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Punjab State Board PSEB 12th Class Biology Important Questions Chapter 3 Human Reproduction Important Questions and Answers.

PSEB 12th Class Biology Important Questions Chapter 3 Human Reproduction

Very short answer type questions

Question 1.
Why are the human testes located outside the abdominal cavity? Name the pouch in which they are present.
Answer:
The human testes need lower temperature, 2-2.5°C less than the body temperature, for the formation of sperms which is provided outside the body. Testes are present in scrotal sac or scrotum.

Question 2.
Write the location and function of the sertoli cells in humans.
Answer:
Sertoli cells are present in seminiferous tubules. They provide nutrition to the germ cells or sperms.

Question 3.
Mention the location and the function of leydig cells in humans.
Answer:
Leydig cells are present in seminiferous tubules. They synthesise and secrete androgens.

Question 4.
The path of sperm transport is given below. Provide the missing steps in blank boxes. [NCERT Exemplar]

Answer:
Vasa efferentia, Vas deferens.

Question 5.
Female reproductive organs and associated functions are given below in column A and B. Fill in the blank boxes. [NCERT Exemplar]

Answer:
A – Fertilisation
B – Uterus

Question 6.
What is the role of cervix of the human female system in reproduction? [NCERT Exemplar]
Answer:
Cervix helps in regulating the passage of sperms into the uterus and forms the birth canal to facilitate parturition.

Question 7.
When do the oogenesis and the spermatogenesis initiate in human females and males respectively?
Answer:
In females; oogenesis initiates during foetal life. In males, spermatogenesis begins at the time of puberty.

Question 8.
Mention the importance of LH surge during menstrual cycle. [NCERT Exemplar]
Answer:
LH surge is essential for the events leading to ovulation.

Question 9.
Menstrual cycles are absent during pregnancy. Why? [NCERT Exemplar]
Answer:
The high levels of progesterone and estrogens during pregnancy suppress the release of gonadotropins required for the development of new follicles. Therefore, new cycle cannot be initiated.

Question 10.
How does the sperm penetrate through the zona pellucida in [ human ovum?
Answer:
The sperm penetrates through zona pellucida with the help of secretions from acrosome.

Question 11.
Mention the function of trophoblast in human embryo.
Answer:
Trophoblast is the outer layer of blastocyst which helps in the attachment of blastocyst to the endometrium of the uterus.

Question 12.
Explain the function of umbilical cord.
Answer:
It transports nutrients and respiratory gases and metabolic wastes to and from mother and foetus.

Question 13.
Given below are the stages in human reproduction. Write them ‘ in correct sequential order.
Insemination, Gametogenesis, Fertilisation, Parturition, Gestation, Implantation. [NCERT Exemplar]
Answer:
Gametogenesis, Insemination, Fertilisation, Implantation, Gestation, Parturition.

Question 14.
What stimulates pituitary to release the hormone responsible for parturition? Name the hormone.
Answer:
The signal from the fully developed foetus and placenta or the foetal , ejection reflex induces mild uterine contraction. The hormone released is oxytocin.

Question 15.
Name the important mammary gland secretions that help in resistance of the new bom baby. [NCERT Exemplar]
Answer:
Colostrum

Question 16.
Mention the function of mitochondria in sperm.
Answer:
It provide energy for the movement of sperm tail.

Short answer type questions

Question 1.
Write the function of each of the following:
(a) Middle piece in human sperm.
(b) Luteinising hormone in human males.
Answer:
(a) Provides energy for movement.
(b) Stimulates synthesis and secretion of androgens or male hormones for spermatogenesis.

Question 2.
Differentiate between mayor structural changes in the human ovary during the follicular and luteal phase of the menstrual cycle.
Answer:

Question 3.
Explain the events in a normal woman during her menstrual cycle on the following days :
(a) Pituitary hormone levels from 8 to 12 days.
(b) Uterine events from 13 to 15 days.
(c) Ovarian events from 16 to 23 days.
Answer:
(a) The level of LH and FSH secreted by anterior lobe of pituitary, stimulated by GnRH, increases.

(b) The endometrium of the uterus regenerates through proliferation. It grows and become thickened. There is repair of ruptured blood vessels and new blood capillaries develop. Uterine glands elongate.

(c) The remnant of Graafian follicle forms corpus luteum which secretes large amount of progesterone essential for maintenance of endometrium for implantation and for pregnancy.

Question 4.
What happens to corpus luteum in human female if the ovum is (a) fertilised, (b) not fertilised?
Answer:
(a) In case the ovum is fertilised, the corpus luteum persists and secretes a large amount of progesterone. The progesterone is essential for maintenance of endometrium, a necessity for implantation and for pregnancy.

(b) In the absence of fertilisation, corpus luteum degenerates. The level of LH and progesterone decreases very low. The absence of hormonal support, leads to the disintegration of endometrium and results in menstrual flow.

Question 5.
A large number of married couples the world over are childless. It is shocking to know that in India the female partner is often blamed for the couple being childless.
(a) Why in your opinion the female partner is often blamed for such situations in India? Mention any two values that you as a biology student can promote to check this Social evil.
(b) State any two reasons responsible for the cause of infertility.
(c) Suggest a technique that can help the couple to have a child where the problem is with the male partner.
Answer:
(a) The female partner is wrongly blamed for not bearing the child. It is due to the lack of proper information and knowledge about the reproduction and reproductive organs. Being a biology student I will advise and explain the couple as well as their other family members. Both male and female are equally responsible for bearing child. The two value, promoted are (i) concern for others (ii) scientific
temperament.

