CBSE Class 10 Science Population Notes

POPULATION

INTRODUCTON :

1. With reference to ecology. a population is defined at the total number of individual of a species in a bitotic community.
2. The indiviuald of population are capacble of interbreeding mong thermsevls. Due to this mating, there is free flow of genges in sepecties.

(a) Characteristics of a population :

(i) Population density : Population is called as density of a species is the number of individuals of species per unit area of volume. Population density can be calculated as.

Where N = N Population density of a region

S = Number of unit areas in a region

(ii) Birth arte or Natality rate : The number of birher per 100 individulas of a population per year is called as birth rate.

(iii) Death rate or Mortality rate : The number of births per 1000 individuals of a population per year is called as birth rate.

(iv) Dispersal : The movement of majority of individuals form the population r into the population at one or the time during their life cycle is called as dispersal. This can be of two types.

(v) Age distribution : The relative abundance of the organisms of various age groups in the population is called age distribution of population. In a population three age groups are classified.

(A) Prereproductive     (B) Reproductive      (C) Post reproductive

(vi) Populatio growth : If more individuals ar e added in a population than lost, the population will show positive growth. But if more individuals are lost than added, then the population show negative growth. If the two rates are equal then the population will be stationary and is called zero growth.

Population growth = (Birth+Immigratio) – (Deaths+Emigration)

OVER POPULATIOBN :

Uncontrolled growth of population decreases the growth of any country and also causese many socioeconimi disturbances.

(a) Consequences of Overpopulation :

(i)   Space shortage    (ii) Food supply shortage      (iii) Unemployment

(iv) Education             (v) Pollution                           (vi) Price rise

(vii) Energy crisis        (viii) Eco-degradation            (ix) Nonhygienic condition

SEX RATIO :

The number of females in a population per1000 males is called sex ratio.

Sex ratio = Number of females / 1000 males.

(a) Inequality of Sexes :

Human female is homogametic and produces onluy one type of aggs. Each having one X – chromosome. While human male is heterogametic and produces two types of sperms. 50 % with X-chromosome and 50 % with Y-chromosomes. The sex of the newly born child is solely determined by the type of sperm that fusses with the ovum.

REPRODUCTIVE HEALTH :

In human population size, health and prosperity are determined by the young people (i.e. between 10 to 25 years) of the population.

(a) Factors Affecting Reproductive Health :

(i) Education of young people : There is a correlation between the state of education and birth rate. Indian states with low literacy rate e.g. Bihar, Rajasthan etc. have high population growth rate while literate states as Kerala have low population growth rate.

(ii) Health of young people : Healthy women tend to have fewer and healthier children. Due to this National Welfare Programme has shifted from reduction of infertility and growth rate to reproductive health care.

(a) Early marriage and child bearing : Young women from 15 to 19 years face more comlications of child birth and abortion which lead to their death. Their children are premature, with low birth rate, weak and anemic..

(b) Methods to improve the Reproductive Health of Human Population:

(i) More enrolments of girls and their staying in the schools.

(ii) To avoid early marriage and child bearing tendency.

(iii) Responsible sexual behavior of the male partners towards their female partners. Boys should support their

female partners in their reproductive health.

RAJASTHAN POPULATION POLICY :

India is a federation of 28 sates and 7 union territories with varying developmental status. Although population management falls in the concurrent list of activities envisaged in the constitutional framework of India.

It’s population growth rate is above the national average.

Population Intervention in State’s Population Policy of Rajasthan 2000 :

(i) Upgradation of skills.    (ii) Improved access to services.      (iii) Services for deliveries.

(iv) Immunisation      (v) Child care           

NATIONAL HEALTH PROGRAMME :

It includes :

(a) National Malaria Eradication Programme :

NMEP is a centrally sponsored National Health Programme Malaria in Urban Areas : Urban Malaria scheme (UMS) was launched in 1971 with the objective to control malaria by reducing the vector population in the urban areas through recurrent antilarval measures and detection and treatment of cases through the existing health services.

The National filaria Control Programme ;

It was launched in 1955, Delimitation of the problem in unsurveyed areas, control in urban areas through recurrent anitilarval measures and anti parasitic measures by 206 control units were the measures undertaken in this programme.

