Bihar Board 12th Biology Important Questions Short Answer Type Part 3 are the best resource for students which helps in revision.
Bihar Board 12th Biology Important Questions Short Answer Type Part 3
Name the hormones that control the growth, maintenance and functions of duct system, accessory, glands, penis, seminiferous tubules and leydig cells.
- Testosterone promotes the growth, maintenance and functions of duct system, accessory gland and penis.
- FSH regulates the growth maintenance and functions of seminiferous tubules.
- L. H (Luteinizing Hormones) regulates the growth maintenance and functions of leydig cells.
Mention the functions of (i) Fallopian tubes, (ii) Uterus and (iii) Vagina.
- Fallopian tubes: These conducts the ovum towards the uterus and ovum may be fertilized by a sperm in it.
- Uterus: The fertilized ovum at the blastocyst stage gets implanted on the wall of the uterus and develops into the growing foetus during pregnancy.
- Vagina: It receives the semen from the male during mating. During childbirth, it conveys child to the outside.
Distinguish between Menstrual and Oestrous cycle.
- It occurs only in primates.
- Menstruation occurs at the end of cycle.
- Endometrium goes out with menstrual flow.
- Copulation can be any time of year
- Occurs in most of the mammals.
- Menstruation does not occur.
- Endometrium is reabsorbed.
- Copulation occurs only when female in oestrous or heat period.
Differentiate between insitu and exsitu conservation.
Insitu Conservation – It include protection or conservation of whole ecosystem and its biodiversity in natural condition.
Exsitu conservation – It includes conservation of rare plant/animal in place outside their natural home.
Name and assign the aim of different zones of biosphere reserve.
- Corse or Natural zone
- Buffer zone
- Transition zone.
Giving example of each differentiate between biodegradable and non-degradeble pollutants.
Biodegradable Pollutants – Garbage, Sewage, Livestock, Wastes.
Nonbiodegradable Pollutants – DDT, BHC, Plastics, Polyethylene, Cans, broken glass.
Mention any two effects of air pollution on plants.
- Closing of Stomata
Write a note on puberty.
Puberty is the period of sexual maturity. It comes between 13 to 16 years in the male and between 10 to 14 years in the female. It is controlled by testosterone in the male and estrogens in the female. It is characterized by the development of secondary sexual characters.
What is parthenogenesis?
Parthenogenesis is the development of an unfertilized ovum into a fully formed haploid organism. It is nonparental i.e. honey bees, wasps, aphids. The offsprings thus produced are exactly similar to the parents. It permits. triploid and aneuploid chromosomal combination. At the same time it stops the chances of new combinations of genes.
Draw well labelled diagram of male reproductive system.
Mention three advantages of sexual reproduction.
Sexual reproduction involves formation and fusion of sex called (gametes). Its main advantages are:
- The haploid (n) gametes fuse together and the chromesome number of the species (2n) is restored
- Variations are produced in the off-springs
- Off-springs are better adapted to the environment and it leads to evolution.
Draw a labelled digram of a human sperm.
Give a diagramatic representation of female reproductive system.
Name two basic processes involved in sexual reproduction.
Two basic processes involved in sexual reproduction are:
- Gametogenesis: It involves the formation of haploid gametes (sperms and ova) in the primary sex-organs called gonads.
- Syngamy: Syngamy (fertilization) involves the complete and permanent fusion of two haploid gametes to form a diploid zygote.
Differentiate between fission and budding.
- It involves the division of whole organism into more than one new organism. It may be binary fission or multiple fission.
- Binary fission may be longitudinal or transverse fission.
- There is neither proliferation nor differentiation of some vegetative cells, e.g. Planaria.
- It involves the enlargement of a vegetative part of the body to form a bud, which detaches from the parent body to form a new organism.
- A bud is constructed to the parent body.
- Proliferation and differentiation of some ordinary vegetative cells on the body surface form a bud. e.g. Hydra.
Why is endosperm in angiospermic ovule considered as more efficient?
In angiosperms, the cells of endosperm are triploid due to double fertilization. Thus they are considered more efficient in supplying food materials to the developing embryo.
Why is the process of fertilization in a flowering plant referred to as double fertilization? Explain.
Fertilization in flowering plants is referred to as double fertilization because two male gametes from the same microspore takes part in fusion. One male gamete fuses with the egg to form a diploid zygote and the other male gamete fuses with the two polar nuclei or secondary nucleus to form the triploid primary endosperm nucleus.
Write the functions of flowers.
Functions of a flower are as follows:
- Flowers are modified to perform the function of sexual reproduction.
- They are shaped variously to help in pollination.
- They provide seat for germination of pollen, development of pollen, tube, formation of gametes and fertilization.
- Some floral parts help in dispersal of fruits and seeds.
- The ovary transforms into fruit and ovules into seeds after fertilization in flowers.
