Heredity and Evolution
Heredity is the transmission of the characters of the parents to their offspring from one generation to the next. The characteristics include physical, physiological and psychological behavior of the organisms. Gregore Mendel carry out his experiment with the pea plant, as they show many contrasting traits, that were easy to track through the generations. In his first experiment, he considered only one trait, such as, height, colour, shape of the seed, etc. This is known as monohybrid. According to him, the genotype is made of certain structure, which controls the inheritance of all traits. The different expression of the gene is called alleles, in which each trait is represented by a letters. According to law of inheritance, all the traits have separate entities by themselves, which are controlled by the genes. The genetic material is a nucleoprotein called chromatin. It is made up of DNA and protein.
Variation
It is defined as the difference among individuals of the species. There are two types of variations, such as, somatic and non-inheritable. Variation helps the organisms to adapt to the changing conditions. The different theories of evolutions are:
Organic Evolution
Evolution is regarded as the gradual development of more complex species from the pre-existing simpler species. This takes place over the millions of years, which is clear from the evidences of fossils. According to the theory of organic evolutions, continuous use of an organ results in well developed organs and less used or unused organ over a long period of time will result in disintegration of the organ. For example, the giraffes were forced to extend their neck, and stretch their legs to reach higher vegetations. There are many evidences of evolutions; study of fossils of plants and animals helps us to understand the theory of evolutions. The geological distribution of organisms on the earth is also an important part of study. The embryological study of the organisms also helps to study the evolution theory.
Heredity is the transmission of character from one generation to the next. The genotype is made of certain structure, which controls the inheritance of all traits. The different expression of the gene is called:
(a) Genotype
(b) Alleles
(c) Phenotypes
(d) Inheritance
(e) None of these
Answer: (b)
Variation is defined as the difference in the organisms, which arises from one generation to the next. The variation which arises in the organism is either due to the genetic mapping or due to the external conditions. The traits, which the organisms develop due to the external conditions are called:
(a) Inherited traits
(b) Desired traits
(c) Acquired traits
(d) Mixed traits more... 
Sex Determination
The sex of an individual is determined by the combination of sex chromosomes X and Y. If the chromosomal combination is XX, it results in female child. On the other hand, if it is XY, it results in male child. These chromosomes help in the exchange of genetic material.
Puberty and Adolescence
At the age of adolescence, some major changes occur in boys and girls, in physic as well as, in behavior. Some of the changes seen in boys are, cracking of voice, cranky, growth of hair in armpit and genital areas, growth of body muscles and more importantly production of sperms and arousal of sexual feelings. On the other hand, in girls growing of breast, growth of hair in genital areas, onset of menstrual cycle and growth of body muscles are seen. They also show behavioral changes. While puberty covers the physical changes, adolescence deals with the mental changes and has been described as a 'psychosocial process characterized by mental and social growth, and often extending from puberty to the early 20 s and sometimes beyond.' These transformations in the girls are seen between the ages of 8 and 12 years, while in boys it is seen couple of years later. But still, there is no strict time frame for the onset of puberty.
Behavior Changes
Most adolescents are uncomfortable and unconscious about their growing breasts and suddenly awkward limbs. They feel that the people are looking at them differently. Every pimple seems magnified a hundred times, and girls hunch overtryingto.concealtheirgrowing waist lines. To make matters worse, most parents are at a loss when faced with their children's budding sexuality. They cannot accept the fact that their 'babies' are talking and thinking about sex. As a result, adolescents are ecstatic one minute, irritable and moody the next. On one hand, they display a new-found maturity in keeping with their 'adult' status. On the other, they throw tantrums, that could rival a three-year-old.
Puberty and adolescence bring with them a lot of emotional baggage. People in their adolescent years feel as if they are in a twilight zone, hanging somewhere in between childhood and adulthood. As if they're sitting on an emotional seesaw, feeling 'up' one minute, down the next; feeling old on some days, and like a child on others. It is a difficult time, but it makes one feel better to think that everyone has gone through it.
Endocrine System
The endocrine system is made up of a series of ductless glands that produce hormones. A number of glands that signal each other in sequence are usually referred as axis. Some of the endocrine glands are pituitary, thyroid and adrenal glands. The features of endocrine glands in general are, their ductless nature, more... 