National T.B. (Tuberculosis) Control Programme (NTCP) :

It was launched in 1962 in regard to supply of anti – T.B. drugs. The objective of the programme is to detedct as many cases as possible and effectively threat them so as the render infectious cases as non infections. Govt. of India evoloved th Revised National TB ControlProgrammme (RNTCP) based on DOTS Directly Observed Traetment Short Course) strategy with the objective of curing atleast 85% of new sputum positive patients and detecting atleast 70% of such patients. Under th DOTS strategy the. Patents swallow the drug under direct observations of the health worker or the DOT provider.

National Goitre Control Programme (NGCP) :

This programme was launched in 1962 with the following objectives:

(i)   Initial surveys to assess the magnitude of lodine Deficiency Disorder.

(ii)  supply of iodated salt in place of common salt.

(iii) Health education and publicity.

(iv)  Resurveys to assess the impact of iodated salt after every 5 years.

(v)  Laboratory monitoring of iodated salt and urinary iodine excretion.

(e) The national mental health  Programme :

It was initiated into the central scheme in 1982 considering the magnitude of the problem in the country.

(e) National AIDS Control Programme :

Realising the gravity of epidemiological situation of HIV infection prevailing in the country, the Govet. Of India launched a National AIDS Control Programme in 1987. A comprehensive five year strategy plan was launched during the 8^th plan period with the assistance form Wold Bank. Naco (Natinal AIDS control Organisation) is working for the prevention  of AIDS.

The programme has the following components:

(i)  Strengthening the programme management capacity at National and State levels.

(ii) Surveillance & clinical management.

(iii) Ensuring blood safety.

(iv) Control of Sexually Transmitted Diseases.

(v) Public awareness and community support.

(vi) Recognising the importance of STD control measures as one of the main strategies in prevention and control of HIV/AIDS, steps have been taken to strengthen the existing STD Control Programme.

(g) Pilot Project on Programme Against Micronutrient Malnutrition:

It was launched with the following objectives :

(i) To asses the magnitude of fluorosis including dental caries and to prevent and control the same.

(ii) To assess the level of zink deficiency at source especially in soil and different foods.

(iii)To assess and improve the iron and vitamin A status in school children, adolescence girls and boys, non-

pregnant moment and elderly population who are suffering from iron and vitamin A deficiency by supplementing iron and folic acid tablets and vitamin A.

(iv)To launched extensive information, education and communication campaign through mass media for

micronutrient malnutrition in order to improve the dietary habits of the population.

(v) To coordinate with similar ongoing programmes being implemented in the country.

(h) National Cancer control Programme :

This programme was started in 1975-76 it’s goals and objectives are as follows:

(i) Primary prevention of cancers by health education regarding hazards of tobacco consumption and necessity of genital hygiene for prevention of cervical cancer.]

(ii) Secondary prevention i.e early detection and diagnosis of cancers. e.g. cancer of cervix, breast cancer and of the oro-pharyngeal cancer by screening methods and patients education on selefexamining methods.

(iii) Strengthening of existing cancer treatment facilities, which were inadequate.

(i) National Diabetes Control Programme :

This programme was started on a pilot basis during the seventh five year plan in some districts of Tamil Nadu, Jammu & Kashmir and Karnataka, but, due to the lack of funds this programme could not be expanded further. The objectives of programme are :

(i)Primary prevention by identifying high risk subjects art an early stage and imparting  appropriate risk recucing health education to them, their family and community by IEC programme.

(ii) Secondary prevention through early diagnosis and appropriate treatment of the disease to reduce mortality with special reference e to group at risk.

(iii) Prevemtiom ention of acute metabolic and chronic cardiovascular, renal and ocular complications of the

diseases.

(iv) Provision of equal opportunities for physical attainment scholastic achievement for the diabetic patients.

(j) Pilot Project on Control of Cardiovascular Disease and Stroke :

(i) As a part of the Pilot Project on Control of Cardiovascular Diseases and Stroke  (CVD) initiated by Govt. of India in 1995-96.

(k) Guinea worm eradication Programme (GWEP) :

The programme was implemented througyh well defined strategies like case detectin & surveillance, management, vector control, used of nylon cloth strainers form fitering water by the community, health eduction and priritisation of provision of safe water to the endemic villages.