(b) Infertility is the inability to produce children inspite of unprotected sex and sexual co-habitation. It may be due to (i) physical/congenital disease (ii) immuno- logical or even physiological reason.

(c) In case, the problem is with male partner, artificial insemination (AI) is adopted. Semen collected either from the husband or a healthy donor is artificially introduced in the vagina or into the uterus of the female.

Question 6.
Name and explain the role of inner and middle walls of the human uterus.
Answer:
The inner wall of the uterus is called endometrium. It supports foetal growth and helps in placenta formation after implantation.
The middle wall of the uterus is called myometrium, exhibits strong contraction during delivery of baby.

Question 7.
Write a brief account of the structure and functions of placenta. [NCERT Exemplar]
Answer:
Placenta connects the foetus to the uterus through an umbilical chord. Both the foetal and the maternal tissues contribute to its formation. The foetal part is the chorionic villi and the maternal part is the uterine mucosa.

Long answer type questions

Question 1.
(a) Briefly explain the events of fertilisation and implantation in an adult human female.
(b) Comment on the role of placenta as an endocrine gland.
Or
Name the stage of human embryo of which it gets implanted.
Explain the process of implantation.
Or Draw a labelled diagram of a human blastocyst. How does it get implanted in the uterus?
Answer:
(a) (i) Fertilisation : Fertilisation occurs, if the ovum and sperms are transported simultaneously to the ampullary-isthmic junction and involve fusion of sperm with an ovum.
Secretions of acrosome of sperm help it to enter into the cytoplasm of ovum through zona pellucida and the plasma membrane. It induces meiotic division-II to form haploid ovum (ootid) and secondary polar body. The fusion of sperm with ovum to form diploid zygote is called fertilisation.

(ii) Implantation: Zygote undergoes cleavage to form a solid mass of 16 cells-morula, with daughter cells called blastomeres. Morula develops into a embryo with about 64 cells and with a cavity called blastocoel and the embryo is termed as blastocyst. It consists of outer layer of cells-trophoblast and inner cell mass.

The trophoblast gets attached to the endometrium- uterine wall of mother, after 7 days of fertilisation by a process called implantation leading to pregnancy. The uterine cells divide rapidly and cover blastocyst. The blastocyst gets embedded in the endometrium. Inner cell mass forms embryo.

(b) Placenta beside providing nutrients to the foetus also act as an endocrine gland. Placenta secretes human chorionic gonadotrophin (hCG), human placental lactogen (hPL), estrogen, progesterone etc., and later relaxin is secreted by ovary which facilitates parturition. Increased level of hormones like cortisol, prolactin and thyroxine etc., help in foetal growth, metabolic changes in the mother and maintenance of pregnancy.

Punjab State Board PSEB 12th Class Biology Important Questions Chapter 15 Biodiversity and Conservation Important Questions and Answers.

PSEB 12th Class Biology Important Questions Chapter 15 Biodiversity and Conservation

Very short answer type questions

Question 1.
Why is genetic variation important in the plant Rauwolfia vomitoria? [NCERT Exemplar]
Answer:
Genetic variation affects the variation in potency and concentration of me drug reserpine in the medicinal plant Rauwolfia vomitoria.

Question 2.
Name the type of biodiversity represented by the following:
(i) 50,000 different strains of rice in India
(ii) Estuaries and alpine meadows in India.
Answer:
(i) Genetic diversity
(ii) Ecological diversity

Question 3.
Identify ‘a’ and ‘b’ in the figure given below representing proportionate number of major vertebrate taxa.

Answer:
(a) Mammals
(b) Amphibians

Question 4.
Suggest two practices giving one example by each, that help protect rare or threatened species.
Answer:

1. By using cryopreservation (preservation at -196°C) technique, sperms, eggs, tissues, and embryos can be stored for long period in gene banks, seed banks etc.
2. Plants are propagated in vitro using tissue culture methods.

Question 5.
According to David Tilman, greater the diversity greater is the primary productivity. Can you think of a very low diversity man-made ecosystem that has high productivity? [NCERT Exemplar]
Answer:
Agricultural fields like wheat field or paddy field which are also examples of monoculture practices.

Question 6.
What is Red Data Book? [NCERT Exemplar]
Answer:
The Red Data Book is a compilation of data on species threatened with extinction and is maintained by IUCN. ‘

Question 7.
What is the expanded form of IUCN? [NCERT Exemplar]
Answer:
International Union for Conservation of Nature.

Question 8.
Why Western Ghats in India have been declared as biological hotspots?
Answer:
Western Ghats are biological hotspots because they have species richness and species evenness.

Question 9.
What is a national park?
Answer:
It is a protected area reserved for wildlife where human activities are not permitted.

Question 10.
What is the difference between endemic and exotic species? [NCERT Exemplar]
Answer:
Endemic species are native species restricted to a particular geographical region. Exotic species are species which are introduced from other geographical regions into an area.

