Tuesday, December 29, 2020
Wednesday, December 23, 2020
Monday, December 21, 2020
Sunday, March 13, 2016
You have learnt that meiosis is the reduction division and occurs in the germ cells that produce gamets. Majot difference between mitosis and meiosis is in the number of chromosomes in daughter cells.
In mitosis, daughter cells have exactly the same number of chromosomes as the mother cell while, in meiosis the daughter cells have half the number of chromosomes of mother cell.
Daughter cells formed by meiotic division lead to the formation of male of female gametes. Each gamete has half the number of chrosomes of mother cell. During fertilization, the gametes fuse to form zygote.
In zygote has two sets of chromosomes – one from the male parent (sperm) and other from female parent (ovum). Zygote develops into an organism by repeated mitotic divisions.
A CELL with only one set of chromosomes is called a haploid cell. As the number of chromosomes in the daughter cell are reduced by half, meiosis is also called reduction dividsion. In general, the male and female gametes are haploid cells.
In majority of organisms, each cell has two sets of chromosomes are passed in to the two daughter cells. However, in meisosis only one of the two sets of chromosomes is passed on to each of the daughter.
During meiosis nucleus divides twice- these division are called meiosis-I and meiosis-II. In meiosis-I the daughter cells receive only one set of chromosomes that is reduction in the number of chromosomes occurs in meiosis-I.
MEIOSIS-II is a simple mitotic division which occurs immediately after meiosis-I. daughter cells of meiosis-I divide into a second generation of daughter cells- there are total four daughter cells each of with only one set chromosomes of four hploid cells are formed at the end of meiosis.
Meiosis –I This occurs in 5 stages .1. Prophase 2. Metaphase 3. Anaphase-I 4. Telophase-I and cytokinesis-I.
1. Prophase - number of changes occur in the cell during prophase-I. to und prophase-I is divided into five sub-stages. They are leptotene, zygotene, pacheytene, diplotene,and diakinesis. Chromatin in the nucleus of the mother cell condenses and forms chromosomes.
Following this, chromosomes start pairing. Each pair has two identical chromosomes. One chromosome of the pair is derived from the father and the ofther from the mother. In this stage, appear like letter’X’. this is called crossing over the chromosomes move towards the centre of the cell. Centrioles also move to the opposite ends over to the cell and spindle fibre formation begins. Nucler envelope and nuleous disappear.
Chromosomeal movement is completed. Chromosomes lie in the centre of the cell in the form pf plate- called quatorial plate. Some of the spindle fibres are attached to the centromere of the chromosome and rest of the spindle fibres attach to the centrosome of the opposite end of the cell.
Length of spindle fibres is reduced. As a result chromosome are pulled apart. Each chromosomes splits into two sister chromosomes. Each sister chromosomes has a segment of chromatid derived from mother cell and the father cell. Chromosome move towards opposite end of the cell.
Chromosomal movement towards opposite poles of the cells completed. Spindle fibres disappear. Nuclear envelope reappears around chromosomes and the nucleus is also formed again. With these meiosis-I is completed and the diploid parental cells has given rise to daughters cells with haploid
numbers of chromosomes.
This is the second division nuceus in meiosis. Haploid daughter cells formed in meiosis-I participate in this division and as parental cells. They divide to produce two haploid daughter cells each. Before dividing, chromosomal number of the haploid cell doubles. As the end of meiosis-II four haploid daughter cells are formed. meiosis-II also proceeds in stages – prophase-II 2. Metaphas--II 3. Anaphase-II 4. Telophase-II and cytokinesis-II .
This division is similar to mitotic division.. you may refer the chapter on mitosis for the change in the cell that occur in this division and for the process of cell division.
Points to remember-
During meiosis, only one set of chromosomes are passed on to the daughter cells. Hence daughter cells have hald the number of the chromosomes of the mother cell.
In meiosis , karyokinesi and cytokinesis occur two times.
Chromosomes number is not doubled during meiosis-I . during this division, the chromosomes number is reduced by half. The diploid mother cell gives to two haploid daughter cells.
Prophase-I of meiosis is divided into five sub-stages.
Before meiosis-II, chromosomes number is doubled and the haploid mother cell gives rise to two haploid daughter cells.
The events in meiosis-II are similar to mitotic division.