(i) National surveillance Programme for Communicable Diseases :

It has been launched to strengthen the disease surveillance system so that earning signals are recongnised and appropriate timely followup action is initiated. The main objective of the programme is capacity building at district and state levels.

(Source : http://mohfw.nic.in/kk/95/19/toc. htm) 

HEALTH ECUCATION : 

1. Being healthy means that man should remain free from trouble or pain and the oragans of the body, should fuction properly.
2. Health education may mean different things to different people. It is a matter of public relations about health policies and knowledge about health policies and knowledge about health and diseases by experts in the field. 

AWARENESS OF PEOPLE : 

(i)   People should be aware of preventing diseases and enjoying health.

(ii)  People should change their ways and habits of living.

(iii) They should change their surroundings and environmental conditions considered to health as water pollution, smoking etc.

(iv) People should change their ways and habits of living.

(v) People should improve their personal hygiene and cleanliness. Weather at home or at school, children need to instructed to cultivate healthy habits of eating, drinking, sleeping etc. 

(vi) Training of first aid should be given to children and people.

(vii) The local and state governments should not onl provide essential health services but also initiate helth traning and health education programme.

SOME IMPORTANT POINTS : 

1. Death rate, birth rate and growth rate are called as vital rates.
2. Country with negative growth is Australia.
3. World population day is on 11^th of July.
4. Indian population is a young population.

Multiple Choice Questions

Question. During adolescence, several changes occur in the human body. Mark one change associated with sexual maturation in boys.
(a) loss of milk teeth
(b) increase in height
(c) cracking of voice
(d) weight gain
Answer : C

Question. Which among the following is not the function of testes at puberty?
(i) formation of germ cells (ii) secretion of testosterone
(iii) development of placenta (iv) secretion of estrogen
(a) (i) and (ii) (b) (ii) and (iii)
(c) (iii) and (iv) (d) (i) and (iv)
Answer : C

Question. In human females, an event that reflects onset of reproductive phase is
(a) growth of body
(b) changes in hair pattern
(c) change in voice
(d) menstruation
Answer : D

Question. Fertilisation is the process of
(a) transfer of male gamete to female gamete.
(b) fusion of nuclei of male and female gamete.
(c) adhesion of male and female reproductive organs.
(d) the formation of gametes by a reproductive organ.
Answer : B

Question. In human males, the testes lie in the scrotum, because it helps in the
(a) process of mating
(b) formation of sperm
(c) easy transfer of gametes
(d) all the above
Answer : B

Assertion-Reason Type Questions

For question numbers 1 and 2 two statements are given-one labeled as Assertion (A) and the other labeled
Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:
(a) Both ‘A’ and ‘R’ are true and ‘R’ is correct explanation of the assertion.
(b) Both ‘A’ and ‘R’ are true but ‘R’ is not correct explanation of the assertion.
(c) ‘A’ is true but ‘R’ is false.
(d) ‘A’ is false but ‘R’ is true.

Question. Assertion: Pollination is different from fertilisation.
Reason: The process of transfer of pollens from anther to stigma is called pollination which takes place in plants.
Answer : B

Question. Assertion: Pistil is male reproductive part of flower.
Reason: Pollen grain land on stigma and germinate.
Answer : D

Very Short Answer Type Questions

Question. If a women is using copper-T, will it help in protecting against sexually transmitted diseases?
Answer : No, it can only prevent unwanted pregnancy. It will not be able to prevent contact of body fluids

Question. List two reasons for the appearance of variations among the progeny formed by sexual reproduction.
Answer : (i) Special cell division involved in the process of gametes formation is the cause of variations.
(ii) Genetic material comes from two parents, which brings variations in offsprings

Question. What are those organisms called which bear both the sex organs in the same individual? Give one example of such organisms.
Answer : These are called hermaphrodites, e.g. earthworm and leech.

Question. List two unisexual flowers.
Answer : Watermelon, Cucumber and Willows (Any two)

Question. Differentiate between pollen grain and ovule.
Answer : Pollen grains contain male gametes in plants and ovules contain female gametes

Question. List two functions performed by testis in human beings.
Answer : (i) Testis produces sperms.
(ii) It produces testosterone hormone

Question. List two functions of ovary of human female reproductive system.
Answer : (i) Ovary produces eggs for fertilisation.
(ii) They also produces hormones oestrogen and progestrone.

