Here is a compilation of term papers on ‘Reproduction’ for class 9, 10, 11 and 12. Find paragraphs, long and short term papers on ‘Reproduction’ especially written for school and college students.
Term Paper on Reproduction
Term Paper Contents:
- Term Paper on the Introduction to Reproduction
- Term Paper on the Characteristics of Reproduction
- Term Paper on Asexual Reproduction
- Term Paper on Sexual Reproduction
- Term Paper on Pollination
- Term Paper on the Fertilisation in Flowering Plants
- Term Paper on the Development of the Fruit
- Term Paper on the Germination of Seeds
1. Term Paper on the Introduction to Reproduction:
Reproduction:
Reproduction is the biological process by which new individual organisms are produced. It is the process by which living organisms produce copies of themselves (off-springs) which means existing generation produces a new generation.
Reproduction is a fundamental feature of all the species; each individual organism exists as the result of reproduction and hence species are still present till date with evolution over time.
Example:
When two lions mate; they produce lion cubs as offspring. Bee carrying pollen from one daisy to another fertilizes it, causing it to reproduce in the form of fertilized seeds. In these and all other examples of reproduction, new individuals are produced from existing ones.
Reproduction Helps in Keeping a Species Alive:
If a particular animal or a plant in the species does not reproduce at all, it is very likely that they may vanish from the earth in a span of a few years. Therefore, reproduction is necessary for maintaining a species alive but is not necessary for an individual’s survival.
2. Term Paper on the Characteristics of Reproduction:
a. Reproduction Maintains Continuity of Life:
Life perpetuates through reproduction producing new organisms from a cell derived from both the parents.
b. Reproduction is Specific:
A dog produces a dog; neem tree give neem seeds and so on. Thus the offspring resembles its parents.
c. Reproduction is Cellular:
Each organism begins life from one or many cells derived from the parents.
d. Reproduction is Developmental:
All organism are produced from a single cell that develops from a tissue to an organ following a long process of development.
3. Term Paper on Asexual Reproduction:
Asexual Reproduction is the production of genetically identical offspring from one parent.
A population of organisms produced in this way, and all genetically identical, is known as a clone.
The advantages of asexual reproduction are:
(i) Only one parent organism is required.
(ii) It is a relatively certain method of reproduction.
(iii) Because the parent can survive in that particular habitat, the genetically identical offspring should be suited to the environment as well.
The disadvantages of asexual reproduction are:
(i) A lack of variation in offspring prevents evolution.
(ii) Adverse conditions and disease will be likely to affect all members of the population.
(iii) Overcrowding and competition for resources (water, nutrients and, importantly for plants, light).
(iv) Distribution of the species is likely to be limited.
However, asexual reproduction in plants is an important commercial process, since it produces large numbers of offspring quickly, all of which have known characteristics (such as flavour, appearance, yield and disease resistance).
Tissue Culture:
A commercial application of asexual reproduction in plants is the use of a technique called tissue culture. A technique for keeping alive cells or tissues of living organisms after their removal from an organism. Plants reproduced in this way include food plants (the oil palm, the date palm and the banana) and horticultural plants such as the begonia.
Experiment 1:
Method:
Some actively dividing (‘meristematic’) cells are taken from the parent plant, and placed on a sterilised culture medium in many separate sterilised dishes. The culture medium is a jelly-like substance called agar containing plant growth hormones and the ions necessary for healthy growth.
The dishes are kept at a suitable temperature, and are covered to prevent the cells drying out.
Results:
The cells continue to divide, then some of them become modified to produce small (‘adventitious’) roots and some become modified to produce small shoots bearing lateral buds.
These plantlets can then be transferred to compost and will develop into clones of their parent.
The commercial advantages of using tissue culture to produce plants are:
(i) It is quick
(ii) It is reliable
(iii) It gives plants of guaranteed type
(iv) It is profitable.
4. Term Paper on Sexual Reproduction:
Sexual reproduction is the fusion of male and female nuclei to form a Zygote. Zygotes develop into offspring genetically different from each other, and from their parents. The nuclei are contained within gametes. As a result of a special type of nuclear division (‘reduction division’), the nuclei of gametes contain only half the number of chromosomes found in normal body cells.
Sexual Reproduction in Plants:
The flowers of plants are the organs of sexual reproduction.
Flowers have the following parts:
i. Sepals:
Sepals are (usually) green, leaf-like structures which protect the flower when it is in bud.
ii. Petals:
Petals may be large, colourful and scented with lines on them (nectar guides) if the flower is pollinated by insects. But if the flower is wind-pollinated, the petals are small and green, or not present at all.
iii. Anthers:
Anthers contain pollen sacs which make and then release pollen grains. Each pollen grain contains the male gamete(s). An anther is situated at the end of a stalk-like filament – an anther and a filament together form a stamen.
iv. Carpels:
Carpels are the female part of the flower. Each carpel is made up of a (sticky) stigma (for receiving pollen during pollination), connected by a style to the ovary, in which lie the ovules which contain the female gamete.
5. Term Paper on Pollination:
Pollination is the transfer of pollen from an anther to a stigma.
Self-pollination occurs when the anther and stigma are either in the same flower, or in different flowers on the same plant.
Cross-pollination occurs when the anther and stigma are in flowers on different plants of the same species.
The two most common agents for carrying pollen are the wind, and insects. Wind- and insect-pollinated flowers have structural differences, adapted according to their method of pollination.
Examples of wind-pollinated flowers are maize and grasses.