Question 11.
How is the presently occurring species extinction different from the earlier mass extinctions? [NCERT Exemplar]
Answer:
Species extinction occurring at present is due to anthropogenic or man-made causes whereas the earlier extinction was due to natural causes.

Question 12.
Differentiate between in situ and ex situ approaches of conservation of biodiversity.
Answer:

Short answer type questions

Question 1.
What is biodiversity? Why is it a matter of concern now?
Answer:
Biodiversity is the occurrence of different types of genes, gene pools, species, habitats and ecosystems at a particular place and various parts of earth. It is a matter of concern because species are continuously lost, limiting the diversity and this will affect our survival and well-being on earth due to the changes in environment.

Question 2.
Where would you expect more species biodiversity-in tropics or in polar regions? Give reasons in support of your answer.
Answer:
More biodiversity is found in the tropics. This is because tropical regions remain undisturbed from frequent glaciations as in polar regions. Also, the tropics are less seasonal/more constant.

Question 3.
Is it true that there is more solar energy available in the tropics? Explain briefly. [NCERT Exemplar]
Answer:
As one moves from the equator to the polar regions, the length of the day decreases and the length of the night increases. The length of day and night are same at the equator. Therefore, it is true that there is more solar energy available in the tropics.

Question 4.
The given graph alongside shows species-area relationship. Write the equation of the curve ‘a’ and explain.
Answer:

The equation of the curve ‘a’ is S = CA^Z.
(i) Within a region, species richness increases with increasing explored area but only up to a limit.
(ii) Relationship between species richness and area for a wide variety of taxa turns out to be a rectangular hyperbola.

Question 5.
Explain ‘rivet popper hypothesis. Name the ecologist who proposed it.
Answer:
Paul Ehrlich proposed the rivet popper hypothesis. This hypothesis states that in an airplane (ecosystem) all parts are joined together using thousands of rivets (species). If every passenger traveling in it starts popping a rivet to take home (causing a species to become extinct), it may not affect flight safety (proper functioning of the ecosystem) initially but as more and more rivets are removed, the plane becomes dangerously weak over a period of time. Also, which rivet is removed may also be critical like loss of rivets on the wings (key species) is more serious threat to flight safety than loss of few rivets on the seats or windows inside the plane.

Question 6.
How do human activities cause desertification?
Answer:
Human activities like over-cultivation, unrestricted grazing, deforestation, and poor irrigation practices result in arid patches of land. The fertile topsoil that may take centuries to develop is eroded due to these activities. When large barren patches extend and meet over time, a desert is created. Increased urbanization is also one of the causes of desertification.

Question 7.
Why are conventional methods not suitable for the assessment of biodiversity of bacteria? [NCERT Exemplar]
Answer:
Many bacteria are not culturable under normal conditions in the laboratory. This becomes a problem in studying their morphological, biochemical, and other characterizations which are useful for their assessment.

Question 8.
List any four techniques where the principle of ex-situ conservation of biodiversity has been employed.
Answer:
Ex-situ Conservation (off-site conservation)

1. Zoological parks and botanical gardens.
2. Wildlife safari parks, aquaria.
3. Preservation of germplasm-seed gene banks, tissue culture, cryopreservation.
4. Sacred plants grown in homes, villages, and religious places.

Long answer type questions

Question 1.
(a) Why should we conserve biodiversity? How can we do it?
(b) Explain the importance of biodiversity hotspots and sacred groves.
Or
Why should biodiversity be conserved? List any two ethical arguments in its support. ‘
Answer:
(a) Need for Conservation of Biodiversity: Reasons for conservation of biodiversity can be grouped into three categories :

1. narrowly utilitarian
2. broadly utilitarian and
3. ethical.

(i) Narrowly Utilitarian: The reasons for conserving biodiversity are obvious because of their :
(a) direct economic benefits such as

• food (cereals, pulses, fruits)
• firewood
• fiber
• construction material
• products of medicinal importance
• industrial products (tannins, gums, lubricants, dyes, resins, perfumes).

(b) More than 25% of the drugs are derived from plants.

(c) 25,000 species of plants are used as traditional medicines by native people.

(ii) Broadly Utilitarian: Biodiversity plays a major role in providing ecosystem services that nature provides and which cannot be given a price tag are :

• Production of Oxygen
• Pollination of flowers by bees, bumblebees, birds, and bats, etc.
• Resulting in the formation of fruits and seeds.
• Aesthetic pleasures like bird watching, walking through the thick forests, waking up to bulbul’s song, etc.

(iii) Ethical :
(a) We share this planet with millions of plants, animals, and microbe species. Every species has an intrinsic value even if it is not of current or any economic value to us.

(b) We have an essential duty to care for their well-being and pass on the biological legacy in a proper form to our future generations. We can conserve biodiversity by two major approaches

• In situ conservation (on site/ conservation)
• Ex situ conservation (off-site conservation).

(c) Hotspots are the areas identified by conservationists for the very high level of species richness and high degree of endemism (species confined to a particular area and not found anywhere else). Hotspots help in protection of certain biodiversity-rich regions.

Sacred groves are the tracts of forest set aside where all the trees and wildlife within are given religious sanctity and total protection. Such sacred groves are found in Khasi and Jaintia hills in Meghalaya, Aravalli Hills of Rajasthan etc.

