Suggest a possible explanation why the seeds in a pea pod are arranged in a row, whereas those in tomato are scattered in the juicy pulp.
In pea, fruit is legume. The pea pod is developed from monocarpellary, unilocular and half superior ovary. At maturity, the fruit splits along the dorsal and ventral sutures and discharge its seeds.
In gynoecium with single carpel, ovules are always attached to the ventral suture. This results in the fruit with marginal placentation. Thus, the seeds are arranged in a row in legume (pea) pod.
In tomato, the fruit is berry. It is fleshy fruit develop from superior or inferior ovary. In this, the margins of the carpels grow inward to the centre of the ovary dividing the central chamber into compartments called locules.
So that, the ovules are arranged radially on the axis, attached by placenta that is called axial placentation. That's the reason the seeds are embedded in the juicy pulp.
Draw the sketches of a zoospore and a conidium. Mention two dissimilarities between them and atleast one feature common to both structures.
The feature common to zoospores and conidia is that both of these are the asexual reproductive structures, which facilitate the process of reproduction in asexually reproducing organisms.
$$ \text { The two dissimilarities between these (zoospore and conidium) are as follows } $$
| Zoospore (Found usually in Algae) |
Conidium (Found usually in Fungi) |
|---|---|
| Flagellated Formed inside a sporangium (endogenously) |
Non-flagellated Formed at the tip of conidiophores (exogenously) |
Justify the statement 'vegetative reproduction is also a type of asexual reproduction'.
In flowering plants, the units of vegetative reproduction such as runners, stolons, suckers, offsets, rhizome, corm, tuber, etc., are capable of giving rise to new offsprings. These structures are called vegetative propagules.
In all these plants the formation of these structures does not involve two parents, the process involved is asexual. So, it can be said that vegetative reproduction is also a type of asexual reproduction.
Enumerate the differences between asexual and sexual reproduction. Describe the types of asexual reproduction exhibited by unicellular organisms.
The differences between asexual and sexual reproduction are mentioned below
| Asexual Reproduction | $$ \text { Sexual Reproduction } $$ |
|---|---|
| Uniparental Somatic cells are involved. It involves the production of asexual spores Offsprings are genetically similar to parents. The rate of reproduction is faster. |
Biparental Germ cells are involved. It involves the formation and fusion of gametes. Offsprings are genetically dissimilar to parents. The rate of reproduction is slower. |
Asexual reproduction occurs usually in unicellular organisms, such as monerans and protists and in plants and certain animals.
It takes place in the following ways
(i) Binary Fission In this type of asexual reproduction, the parent organism divides into two halves, each half forming an independent daughter organism. e.g., Amoeba, Euglena, Paramecium.
(ii) Budding In this type of asexual reproduction, a daughter individual is formed from a small projection, the bud, arising from the parent body. e.g.,yeast, Hydra.
(iii) Fragmentation In this type of asexual reproduction, the parent body breaks into two or more fragment. Each body fragment develops into an organism. e.g., sponges, Selaginella.
(iv) Gemmule In this type of asexual reproduction, internal buds, called gemmules are involved. Gemmules are asexually reproduced mass of cells, that is capable of developing into a new organism. e.g., sponges.
(v) Sporulation In this type of asexual reproduction, dispersive structures called spores are released from the parent body that germinate under favourable conditions form new individuals.
(a) Motile spores are called zoospores and are found in aquatic animals. e.g., Albugo, Chlamydomonas.
(b) Non-motile spores are named as sporangiospores (e.g., Rhizopus, Mucor) and conidia e.g., Penicillium.
Do all the gametes formed from a parent organism have the same genetic composition (identical DNA copies of the parental genome)? Analyse the situation with the background of gametogenesis and provide or give suitable explanation.
No, all the gametes formed from a parent organism do not have the same genetic composition.
It can be better understand with the help of the explanation given below
Sexual reproduction in organisms generally involves the fusion of gametes from two different individuals. These gametes form by the process of gametogenesis. In the heterogametic species, gametes are of two types namely male and female. Gametes are haploid though the parent body from which they arise may be either haploid or diploid.
(a) A haploid parent like Monera, fungi, algae and bryophytes produce gametes by mitotic division. The number of chromosomes, i.e., the genetic composition remain same after such type of division.
(b) The diploid parent like pteridophytes, gymnosperms, angiosperms and most of the animals including human beings produces gametes by meiosis. In such organisms (diploid), specialised cells called meiocytes (gamete mother cell) undergo meiosis.
At the end of meiosis only one set of chromosomes gets incorporated into each gamete. It means the gametes formed contain a haploid number of chromosomes in contrast to the number of chromosomes in mother cells.