- Why do fish and frog produce a huge number of eggs each year? (AS1)…
- Give examples and explain what is meant by external fertilization? (AS1)…
- Grafting - layering Write differences between (AS1)
- Stamen - carpel Write differences between (AS1)
- Explain the process of fertilization in plants. (AS1)
- Fission: What are the different modes of asexual reproduction? Cite them with examples.…
- Budding: What are the different modes of asexual reproduction? Cite them with examples.…
- Fragmentation: What are the different modes of asexual reproduction? Cite them with…
- Regeneration: What are the different modes of asexual reproduction? Cite them with…
- Parthenogenesis: What are the different modes of asexual reproduction? Cite them with…
- Vegetative propagation: What are the different modes of asexual reproduction? Cite them…
- Spore formation: What are the different modes of asexual reproduction? Cite them with…
- In what ways does sexual reproduction differs from asexual one? State at least three…
- How are sperm cells adapted for their function? (AS1)
- The menstrual cycle prepares the uterus for a fertilized egg. How long is an average…
- When the fetus is growing inside the uterus it needs nutrients. What provides these…
- Which type of substances are absorbed by fetus from the mother? (AS1)…
- What is the job of the amniotic sac? (AS1)
- What are the advantages of sexual reproduction? (AS1)
- How does reproduction help in providing stability to the population of species? (AS1)…
- Write the differences between mitosis and meiosis. (AS1)
- What happens to the wall of the uterus during menstruation? (AS1)…
- “All unicellular organisms undergo only mitotic cell division during favorable conditions”…
- Vicky’s father wants to grow a single plant having two desirable characters colourful…
- Uproot an onion plant and take a thin section of its root tip. Stain it and observe under…
- Visit a nearby village and collect information how farmers grow sugarcane, flowering…
- Collect information from the school library or using internet what vegetative methods are…
- Make a flow chart to show the cell cycle and explain cell division describing different…
- Draw neatly labeled diagrams of male and female reproductive system of the plant. (AS5)…
- Observe the following part of a flowering plant prepare a note. (AS5)…
- Prepare a flow chart to explain the process of sexual reproduction in plants. (AS5)…
- Draw a neatly lablled diagram to explain plant fertilization. Write few points on pollen…
- What would be the consequences if there is no meiosis in organisms that reproduce…
- How will you appreciate cell division that helps in the perpetuation of life? (AS6)…
- What precautions will you take to keep away from various sexually transmitted diseases?…
- Conduct a seminar on child marriages and foeticide. (AS7)
- The part of the female reproductive system that produces the eggs? ()A. Ovary B.…
- The term that we use to describe a sperm cell fusing with an egg cell? ()A. Fragmentation…
- Which part of the male reproductive system produces (human) the sperm cells? ()A.…
- How does the sperm break through the egg cell membrane? Choose the option you think is…
- Why are egg cells larger than sperm cells? Choose the option you think is right. ()A. Egg…
- Which of these things will affect the way a foetus grows? Choose the option you think is…
- Which of the following is the correct sequence of steps in the human life cycle? Choose…
Improve Your Learning
Question 1.Why do fish and frog produce a huge number of eggs each year? (AS1)
Answer:
a) Aquatic animals such as fishes and frogs reproduce through sexual reproduction by external fertilization i.e. the fertilization occurs outside the female’s body.
b) In external fertilization, since the chances of fertilization, or the development and survival of the zygote are totally dependent on nature, large number of eggs and sperms are produced and released every cycle.
c) Most of the times, the unfertilized or the fertilized eggs are lost to predators, water currents, and other environmental factors, so in order to compensate for the loss, a huge number of eggs are produced.
Question 2.
Give examples and explain what is meant by external fertilization? (AS1)
Answer:
a) External fertilization can be defined as the fertilization that takes place outside the female’s body.
b) External fertilization is mostly common in aquatic organisms such as fishes and amphibians.
c) During the time of mating, the female lays a large number of eggs in the water and male releases millions of sperms on them in water. The zygote thus formed after the fusion of gametes is protected in a jelly-like structure where it grows and develops.
d) Since the chances of fertilization or the development and survival of the zygote are totally dependent on nature, a large number of eggs and sperms are produced and released every cycle.
e) For example: Fishes, frogs and other amphibians.
