What is Binary fission?
Reproduction The Generating system
One Mark Question
1. What is Reproduction?
A: The production of new organisms from the existing organism of the same species is known as Reproduction.
2. What is the difference between Sexual and Asexual Reproduction?
A: Only one parent is needed in Asexual reproduction whereas two parents are needed in Sexual reproduction.
3. What is Budding?
A: A small part of the body of the parent organism grows out as a bud; which then detaches and then become a new organism.
4. What is Binary fission?
A: In unicellular organism like euglena asexual reproduction takes place by a method binary fission in which single cell divides into two daughter cell identical to the parent cell.
5. What are Epiphyllous bud?
A: In Bryophyllum buds are present in the depression of leaf margin. They are called epiphyllous buds. When they are placed in soil they develop into young plants.
6. What is Grafting?
A: Grafting is a technique of inserting a part of one plant into another plant in such a way that the two will unite and continue their growth.
1/2 Mark Question
1. What is Progeny?
A: Off springs (or) next generation of existing species
2. What is scion?
A: The upper part of the union in grafting is called scion.
3. What is root stock?
A: The lower part of the union in grafting is called root stock.
4. What are layers?
A: Stem (or) Branches that form roots while still attached to the parental plants are called layers.
5. What is foetus?
A: Embryo from third onwards is called foetus
6. What is ovulation?
A: The discharge of ovum from the ovarian follicle is called ovulation.
2 Mark Questions
1. Why do fish and frog produce a huge number of eggs each year?
A: 1) Fish and frogs are oviparous animals
2) They lay eggs in water which results in external fertilisation.
3) There is high risk in external fertilisation and minimises the chances of fertilisation due to external factors.
4) If they lay eggs in little quantities there will be no chance of fertilisation because some of them may be washed away (or) become prey to predators. Hence, fish and frog lay eggs in huge number to improve the chances of fertilisation.
2. Give examples and explain what is meant by external fertilization?
A: 1) If the fusion of sperm and ova occurs out side the body of the animal is called external fertilisation.
2) It occurs mostly in aquatic animals like fish and frogs.
3. What is job of Amniotic Sac?
A: 1) The Amnion grows around the embryo.
2) The cavity within the amnion become filled with a fluid called Amniotic fluid.
3) The embryo develops in the amniotic cavity which keeps the embryo moist and protects it from minor mechanical injury.
4. When the foetus is growing inside the uterus it need nutrients. What provide nutrients?
A: 1) Nutrients need for growth and development
2) Placenta is a tissue formed by the cells from embryo
3) Placenta is formed around 12 weeks of pregnancy and provides nourishment to embryo
4) The blood system of mother and foetus are separated by a thin membrane made of cells that allows exchange mainly by diffusion.
5) So, the nutrients diffuses from the blood system of mother into blood system of the foetus in placenta.
5. What would be the consequences if there is no meiosis in organisms that reproduce sexually.
A: 1) If meiosis not occurs the chromosome number will be doubled in the formed zygote.
2) The characters of the off spring are unusual and it may leads to the death of individual and eventually extinction of that species takes place.
4 Marks Questions
1. What are the different modes of sexual reproduction. Give examples.
Organisms can reproduce asexually in many ways.
a. Fission: Single celled organism such as paramecium, and bacteria reproduce by splitting into two (or) more offsprings.
1) This usually occurs in a symmetrical manner. They split into two by binary fission. When more cells are formed it is called multiple fission.
2) This often the only mode of reproduction in their organism.
1) A growth on the body as a bud that grow to form nearly identical copy of parent.
2) When the bud totally grow then it separates from parent and survive independently.
e.g.: Yeast Hydra
1) Some organisms can grow from a separate piece of parent organism.
2) This can be any part of parent body.
3) This happens only in the simplest organisms such as some flat worms, moulds, lichens, spirogyra etc.
1) Cutting - Rose
2) Grafting - Mango, Apple
3) Layering - Nerium
4) Tissue culture
2. How are sperm cells adapted for their function.
A: 1) Sperms are male gamates
2) Millions of sperms are produced by testes.
3) Sperm cell is adopted to carry genetic information to an egg.
4) The head of sperm cell is pointed like an arrow that allows it to piece through the egg more easily.
5) The tail allows it to swim towards the egg for fertilisation.
6) The middle piece of the sperm contains Mitochondria which provides energy for its movement towards ovum.
7) Millions of sperms compete to fertilize the ovum.
8) Semen provides nutrients for sperm to keep alive and help as a medium for the movement of sperms.
3. The menstrual cycle prepare the uterus for a fertilised egg. How long is an average menstrual cycle from start to finish.
A: 1) The uterus at the time of fertilisation is beautifully adopted to receive the developing embryo providing it with food and disposing of its wastes.
2) For fertilisation it is essential for production of Eggs.
3) A few days prior to this time, the uterus was normal in condition.
4) When the zygote is about to enter; the uterus enlarge and become much larger its inner wall is thick, soft and moist with fluid, its blood supply is greatly increased.
5) Menstruation cycle takes place once every 28 days from the age of puberty.
1. Germination of seed
i) Aim: Germination of seed
ii) Material Required: Bengal Gramseed, Water Beaker
a) Soak a few Bengal gram seeds in a water beaker over night.
b) Drain the excess water and cores the seeds with wet cloth and leave them for a day.
c) Keep sprinkling water at regular intervals so that they do not dry up.
Observation: The germinating seed had
cotyledons, plumule and radicle as its parts.
2. How do you observe the pollen grain.
Aim: To observe the structure of pollen grain.
b) Marigold flower
1) Take a slide and put a few drops of water on it.
2) Now take the flower tap it over the drop of water.
3) We can observe small dot like structures in water.
Observation: Dot like structures are called pollen grain. Two nuclei are present, and has a pollen tube.
Inference: Pollen tube reach the stigma and fertilise the egg to form zygote.
3. Formation of Bacterial colony in Milk.
Aim: To observe the formation of Bacterial colony in milk.
Requirements: Glass of milk, small quantity of curd, bowl.
1) Take a teaspoon full of curd and mix it with around 30 teaspoons full of luke warm milk in bowl.
2) Take another spoon full of curd and mix it in 30 spoon full of cold milk in another bowl.
3) Cover both the bowl and note the time taken.
Observation: Curdling occur in the bowl having luke warm milk.
Inference: Curdling indicates the presence (or) increase of lacto bacillus bacteria in the luke warm milk bowl.
Cold milk has not provided the medium for the rapid growth of lacto bacillus. Hence in cold milk curdling is not occurred.
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