Crossing over of chromosomes occur during meiosis.
Sunday, March 6, 2016
LIKE FATHER, LIKE DAUGHTER
Ashima was sitting near the window and reading. It was windy and there was a lot of dust in the air. Suddenly Ashima sneezed loudly—aaa chhee!
Ashima’s parents were sorting out vegetables in the kitchen. Her mother said, “She sneezes just like you do. If you were not here, I would have thought it was your sneeze.”
Does your face or anything else look similar to that of someone else in your family? What is it? Did someone tell you this or did you find it out yourself? How do you feel when people compare you with someone else in your family? Why do you feel so? Who laughs the loudest in your family? Laugh like that person.
Who is whose aunt?
Nilima had gone to the house of her nani (mother’s mother) in the school holidays. She saw someone coming and went to tell her mother, “Amma, a mausi (mother's sister) has come to meet you.”
Her mother came out to see who had come. She told Nilima, “No, this is not your mausi ! She is your sister Kiran. You know your eldest nani ? Kiran is the daughter of her elder son. Kiran is your cousin sister. In fact, you are her cute son Samir’s mausi !”
How we are all related!
Nilima started playing with Samir. Her mother called Kiran and said, “See, my Nilima’s hair is a lot like yours – thick, curly and black. It’s good she does not have hair like mine – straight, limp and brown!”
Nilima’s nani laughed and said, “Yes, isn’t it strange? We sisters had thick curly hair and now our second generation has similar hair.” Nilima was listening to all this. She thought, “We are called ‘distant’ relatives, but, how closely related we are in many ways!”
Is this a mirror?
Look at the next page. Is Saroja standing in front of a mirror? No, this is her twin! Did you get confused? Their mother's brother (mama) also gets confused when he sees them together.
At times Saroja gets scolded for mischief done by Suvasini. Sometimes Suvasini tricks her mama and says, “Suvasini has gone out.” But now mama has learnt a trick. He says – Sing a song in Marathi ! Why this funny trick?
Read about them and you will understand. The sisters were just two weeks old when Saroja's father's brother's wife (chachi) adopted her and took her to Pune.
Everyone in chachi's house is very fond of music. Mornings begin with music in the house. Saroja knows many songs in both languages – Tamil and Marathi.
At home everyone speaks Tamil and at school most children speak in Marathi. Suvasini stays with her father in Chennai. Her father is a karate coach.
Since she was three, Suvasini started doing karate with the other children. On holidays, both father and daughter start practicing in the morning. Saroja and Suvasini look alike but are also quite different.
Do you now know why mama has his way of finding out who is who? Saroja and Suvasini look a lot like each other yet are different. For example, Saroja knows two languages.
If Suvasini's family also talked in two languages she could also learn both. We learn many things like language, music, love for reading, or knitting, when we get a chance and an environment to do so.
This from the family
Do this interesting survey in your class. Write how many children can do this :
1. Without touching your teeth fold your tongue towards the back of your mouth.
2. Roll your tongue by lifting it from the sides.
3. Open all the toes of your feet. Now without moving the others, move the little toe.
4. Touch the thumb to your wrist.
5. Make a ‘V’ by separating two fingers of your hand to each side.
6. Move your ears, without holding them. Those children who could do any of these should ask their family members also to do so. So, how many children have got this trait from their family?
But not this from parents...
Satti was only a few months old when one of her legs was affected by polio. But she never let this come in the way of her work and her life.
Walking long distances and climbing many stairs has been a
part of her work. Now Satti is married. Some people tell her not to have any children. She is also worried that her children may also get polio. She spoke to a doctor about this.
Experiments with peas – rough or smooth?
Gregor Mendel was born in a poor farmer’s family in Austria in 1822. He was very fond of studies but the very thought of examinations made him nervous (Oh! you too feel the same!). He did not have money to study at the University so he thought of becoming a ‘monk’ in a monastery.
He thought from there he would be sent to study further. Which he was. But to become a science teacher he had to take an exam. Oh no! he got so nervous that he kept running away from the exam, and kept failing!
But he did not stop doing experiments. For seven years he did experiments on 28,000 plants in the garden of the monastery. He worked hard, collected many observations, and made a new discovery! Something which scientists at that time could not even understand!
