03 March 2014

CBSE VIII Reproduction in plants and animals practice notes study

The life process that help to produce new ones of their own kind is called reproduction. This help in continuation of life from one generation to other
There are two kinds of reproduction: 
When two individuals are involved in reproduction, it is termed sexual reproduction.

When only one individual is involved in reproduction, it is termed asexual reproduction.
Binary fission is a kind of asexual reproduction in which a cell may divide to give rise to two individuals and lose its own identity . Binary fission that takes place in amoeba and bacteria

Budding is kinds of asexual reproduction in which bud develops on the body detaches from the parent body and give rise to new individual. Example: yeast, sponges and hydra.

Spore formation is kind of asexual reproduction in which new individual arises when globular structure known as sporangia, which contains spores burst. Example: fungus, moss and fern.

Vegetative reproduction : It is a method of producing new plants without using male or female gamete.It is known as Vegetative Propagation  as new plant grow from the vegetative part of plants

Cutting: A piece of branch is cut and embedded in the soil. Roots form and a new plant results.

Layering: A branch of the plant is laid on the ground and a portion is embedded in the soil. This part strikes root and gives rise to new plant.

Grafting: The lower part of the stem or scion is cut in a wedge, The shoot of the plant to be used as a stock is cut off. The stem is slit vertically and the scion is inserted into the stock and tied with a tape.
Image result for Grafting:
Tissue culture :The process of formation of new plants with the help of a small tissue removed from a growing tip of a plant in a favourable medium(culture solution) is call tissue culture

Cloning: Cloning is the creation of an organism that is an exact genetic copy of another. The sheep Dolly is the first colon. Her mother’s udder cell nucleus was transferred into the egg of a “surrogate mother”, after removing the nucleus. Dolly’s mother provided her genes while the surrogate mother provided the womb for Dolly to develop from an embryo to a full fledged individual.

Why is binary fission considered to be an asexual form of reproduction? 
This is because it involve single parent.
Sexual reproduction in flowering plants occurs with the help of flower.  
Stamens (Androecium) which produce pollen are the male part. Pollen grains contain male sex cells. There may be several stamens in each flower. Each stamen (Androecium) has two parts. The upper part is known as anther which produce  pollen. It is held on the lower part called filament.

The pistil (Gynoecium) is the female part and its basal part is the ovary produce eggs or ovules called  female sex cells. The parts of the pistil are the stigma, style and ovary.

If  flower of plant bears both male and female parts. They are termed bisexual or hermaphrodites.

In some plants there are male flowers with only androecium and female flowers bearing only gynoecium. They are unisexual.  

Several agents like the wind, water, and insects. transfer pollen grain from anther to the stigma of a flower called pollination.

When pollen is brought on the stigma of the pistil reaches the ovule as pollen tube pushes through the pistil get fertilized.
The fertilized ovules develop into seeds which are capable of germinating into seedlings and new plants

« What will happen if the pistil of the flower is removed?  
 If the pistil of the flower, which is the female portion of the flower, is removed the flower would no longer be able to produce seed
Hydroponics: It is a method of growing plants using mineral nutrient solutions, in water, without soil.

In all animals, the female produces eggs within ovaries and the male produces sperms within testes.
An egg and a sperm fuse to form the zygote and takes place in the fallopian tube (the oviduct) which then develops into the embryo and the embryo into a full-fledged individual.

If fusion or fertilization takes place inside the mother’s body. They are termed viviparous. 
Animals that lay eggs include fish, frog, reptiles and birds and are thus called oviparous. 
if both female and male sex organs are in the same individual. Such individuals are termed hermaphrodite.

An embryo obtains nutrition for growth and development its body parts from mother’s blood through placenta. The embryo attached to the wall of uterus by placenta.

The close attachment of the embryo with the walls of uterus is called implantation.

A special tissue between the uterus wall and the embryo (foetus) that fulfils the nutritional, respiratory and excretory needs of the foetus from mother's body is called placenta.

The function of amniotic fluid is to protect the foetus against temperature changes and mechanical shocks.

The development of the foetus inside the uterus till birth is called gestation.

The birth of a fully developed foetus after the completion of gestation period is called parturition.

The embryo continues to develop in the uterus body parts such as hands, legs, head, eyes, ears, etc.
The stage of the embryo in which all the body parts can be identified is called a foetus . When the  development of the foetus is complete, the mother gives birth to the baby.

While in the womb, the baby floats in the amniotic fluid. The function of amniotic fluid is to protect the foetus against temperature changes and mechanical shocks.

Metamorphosis is the process of the transformation of larva into an adult through drastic change. For example  pupa into adult butterfly. Metamorphosis does not occur in viviparous animals because the young one resembles the adult at the time of birth.

In the hen, new individual hens [chick] develop from hen’s egg in about 3 weeks. He provides sufficient warmth to the egg to develop by sitting over it. This is called brooding. 
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