Punjab State Board PSEB 11th Class Biology Important Questions Chapter 10 Cell Cycle and Cell Division Important Questions and Answers.

PSEB 11th Class Biology Important Questions Chapter 10 Cell Cycle and Cell Division

Very short answer type questions

Question 1.
During which phase of mitotic cell division, chromosomes gets separated?
Answer:
During anaphase.

Question 2.
Does mitosis occurs before or after the interphase?
Answer:
Yes, mitosis occurs before or after the interphase, as dividing phase (meiosis or mitosis) and interphase are considered only as the major phases of a cell cycle.

Question 3.
Mitosis cell division helps in regeneration process. How?
Answer:
Mitosis helps in regeneration by keeping all the somatic cells of an organism genetically similar, so that they are able to regenerate part or whole of the organism.

Question 4.
Given that average duplication time of E. coli is 20 minutes. How much time will two E. coli cells take to become 32 cells?
Answer:
2 hours (2ⁿ = 2⁵ = 2 × 2 × 2 × 2 × 2 = 32 generations).

Question 5.
If a tissue has 1024 cells at a given time, how many cycles of mitosis had the original parental single cell undergone?
[NCERT Exemplar]
Answer:
10 (2ⁿ, where n =10 generations).

Question 6.
Two key events take place during S-phase in animal cells, i.e., DNA replication and duplication of centriole. In which parts of the cell do these events occur? [NCERT Exemplar]
Answer:
DNA replication in the nucleus. Centriole duplication in the cytoplasm.

Question 7.
At what stage of meiosis, formation of tetrads occurs? Name it.
Answer:
Tetrads are formed during pachytene of prophase-I (meiosis-I).

Question 8.
Meiosis is essential in sexually reproducing organisms. How?
Answer:
Meiosis is essential in sexually reproducing organisms because it keeps the chromosome number constant.

Question 9.
Which cells of our body do not divide?
Answer:
Neuron cells stops dividing soon after the birth of a child.

Question 10.
The diagram shows a bivalent at prophase-I of meiosis. Which of the four chromatids can cross over? [NCERT Exemplar]
Answer:
The non-sister chromatids of homologous pair of chromosome undergo meiosis.

Short answer type questions

Question 1.
Imagine a situation if there was no meiosis. Then what would have happened to the next generation?
Answer:
In the absence of meiosis the next generation would have double the number of chromosomes after fusion of gametes. This would have resulted in the birth of an altogether new species. The maintenance of characters set would have been possible only through asexual reproduction.

Question 2.
Give a description of metaphase I of meiosis.
Answer:
Metaphase I: The bivalent chromosomes align on the equatorial plate. The microtubules from the opposite poles of the spindle attach to the pair of homologous chromosomes.

Question 3.
Describe telophase I of meiosis.
Answer:
Telophase I

• The nuclear membrane and nucleolus reappear, cytokinesis follows and this is called as diad of cells.
• Although in many cases the chromosomes do undergo some dispersion, they do not reach the extremely extended state of the interphase nucleus.
• The stage between the two meiotic divisions is called interkinesis and is generally short lived. Interkinesis is followed by prophase II, a much simpler prophase than prophase I.

Question 4.
What is the process of cell division in prokaryotes?
Answer:
Prokaryotes do not have nucleus. So, there is no elaborate karyokinesis, as seen in eukaryotes. In prokaryotes the replication of DNA starts the process of cell division. Once genetic material is replicated, it is followed by division of cytoplasm. The process is known as binary fission.

Question 5.
How does meiosis facilitate creation of offsprings, with distinct characters?
Answer:
Meiosis happens during gametogenesis and as a result gametes have half the number of chromosomes. During fertilization, when gametes fuse together two different sets of chromosomes make a new set. This results in an offspring, who has distinct characters, compared to parents.

Question 6.
What is the significance of mitosis?
Answer:
Significance of Mitosis

• In multicellular organisms, body growth is by mitotic divisions of the cells.
• Replacement of worn out tissues/cells (e.g., blood cells, skin cells) and repair of the injured tissues is by mitosis.
• In unicellular organisms, mitosis are involved in asexual reproduction
  (multiplication of cells).
• In plants, vegetative propagation involves only mitotic divisions and genetically identical individuals are produced.
• Uncontrolled cell divisions in certain tissues/organ (cancer) result in tumours.

Long answer type questions

Question 1.
Briefly describe the significance of cell division.
Answer:
Cell division is significant in the following ways :

• Cell Multiplication: Cell division is a means of cell multiplication or formation of new cells from pre-existing cells.
• Continuity: It maintains continuity of living matter generation after generation.
• Multicellular Organisms: The body of a multicellular organism is formed of innumerable cells. They are formed by repeated divisions of a single cell or zygote. As the number of cells increases, many of them begin to differentiate, form tissues and organisms.
• Cell Size: Cell division helps in maintenance of a particular cell size which is essential for efficiency and control of cell activities.
• Genetic Similarity: The common type of cell division or mitosis maintains genetic similarity of all the cells in an individual despite being different, i.e., structurally and functionally.

Question 2.
Explain meiosis-II in an animal cell.
Answer:
All these happen in the two haploid nuclei simultaneously.