Question 3.
Write differences between (AS1)
Grafting – layering
Answer:
Grafting – layering
Question 4.
Write differences between (AS1)
Stamen – carpel
Answer:
Stamen – carpel
Question 5.
Explain the process of fertilization in plants. (AS1)
Answer:
a) The pollen grain reaches the stigma of the flower called pollination.
b) The pollen tube starts germinating, the pollen contains 2 cells- generative cell and a vegetative cell.
c) Both the cells travel through the pollen tube which leads them to the embryo sac.
d) The embryo sac is a 7 celled 8 nuclei structure.
e) One of the male gametes fuses with the female egg- called syngamy, while the other fuses with the 2 polar nuclei forming a triploid- called triple fusion.
f) Since 2 kinds of fertilization take place in a plant, it is also called double fertilization.
g) After fertilization, the triploid central cell develops into endosperm while the zygote develops into an embryo.
Question 6.
What are the different modes of asexual reproduction? Cite them with examples. (AS1)
Fission:
Answer:
The different modes of asexual reproduction are as follows:
Fission: The splitting of unicellular organisms into daughter cells is called fission. If the parent cell splits into two daughter cells, it is called binary fission whereas splitting of parent cells into more than 2 cells is called multiple fission. For example binary fission in Amoeba and multiple fission in Plasmodium.
Question 7.
What are the different modes of asexual reproduction? Cite them with examples. (AS1)
Budding:
Answer:
Budding: An outgrowth called bud starts forming on the body of the parent organisms. When the bud is fully grown, it detaches itself from the parent body and starts acting as an individual. For example Yeast.
Question 8.
What are the different modes of asexual reproduction? Cite them with examples. (AS1)
Fragmentation:
Answer:
Fragmentation: Fragmentation is a mode of reproduction in which an organism divides into 2 or more fragments and each fragment acts as a new individual. It is more common in simpler organisms such as algae, fungi, and flatworms.
Question 9.
What are the different modes of asexual reproduction? Cite them with examples. (AS1)
Regeneration:
Answer:
Regeneration: The ability of an organism to grow from a part is called regeneration and is useful in case the organism gets cut up into pieces. For example Planaria.
Question 10.
What are the different modes of asexual reproduction? Cite them with examples. (AS1)
Parthenogenesis:
Answer:
Parthenogenesis: The process of reproduction where there is a shift from sexual to asexual mode of reproduction due to various environmental changes. It can be both natural such as in bees, wasps or induced such as in various seedless fruits.
Question 11.
What are the different modes of asexual reproduction? Cite them with examples. (AS1)
Vegetative propagation:
Answer:
Vegetative propagation: The mode of reproduction in which vegetative propagules rather than seeds are used to grow plants. It is useful to grow seedless plants, the plant who have lost the ability to produce seeds or to grow a number of plants in a short duration. It can be both natural such as in Bryophyllum, strawberries, or artificial such as grafting, layering etc.
Question 12.
What are the different modes of asexual reproduction? Cite them with examples. (AS1)
Spore formation:
Answer:
Spore formation: Spores are microscopic unicellular structures produced inside sporangium in various fungi, bacteria and non-flowering plants. These spores are produced in very large number.
Question 13.
In what ways does sexual reproduction differs from asexual one? State at least three reasons. (AS1)
Answer:
Question 14.
How are sperm cells adapted for their function? (AS1)
Answer:
a) The major function of the sperm is to travel to the egg cell so as to fertilize it.
b) For this, sperm has to travel a large distance in short amount of time. The sperm cell consists of a long tail that helps in its movement.
c) Also, in order to introduce its nucleus into the female cell for fusion, the sperm has to break through the various layers enveloping the egg. For this, acrosome is present on the head of the sperm which releases enzymes that help in dissolving the layers around the egg.
Question 15.
The menstrual cycle prepares the uterus for a fertilized egg. How long is an average menstrual cycle from start to finish? (AS1)
Answer:
a) An average menstrual cycle extends between a period of 28-30 days from the onset of puberty in girls.
b) It starts with the end of the previous menstruation.
c) One of the ovaries develop an egg and release it on the 14th day. This process is called ovulation.
d) The uterus prepares itself for receiving a zygote if fertilization takes place.
e) The walls of the uterus get thick and richly supplied with blood vessels. The uterus also increases in its size.
f) If the egg is not fertilized between the 14th-18th day, the egg is shed off the body.
g) As there is no use of the uterine lining, it too comes off the vagina around 28th day in the form of menstrual flow.