Question. Name the parts of a bisexual flower that are not directly involved in reproduction.
Answer : Sepals and petals are not directly involved in reproduction.

Question. Differentiate between germination and fertilisation
Answer : Germination: Involves development of embryo into a seedling.
Fertilisation: It involves fusion of male with female gametes.

Question. What is the role of scrotum?
Answer : Scrotum regulates the temperature of testes and maintains it at 35°C, two degree below the body temperature, so as to protect sperms from high temperature

Question. Give one difference between zygote and embryo.
Answer : Zygote is a single celled fusion product of sperm and ovum whereas embryo is a multicellular product produced by mitotic divisions from zygote.

Question. Why is temperature of scrotal sac 2°C less than the body temperature?
Answer : Scrotal sac temperature is less by 2° because sperms are safe at a little lower temperature than body temperature. It is outside the body that is why it has lower temperature than body

Question. What are sexually transmitted diseases? Name a STDs which damages the immune system of human body.
Answer :Diseases that spread through the sexual contact are called STDs
AIDS damages the body’s immune system.

Question. Write the expanded form of AIDS.
Answer : Acquired Immuno Deficiency Syndrome

Question. What happens when egg is not fertilised?
Answer : When egg is not fertilised, blood and mucus comes out through vagina. This process is called menstruation

Question. Why is fertilisation not possible without pollination in plants?
Answer : Fertilisation is the process in which pollen grain and egg fuse to form zygote. Pollination is the process of transfer of pollen grains from stamen to the stigma of carpel. It means that fertilisation is not possible without pollination.

Question. Why does the lining of uterus becomes thick and spongy during every month?
Answer : The lining of uterus becomes thick and spongy by the action of progesterone to receive and nurture the development of embryo.

Question. How can the chromosomes be identified?
Answer : Chromosomes can be seen as thread like structure having specific shape when cell is dividing by which they can be identified

Question. Give an example of a flower which contains both stamens and carpels.
Answer : Hibiscus, Mustard (Any one)

Question. Trace the path of sperms from where they are produced in human body to the exterior.
Answer : Testes Æ vas deferens Æ urethra Æ penis and then opens to outside

Short Answer Type Questions

Question. How is the process of pollination different from fertilisation?
Answer : The process of transfer of pollens from anther to stigma is called pollination, which takes place only in plants.
Fertilisation is a process in which male sex cell and female sex cell join or fuse together to form zygote. It happens in all living organisms, in sexual reproduction.

Question. What is the main difference between sperms and eggs of humans? Write the importance of this difference.
Answer : Sperms are motile (movable) and have X or Y chromosomes whereas eggs are non-motile and have X chromosome only.
The sperms can reach to egg for fertilisation because these are motile. Chromosomes in them help in determination of sex of a new born child.

Question. Write the number of immature eggs present in the ovaries of newly born baby girl. Mention what happens to these immature eggs when the girl attains maturity.
Answer : Ovaries contain thousands of immature eggs at the time of birth. Some of these eggs start maturing when girls attain puberty. One egg is produced every month by one of the ovaries

Question. The chromosomal number of the sexually producing parents and their offspring is the same. Justify this statement.
Answer : (i) In sexual reproduction, fusion of male and female gametes takes place, each of their germ cells or gametes contain half the number of chromosomes.
(ii) When male and female gametes fuse at the time of fertilisation it restores the original number of chromosomes of parent.

Question. Differentiate between the following:
(i) Role of placenta and uterus in pregnancy (ii) Unisexual and bisexual flowers
Answer : (i) Placenta: The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta.
Uterus: After fertilisation, embryo gets attached to the walls of uterus.
(ii) Unisexual flowers: Flowers which contain either stamens or carpels.
Bisexual flowers: Flowers which contain both stamens and carpels

Question. List two preparations shown every month by the uterus in anticipation of pregnancy in the humans.
Answer : (i) The inner uterine wall becomes thick.
(ii) More blood vessels develop in its lining

Question. Why do we need to adopt contraceptive measures?
Answer : (i) To prevent unwanted pregnancies.
(ii) To prevent STD (Sexually Transmitted Diseases).
(iii) To have proper gap between two children.
(iv) To control population.
(v) To have sound health.

