Answer:
The average decline in overall amphibian populations is 3.79 percent per year, though the decline rate is more severe in some regions of the U.S., such as the West Coast and the Rocky Mountains. If this rate remains unchanged, some species will disappear from half of the habitats they occupy in about 20 years.
Explanation:
cuz
If it has a nucleus or not
The primary function of major organs shown in the figure include;
1. Sporangia; its functions is to produce spore structures which are aggregated to bigger structures.
2. Rhizoids; are structures which are being projected from prothallium and its function is anchoring structures.
3. Prothallus; is the gametophyte and its functions are the carrier of both female and male sex organs.
4. Antheridium; it is the female sex organ and its functions are to produce eggs.
Answer:
Hi
Explanation:
It separates the content of cell from their external environment.
It controls the entry and exit of materials in nd out of cell
Answer:
Occurrence and accumulation in time of new mutations in each of the separated populations. This leads to a gradual differentiation.
Explanation:
Allopatric speciation consists of the geographic separation of an original population so that it can give place to two or more new geographically isolated populations. These separations might be due to migration, extinction of geographically intermediate populations, or geological events. In this speciation, some barriers impede genetic interchange, or genetic flux, as the two new populations that are separated can not get together and mate anymore. These barriers might be geographical or ecological.
The process of allopatric speciation involves different steps:
- The emergence of the barrier,
- Interruption in the genetic interchange,
- The occurrence of new mutations and their accumulation in time in each population. Slow and gradual differentiation,
- Genetic divergence by natural selection and reproductive isolation, which makes it impossible for the two groups to cross even if the barrier disappears,
- Prezigotic isolation mechanisms favored by selection once it occurs a secondary contact between the new species in formation.