• Prophase-II: It takes short time. Spindle formation begins and the chromosomes become short. Two chromatids, are joined to a single centromere. Nuclear membrane and nucleolus disintegrate.
• Metaphase-II: At the equator, the chromosomes lie and spindle is formed. The centromere of every chromosomes is joined to the spindle fibre and centromere also divides.
• Anaphase-II: The daughter chromosomes are formed. Chromatids move towards their poles with the spindle fibres.
• Telophase-II: Reaching at the poles, chromosomes form nuclei which are haploid (n) daughter nuclei. Again nuclear membrane is constructed. Nucleolus now becomes clearly visible.
• Cytokinesis: It occurs and four daughter cells are formed which are haploid (n). It may occur once or twice (i.e., in meiosis-I and II) or only after the meiosis-II cell division.

Question 3.
Describe briefly the phases of meiotic division.
Answer:
Meiotic division takes place in germ cells. The number of chromosomes is reduced to half in daughter cells.

Meiotic cell division is divided into two phases, i.e., meiotic-I and II.
In the meiotic-I division, the homologous chromosomes pair to form bivalent. Exchange of genetic material takes place. The chromosomes now separate and get distributed into daughter cells.

Long prophase-I is divided into five sub-stages, i.e., leptotene, zygotene, pachytene, diplotene and diakinesis. During metaphase-I, the bivalents arrange themselves on equatorial plate with their arms on the plate but the centromere is directed towards opposite pole. It is followed by anaphase-I. Now, the homologous chromosomes repel each other, move to the opposite poles with both their chromatids. In this way each pole gets half the chromosomes number of the parent cell.

In telophase-I, the nuclear envelope and nucleolus again appear. The centromere of each chromosome breaks, separating the chromatids, one each to a daughter cell. The meiotic cell division maintains chromosome number of a species.

As a result of meiotic division, the four daughter cells are formed with half the chromosome number (haploid) in each cell.

Punjab State Board PSEB 12th Class Biology Important Questions Chapter 2 Sexual Reproduction in Flowering Plants Important Questions and Answers.

PSEB 12th Class Biology Important Questions Chapter 2 Sexual Reproduction in Flowering Plants

Very short answer type questions

Question 1.
An anther with malfunctioning tapetum often fails to produce viable male gametophytes. Give any one reason.
Answer:
A malfunctioning tapetum does not provide enough nourishment to the developing male gametophytes and thus fail to produce viable male gametophytes.

Question 2.
Complete the following flow chart
Pollen mother cell → Pollen tetrad

[NCERT Exampler]
Answer:
Generative cell.

Question 3.
Gynoecium of a flower may be apocarpous or syncarpous. Explain with the help of an example each.
Answer:
Gynoecium of a flower may be apocarpous means the carpels are free from one another and there is no fusion of any part e.g., Ranunculus, Rose. Gynoecium of a flower is syncarpous, means the carpels are fused by their ovaries. The number of fusing carpels may vary from 2 (Petunia) to ∞ (Hibiscus).

Question 4.
Name the parts of the gynoecium which develop into fruit and seeds. [NCERT Exemplar]
Answer:
Ovary develops into fruit and ovules develop into seeds.

Question 5.
How many haploid cells are present in a mature female gametophyte of a flowering plant? Name them.
Answer:
One dikaryotic polar cell with two haploid nuclei and six haploid cells, viz, 3 antipodal, 2 synergids and 1 egg.

Question 6.
Name the type of pollination in self-incompatible plants. [NCERT Exemplar]
Answer:
Xenogamy.

Question 7.
How do flowers of Vallisneria get pollinated?
Answer:
In Vallisneria, the female flower stalk is coiled to reach the water surface to receive the pollen grains carried by water currents.

Question 8.
What is pollen-pistil interaction and how is it mediated?
Answer:
The pistil accepts the right type (compatible) of pollen and promotes fertilisation and rejects the pollen of other species and incompatible pollen of the same species. It is the result of interaction between the chemicals of the pollen and those of stigma.

Question 9.
State the function of filiform apparatus found in mature embryo sac of an angiosperm.
Answer:
Filiform apparatus plays an important role in guiding the path of pollen tubes into the synergids.

Question 10.
Normally one embryo develops in one seed but when an orange seed is squeezed many embryos of different shapes and sizes are seen. Mention how it has happened?
Answer:
An orange seed has many embryos because of polyembryony.

Question 11.
Name the component cells of the ‘egg apparatus’ in an embryo sac. [NCERT Exemplar]
Answer:
Two synergids and an egg.

Question 12.
Name the common function that cotyledons and nucellus perform. [NCERT Exemplar]
Answer:
Cotyledons and nucellus provide nourishment.

Question 13.
In the embryos of a typical dicot and a grass, which are the true homologous structures? [NCERT Exemplar]
Answer:
Cotyledons and scutellum.

Question 14.
In a case of polyembryony, if an embryo develops from the synergid and *another from the nucellus, which is haploid and which is diploid? [NCERT Exemplar]
Answer:
Synergid embryo is haploid and nucellar embryo is diploid.

Short answer type questions

Question 1.
Name the organic materials the exine and intine of an angiosperm pollen grains are made up of. Explain the role of exine.
Answer:
Exine is made up of sporopollenin and intine is made up of cellulose and pectin.
Due to the sporopollenin, exine can withstand high temperature and strong acids. It is also not affected by enzymes. It is because of this reason that pollen grains are well preserved as fossils.

