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Posted by Riya Kavathe 5 years ago
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Yogita Ingle 5 years ago
The dielectric constant is the ratio of the permittivity of a substance to the permittivity of free space. It is an expression of the extent to which a material concentrates electric flux, and is the electrical equivalent of relative magnetic permeability.
Posted by Divy Thakkar 5 years ago
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Yogita Ingle 5 years ago
This process of formation of embryo sac from a single megaspore is termed as Monosporic development.
Following changes lead to Monosporic development:
- Nucleus undergo mitotic division
- 2-nucleate embryo-sac is formed
- Nuclei undergo mitotic division again
- 4-nucleate embryo-sac is formed
- Nuclei undergo yet another mitotic division
- 8-nucleate embryo-sac is formed
- Cell wall formation takes place
- Embryo sac is formed
Posted by Divy Thakkar 5 years ago
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Meghna Thapar 5 years ago
Malaria is caused by the Plasmodium parasite. The parasite can be spread to humans through the bites of infected mosquitoes. There are many different types of plasmodium parasite, but only 5 types cause malaria in humans. The phylum Apicomplexa contains several important pathogens such as Plasmodium falciparum, the causative agent of the most dangerous form of human malaria. Human cerebral malaria (HCM) is the most severe complication of P. falciparum infection and has attracted the attention of both clinicians and scientists since the discovery of the malaria parasite. HCM can occur in less than two weeks after a mosquito bite and may develop after 2 to 7 d of fever.
Posted by Yadav Ritik 5 years ago
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Yangzee Sherpa 5 years ago
Yogita Ingle 5 years ago
| Zygote | Embryo |
| The term zygote is from Greek word “zygotos” which means to “join” | The term embryo is from Latin work “embryum” which means “that which grows” |
| Zygote is unicellular | Embryo is multicellular |
| The process of formation of zygote is known as fertilization | The process of formation of embryo is known as embryogenesis |
| In medical terms, zygote is known as zygocyte | In medical terms, embryo is known as diploid eukaryote |
Posted by Ølí ?? 5 years ago
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Yogita Ingle 5 years ago
The harmful alleles get eliminated from population over a period of time, yet sickle cell anaemia is persisting in human population because SCA is a harmful condition which is also a potential saviour from malaria.
Those with the benign sickle trait possess a resistance to malarial infection. The pathogen that causes the disease spends part of its cycle in the red blood cells and triggers an abnormal drop in oxygen levels in the cell. In carriers, this drop is sufficient to trigger the full sickle-cell reaction, which leads to infected cells being rapidly removed from circulation and strongly limiting the infection’s progress. These individuals have a great resistance to infection and have a greater chance of surviving outbreaks. This resistance to infection is the main reason the SCA allele and SCA disease still exist. It is found in greatest frequency in populations where malaria was and is still often a serious problem.
Posted by Divy Thakkar 5 years ago
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Yogita Ingle 5 years ago
Testes-
- Smooth organ situated outside the abdominal cavity within a pouch called
- The ******* helps in maintaining the low temperature of the testis which is 2-2.5O C which is below than the normal internal body temperature.
- Each testisis 4 to 5 cm in length and 2 to 3 cm in width in adults.
- Each testis contains about250 compartments called testicular lobules.
- Each testicular lobules contain one to three highly coiled seminiferous tubules, in which sperms are produced.
- The wall of each seminiferous tubuleis lined by two types of cells called male germ cells (spermatogonia) and Sertoli cells.
- The male germ cells undergo meiosis leading to sperm formation and Sertoli cells provide nutrition to the germ cells.
- The regions outside the seminiferous tubules called interstitial spaces contain small blood vessels and interstitial cells or Leydig cells.
- Leydig cells synthesize and secrete testicular hormones called androgens.
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Yogita Ingle 5 years ago
Ferns have both roots and vascular tissue and therefore, can grow larger than moss species, but like the mosses, ferns require water for reproduction. The sperm cells have flagella and must swim through a water film to fertilize the egg.
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Yogita Ingle 5 years ago
The reproductive cycle starting from the one menstruation till the next one in the female primates is called menstrual cycle. The first menstruation which begins at puberty and is called menarche . The cycle is repeated at an interval of 28-29 days. Menstrual cycle involve three phases- menstrual phase, follicular phase and luteal phase.
The menstrual cycle is divided into four phases, namely:
- Menstrual phase: Day 1, uterus lining which is prepared for implantation starts to shed which lasts 3 to 5 days.
- Follicular phase: A matured egg follicle releases an egg from one of the ovaries. Also, uterus starts preparation for another pregnancy.
- Ovulatory phase: Mid-cycle phase, this is the phase in which ovulation takes place i.e., day 13-17. End of follicular phase along with ovulation period defines the fertilization period.
- Luteal phase: Post ovulation phase where the fate of corpus luteum is decided. If fertilization occurs, pregnancy starts. If fertilization doesn’t occur, it marks the onset of another cycle.
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Any techniques that can prevent the unwanted pregnancies are termed as contraceptive methods. Surgical removal of gonads causes sterility of individual and is irreversible process while contraceptive methods can be reversed when pregnancy is desired. Thus, it is not considered as a contraceptive option.
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The Watson and Crick were the two scientists who proposed the double helical structure of DNA. They proposed that the double helical structure is held together by the hydrogen bonds which are present in between the nitrogenous bases present on the opposite strands of the DNA. The double stranded DNA is supported by the phosphate back bone.
The salient features of double helix structure of DNA are as follows:
- There are two polynucleotide chains in a double stranded DNA.
- The backbone is constituted by sugar phosphate.
- The two strands possess anti-parallel polarity, means one chain has polarity 5’-3’ and the other has 3’-5’.
- The two strands of DNA are joined together by hydrogen bonds between purines and pyrimidines.
- Adenine always pairs with Thymine by two hydrogen bonds and Guanine always pairs with Cytosine by three hydrogen bonds.
- The two chains are coiled around each other where the pitch of the helix is 3.4 nm and distance between two base pairs is 3.4 A° (as in case of B-DNA)
- The backbone of DNA double helix is formed by sugars and phosphates where bases are projecting inwards.
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Yogita Ingle 5 years ago
Animal tissues are grouped into four types:
The classification of plant tissues are mainly based on the two important criteria:
Plant Tissues are broadly categorized into three tissue systems. This classification is on the basis of parts of the plants they are present.
Plant tissue is divided into two types. This classification is on the basis of the types of cells, they comprise.
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