They understood it many years after his death, when other scientists did such experiments and read what Mendel had already written. What did Mendel find in those plants? He found that the pea plant has some traits which come in pairs.
Like the seed is either rough or smooth. It is either yellow or green, and the height of the plant is either tall or short. Nothing in between. The next generation (the children) of a plant which has either rough or smooth seeds will also have seeds which are rough or smooth.
There is no seed which is mixed a bit smooth and a bit rough. He found the same with colour. Seeds which are either green or yellow give rise to new seeds which are either green or yellow.
The next generation does not have seeds with a mixed new colour made from both green and
Mendel showed that in the next generation of pea plants there will be more plants having yellow seeds. He also showed that the next generation will have more plants with smooth seeds. What a discovery!
Some from the family, some from the environment From a distance Vibha knows that her nana (grandfather) is coming – from his loud laughter. Nana also talks loudly and hears with difficulty. Are there people in your house who talk loudly?
Is it their habit, or they cannot also hear very well? Are there times when you do not talk loudly in front of some people? When? With whom? Why? When can you speak loudly?
Some people use a machine in their ear to help them hear better. Some use a stick or spectcles to help them in other ways. Do you know someone who does so?
We have seen that some traits or habits we get from our family. Some things and skills we learn from our environment. At times our abilities change because of some illness or old age. All these together make us what we are!
Daughter of the jungle
Look at the picture. Where do you think these children are off to, with little bundles on their sticks? When you find out you too would want to go with them!
The children are going to the forest. There they jump, run, climb trees and sing songs in their language called Kuduk. They pick the fallen flowers and leaves, to weave them into necklaces.
They enjoy the wild fruits. They look for birds, whose calls they imitate. Joining them in all this fun is their favourite didi – Suryamani. Every Sunday Suryamani takes the children to the forest.
As they move around, she shows them how to recognize the trees, the plants, and animals. Children enjoy this special class in a forest! Suryamani always says, “To learn to read the forest is as important as reading books.”
She says,”We are forest people (adivasis). Our lives are linked to the forests. If the forests are not there, we too will not remain.”
Suryamani’s story is a true story. Suryamani is a ‘Girl Star’. ‘Girl Stars’ is a project which tells extraordinary tales of ordinary girls, who have changed their lives by going to school.
Suryamani loves the forest since she was a child. She would not take the direct road to school, but would choose the path through the forest. Suryamani’s father had a small field.
Her family used to collect leaves and herbs from the forest and sell these in the bazaar. Her mother would weave baskets from bamboo or make leaf plates out of the fallen leaves.
But now no one can pick up a single leaf from the forest. That is since Shambhu the contractor came there. The people of Suryamani’s village were afraid of the contractor.
Everyone except Budhiyamai. She would say, “We the people of this forest have a right over it. We look after our forests, we don't cut trees like these contractors do. The forest is like our ‘collective bank’ – not yours or mine alone. We take from it only as much as we need. We don’t use up all our wealth.”
Suryanani’s father could no longer support the family on the small land. He moved to the town in search of work. But things did not improve. Sometimes there would be no food in the house.
At times Maniya Chacha (uncle) would send some grain from his small shop to Suryamani’s house. Chacha tried hard and got admission for Suryamani in the school in Bishanpur.
Here they would not have to pay for the fees, uniforms and books. Suryamani would have to stay there and study. Suryamani didn't want to leave her village and forest. But Maniya Chacha was firm.
“If you do not study, what will you do? Go hungry?” Suryamani would argue, “Why should I go hungry? The jungle is there to help!” Chacha tried
to explain, “But we are being moved away from our forests.
Even the forests are disappearing – in their place mines are being dug, dams are being built. Believe me, it is important for you to study, to understand about the laws. Maybe then you can help to save our forests”. Young Suryamani listened, and tried to understand some of what he said
Suryamani was filled with joy on seeing the school at Bishanpur. The school was near a thick forest. Suryamani studied hard and passed her B.A. after getting a scholarship.
She was the first girl in the village to do this. While she was in college she met Vasavi didi, a journalist. Suryamani soon joined her to work for the Jharkhand Jungle Bachao Andolan (Movement to Save the Forests of Jharkhand).
This work took Suryamani to far off towns and cities. Her father did not like this. But Suryamani continued her work. Not only that, she also started to fight for the rights of the village people. Her childhood friend Bijoy helped her in this work.