Differentiate between self pollination and cross pollination
|Self pollination||Cross pollination|
|1. Migration of pollen grains from to the stigma of the same flower (or same plant) is called self pollination.||1. Migration of pollen grains from to the stigma of another flower to another plant is called cross pollination.|
|2. Mode of pollination is always wind or by touch.||2. Modes of pollination are external e.g. wind, water or animals.|
|3. Anthers and stigma mature at same time and lie close to each other.||3. Anthers and stigma may mature at different times and not essentially lie in proximity.|
|4. No chances of new varieties.||4. Variations occurs at every new generation and thus leads to evolution.|
Draw a labelled diagram of the longitudinal section of a maize grain to show the structure of mature embryo.
Name the pollinating agents of flowers like maize and wheat. Give any two favourable features of such a flower.
In case of maize, the pollinating agent is wind. These flowers are unisexual, small, colourless, inconspicuous and odourless. Whereas in wheat, its self-pollination. Both anthers and stigma of bisexual flowers from the same plant mature before the bud opens, thus to ensure complete self-pollination.
Name a plant where vegetative propagation occurs from reproductive organs. What is the special name of the reproductive part of this plant.
In Agave sp. (century plant), the floral buds get modified into bulbils. When these bulbils get detached from the mother plant, they form a new plant. Thus its a form of vegetative propagation which occurs from reproductive organs (fower).
What are the advantages of using plant tissue culture for propagation?
Plant tissue culture is a technique employed for quick, multiplication of plants. It is also used in producing virus-free plants, disease-free plants and homozygous diploids. This technique is highly useful in commercial micropropagation of orchids, carnation, gladiolus, chrysanthemum and some ornamental plants.
Draw a labelled diagram of the longitudinal section of a pistil showing pollen germination.
Fig.: Diagram of sectional view of flower to show germination of pollen grains (male gametophyte)
What are the characteristics of wind pollinated flowers?
Pollination by wind is called Anemophilous. It happens in coconut palm, date palm, maize, grasses etc. Their some characters are as such:
- Flowers are inconspicuous and not showy.
- They are colourless and odourless.
- Produce large quanities of dusty pollens.
- Flowers grow in large groups.
- Stigmas are stickly, hairy, feathery or branched.
Some crop plants can be grown from a seed as well as vegetatively from stem cutting. List any four advantages of vegetative propagation in such cases.
Plants which are grown vegetatively from stem cuttings have following advantages than those produced from seeds.
- They mature early and grow very fast.
- They are healthy and robust.
- The produce flowers and fruits much early.
- They characteristics of parent plant are preserved in them as no recombination occurs.
Draw a labelled sketch of the section of a mature pollen grain.
Name one example for each of the following:
(a) A Plant in which both male and female sex organs occur in the same flower.
(b) A plant in which separate male and female flowers are borne on the same individual at different positions.
(c) A cultivated plant which neither fruits nor seeds are formed.
(d) A species in which the individual plant is either male or female.
(a) Hibiscus rosa-sinensis
(b) Zea-mays (maize)
(c) Sugar cane
Trace the development of microsporocyte in the anther to a mature pollen grain.
Microsporocyte or microspore mother cells are polygonal and closely packed initially. Pollen grains develop from them in pollen sacs of anthers. As anther enlarges, pollen sac becomes loosely arranged. A few microsporocytes become non-functional and are absorbed by developing microspores. Each microsporocyte undergoes meiosis and form four haploid nuclei (microspores or pollen grains). They arrange in a tetrahedral manner. Later on each microspore separates and develops into a mature pollen grain.
What are the fundamental methods of reproduction?
There are two fundamental methods of reproduction:
- Asexual – A single parent is involved. In this case a single celled parent individual either splits or buds or fragments into two identical daughter cells or individuals, for example amoeba, paramoecium etc.
- Sexual – The two parents, each capable of producing gametes, spermatozoa and ova, are required. Many acellular protists, like monocystis plasmodium and all metazoans employ sexual reproduction.
Trace the development of a mature ovule from a megaspore mother cell.
The process of formation of megaspores from megaspore mother cell is called as megasporogenesis. Megaspore mother cell undergoes meiosis to form four haploid megaspores. They arrange in a linear tetyrad, usually the upper three degenerate and lowermost becomes a functional megaspore. This functional megaspore forms female gametophyte or embryo sac.
Write on the roles of lymphocyte in immunity.
Xymphocyte is a main cell of immune system.
It is two types –
1. T-Lymphocyte makes antibody molyced immune system.
2. B-Lymphocytes cells make mediated immune system. These two lymphocytes want antigens for their working but these two lymphocytes do their work separately. Hence, lymphocytes play their role in immunity.
Where do you find corpora cavernosa?
Corpora cavernosa is found under the skin of penis. It is a column of erectile tissue.