The Female Reproductive System in Human
The female reproductive system consists of gonads and ovaries, which are located within the lower abdominal cavity. The ovary contains many follicles consist of developing egg cells. It is surrounded by an outer layer of follicle cells. At birth each female carries a lifetime supply of developing oocytes, each of which is in Prophase I. A developing egg is released each month at the onset of puberty until menopause. After puberty, the menstrual cycle begins. These cyclic phases are interrupted only by pregnancy and continue until menopause, when the reproductive capability ends. The egg cells from ovary then pass onto the fallopian tube, which in turn is connected to the uterus. The fertilized egg cells are then implanted on the inner lining of the uterus. At the lower end of the uterus, lies the cervix, which connects the uterus to the vagina. The vagina receives the penis during the intercourse and serves as the birth route.
The Female Reproductive System
External Genitals
The external genitals of the female are collectively known as the vulva. The labia minora is a thin membrane of folded skinjustoutside the vaginal opening. The labia majora cover and protect the genital area. The clitoris is important in arousal and is a short shaft with a sensitive tip covered by a fold of skin.
Hormones in Female
There are two types of female sex hormones, which help in controlling the process of reproductions. These hormones are estrogen and progesterone. Menstrual cycles varies between 15 to 31 days. The first day of the blood flow (day 0) known as menstruation. During menstruation the uterine lining is broken down and shed as menstrual flow. FSH and LH are secreted on day 0. Both FSH and LH stimulate the maturation of a single follicle in one of the ovaries and the secretion of estrogen. Rising levels of estrogen in the blood trigger secretion of LH, which stimulates follicle maturation and ovulation (day 14, or midcycle). LH stimulates the remaining follicle cells to form the corpus luteum, which produces both estrogen and progesterone.
The external genital of female, which consist of labia minora, labia majora and clitoris collectively called:
(a) Ovary
(b) Fallopian tube
(c) Vagina
(d) Vulva
(e) None of these
Answer: (d)
Explanation
The external genital organ of female is called vulva.
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The Male Reproductive System in Human
The male reproductive system consists of scrotum, which is suspended outside the abdominal cavity. This pouch keeps the testis temperature below the body temperature, which is necessary for the development of sperm. The tubules inside testis are about 250 meter long. The testis is connected to the vas deferens, which carries sperm to the prostate glands where it mixes with the seminal vesicles to form a viscous liquid/ so that it can easily flow out. This in turn is connected with the urethra then to the penis.
The Male Reproductive System
Spermatogenesis
Sperm production begins at the age of puberty. It continues throughout the life, with several hundred million sperm being produced each day. Once sperm is formed/ it moves into the epididymis, where they mature and are stored.
Male Sex Hormones
The pituitary gland produces follicle stimulating hormone (FSH) and luteinizing hormone (LH). It stimulates the cell, which secrete testosterone hormone that helps in productions of sperms.
The male reproductive organ is testis. It lies in the pouch like structure called scrotum. The tube like structure which carries sperm from testis to outside is called:
(a) Ureter
(b) Vas deference
(c) Urethra
(d) Prostate gland
(e) None of these
Answer: (b)
Explanation
All are the parts of male reproductive system, but vas deference helps in carrying of sperm to outside.
The hormones are the substance which regulates the functioning of our body. It also plays important role in our reproductive system. The hormones, which stimulates the formation of sperms in male is called:
(a) Progesterone
(b) Estrogen
(c) Testosterone
(d) FSH
(e) None of these
Answer: (c)
Explanation
All of the options is hormones but option C is male reproductive hormones and the rest are female sex hormones. 
Reproductive Parts of a Flower
The plants, that reproduce sexually have the reproductive structures called the flowers. The flower is a condensed shoot, with the nodes present very close to each other. The different parts of the plant are attached to the nodes. All the structures present at one node are collectively called the whorl. The first or the outermost two whorls are called the non-reproductive whorls. They are, the calyx and corolla. The inner two whorls, which are the reproductive whorls are androecium and gynoecium.
Calyx
It is the outermost and often green in colour. The individual units of calyx is called the sepals. It protects the inner whorls at bud stage.
Corolla
It is the next inner part of the whorl, and is coloured differently. The individual units of the corolla are called petals. They act as an attraction for bees, birds, etc, which are the agents of pollination.
The reproductive part of the flowers
Androecium
It is the male reproductive part of the flowers. The male organ is called stamens. Each stamen has a thread like filament at its free end, which is attached to the four lobed anther. The anther has four pollen sacs in each lobe. These pollen sacs contain microscopic cell called pollen grains. Each microspore divides once mitotically to produce two male gametes or the sperm cell. Each mother cell produces 8 sperm cells.
Gynoecium
It is the female reproductive part of the flower. Each individual unit is called the carpel or pistil. A flower may have one or many carpels. Each carpels is made up of ovary, style and stigma. Ovules are the chamber where many ovules are attached to the axis. Each ovule consist of haploid egg and other associated cells. The stigma receives pollen grains and the style is the hollow tubules, that provides passage from the male gametes to the female ovary.
