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vekshin1
3 years ago
14

Scientists believe that the oldest known fossils discovered to date are that of __________.

Biology
2 answers:
Karo-lina-s [1.5K]3 years ago
7 0
You're answer is A because when you think about it these creatures lived before any of the other creatures on your list

inysia [295]3 years ago
5 0
Scientists believe that the oldest known fossils discovered to date are that of <span>stromatolites.</span>
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Rank the following in order from most general to most specific: 1. gametic isolation 2. reproductive isolating mechanism 3. sper
mihalych1998 [28]
<h2>Reproductive Method </h2>

Explanation:

<em>The rank in order from the most specific which is following .</em>

<em>(1) Reproductive isolating mechanism</em>

<em>(2) Sperm-egg incompatibility in sea urchins</em>

<em>(3) Gametic isolation </em>

<em>(4)Prezygotic isolating mechanism</em>

<em>(1) Reproductive isolating mechanism-</em> The components of regenerative confinement are an assortment of transformative instruments, practices and <em>physiological procedures basic for speciation.</em> They keep individuals from various species from delivering posterity, or guarantee that any posterity are sterile.

(<em>2) Sperm-egg contradiction in ocean urchins-</em> Bindin is a gamete acknowledgment protein known to control species-explicit <em>sperm-egg grip</em> and layer combination in ocean urchins.

<em> (3)Gametic isolation - Prezygotic hindrances </em>keep preparation from occurring. Gametic disengagement is a sort of prezygotic hindrance where the<em> gametes (egg and sperm) </em>come into contact, yet no preparation happens. Gametes might be not able to remember each other in various species  

<em> (4) Prezygotic isolating mechanism- </em>while postzygotic segregation forestalls the arrangement of rich posterity. Prezygotic systems incorporate environment segregation, mating seasons, "mechanical" disconnection, gamete detachment and conduct seclusion. 

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3 years ago
Acetylcholine binds to a GPCR on heart muscle, making the heart beat more slowly. The activated receptor stimulates a G protein,
kogti [31]

Answer:

The correct answer is option (b) "addition of a drug that prevents the α subunit from exchanging GDP for GTP".

Explanation:

The G protein is a name given to a family of proteins that act as a switch in diverse cellular processes, transmitting signals from outside to inside of the cells. When a G protein receptor is activated by a neurotransmitter such as dopamine, the alpha subunit exchanges its GDP for a GTP and disassociates G-protein itself. An addition of a drug that prevents this action would prevent  G protein disassociation, which would enhance the effect of stimulating G protein that acetylcholine does.

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3 years ago
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Nadya [2.5K]

Answer:

about 525 billion sperm cells

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In fact, the average male will produce roughly 525 billion sperm cells over a lifetime and shed at least one billion of them per month. A healthy adult male can release between 40 million and 1.2 billion sperm cells in a single ejaculation.

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2 years ago
Read 2 more answers
. Which two biomes have the least precipitation?
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"Tundra and desert" are the two biomes among the choices given in the question that <span>have the least precipitation. The correct option among all the options that are given in the question is the third option.

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3 years ago
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A reasonable speed for a snail is _____.
lisabon 2012 [21]

A, the others are unrealistic speeds.


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3 years ago
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