Fossils are the sediment layers trapped between plants and animals.They are <span>the remains or impression of a prehistoric organism preserved in petrified form or as a mold or cast in rock.</span>
Answer:
Here are the answers:
a. 4 Cell determination as an issue in the *rest is missing*
b. 4 They assumed that different ways of separating an embryo into two parts would be equivalent as far as the fate of the two parts was concerned.
c. 4 I and III only
Explanation:
The passage demonstrates the importance of two factors in the development of an embryo: cleavage planes of division of embryonic cells and cell differentiation.
Cleavage Planes:
Cleavage basically refers to the division of the zygote into a large number of cells called blastomeres. Cleavage planes are geometrical lines or orientations along which cleavage takes place. Since, all embryonic cells are the precursors of some type of body cells, the cleavage planes determine if the cells are adequate for growth and development.
Cell Differentiation:
Cell differentiation is the transition of an undifferentiated cell into a specialized one. For example, stem cells are undifferentiated cells that develop into progenitor cells that mature into a specific cell lineage. For an embryo to regenerate, the presence of adequate embryonic stem cells is crucial. Embryonic stem cells are present in abundance before the gastrulation phase of embryonic development, after which they rapidly start differentiating.
Complete question:
In the 1890s, Northern elephant seals were hunted almost to extinction. An unknown population of less than one hundred animals managed to survive on the tiny island of Guadalupe off of Mexico. The current population of over 100,000 is thought to be derived from that tiny remnant population. Compared to the Southern elephant seals (which did not experience such a bottleneck), the Northern elephant seals likely have -------- (Lower - Higher) genetic diversity and -------- (Lower - Higher) levels of genetic diseases.
Answer:
In the 1890s, Northern elephant seals were hunted almost to extinction. An unknown population of less than one hundred animals managed to survive on the tiny island of Guadalupe off of Mexico. The current population of over 100,000 is thought to be derived from that tiny remnant population. Compared to the Southern elephant seals (which did not experience such a bottleneck), the Northern elephant seals likely have Lower genetic diversity and Higher levels of genetic diseases.
Explanation:
Genetic drift is the random change that occurs in the allelic frequency of a population through generations. The magnitude of this change is inversely related to the size of the original population. These changes produced by genetic drift accumulate in time. Eventually, some alleles get lost, while some others might set. Genetic drift affects a population and reduces its size dramatically due to a disaster or pressure-bottleneck effect- or because of a population split -founder effect-.
In the exposed example, extensive hunting acted as a pressure that reduced the number of Northern elephant seals to fewer than 100. This population experienced one or many generations of small size since these animals were affected by hunting. As the survivors did not have the whole genetic pool of the original population, the population size might have recovered to a current population size of 1000,000 individuals, but <u>the genetic pool might have not</u>. When the small population increases in size, it will have a genetically different composition from the original one. In these situations, there is a<u> reduced genetic variability</u>, with a possibility of developing a peculiar allelic component. If the survivors in the population carried or developed a mutation, probably this mutation passed from generation to generation. It will involve more individuals each time and<u> increase the probability of developing a genetic disease</u>.
-Shower with a shorter amount of time
-Fix leaks at home
