Excitation-contraction coupling refers to the series of events that begins with the excitation of the sarcolemma in response to stimulation by a neurotransmitter, and results in the release of calcium ions from the sarcoplasmic reticulum.
Hence, option D is the 1st process that starts the excitation-contraction coupling.
Answer: dinosaurs and birds
Plentiful collection of f<span>ossils of early birds and their most immediate predecessors has settled the century-old controversy about the origin of birds. Birds are now safely declared to evolve from a group of dinosaurs known as maniraptoran theropods. Birds have similar shape of the bones as a variety of maniraptorans have. A host of fossils have shown also that the maniraptorans lay looked alike eggs as that of birds and they resemble the birds in the way they laid their eggs also. Those reasons prove that they are most closely related.</span><span>
</span>
The answer would be - It untwists the double helix and separates the two DNA strands. A helicase is an enzyme used to separate strands of a DNA double helix by breaking hydrogen bonds between annealed nucleotide bases.
Mitochondria is the 'factory' or the 'powerhouse' of the cell! I've just been learning about them too!
The main reason that most farmers use stem cuttings rather than just planting a seed is that a tree's genetic variation will occur. The seeds of many fruit trees tend to vary differently from the parent, because seeds themselves are produced by sexual reproduction (i.e they receive genes from a male and female to form). As they are a cross from two sets of genes, many fruit trees are not “true to seed”. Their seeds will produce a generally different variety of tree from the parent. When using stem cuttings, it's almost like a cloning process.
