a risk of predators. In case of
viviparous animals ( examples – mammals including human beings), the zygote develops into a
young one inside the body of the female individual where it gets proper nourishment, care and
protection. Therefore, the chances of survival of young ones are more in viviparous animals as
compared to those of oviparous animals.

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