In the block to polyspermy, entry of the sperm's contents causes calcium ion levels in the oocyte's cytoplasm to rise, triggering the cortical reaction.
In biology, polyspermy describes the fertilization of an egg by more than one sperm. Diploid organisms normally contain two copies of each chromosome, one from each parent.
The cell resulting from polyspermy, on the other hand, contains three or more copies of each chromosome—one from the egg and one each from multiple sperm. Usually, the result is an unviable zygote. This may occur because sperm are too efficient at reaching and fertilizing eggs due to the selective pressures of sperm competition.
The cortical reaction is a calcium-dependent exocytotic process in which the content of secretory granules is released into the perivitellin space immediately after fertilization, which serves to prevent polyspermic fertilization.
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When an antibiotic is given for a non- resistant bacteria it inactivates or kills the bacteria however some microbes do not die and survive and multiply and pass the infection to other people making the bacteria antibiotic resistant.
Explanation:
The antibiotic resistant bacteria are those that are able to resist the effect of antibiotic and renders them ineffective that was once able to kill or inactivate bacteria.
While antibiotic non-resistant bacteria are those that are not able to resist the effect of antibody.
The reason some non-resistant bacteria becomes resistant is that a mutation in the nonresistant bacteria may occur or continuous exposure of the antibiotic would make it resistant to it.
Every time an antibiotic is taken for some bacterial infection it kills the bacteria but some that survive become resistant and grow in numbers and get transfer to other people causing them to be antibiotic resistance. The infection transfer to other people would not be treated by once used antibiotic as the microbe has become resistant.
During the cell replication due to some mutation caused they get resistant to antibiotic by a process called selective pressure.
The option D is correct :The gametophytes of seed plants are never exposed to the external environment. Unlike spores, The gametophyte in seed plants is often tiny and is kept in the tissues of the sporophyte. The integument refers to the layers of sporophyte tissue that encircle the megasporangium.
seeds carry food reserves that can be used to support a young plant. While spores are distributed by the wind, seeds can be spread by animals. While spores only live a few days, seeds can slumber for weeks or even years. Seeds contain a supply of food in storage, in contrast to spores. If the conditions are right, seeds that have been transported far from the parent sporophyte may germinate and rely on stored nourishment to develop into seedlings. Spores and seeds vary primarily in that seeds have stored nourishment in their endosperm, which allows them to germinate in adverse conditions whereas spores do not, making them more dependent on good conditions for germination.
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Full Question :
Which of the qualities is a major difference between all spore-dispersing and seed-dispersing plants? select all that apply.
A In seed plants, dispersed spores contain a multicellular gametophyte.
B Seed plants disperse gametes and seeds instead of spores.
C The sporophyte of seed plants is photosynthetically independent.
D The gametophytes of seed plants are never exposed to the external environment.
Answer:
Rain that falls in liquid form but freezes on impact with the ground or solid objects. In other words, it's rain that freezes when it hits the ground.
Explanation:
(self-explanatory)
I hope this helped, have a nice day.
