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Why is variation beneficial to the species but not necessarily for the individual?
Variations are beneficial to the species than individual because sometimes for a species, the environmental conditions change drastically and their survival becomes difficult. For example, if the temperature of water increases suddenly, then most of the bacteria living in that water would die. Only few variants that are resistant to heat would be able to survive. However, if these variants were not there, then the entire population of bacteria would have been destroyed. Thus, variants help in the survival of the species. However, all variations are not necessarily beneficial for the individual organisms.
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How does binary fission differ from multiple fission?
In binary fission, a single cell divides into two equal cells. Amoeba and Bacteria divide by binary fission.Binary fission in Amoeba In multiple fission, a single cell divides into many daughter cells simultaneously. Amoeba and Plasmodium divides by multiple fission.
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How will an organism be benefited if it reproduces through spores?
Spores are dormant and hard structures produced by some organisms in order to tide over unfavorable conditions. It is also easy for spores to spread around and foster pollination.
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Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?
Simple organisms such as Hydra and Planaria are capable of producing new individuals through the process of regeneration. The process of regeneration involves the formation of new organisms from its body parts. Simple organisms can utilize this method of reproduction as their entire body is made of fewer and similar kind of cells in which any part of their body can be formed by growth and development. However, complex organisms have organ-system level of organization. All the organ systems of the body work together as an interconnected unit. They can regenerate their lost body parts such as skin, muscles, blood, etc. However, they cannot give rise to new individuals through regeneration as a specific cell or tissue cannot form a complete organ. Therefore, it would not be possible to completely regenerate an entire new organism. Organisms like lizards and starfish can regenerate broken part of the body through the process of regeneration.
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Why is DNA copying an essential part of the process of reproduction?
DNA (Deoxyribonucleic acid) copying is an essential part of reproduction as it passes genetic information from parents to offspring. It determines the body design of an individual. The reproducing cells produce a copy of their DNA through chemical reactions and result in two copies of DNA. The copying of DNA always takes place along with the creation of additional cellular structure. This process is then followed by division of a cell to form two cells.
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What is the role of the seminal vesicles and the prostate gland?
The secretions from seminal vesicles and prostate glands lubricate the sperms and provide a fluid medium for easy transport of sperms. Their secretion also provides nutrition to the flowing sperm in the form of fructose, calcium, and some enzymes to enable the sperm to survive for a few days until they can fertilize the egg.
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What are the changes seen in girls at the time of puberty?
▪ Increase in breast size and darkening of the skin of the nipples present at the tips of the breasts. ▪ Appearance of hair in the genital area. ▪ Appearance of hair in other areas of skin like underarms, face, hands, and legs. ▪ Increase in the size of uterus and ovary. ▪ Beginning of menstrual cycle. ▪ More secretion of oil from the skin, which results in the appearance of pimples. ▪ Widening of the hips
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The anther contains (a) sepals. (b) ovules. (c) carpel. (d) pollen grains.
(d) The anther contains pollen grains.
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Why does menstruation occur?
All females, after reaching their puberty produce a mature egg cell every month during a process called the menstrual cycle. ● During this period, an ovary releases a mature egg. ● If the egg is not fertilized, the uterine lining is shed and a new cycle begins. ● Overall a menstrual cycle lasts for 28 days.
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What are the different methods of contraception?
Contraception is the method employed to prevent pregnancy. The contraceptive methods can be broadly divided into the following types: • Natural method → It involves avoiding the chances of meeting of sperm and ovum. In this method, the sexual act is avoided from day 10th to 17th of the menstrual cycle because during this period, ovulation is expected and therefore, the chances of fertilization are very high. • Barrier method → In this method, the fertilization of ovum and sperm is prevented with the help of barriers. Barriers are available for both males and females. Condoms are barriers made of thin rubber that are used to cover penis in males and vagina in females. • Oral contraceptives →In this method, tablets or drugs are taken orally. These contain small doses of hormones that prevent the release of eggs and thus fertilization cannot occur • Implants and surgical methods →Contraceptive devices such as the loop or Copper-T are placed in the uterus to prevent pregnancy. Some surgical methods can also be used to block the gamete transfer. It includes the blocking of vas deferens to prevent the transfer of sperms known as vasectomy. Similarly, fallopian tubes of the female can be blocked so that the egg will not reach the uterus known as Tubectomy.
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How are the modes for reproduction different in unicellular and multicellular organisms?
In unicellular organisms, reproduction occurs by the division of the entire cell. The modes of reproduction in unicellular organisms can be fission, budding, etc. whereas in multicellular organisms, specialized reproductive organs are present. Therefore, they can reproduce by complex reproductive methods such as vegetative propagation, spore formation, etc. In more complex multicellular organisms such as human beings and plants, the mode of reproduction is sexual reproduction.
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