Suryamani had another friend ‘Mirchi’, who stayed with her day and night. Suryamani would share all her thoughts and dreams with Mirchi. Mirchi would listen and say “Keee Keee.” Suryamani had a dream. for her Kuduk community. She wanted all her people to feel proud of being adivasis.
Suryamani was 21 when she opened a centre, with the help of Vasavi didi and others. She called it ‘Torang’, which means jungle in the Kuduk language.
Suryamani wanted that on festivals people should sing their own songs. They should not forget their music and should enjoy wearing their traditional clothes.
Children should also learn about herbs, medicines, and the art of making things from bamboo. Children should learn the language of school but must link it with their own language.
All this happens in the ‘Torang’ centre. Many special books about the Kuduk community and other adivasis have been collected. Flutes and different types of drums are also kept there.
Whenever something is unfair, or if someone is afraid that his land and livelihood would be taken away, they turn to Suryamani. Suryamani fights for everyone’s rights.
Suryamani and Bijoy have got married and work together. Today their work is praised by many people. She is invited, even to other countries, to share her experiences. People of her area are also raising their voice for a new forest law.
Right to Forest Act 2007
People who have been living in the forests for at least 25 years, have a right over the forest land and what is grown on it. They should not be removed from the forest.
The work of protecting the forest should be done by their Gram Sabha. A forest is everything for us adivasis. We can’t live away from the forests even for a day. Government has started many projects in the name of development – dams and factories are being built.
Forests, which are ours are being taken away from us. Because of these projects, we need to think where the forest people will go and what will happen to their livelihood?
Where will the lakhs of animals living in the forests go? If there are no forests, and we dig out our lands for minerals like aluminium, what will be left? Only polluted air, water, and miles and miles of barren land...
Lottery for farming in Mizoram:
You read about the forests of Jharkhand in Suryamani’s story. Now read about forests on the hills of Mizoram. See how people live there, and
how farming is done.
Ding, Ding, Ding.... As soon as the school bell rang Lawmte-aa, Dingi, Dingima picked their bags and hurried home. On the way they stopped to drink water from a stream in a cup made of bamboo which was kept there.
Today not only the children, even ‘Saima Sir’ was in a hurry to get back. Today there would be a special meeting of the Village Council (Panchayat). At the meeting there would be a lottery to decide which family will get how much land for farming.
The land belongs to the whole village, not to separate people. So they take turns to do farming on different parts of the land. A beautiful pot made of bamboo was shaken well. One chit was taken out. Saima Sir’s family got the first chance.
He said, “I am happy that my family gets to choose first. But, this year we cannot take more land. Last year I had taken more and was not able to farm it well. After my sister Jhiri got married and went away it is difficult to manage farming alone.”
Saima Sir asked for ‘three tin’ of land. Little Mathini asked, “ What is three tin of land? Chamui explained, “The land on which we grow one tin of seeds is called one tin of land.” One by one, the village families got their piece of land for farming.
Jhoom farming is very interesting. After cutting one crop, the land is left as it is for some years. Nothing is grown there. The bamboo or weeds which grow on that land are not pulled out. They are cut and burnt.
The ash makes the land fertile. While burning, care is taken so that the fire does not spread to the other parts of the forest. When the land is ready for farming it is lightly dug up, not ploughed.
Seeds are dropped on it. In one farm different types of crops like maize, vegetables, chillies, rice can be grown. Weeds and other unwanted plants are also not pulled out, they are just cut. So that they get mixed with the soil.
This also helps in making the soil fertile. If some family is not able to do farming on time, others help them and are given food.
The main crop here is rice. After it is cut, it is difficult to take it home. There are no roads, only hilly paths. People have to carry the crop on their
backs. This takes many weeks. When the work is over the entire village celebrates.
People get together to cook and eat, sing and dance. They do their special ‘cheraw’ dance. In this dance people sit in pairs in front of each other, holding bamboo sticks on the ground.
As the drum beats, the bamboos are beaten to the ground. Dancers step in and out of the bamboo sticks, and dance to the beat.
Find out more about the ‘cheraw’ dance. Do it in your class. But be careful and don’t hurt yourself. About three-fourth people in Mizoram are linked to the forests.
