A temperature scale whose zero point is absolute zero, the temperature of 0 entropy at which all molecular motion stops, -273.15° C<span>.</span>
We do quite often have mutt birds. (the correct name for such a mutt is a hybrid. <span>They are way more common than most people think, but unless you are a birdwatcher you probably wouldn’t even spot them. People often see an odd looking birds and simply think it’s a type they haven’t seen before, when in fact it is a hybrid of two well-known species.
Having said that, for birds to hybridized they have to be fairly closely related to start with. Robins and blue jays are no more closely related than humans are to baboons. You wouldn’t expect a human and a baboon to be able to mate and produce babies would you? So no, robins and blue jays can’t interbreed.
However there are many different species of animal that CAN interbreed and produce offspring. But the different species need to be fairly closely related, far more closely than human and baboon… or a blue jay and a robin.
For example we can interbreed horses and donkeys to produce baby mules, and we can breed cattle and buffalo, or camels and llamas. And the same is true of birds. While blue jays can’t be bred with robins in the wild we quite frequently find mutt birds.
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Ducks are particularly noted for forming wild mutts and many if not all north American mallards for example are of mixed species ancestry.</span>
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Striated muscles contain repeating sarcomeres of overlapping arrays of long, thin actin and thicker myosin filaments. Myosin filaments contains the myosin heads, which are enzymes that can bind to actin, split and make use of the energy from ATP. When muscle contraction starts, myosin heads bind to actin, change their configuration on actin, liberating the products of ATP hydrolysis and causing slide of the actin and myosin filaments. The action of the proteins troponin and tropomyosin on the actin filaments regulates vertebrae striated muscle contraction. The release of calcium ions from the sarcoplasmic reticulum is triggered by the nervous stimulation which causes depolarization of muscle membrane. Calcium ions bind to troponin and thus cause or allow the tropomyosin strands on the actin filament to move so that the part of the actin surface where myosin heads need to bind is uncovered. Contraction then occurs and only stops when the sarcoplasmic reticulum pumps calcium out of the muscle interior.
So basically, what triggers the uncovering of the myosin binding site on actin is the calcium ions binding to troponin and changing configuration.
Answer:
Punctuated Equilibrium
Explanation:
The phyletic gradualism model and the punctuated equilibrium are aspects models of macroevolution that are characterised with varying patterns.
However, the punctuated equilibrium model of evolutionary history consists of geologically long periods of inactivity (stasis) with little or no evolution, interrupted or "punctuated" by geologically short periods of rapid evolution.
Answer:
Meiosis and Genetic Variation.
Explanation:
When homologous chromosomes form pairs during prophase I of meiosis I, crossing-over can occur. Crossing-over is the exchange of genetic material between non-sister chromatids of homologous chromosomes. It results in new combinations of genes on each chromosome.
When cells divide during meiosis, homologous chromosomes are randomly distributed during anaphase I, separating and segregating independently of each other. This is called independent assortment. It results in gametes that have unique combinations of chromosomes.
In sexual reproduction, two gametes unite to produce an offspring. But which two of the millions of possible gametes will it be? This is likely to be a matter of chance. It is obviously another source of genetic variation in offspring. This is known as random fertilization.