Pollination
It is the process of the transfer of pollen grains from stamen to stigma. It is of two types:
(i) Self pollination
(ii) Cross pollination
The self pollination, also known as autogamy, is the pollination in which pollens are transferred to the stigma of the same flower. Whereas, in cross pollination the pollens are transferred to the stigma of the different flowers. It is also known as allogamy. The various agents of cross pollinations are wind, water, bees, bats and many other animals.
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Sexual Reproduction
The method of reproduction, in which both male and female are involved, is called sexual reproduction. The male and female mate with each other, and their egg fertilized to produce the new offspring. Each of the two parents contributes half of the offspring genetic makeup by creating the haploid gametes. In these anisogamous species, the male produces sperm and female produces ova. In isogamous species, the gametes are similar, but they have separable properties. For example, the green algae, chlamydomonas, reinhardtii. There are many animals and plants, which reproduce sexually. The new offspring inherit the trait of both the parents. In plants, Bryophytes reproduces sexually; but they are normally haploid which produce gametes.
Allogamy
In this method, the ovum of one individual fertilized with the spermatoza of another individual.
Autogamy
It is also known as self fertilization, which occurs in hermaphrodite organisms. In this organisms, both the male and female sex are present in the same individual.
Mitosis and Meiosis
There are the two methods of cell division, mitosis and meiosis. The mitosis occurs in somatic cells, where as meiosis occurs in reproductive cell orgametes. In mitosis, the number of cell after the cell division is doubled, but the number of chromosomes remains the same as in the parent cell. In meiosis, the number of cell becomes four times, but the number of chromosomes is reduced to half. This process occurs in two phase, meiosis I and meiosis II.
There are different methods of cell division in the multicellular organisms, which helps in its growth and development. The method of cell division, which takes place in the reproductive cell for reproductions is?
(a) Mitosis
(b) Meiosis
(c) Prophase
(d) Anaphase
(e) None of these
Answer: (b)
Explanation
The cell division in the reproductive cell is by the method of meiosis and cell division in rest of the body parts is through mitosis.
Some organisms have both the sex, while, most of the other multicellular organisms have male and female on different organisms. The organisms, in which have both male and female sex are present is called hermaphrodite. Which one of the following organisms given below is hermaphrodite?
(a) Leach
(b) Earthworm
(c) Tapeworm
(d) Silkworm
(e) None of these
Answer: (b)
Asexual vs. Sexual Reproduction
The organisms, which reproduces sexually tend to grow exponentially in numbers, but rely on mutation for variations in DNA. They have similar vulnerabilities. The organisms that reproduce sexually, yield less more... 
Introduction
Reproduction is the biological process, which helps us to produce new offspring or individuals of similar types. It is a fundamental feature of all living organ isms.
There are two methods of reproductions: sexual and asexual.
In asexual reproduction, single individual can reproduce without involvement with another individual of that species. For example, the division of a bacterial cell into two daughter cells or reproductions in plant. In sexual reproduction, two organisms are involved in the process of reproduction. The two organisms are male and female of a particular species.
Asexual Reproduction in Plants
In asexual reproduction, the organisms creates genetically similar or identical copy of itself. There is no contribution of genetic material from other individuals. Many single cellular organisms, like bacteria can divide asexually via binary fissions. Some other organisms, like amoeba and hydra also produce by binary
fissions. The different methods of asexual reproductions are: fission, regeneration, budding, spore formations, vegetative propagations and fragmentations. Virus reproduces in the body of the host to produce more organisms of its kind. Hydra and yeasts are produced by budding. These organisms often do not possess different sexes. They are capable of breaking themselves into two or more cell and develop into individuals. Most of the plants are capable of reproducing by the process of vegetative propagations. In this process, the new plants are produced form the parts of the parent plants. For example, Bryophyllum, potato, tuber plants etc.
Bryophyllum Tuber Potato
Stems
In some plants species, stems develop new roots when exposed to suitable conditions, forming new plants. The horizontal above-ground stems, called stolons, of the strawberry produce new daughter plants at alternate nodes. In some plants underground stems produce new plants. For example, rhizomes, bulbs, corns and tubers.
Leaves
Some plants, such as, Bryophyllum reproduce through their leaves.
Roots
Some plants such as dandelion, poplar or aspen, use their root for reproduction.
They send up new stems from their roots, which develop into new plants.
Grafting
This method is widely used for propagating desired variety of shrub or tree. All the varieties of apple is propagated by this method.
There are more... 