Question. Give two differences between male gametes and female gametes.
Answer : Male gamete
It is smaller in size
It is motile.
Female gamete
It is bigger in size
It is non-motile

Question. Differentiate between plumule and radicle.
Answer : Plumule
It is part of growing embryo which gets converted into shoot of young plant.
It shows positive photoropism and negative geotropism
Radicle
The part of growing embryo which later forms the root of plant.
It shows negative phototropism and positive geotropism

Question. State one function each performed by following organs in human beings.
(a) Testes (b) Prostate gland.
Answer : (a) Formation of sperms takes place in testes.
(b) Prostate gland contributes fluid to the semen.

Question. What is the role of seminal vesicles and prostate gland?
                                    OR
Write the functions of secretions of prostate gland and seminal vesicles in humans.
Answer : Seminal vesicle: It holds the liquid that mixes with sperm to form semen. Prostate gland: It secretes fluid adding upto the semen and contains enzymes and other substances. It also provides nutrition to the sperms, in the form of fructose and calcium. It protects sperms.

Long Answer Type Questions

Question. Trace the changes that take place in a flower from gamete formation to fruit formation.
Answer : [Diagram drawn and annotated with the following points will also be considered]
– Stamen is the male reproductive part and it produces pollen grains.
• The ovary contains ovules and each ovule has an egg cell.
• The pollen needs to be transferred from the stamen to the stigma.
• If this transfer of pollen occurs in the same flower, it is referred to as self-pollination./ On the other hand, if the pollen is transferred from one flower to another, it is known as crosspollination. After the pollen lands on a suitable stigma, it has to reach the female germ-cells which are in the ovary.
For this, a tube grows out of the pollen grain and travels through the style to reach the ovary/Figure 
• The male germ-cell produced by pollen grain fuses with the female gamete present in the ovule.
• This fusion of the germ-cells or fertilisation gives the zygote.
• After fertilisation, the zygote divides several times to form an embryo within the ovule 
• The ovule develops a tough coat and is gradually converted into a seed. The ovary grows rapidly and ripens to form a fruit.
• Meanwhile, the petals, sepals, stamens, style and stigma may shrivel and fall off.

Question. State the basic requirements for sexual reproduction. Write the importance of such reproduction in nature.
Answer : The basic requirements for sexual reproduction to take place are involvement of two parents and fusion of their haploid gametes. In the sexual reproduction, a new individual is formed by the fusion of two haploid gametes, one from the male parent and the other from the female parent. Since the new individual formed is diploid in nature, the gametes must be formed by meiosis, so that chromosome number can be reduced to half. When fusion of gametes occurs, the two nuclei of these two gametes fuse and the chromosome number is restored to normal. The zygote, thus formed is diploid in nature.
Importance of sexual reproduction:
Sexual reproduction involves fusion of male and female gametes coming from both the parents. The fusion of these gametes results in genetic variations in the offsprings. This way sexual reproduction promotes diversity of characters in offsprings by providing genetic variations. These genetic variations, thus lead to evolution of species as well as allow the organisms to become better adapted in the changing environment.

Question. (i) Identify A, B, C and D in the given figure. Write their names.
(ii) What is pollination? Explain its significance.
(iii) Explain the processes of fertilisation in flowers. Name the parts of the flower that develop after fertilisation into (a) seed (b) fruit.
Answer : (i) ‘A’ is stigma, ‘B’ is pollen tube, ‘C’ is ovary and ‘D’ is egg cell (female germ cell).
(ii) Pollination is a process of transfer of pollen grains from the anther of stamen to the stigma of carpel. It is necessary for fertilisation by sexual reproduction.
(iii) When male gamete and egg fuse together to form zygote, it is called fertilisation.
It takes place in ovule. After that the ovule develops a tough coat and is gradually converted into seed.
Fruit: The ovary grows rapidly and ripens to form a fruit after ovule has been fertilised.

