The right answer is option d as its absence would impact many organisms in the ecosystem.
Keystone species are crucial for the ecosystem's health. If such a species were to disappear from an ecosystem, it would disrupt the ecosystem's functioning, leading to significant consequences. Therefore, keystone species are vital for the ecosystem's survival.
Answer:
In multicellular organisms, development and maintenance of various tissues, organs, and systems begin from an egg or zygote, with mitotic cell division being crucial. The new cells produced through mitosis are genetically identical to the parent stem cell, which is made possible by intricate regulatory mechanisms ensuring the genomic material’s integrity and proper segregation.
Explanation:
Segurine plays a critical role as it restrains the protease separase; its release prompts the breakdown of the cohesin that binds sister chromatids. This cohesion facilitates chromosomal separation, while the degradation of cyclin leads to the inactivation of CDK1 (cyclin-dependent kinase).
When chromosome alignment fails to satisfy the SAC (spindle assembly checkpoint), non-anchored kinetocores trigger protein recruitment at the checkpoint. This results in forming two distinct complexes which merge to create a mitotic control complex. Consequently, segurin is protected from degradation, preventing separase release and chromosome separation until SAC requirements are fulfilled.
The second option is correct. Carbohydrate digestion initiates in the mouth, while protein digestion begins in the stomach. Specifically, carbohydrate breakdown starts in the mouth through mechanical chewing and the enzyme salivary amylase present in saliva. In contrast, protein digestion takes place in the stomach where enzymes such as pepsin (from the stomach), trypsin, and chymotrypsin (from the pancreas) act to decompose the food proteins into polypeptides and progressively into amino acids.
Becher suggested that the combustion of a material stems from a substance known as phlogiston.
Answer:
Options (A), (C), and (D).
Explanation:
Introns constitute the non-coding nucleotide sequences of genes. They may either be found within genes or exist outside of exons, playing a role in gene evolution.
Introns can also facilitate the encoding of protein subunits and must be excised from exons through a process called splicing. Various forms of splicing include alternate splicing, group I, and group II introns. Genes can contain multiple introns.
Therefore, the correct selections are (A), (C), and (D).
