Sperm cells inside the pollen grain travel down the pollen tube and into the ovary which contains the ovules. Fertilization occurs when one of the sperm cells fuses with the egg inside of an ovule
Answer:
The correct option is D.
Explanation:
In the year 1952, two scientists, Hershey and Chase conducted a series of experiments that helped to establish the fact that DNA is a genetic material. The DNA is located inside the nucleus of living cells in form of chromosomes and its the determinant of traits that are found in living organisms. During protein synthesis, the information in the DNA molecule is encoded into an RNA molecule and this is used in the production of protein, thus, DNA actually directs all the happen in the living cells.
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Two factors contributed to the success of the pteridophytes: the extreme miniaturization of the gametophytic generation and an important development of the sporophytic generation (development of the tree forms).
Pteridophytes are a group of plants that peaked in the Carboniferous (-300 million years). It is the first great terrestrial plant civilization. These plants would have appeared in the Devonian -400 million years ago, perhaps from certain primitive terrestrial plants which, unlike bryophytes, would have favored the diploid generation on the haploid generation.
Particularly well adapted to terrestrial life, they have created, thanks to the development of tree forms, immense forests whose fossilization is at the origin of coal deposits.
Pteridophytes are at the origin of an evolutionary lineage based on the extreme miniaturization of gametophytic generation and an important development of sporophytic generation, leading to all tracheophytes including current flowering plants. Pteridophytes are well adapted to terrestrial life, however fertilization still requires the presence of water since male gametes are swimmers.
Answer:
The correct answer is- Normal vaginal pH is acidic (4 to 5), which protects from infection.
Explanation:
The vaginal part in woman have high tendency to get infection because of moist internal condition and its location but vagina also have a protective mechanism which protect it from the infection.
A woman's vagina contains many species of Lactobacillus genus which secrete lactic acid and hydrogen peroxide that maintains the low pH level in the vagina. So due to this reason, the normal pH of the vagina remains between 4-5 which does not allow pathogenic bacteria to flourish and cause infection.
