A. Genesis as well as C. Traits that can both be passed on
Answer:
Early in gestation, a fetus has a cartilaginous skeleton that becomes bone in ... At birth, a newborn baby has over 300 bones, while on average an adult human has 206 bones ... It is composed of fibers and granular cells in a matrix. ... The hypertrophic chondrocytes (before apoptosis) secrete vascular endothelial cell growth ...
Explanation
n:When does the fetal cartilage turn to bone?
Key milestones in fetal bone development
Weeks pregnant Milestone
7 weeks Bone outlines for entire skeleton established; cartilage is forming
8 weeks Somites disappear; joints start forming
10 weeks Bone tissue forms and starts hardening (ossification)
16 weeks Your baby can move his limbs
Answer:
there are tree hypothesis
Explanation:
There are several mechanisms by which multicellularity could have evolved:
1. A group of cells were added in a slug-shaped mass called grex, which was moved as a multicellular unit, as the Myxomycota do.
2. The primitive cell suffered an incomplete division of the cell nucleus generating a cell with multiple nuclei or syncytium. Next, membranes formed around each nucleus and the space was occupied by organelles. This resulted in a group of cells connected in an organism, an observable mechanism in Drosophila.
3. Daughter cells did not separate after cell division, resulting in a conglomeration of identical cells in an organism, which later developed specialized functions. This is observed in embryos of plants, animals and colonial cyanoflagellates.
Should read more about the topic here, google it:
<em>Multicellular development in a choanoflagellate; Stephen R. Fairclough, Mark J. Dayel and Nicole King
</em>
<em>In a Single-Cell Predator, Clues to the Animal Kingdom’s Birth</em>
Answer:
Yes, the nodes of Ranvier spaced equally along the axon to allow the action potential at first node to cause depolarization of second node.
Explanation:
Yes, nodes of Ranvier are equally spaced along the length of the axon. When an action potential reaches the first node, it generates the ionic movement in the cytosol and extracellular fluid so as to depolarize the membrane up to the threshold at the second node. This opens the voltage-gated Na+ channels at the second node to allow the ions to flow followed by generation of an action potential at the second node.
Now, as the action potential is generated at the second node, the stimulated ionic movement opens the voltage-gated Na+ ion channels at the third node and the process is repeated. Hence, equally spaced nodes of Ranvier ensure that the action potential at one node can stimulate the depolarization at the next node.
Answer:
All living objects are composed of cells, including you. Cells are the basic element of existence. Such cells are known as prokaryotes and eukaryotes. Procaryotes are cells not possessing a nucleus, or organelles comprising the genetic material of a cell, or other membrane-bound organelles.
Explanation: