Protists are the eukaryotes which are neither plants, animals nor fungi. But they are plant-like, fungi-like and animal-like organisms. It is difficult to classify all the protists in one kingdom Protista because of their numerous diversified traits. There are a few parasites, predators and also producers among the protists. Some have a cell wall, while others have a cell membrane. Mode of locomotion can be flagella, cilia or the pseudopodia. The best example is the <em>Euglena</em> exhibiting both plant and animal like characteristics in having a chloroplast performing photosynthesis and exhibiting locomotion by flagella. These diversified traits made the scientists to reclassify the protists. The kingdoms which arose from protist ancestors include the kingdom animalia, plantae and mycota sharing common characteristic features with their ancestor. Scientists say that we should not look for the earliest ancestors of animals among modern-day protists because, the modern day protists have gone through a process of evolution which makes them different from their early ancestors. The gradual changes during the course of evolution has made them different from their ancestors with respect to their structure, adaptations and also the genetic composition.
Answer: All of the statements are true.
Explanation:
Purines are biologically synthesized as nucleotides and in particular as ribotides, that is, bases attached to ribose 5-phosphate. Adenine and guanine are both derived from the nucleotide inosine monophosphate (IMP), which is the first compound in the pathway to have a completely formed purine ring system.
Purine nucleotides can be synthesized in two distinct pathways. First, purines are synthesized de novo, starting with simple starting materials such as amino acids and bicarbonate. the purine bases are assembled already attached to the ribose ring. Alternatively, purine bases, released by the hydrolytic degradation of nucleic acids and nucleotides, can be salvaged and recycled. Purine salvage pathways are mostly noted for the energy that they save and the remarkable effects of their absence.
All statements are correct because the organization of purine synthetic enzymes involves multifunctional enzymes, reversible enzyme formations, through out the sequence there is maintenance of high local concentration and the ten steps requires only six enzymes.
In the spermatheca, females of many insect species, including honeybee queens, can store gametes secreted by their sex partners.
<h3>What is Spermatheca ?</h3>
The female insect's spermatheca is an ectodermal structure that receives, stores, and releases sperm for egg fertilization. According to the species, spermathecae differ in size and shape.
- They often come from the median oviduct, which is located close or on the genital chamber. A secretory duct called the ductus seminalis connects the spermathecal sac, also known as the receptaculum seminis, to the genital chamber, where the sperm are released.
- The number of spermathecas varies among taxa, however the majority of insects only have one. Depending on the species of insect, the spermatheca has different morphologies. The spermatheca is composed of the spermathecal gland, duct, and reservoir. Both of these fluids feed the sperm. Both the spermathecal glands and the male accessory glands secrete substances that feed the sperm.
So lastly we can say that, t females of many insect species, including honeybee queens, can store gametes shed by their mating partners in - the spermatheca.
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If these are the choices:
The ability to halt the cell cycle in response to DNA damage.
The ability to halt the cell cycle in response to the chromosomes not properly aligning on the metaphase plate.
The ability to repair DNA damage.
The ability to activate Cdks.
The ability to stimulate cell death processes if the cell is irreparably damaged.
MY ANSWERS ARE:
<span>The ability to repair DNA damage. </span>
<span>The ability to halt the cell cycle in response to DNA damage. </span>
<span>The ability to stimulate cell death processes if the cell is irreparably damaged.</span>
Answer:
True
Explanation:
Meiosis can be described as a type of cell division in which four daughter cells are produced. The number of chromosomes in each of the daughter cells formed is half the number of chromosomes of the parent.
During this type of cell division, the processes of homologous recombination and crossing over occur. During crossing over, segments of DNA are exchanged between the homologous chromosomes due to which genetic diversity occurs.