Examples of insect-pollinated flowers are beans and black-eyed Susan.
6. Term Paper on the Fertilisation in Flowering Plants:
When the pollen grain arrives on the stigma of the correct species of plant, the sugary solution on the stigma forms a medium in which the pollen grain will germinate.
Germination of the pollen grain involves the growth of a pollen tube, which releases enzymes at its tip in order to digest the cells of the style beneath. In this way, the cells of the style are removed to allow the pollen tube to grow down the style towards the ovary.
On arrival at the ovary, the end of the pollen tube enters an ovule through a small hole called the micropyle. Inside the ovule is the embryo sac which contains the female gamete, within which is the female nucleus.
The end of the pollen tube then bursts to release the male gamete, which has travelled down the pollen tube from the pollen grain. Fertilisation occurs as the nuclei of the male and female gametes fuse.
7. Term Paper on the Development of the Fruit:
Once fertilisation has occurred, the ovule is then called a seed. The ovary wall then becomes the pericarp, and the (protective) pericarp with the seed(s) inside is called the fruit.
Seed Structure:
Sugars and amino acids travel through the phloem of the parent plant, and enter the seed. Sugars are converted to starch and, in some cases, fat (e.g. the sunflower). Amino acids are converted to protein. Starch and protein are then stored in the seeds of dicotyledonous plants in two large storage organs called cotyledons. Between the two cotyledons lies the plumule (or young shoot) and the radicle (young root) of the embryo plant.
The embryo within the seed of a dicotyledonous plant is made up of cotyledons, plumule and radicle. The embryo is protected within a seed coat or testa.
Seed Dispersal:
Once it has developed within the fruit, the seed containing the embryo plant must break free from the parent and be dispersed. In this way, the plant species is able to colonise new areas. It also prevents overcrowding and avoids competition with its fellow offspring for light and for nutrients.
It may be some time before the embryo is in a suitable environment for growth. The food stored in the cotyledons will keep it alive. However, many seeds never find a suitable environment and there is great wastage. There are two main agents of dispersal responsible for carrying away the seed (often still part of a fruit and still inside its pericarp)- wind and animals.
Wind-dispersed seeds (or fruits) are usually:
(i) Light in weight, and
(ii) Have their testa (if it is a seed) or pericarp (if it is a fruit) extended to provide a large surface area. This allows the seed or fruit to catch in the wind and be pulled clear of the parent. It also slows the seed’s fall to the ground, allowing the wind to carry it some considerable distance away.
Animal-dispersed seeds may rely on coloured, sweet and juicy pericarps around them to entice an animal (often a bird) to eat them. In this case, the seeds will also have enzyme-resistant testas, so that they can pass through the animal’s intestines intact. They will then be dropped in the animal’s faeces at a distance from the parent plant.
Sometimes animal-dispersed seeds or fruits are dry, with hooks on their testas or on the surrounding pericarps. The hooks catch on a small mammal’s fur and the seeds or fruits are carried some distance before being removed.
8. Term Paper on the Germination of Seeds:
When suitable environmental conditions are available, the seed will germinate.
The conditions necessary for seed germination are:
(i) Water (to activate the enzymes).
(ii) Oxygen (to allow for the release of a great deal of energy from respiration to fuel the greatly increased growth rate).
(iii) A suitable temperature (enzymes operate efficiently only if the temperature is suitable for them).
Note:
Light is not necessary for seed germination, except in a very few cases.
If conditions are suitable, the enzymes work to digest the food stored in the cotyledons. The food is then carried to the growing regions of the embryo.
Experiment 2:
The need for the conditions described below can be demonstrated experimentally, as follows:
Apparatus:
i. Four test-tubes
ii. Cotton wool
iii. Rubber bung
iv. Ignition tube
v. Alkaline pyrogallol
vi. Cotton
vii. Dry seeds (e.g. green beans)
Method:
Set up the experiment as shown in the diagram below, and leave the test-tubes for two to four days.
A. The Control. Seeds left in air at room temperature (a suitable temperature for germination).
B. Seeds left in refrigerator (4°C) – not a suitable temperature for germination.
C. Seeds left in air at room temperature.
D. Seeds left at room temperature.
Results:
Only the seeds in tube A, which has access to all the three conditions (room temperature, water and oxygen), will germinate.
Conclusion:
A suitable temperature, water and oxygen are all necessary for seed germination.
The use of enzymes in the germination of seeds:
Food is stored in seeds in the form of large, insoluble, organic molecules, either in cotyledons, or (in monocotyledonous seeds) in a special storage tissue called endosperm.
These large molecules are usually:
(i) Carbohydrate (usually in the form of starch)
(ii) Protein, and sometimes
(iii) Fat.
When a seed germinates, these food stores must be changed into smaller molecules. These molecules must be able to dissolve in the water which has been absorbed by the seed. They are then transported, in solution, to the growing regions of the seedling to make new cells.
Enzymes, present in the seeds and activated by the absorbed water, bring about these chemical conversions.
The glucose is used in respiration to provide the energy for the process of growth.
The amino acids are used to build up proteins in the cytoplasm of the new cells.
The fatty acids and glycerol recombine to form fats which are used to make important components of cell membranes. Fats also provide a considerable amount of energy.
The enzymes shown in the table above, like many other enzymes, work by digesting larger molecules. In this process, molecules of water are used to split (or hydrolyse) large substrate molecules into smaller product molecules. The enzymes are said to bring about hydrolysis of the larger molecules.