Question 16.
When the fetus is growing inside the uterus it needs nutrients. What provides these nutrients? (AS1)
Answer:
a) While the fetus is growing inside the uterus, it receives nutrition from the body of the mother itself through the placenta.
b) The placenta is a tissue formed by the cells of both the mother and the embryo around the 12th week of pregnancy.
Question 17.
Which type of substances are absorbed by fetus from the mother? (AS1)
Answer:
The foetus absorbs substances such as oxygen and various other nutrients from the mother through the placenta. The blood travels through the membranes surrounding the placenta and the nutrients along with oxygen and other things are diffused in the foetus.
Question 18.
What is the job of the amniotic sac? (AS1)
Answer:
a) Amniotic sac develops from an embryonic membrane called amnion.
b) The amnion grows around the embryo covering it entirely into a cavity.
c) This cavity is filled with a fluid called the amniotic fluid in which the embryo develops.
d) The amniotic fluid along with amniotic cavity helps in keeping the embryo moist and safe from minor mechanical injuries.
e) The amniotic sac provides cushioning whereas the fluid-filled cavity acts as shock absorber.
Question 19.
What are the advantages of sexual reproduction? (AS1)
Answer:
Advantages of sexual reproduction:
a) Sexual reproduction involves the combining of gametes of both the parents to form a zygote. Hence, this zygote consists of the combination of characteristics of both the parents.
b) Every time a new zygote is formed, new combinations take place giving rise to various variations.
c) Accumulation of such variations helps the organisms to adapt and survive better in the environmental conditions and also helps in bringing new characteristics.
Question 20.
How does reproduction help in providing stability to the population of species? (AS1)
Answer:
a) Every organism in a population has a certain life span. In that particular time period, it takes birth, grows, develops and after fulfilling its life expectancy dies.
b) Reproduction ensures that the population of a particular species keeps on surviving by the production of new offspring’s of the same kind.
c) If reproduction does not take place, no new organisms will be produced while the old ones keep on perishing. A time will come when all the organisms are dead and the population of particular species will cease to exist.
d) Hence, reproduction is important for providing stability to a population.
Question 21.
Write the differences between mitosis and meiosis. (AS1)
Answer:
Question 22.
What happens to the wall of the uterus during menstruation? (AS1)
Answer:
a) If the fertilization does no take place, the egg or ova is shed out of the body. The thick uterine lining that developed to receive the embryo also gets wasted.
b) During menstruation, this thick uterine lining/wall is shed out of the body and comes out of the vagina in the form of blood and mucus.
Question 23.
“All unicellular organisms undergo only mitotic cell division during favorable conditions” – Do you support this statement? Why? (AS2)
Answer:
Yes, all unicellular organisms undergo mitotic cell division during favorable conditions in order to increase their population. Whether it be through fission, budding, etc., they reproduce to form daughter cells.
Question 24.
Vicky’s father wants to grow a single plant having two desirable characters colourful flowers and big fruits. What method will you suggest him and why? (AS3)
Answer:
I will suggest the method of either grafting or cross-pollination.
Grafting method:
•In this method, two plants are joined together in such a way that the two stems join and grow as a single plant.
•This technique is used to produce plants with desirable characteristics and is helpful for propagating improved varieties of various flowers and fruits.
•In this technique, the plant attached to the soil is called stock whereas the team attached to it is called Scion.
•Using this technique, we can attach the two plants with desirable characteristics of colourful flowers and big fruits together to get the single plant.
Cross-pollination method:
•In this method, 2 plants of the same species but different characteristics can be cross-pollinated.
•The pollen from one plant having the characteristic of colourful flower can be used to pollinate another plant that bears big fruits.
•The resulting zygote will have the characteristics of both the pants.
Question 25.
Uproot an onion plant and take a thin section of its root tip. Stain it and observe under the microscope. Draw as you see and identify the stages of the cell division. (AS3)
Answer:
Onion root tip consists of meristematic tissues which consist of cells that are continuously dividing. Hence, by observing those cells we can see the various stages of mitosis.