Under the skin, the penis contains three columns of erectile tissue: Two cylinders of the corpara cavernosa of the penis, placed dorsally, one cylinder the corpus cavemosum of the urethra or corpus spongiosum, along the ventral side.
How is corpus luteum formed? What is its function?
After ovulation the granulosa cells and the interstitial cells form a mass of large and yellowish conical cells. This is named as corpus luteum.
Functions: It serves as temporary endocrine gland by releasing progesterone and estrogen.
What is follicular atresia?
Most of the follicular in the two ovaries undergo regression and disappear due to death and disposal by phagocytes. This is referred to as follicular atresia.
Name the accessory structures of female reproductive system.
Vulva or external genitalia are the female accessory genital glands. Vulva has small depression in front of the anus called vestibule.
Vestibule contains following structures:
- Labia Majora: These are two outer skinny, moist hair covered folds forming the outer boundaries of the vulva. Anteriorly the two folds are joined to form monus pubis. A fleshy elevation above the labia is called mons veneris.
- Labia Minora: These are two thin, small, moist folds of connective tissue covered with skin. On stretching over the clitoris to form the prepuce and beneath in form frenulum. The smooth, almond shaped area into which opens the vagina and urethra between the labia minora is called the vestibule.
- Clitoris: It is capable of enlargement but serves no reproductive function.
- Barthclin’s Glands: These secretes clear viscous mucus containing alkaline fluid to lubricate the vulva and vagina during copulation.
- Perineum Jt lies between the anus and vaginal artifice.
How do leyding cell help in spermatogenesis?
Interstitial cells or leyding cells that lie between the seminiferous tubules secrete testosterone. Testosterone is essential for making sperm interstitial cell or leyding cell stimulating hormone (ICSH).
What is spermatogenesis? Write down its steps.
It is process of formation and differentiation of haploid sex cells or garmetes in sexually reproducing animals form undifferentiated diploid germ cells. completed in three major steps:
(a) Spnrmatocutownesis: During this process spermatogonia divide and produce successive generations of cells, which give rise to spermatocytes.
(b) Meiosis: During which the spermatocytes go through one reduction division (meiosis-I) and one equational division (meiosis-II).
(c) Spcrmiogenests: During which the spermatids differentiate into spermatozoa.
What is capacitation?
Sperm motivity occurs due to activation of the sperm by the viscous liquid secreted from the secretory cells of the epithelial lining of oviductal mucosa. The phenomenon of sperm activation in mammals is known as capacitation.
What is cortical reaction?
Cortical reaction are the reaction by which egg-sperm binding takes place.
First: The egg becomes activated and undergoes depolarization of its membrane.
Second: The egg exhibits cortical reaction and shows zona reaction, which makes the egg impervious to any second sperm.
Name some chemicals that are released by acrosome during fertilization.
The activated spermatozoa undergo acrosomal reaction and release various chemicals, like hyaluronidase that acts on the ground substances of follicle cells, corona penetrating enzyme that dissolves corona radiata and zona lysine or acrosin helps to digest the zona pellucida. All these chemicals are collectively termed sperm lysin. Fretilin proteins are present on the sperm surface.
How is polyspermy prevented?
During the process of egg sperm binding, the egg becomes activated and undergoes depolarization of its membrane. The egg exhibits cortical reaction and shows zona reaction, which makes the egg impervious to any second sperm. This is how polyspermy, the entry of more than one sperm into the ovum is prevented.
How does the transmission of malaria and Pneumonia take places?
Malaria is transmitted by female Anopheles mosquito.
Pneumonia is transmitted thourgh deplophatical Pneumonia bacteria.
How is milk production hormonally regulated?
Colostrum is rich in calories and protein. Its synthesis is stimulated by the pituitary hormone prolactin (PRL). Its release is stimulated by a rise in the level of oxytocin when baby begins nursing. Milk contains an inhibitory peptide. If the breasts are not fully emptied, the peptide accumulates and inhibits milk production. This autrorine action, thus, matches supply with demand.
What is the significance of crossing over?
Crossing over provides a proof for the linear arrangement of genes. New gene combinations are produced due to change in coursing over. It has led to the construction of linkage maps or genetic maps of the chromosomes.
Mention three advantages of sexual reproduction.
Sexual reproduction is the process of union of male and female gametes mostly morphologically and physiologically distinct the process is advantageous in the aspect that:
- The haploid gametes unite and the chromosome number of the species is restored.
- Variations are produced in the off-springs.
- Off-springs are better adapted to environmental conditions.
Give an account of accessory or secondary glands in a mammalian male reproductive system.
Secondary glands include a prostate two seminal vesicles and two Cowper’s gland. The prostate is located around the first part of the urethra and secretes its fluid into the urethra walls. These secretion enters the vas deferens through their ducts. Cowper’s gland are situated below the bladder are behind the urethra. Their secretion enters the urethra through their ducts.