Question 2.
Differentiate between geitonogamy and xenogamy in plants. Which one between the two will lead to inbreeding depression and why?
Answer:

Geitonogamy will lead to inbreeding depression because the pollen grains are genetically similar, which results in inbreeding. Continued inbreeding will thus reduce fertility and productivity.

Question 3.
Double fertilisation is reported in plants of both, castor and groundnut. However, the mature seeds of groundnut are non-albuminous and castor are albuminous. Explain the post fertilisation events that are responsible for it.
Answer:
The development of endosperm (preceding the embryo) takes place from primary endosperm nucleus (PEN) in both, castor and groundnut. The developing embryo derives nutrition from endosperm.

PEN undergoes repeated division to give free nuclei. Subsequently cell wall is formed and endosperm becomes cellular. At this stage endosperm is retained in castor or is not fully consumed but in groundnut endosperm is consumed by growing embryo.

Question 4.
Differentiate between albuminous and non-albuminous seeds, giving one example of each.
Answer:

• Albuminous seeds have residual endosperm ip them. For example, maize.
• Non-albuminous seeds do not have any residual endosperm. For example, pea.

Question 5.
A non biology person is quite shocked to know that apple is a false fruit, mango is a true fruit and banana is a seedless fruit. As a biology student how would you satisfy this person?
Answer:
In apple only the thalamus (along with ovary) portion contributes to fruit. Therefore, it is a false fruit. Mango develops only from the ovary, therefore it is a true fruit.
Banana develops from ovary but without fertilisation. The method is known as parthenocarpy. Since there is no fertilisation, no seeds are formed.

Question 6.
Why are some seeds referred to as apomictic seeds? Mention one advantage and one disadvantage to a farmer who uses them.
Answer:
Seeds produced without fertilisation are referred to as apomictic.
Advantage: Desired characters are retained in offspring (progeny) as there is no segregation of characters in offspring (progeny). Seed production is assured in absence of pollinators.

Disadvantage: Cannot control accumulation of deleterious genetic mutation. These are usually restricted to narrow ecological niches and lack ability to adapt to changing environment.

Long answer type questions

Question 1.
A flower of brinjal plant following the process of sexual reproduction produces 360 viable seeds.
Answer the following questions giving reasons:
(a) How many ovules are minimally involved?
(b) How many megaspore mother cells are involved?
(c) What is the minimum number of pollen grains that must land on stigma for pollination?
(d) How many male gametes are involved in the above case?
(e) How many microspore mother cells must have undergone reduction division prior to dehiscence of another in the above case?
Answer:
(a) 360 ovules are involved. One ovule after fertilisation forms one seed.
(b) 360 megaspore mother cells are involved. Each megaspore mother cell forms four megaspores out of which only one remains functional.
(c) 360 pollen grains. One pollen grain participates in fertilisation of one ovule.
(d) 720 male gametes are involved. Each pollen grain carries two male gametes (which participate in double fertilisation) (360 × 2 = 720).
(e) 90 microspore mother cells undergo reduction division. Each microspore mother cell meiotically divides to form four pollen grains (360/4 = 90).

Punjab State Board PSEB 12th Class Biology Important Questions Chapter 16 Environmental Issues Important Questions and Answers.

PSEB 12th Class Biology Important Questions Chapter 16 Environmental Issues

Very short answer type questions

Question 1.
Why are lichens regarded as pollution indicators?
Answer:
Lichens are regarded as pollution indicators because they do not grow in areas that are polluted. So their presence indicates no pollution in that area and their absence indicates that the area is polluted.

Question 2.
Why is the use of unleaded petrol recommended for motor vehicles equipped with catalytic converters?
Or
Why are owners of motor vehicles equipped with catalytic converters advised to use unleaded petrol?
Or
Why is it desirable to use unleaded petrol in vehicles fitted with catalytic converters?
Answer:
Vehicles fitted with catalytic converters need to use unleaded petrol because lead inactivates the catalyst in the catalytic converter and increases hydrocarbon emission, thereby harming the environment.

Question 3.
In which year was the Air (Prevention and Control of Air Pollution) Act amended to include noise as air pollutant? [NCERT Exemplar]
Answer:
The Air (Prevention and Control of Air Pollution) Act 1981 was amended in 1987 to include noise as an air pollutant.

Question 4.
Name an industry which can cause air pollution, thermal pollution, and eutrophication. [NCERT Exemplar]
Answer:
Fertilizer factory.

Question 5.
Mention two advantages for preferring CNG over diesel as an automobile fuel.
Answer:
Advantages of CNG :

1. It burns more efficiently than petrol or diesel.
2. It is cheaper than petrol or diesel and cannot be siphoned off by thieves or adulterated.

Question 6.
What is an algal bloom? [NCERT Exemplar]
Answer:
The excessive growth of algae (free-floating) that causes coloration of water bodies is called algal bloom.

Question 7.
Write the name of the organism that is referred to as the ‘Terror of Bengal’.
Or
Why is Eichhomia crassipes nicknamed as* ‘Terror of Bengal’?
Answer:
Eichhornia crassipes is nicknamed as ‘Terror of Bengal’ because it grows very fast in the water body and depletes the dissolved oxygen. Hence, disturbing the ecosystem dynamics of the water body.