Life is difficult but almost all children go to school. You can see some of them here, playfully blowing their leaf whistles! You too have made many such whistles, haven’t you!
Saturday, January 16, 2016
Have you ever seen the wahida's photograph anywhere?
She is Lieutenant Commander WahidaPrism, doctor in the Indian Navy. She is one of the few women who has worked on a naval ship. She is the first woman to lead a parade. This is considered to be a very big honour in the armed forces.We specially spoke to Wahida for this book. Let us read what we spoke.
Question – Wahida, tell us something about your childhood and school. Wahida- I come from a very small village called Thannamandi. This is in Rajouri district of Jammu and Kashmir. I did my schooling from a government school. Most of the girls from the village studied in my school.
However, few of them ever thought of what they would do after finishing school. I always wanted to become someone special and move forward in life. I was very interested in higher studies and wanted to complete the tenth class.
In my area, it was a new thing at that time. My mother and father had to face many problems because of this.
We even had to move out of our village. We then went to live with my grandmother in Rajouri. I did my twelth class from there.
We even had to move out of our village. We then went to live with my grandmother in Rajouri. I did my twelth class from there.
Question- So you always thought differently right from the beginning? Wahida-Even when I was very young I wanted to do something different. I was very fond of riding a motor-cycle. We are three sisters. My father wanted one of us to become a doctor and one a teacher. He wanted the third daughter to become a lawyer or join the police force. I have become a doctor in the Indian Navy and my sister is in the Jammu Police Force.
Question- How did you become a doctor?
Wahida – I worked very hard. My friends and family members helped me a lot. I got admission in Jammu Medical College. I studied for five years and did my M.B.B.S.
Question – How did you get into the Defence Forces? Didn’t your family stop you? Wahida – Oh, no! They felt that a job in the Forces would be the best thing for me. When I was very small, I would see army officers in our village. I wanted to be like them. This was really a very big dream for me! While in school, I attended camps, climbed mountains and was a ‘Girl Guide’. After I became a doctor, I appeared for an interview to join the Armed Forces. I got selected there and received a training for six months.
Question- – Why did you join the Indian Navy? Do you not have to live on the naval ship?
Wahida – Well, I am very fond of travelling. I like to see different places. I wanted to go to far-off places. I was born in the hills and now I am working in sea. I really enjoy it. Very few lady-officers have worked on a ship. I am one of them.
Earlier, women were not allowed to go on Naval ships. When anopportunity was given, I myself went forward and gave my name. I even want to go in a submarine. I want to do everything which people think women cannot do. At present women are not allowed to go in submarines, but whenever it is allowed, I will certainly go.
Question – So what happened to your degree of M.B.B.S? Wahida – I am a doctor, but in Indian Navy a naval doctor does not just give medicine to patients. She is in fact, a medical officer. The ship goes to sea for three-four months at a time. There, it is my responsibility to make sure that everybody on the ship stays fit and healthy. I carry out medical check-ups of all the officers and sailors.
I also have to make sure that cleanliness is maintained on the ship. I have to ensure that no garbage collects and there are no rats on the ship. Rats and garbage can spread diseases.
I must keep everybody, ready for any medical emergency on the ship. In case there is an accident on the ship, (like a fire), everybody must be ready to deal with it.
Question – Is there a hospital on the ship?
Wahida – ‘First aid’ is given on every naval ship. Each ship has one doctor and two or three assistants. Necessary medicines and some equipment are also available. All these things are kept in a small room.
Question – You are the first woman to lead a parade. You must have worked very hard for this.
Wahida – My seniors gave this opportunity to me after seeing my performance for three years. I felt happy that they had chosen me and showed faith in me. So I practiced very sincerely.
Question– Tell us something about that parade.
Wahida – In a parade, four platoons march behind the leader. Thirty-six commands have to be given during the entire parade. These must be given in a very loud voice so that it is heard till the rear. The voice should also reach the spectators sitting on the other side of the ground.
Question -Didn’t you feel nervous leading four platoons?
Wahida – I was not nervous, but one has to shout thirty-six commands. If you forget even one, the entire parade can get spoiled. I practised every morning and evening for a month. But, I have been participating in parades since school.
Question – What is the meaning of the word ‘Prism’ in your name?