Microorganisms
A microorganism or microbe are the living organisms, which are too small to be visible to the naked eyes. The study of microorganisms is called microbiology. The microorganism are bacteria, fungi, etc. However, viruses and prions are not microorganisms, they are classified as nonliving. They are found everywhere on the earth, including water, air and land. They are also called extermophiles. They act as a decomposer, and help in nutrient recycling in ecosystem. Pathogenic or harmful microbes can invade other organisms and cause disease.
Useful Microbes
There are some microorganisms, which are useful to us; where as some of them are harmful. The useful microorganisms feed on the things that were once living. The decayed materials get mixed with the soil and provide essential nutrients for plants to grow. Such organisms are called decomposers. Without decomposers, the soil would not have got the nutrients, and would have run out of it. They are the natural recyclers of living things on earth.
Harmful Microbes
Some microbes can cause illness or disease, such as, chickenpox, mumps and measles. These are infectious diseases. Some microbes can cause food decay. For example, moldy bread or fruit, sour milk and rotten meat etc. If we take these rotten food, it can cause stomach upset and many other health problems.
Haden prepared soup for himself. Due to some urgent work, he could not take the soup and went to his office. When he returned next day from his office, he found that the soup was spoiled and emitting bad smell. Which one of the following microorganism had spoiled the soup?
(a) Bacteria
(b) Virus
(c) Fungus
(d) Plasmodium
(e) None of these
Answer: (a)
Explanation
The microorganism which spoils the liquid food is bacteria.
The microorganisms, which are found everywhere on the earth i.e. on the land, water, and air are called:
(a) Extermophiles
(b) Prions
(c) Pathogens
(d) Moulds
(e) None of these
Answer: (a)
Explanation
Extermophiles are the microorganisms, which are found everywhere on the earth.
Difference between Plant Cell and Animal Cell
| Plant Celt | Animal Cell |
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 Multicellular Organism
The organisms made up of more than one cell are called multicellular organisms. These organisms have specialised cell structures for performing different types of functions. Multicellular organisms are either unisexual or bisexual. The bisexual organisms are called hermaphrodite, in which both the male and female sex are present.
A living example of the attempts to become multicellular organism is represented by the slime moulds, which are transformed from single cells to multicellular organism under adverse condition. Another example is found among the green alga Volvox and its relatives. The ranges of sizes goes from the single cell Chlamydomonas to the 16-cell Gonium, Eudorina and finally to the largest species of viovox, which may consist of 50000 or more cells. Biologists have thought that new genes would be required for the transition to multicellularity. But a comparison between the genomes of the 2000-cell volvox carten and a single celled chlamydomonas indicates that the biological complexity can arise without major changes in genome content..
Multicellular Organism
 All the higher organisms are made up of more than one cell. All the multicellular organisms have specialized organs for the specific functions. But there are some organs in the body of organisms, which are functionless or useless. Name the vestigial organ in the body.
(a) Vermiform Appendix
(b) Hum
(c) Caecum
(d) Taenia
(e) None of these
Answer: (a)
Explanation
The vestigial organ in the human is vermiform Appendix.
Which organism is transformed from single cellular to multicellular in adverse condition?
(a) Gonium
(b) Edorina
(c) Volvox
(d) Slime moulds
(e) None of these
Answer: (d)
Explanation
The organism which gets transformed from singular cellular to multicellular is slim moulds..  Animal Cell
The cell organelles in plant cell and animal cell are almost similar. However, there are few organelles, which are present in plant cell; but not found in animal cell and vice versa. For example, plastids and cell wall is present in plant cell, but not in animal cell. On the other hand, centrosomes and lysosome is present in animal cell, but not in plant cell.
 Lyosome
It is also called cell vesicles. It is surrounded by a membrane that contains digestive enzymes, which digests the dead cell and destroy the foreign materials within the cell. The digestion of cell nutrient takes place within the lyosomes.
Centrosomes
It plays an important role in reproduction of cells and cell division within the organisms.
 Army of a country protects its border from the enemy and from any types of invasion from out side. Similarly, in our body we have the cells that protects our body from harmful materials or digest the dead cell within. Name the cells which perform this function for the cell.
(a) Ribosomes
(b) Lysosomes
(c) Centrosomes
(d) SER
(e) None of these
Answer: (b)
Explanation
The digestive bag of the cell is Lysosomes.
Henery plants some seedlings of same flowering plants in the garden. When the flowers start blooming in those plants, they are of different colours. Henery can not understand the reason for the different colours in flowers. Which cell organelle is responsible for this?
(a) Nucleus
(b) Plastid
(c) Cytoplasm
(d) Cell wall
(e) None of these
Answer: (b)
Explanation
The different colours, which arises in plants is due to the presence of cell organelle plastids.. Current Affairs CategoriesArchive
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