Answer is A. A population becomes separated by environmental factors into two groups that do not reproduce with one another.
When a population of a species become geographically separated then gene flow between them stops. Over a period of time, the population may become genetically different in response to the natural selection due to different environments. Selection and genetic drift will act differently on these two separated populations. This will results into two separate species. This type of speciation is called allopatric speciation.
Answer:
A magnet keeps a cabinet door closed. The Sun pulls on Earth as Earth moves around the Sun. The protons in the nucleus of a carbon atom are held together.So this is an example of the strong force in action.
The given statement is False.
The bacterial cells walls are composed of peptidoglycan, also known as murein. It comprises polysaccharide chains cross-linked by unusual peptides, involving D-amino acids. The bacterial cell walls are distinct from cell walls of fungi and plants that are made up of chitin and cellulose, respectively.
The cell walls in bacteria allow small molecules to pass through them freely, however, do not permit large molecules to pass through them, in this manner, it function as a coarse filter.
The main function of the cells wall is to sustain the shape of the cell and inhibit the cell from bursting due to osmotic pressure. The cell wall allows the components to pass, which are essential for bacterial nutrition.
Explanation:
Sediment discharge was historically approximately 270 million cubic meters/year of suspended load and 130 million cubic meters/year of bedload. This has decreased 80% since 1850 and can be divided into three periods: historical period (pre 1900), pre-dam period (1932-1952), and post dam (1963-1982). Suspended sediment loads declined 43% between the historical and pre-dam and 51% from pre-dam to post-dam periods. The size of sediment also decreased drastically including a 72% decrease in the sand fraction. Most of this is due to dams on the tributaries acting as sediment traps primarily for the coarser sediments. Large-scale land clearing for agriculture contributed to increased sediment loads in the historic period.
Given the age of the meteorite is 4.5 billion years old with 78 atoms of lead-206 the answer should be B. 156. The half-life of uranium-238 in order to decay into lead-206 is 4.46 billion years, which means that the original number of atoms is 156.