Question 8.
What is the raw material for polyblend? [NCERT Exemplar]
Answer:
Polyblends are natural man-made fibres, made by the mixture of two or more polymers, especially plastic waste products.

Question 9.
Mention the effect of UV rays on DNA and proteins in living organisms.
Answer:
The high energy of UV rays breaks the chemical bonds within DNA and protein molecules.

Question 10.
Write the unit used for measuring ozone thickness.
Answer:
Dobson unit.

Question 11.
State the purpose of signing the Montreal Protocol.
Answer:
Montreal Protocol was signed at Montreal, in 1987 to curb the emission of ozone-depleting substances.

Question 12.
What is reforestation? [NCERT Exemplar]
Answer:
Reforestation is the process of restoring a forest that once existed but was removed at some point of time in the past.

Short answer type questions

Question 1.
It is a common practice to plant trees and shrubs near the boundary walls of buildings. What purpose do they serve?
[NCERT Exemplar]
Answer:
The practice of growing and maintaining trees and shrubs near the boundary wall of residential or official buildings is a common practice. This is because it acts as a barrier for sound and check noise pollution. This green belt of trees and shrubs also acts as an effective measure to check primary air pollutants like dust, fly ash, etc.

Question 2.
‘Determination of Biological Oxygen Demand (BOD) can help in suggesting the quality of a water body. Explain.
Answer:
Biochemical Oxygen Demand (BOD) is the amount of dissolved oxygen required for microbial breakdown of biodegradable organic matter. Aerobic organisms use a lot of oxygen and as a result, there is a sharp decline in Dissolved Oxygen (DO) in the water body. This Can cause death of fishes and other aquatic species. The relationship between BOD and sewage can be understood from the graph given below :

Determination of BOD is thus an important parameter in suggesting the quality of a water body. The presence of more organic waste increases the microbial activity thus decreasing the DO. BOD is higher in polluted water and lesser in clean water.

Question 3.
Explain the process of secondary treatment given to the primary effluent up to the point it shows a significant change in the level of biological oxygen demand (BOD) in it.
Answer:
The primary effluent is passed into large aeration tanks where it is constantly agitated. Air is pumped into it mechanically. This allows vigorous growth of useful aerobic microbes into floes. These microbes consume the major part of organic matter in the effluent (this significantly reduces the BOD of the effluent).

Question 4.
Excessive nutrients in a freshwater body cause fish mortality. Give two reasons.
Answer:
Excessive nutrients in the water body result in the excessive and rapid growth of plants and animals, resulting in formation of increased organic matter, death of plants and animals increased the organic matter at the bottom which decomposes, increased BOD deplete the oxygen content, resulting in fish mortality.

Question 5.
Is it true that, if the dissolved oxygen level drops to zero, the water will become septic? Give an example which could lower the dissolved oxygen content of an aquatic body. [NCERT Exemplar]
Answer:
Yes, it is true. In case of zero level of Dissolved Oxygen (DO), the water becomes septic. Organic pollutants like fertilizer in aquatic bodies are responsible for lowering (up to zero) the level of dissolved oxygen.

Question 6.
Explain giving reasons why thermal power plants are not considered eco-friendly?
Answer:
Thermal power plants release particulate and gaseous pollutants in the environment. Inhalation of these pollutants can cause breathing or respiratory symptoms^irritation, inflammation, damage to lungs, and even premature death.

Question 7.
Blend of polyblend and bitumen, when used, helps to increase road life by a factor of three. What is the reason? [NCERT Exemplar]
Answer:
Polyblend is a fine powder of recycled modified plastic. The binding property of plastic makes the road last longer besides giving added strength to withstand more loads. This is because: plastic increases the melting point of the bitumen which would prevent it from melting in India’s hot and extremely humid climate, where temperature frequently crosses 50°C. rainwater will not seep through because of the plastic in the blend.

Question 8.
What is the main idea behind ‘Joint Forest Management Concept’ introduced by the Government of India?
[NCERT Exemplar]
Answer:
The main idea behind joint forest management concept introduced by the Government of India was involving the local communities in forest conservation. This concept was adopted considering the extraordinary courage and dedication the local people showed in protecting the wildlife through the movements like Bishnoi’s movement in Jodhpur and Chipko Movement in Garhwal Himalayas.

Long answer type questions

Question 1.
Explain giving reasons the cause of appearance of peaks ‘a’ and ‘b’ in the graph shown below:
img
Answer:
‘a’-High BOD due to sewage discharge.
‘b’-Increase in dissolved oxygen due to sewage decomposition. Micro-organisms involved in biodegradation of organic matter consume a lot of oxygen, therefore, there is a sharp decline in dissolved oxygen. When the sewage is completely degraded, oxygen concentration again increases.

Question 2.
Why is the concentration of toxins found to be more in the organisms occupying the highest trophic level in the food chain in a polluted* water body? Explain with the help of a suitable example.
Answer:
The concentration of toxic materials like heavy metals and pesticides increase at each trophic level of a food chain and is more in organisms of highest trophic level due to their accumulation at each trophic level For example, when DDT was used to control mosquitoes in a lake of USA, 800 times more DDT was found in the phytoplanktons than in the water of the lake. Zooplanktons had about 13 times more DDT than phytoplanktons. It was also observed that the fishes population had 9-40 times more DDT than zooplanktons and fish-eating birds had 25 times more DDT than fish.