Question. (a) Draw the diagram of female reproductive system and match and mark the part (s):
(i) Where block is created surgically to prevent fertilisation.
(ii) Where CuT is inserted. (iii) Inside which condom can be placed.
(b) Why do more and more people prefer to use condoms? What is the principle behind use of condoms?
Answer : (a) (i) Fallopian Tube/Oviduct
(ii) Uterus
(iii) Vagina

(b) People prefer use of condoms as it prevents STDs/gives privacy to the user. Condoms help create a mechanical barrier preventing meeting of sperms and ovum.

Question. List any four steps involved in sexual reproduction and write its two advantages. 
Answer : The four main steps involved in sexual reproduction are:
(i) In the first stage of sexual reproduction, meiosis process occurs and the number of chromosomes reduces from diploid (2n = 46) to haploid (n = 23) for each gamete.
(ii) In the second stage, there is transfer of male gametes into the female body.
(iii) In the third stage, the two gametes will fuse together after fertilisation, a single male gamete will fuse with a female gamete. i.e. fertilisation process takes place.
(iv) After fusion of male and female gametes, they form a zygote, in which the number of chromosomes is restored to diploid (2n = 46).
The two main advantages of sexual reproduction are:
(i) There are more variations, which leads to better adaptability of the offsprings in the environment.
(ii) Promotes the diversity in the characteristics of offspring, because it results by fusion of gametes

Question. Draw a labelled diagram of longitudinal section of pistil of flower showing germination of pollen grains on the stigma.
Answer : 

Question. Draw the diagram of a female reproductive system and label the part which:
(i) Produces egg in female germ cell (ii) Part where zygote is implanted.
(iii) Path for entry of sperms.
Answer : (i) Ovary produces eggs
(ii) Zygote is implanted in womb or uterus
(iii) Entry of sperms through vagina.

Question. (a) List three different categories of contraception methods.
(b) Why has Government of India prohibited prenatal sex determination by law? State its benefits in the long run.
(c) Unsafe sexual act can lead to various infections. Name two bacterial and two viral infections caused due to unsafe sex.
Answer : (a) (i) Barrier method, (ii) Oral pills, (iii) Use of copper-T, (iv) Vasectomy in males, tubectomy in females.
(b) • It is because female foeticide is increasing.
• It leads to unbalanced sex ratio i.e., more males, less females.
On long run, it will help in maintaining healthier (equal) sex ratio.
It will save mothers from illegal medical termination of pregnancy and health issues.
(c) Gonorrhoea and syphilis are bacterial infections.
Warts and HIV-AIDS are viral infections.

Question. (i) Draw a sectional view of human female reproductive system and label the part where (a) Egg develops, (b) fertilisation takes place, (c) fertilised egg gets implanted.
(ii) Describe in brief the changes that uterus undergoes (a) to receive the zygote (b) if zygote is not formed.
Answer : (i) (a) Egg develops in ovary.
(b) Fertilisation takes place in fallopian tube.
(c) The fertilised egg gets implanted in uterus.

(ii) (a) The inner uterus lining becomes thick to receive the zygote and is supplied with blood and nutrients to nourish the embryo.
(b) The inner uterus lining breaks and released in the form of blood and mucus through vagina.

Question. (a) Name the organ that produces sperms as well as secretes a hormone in human males. Name the hormone it secretes and write its functions.
(b) Name the parts of the human female reproductive system where fertilisation occurs.
(c) Explain how the developing embryo gets nourishment inside the mother’s body.
Answer : a) The organ that produces sperms as well as secretes male hormone is testis. The hormone secreted by it is testosterone. Its important functions are as follows:
It stimulates sperm production.
It stimulates the development of secondary sexual characters in males like growth of beard hairs,
low pitch voice, etc. It involves in the development, maturation and functioning of the male accessory sex organs like vas deferens and seminal vesicles
(b) In human female reproductive system, the process of fertilisation takes place in one of the fallopian tubes.
(c) The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta.
Placenta is a vascular membranous organ that connects the developing foetus to the uterine wall of the mother. It contains villi on the embryo’s side of the tissue. On the mother’s side are blood spaces, which surround the villi. This provides a large surface area for glucose and oxygen to pass from the mother to the embryo. The placenta draws nutrients and oxygen, which it supplies to the foetus, from the maternal circulation. In turn, the placenta receives carbon dioxide and wastes of foetal metabolism and discharges them into the maternal circulation for disposal.