Wahida – My father gave this name to me. A prism is a kind of glass which reflects seven colours. My father wanted me to be like a prism and that is why he started calling me by this name from my childhood itself.
This is the great story what we learnt about of our Indian honour woman Lieutenant Commander Wahida Prism, doctor in the Indian Navy.
Friday, January 15, 2016
Come, let us play a game together. You must be familiar with this game. All the children stand in a circle.
Let one child stand in the centre and play a tune. Everyone must run in a circle as long as the music plays. The child who is playing the music, will suddenly stop it and call out a small number like ‘five’, ‘four’ or ‘two’ loudly. Children have to form groups according to the number called out.
The children who cannot join any group will have to leavethe game. Continue to play this game till only two children are left in the circle.
All of us prefer to live with people than to live alone. We always live in groups. Let’s see one such group – Gurleen, Nagarajan and their children Tanya and Samar.
The people in the picture you saw belong to one family. We often see pictures or photographs of such families. Where do we see such a family? Are all families similar to this one ? Let us read about a few families.
Sitamma lives in her ancestral house in a small city Guntoor. Her dada, dadi, younger chacha and bua live on the ground floor. In one portion of the first floor, Sitamma lives with her father, mother and younger sister Gitamma. In the other portion live her tauji and his three children.
Her taiji died just a few months ago. Her elder chacha and the new chachi live in one of the rooms on the terrace. They are newly married.
Before dinner, Sitamma’s mother teaches all the children. Food for the whole family is cooked in the same kitchen on the ground floor. They all make special effort to be together at dinner time.
Nowadays, tauji ’s younger daughter sleeps with Sitamma’s mother at night. In the morning Sitamma helps her get ready for school.
Tara lives with her amma and nana in Chennai. Her amma Meenakshi is not married. She has adopted Tara. Meenakshi goes to the office in the morning and returns in the evening.
When Tara returns from school, her nana takes care of her. He is the one who feeds her, helps her to do homework and also plays with her.
During vacations, the three of them go to far off places and enjoy themselves. At times, Tara’s mausi, mausa and their children also come to their house. At such times they play together for long hours and also chit chat.
Sara and Habib live in a city. Both are employed. Habib is a clerk in a government office and Sara teaches in a school. Habib’s abbu is retired and lives with them.
In the evening, the three of them sit together and watch television or play cards. Abbu enjoys watching television with the others. He enjoys the discussion as well. On holidays, the neighbour’s children come to their house and create a lot of fun. Everybody enjoys together. They play games, go out and at times go for plays and movies.
Totaram lives with his father, uncle and cousin brothers in a colony in Mumbai. Totaram and his brothers have come to Mumbai to study. His father and uncle work here.
Everybody does the household work together. Food cooked by Totaram’s chacha is liked by everyone.Totaram’s father does the shopping.
A part of the money earned is sent to Totaram’s dada in the village. Totaram’s mother, dada, dadi, chachi and younger brothers and sisters live in their parental house in the village. Once a year, Totaram goes to his village. He misses his mother very much. He writes long letters to her.
Krishna and kavari
Krishna and Kaveri live with their father. In the morning, all the three leave home together. krishna lives kavari at school and goes to college. Their father go to the shop for the day.
and waits for Krishna. On returning from college,Krishna and kavari eat food together.Kaveri goes out to play after doing her school work.
On returning she either plays carom with her brother or watches television. When father returns home, they cook food and then eat together.
During vacations, Kaveri goes to stay with her mother. Krishna
also stays there for a few days, but he likes to stay in his own
house – all his things and his father are here.
There may be other differences: some couples may marry at a young age and some people find a partner when they are older; some families with children are led by one parent because of death, separation, or divorce; some couples have no children, yet they consider themselves to be a family; some people have one child, while others have many children born to them.
Many families adopt a child or several children. When we talk about our family, we usually refer to the people who live with us.
All of our relatives, such as cousins, aunts, uncles, and grandparents, are part of our family. Whether they live in a separate place down the block or across town, or even far away from us in another part of Canada or in a foreign land, they are still part of our family.
Not everyone knows all their grandparents because they are no longer alive. These family members are remembered in stories told about the good times when you were a baby or before you were born.
Nowadays, it is wonderful for families that even those who live far away can both hear and see each other through the use of computer web-cams and other modern communication systems.And all through it shines by God’s love.