Question 3.
Refrigerants arc considered to be a necessity in modem living but are said to be responsible for ozone holes detected in Antarctica. Justify.
Answer:
The widely used refrigerants are CFCs or. chlorofluorocarbons. CFCs discharged in the lower part of atmosphere move upwards to the stratosphere. Here, the UV rays act on them and release chlorine atoms. These free chlorine atoms react with ozone to release molecular oxygen. Chlorine atoms are not consumed in this reaction and hence, these continuously degrade ozone and have resulted in ozone holes.

Punjab State Board PSEB 11th Class Biology Important Questions Chapter 14 Respiration in Plants Important Questions and Answers.

PSEB 11th Class Biology Important Questions Chapter 14 Respiration in Plants

Very short answer type questions

Question 1.
Why does anaerobic respiration/fermentation yields less energy than aerobic respiration?
Answer:
It happens due to incomplete oxidation of the substrate.

Question 2.
Write the overall equation of respiration.
Answer:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy

Question 3.
Name two openings in plants through which exchange of gases takes place?
Answer:
Stomata and lenticels.

Question 4.
Write the reaction where substrate-level phosphorylation takes place in glycolysis.
Answer:
Substrate level phosphorylation takes place during the following reaction

• When 1, 3-bisphosphoglycerate is converted into 3-phosphoglycerate.
• When phosphoenolpyruvate is converted into pyruvic acid.

Question 5.
List two instances where lactic acid is formed by fermentation.
Answer:
Instances, where lactic acid is formed by fermentation, are given below:

1. During fermentation by lactic acid bacteria.
2. During strenuous exercise, in the striated muscles in humans.

Question 6.
Mention the step of citric acid cycle, which is not mediated by dehydrogenase enzyme.
Answer:
Conversion of oxaloacetic acid to citric acid is not mediated by dehydrogenase enzyme.

Question 7.
At which step of respiration, hydrogen of NADH₂ is used?
Answer:
The hydrogen atoms accepted by NADH₂ during glycolysis are introduced to route I of ETS. In this route 3 ATP molecules are produced.

Question 8.
Mention the number of protons that passes through complex V for the synthesis of 2 molecules of ATP.
Answer:
Two pairs of protons (i.e., 4) passes through complex V for the synthesis of two molecules of ATP.

Question 9.
Name the inhibitor of oxidative phosphorylation.
Answer:
Oligomycin.

Question 10.
Name the unit of oxidative phosphorylation.
Answer:
Oxysomes.

Question 11.
F₀ – F₁ particles participate in the synthesis of ……………………. [NCERT Exemplar]
Answer:
ATP (Adenosine Triphosphate), the energy currency of the cell.

Question 12.
What do you mean by respiratory balance sheet?
Answer:
Respiratory Balance Sheet
The calculations of the net gain of ATP for every glucose molecule oxidized, can be made only on certain assumptions.
But this kind of assumptions are not valid in a living system for the following reasons :

• All pathways work simultaneously and do not take place one after the other.
• Substrates keep entering the pathways and are also withdrawn from the pathways.
• ATP is utilized as and when needed,
• Rates of enzyme actions are controlled by multiple means.

Short answer type questions

Question 1.
Why ATP is called an energy currency?
Answer:
The energy produced during various steps of cellular respiration is stored in the form of ATP. This is later utilized on an SOS basis. So, ATP is also called as energy currency.

Question 2.
There is no special respiratory organ in plants, yet plants efficiently manage exchange of gases. Justify.
Answer:
Every part of plant manages its gas exchange need. There is no exchange of gases between different organs. So unlike animals plants do not need special respiratory organs to facilitate exchange of gases. In leaves the exchange of gases takes place through stomata, while in stems it takes place through lenticels.

Question 3.
How glycolysis takes place in anaerobic environment?
Answer:
Glycolysis is the breakdown of glucose into pyruvic acid and it does not need oxygen. So in all living beings, irrespective of them being either aerobic or anaerobic glycolysis takes place. In fact glycolysis is the first step towards oxidation of glucose and oxidation takes place either during anaerobic respiration or during aerobic respiration.

Question 4.
The maximum concentration of alcohol produced by natural fermentation is 13%. But most of the alcoholic preparations for human consumption contain more than this percentage. How this higher percentage is achieved?
Answer:
The higher percentage of alcohol is achieved through distillation of the liquid, which gives pure alcohol as well. The boiling involved in distillation helps evaporate the liquid part and higher concentration is achieved.

Long answer type questions

Question 1.
Oxygen is critical for aerobic respiration. Explain its role with respect to ETS.
Answer:

• Oxygen is an essential requirement for aerobic respiration because an element of strong electronegativity to pull the electrons down the chain is needed.
• It ensures that protons are pumped into the outer lumen of the mitochondria, where they can come down their concentration gradient through ATP-synthase making ATP.
• The oxygen picks up electrons and protons, thus forming water. As the electrons in the ETS are used to do work, the electrons lose energy and reach a point at the end of the ETS, where they have to be gotten rid of.
• The scheme the cell uses to do this is to combine the electrons with hydrogen ions and oxygen to produce water.