Answer:
No short answer.
Explanation:
First and second generation pesticides differ vastly in terms of their contents and effects.
First generation pesticides were used in early 20th century up until the 1940's and they consisted chemicals such as mercury and lead which were not biodegradable and they started adding up in the soil until it was not fertile anymore. Second generation pesticides were divided into three groups as chlorinated hydrocarbon, organophosphates or carbamates and consisted of chemicals that were less harmful for the soil and did not accumulate over time. Some examples to second generation pesticides can be DDT or dimethoate.
Broad spectrum and narrow spectrum pesticides have the difference of effective range between them. Narrow spectrum pesticides are designed to target a specific organism such as a specific plant or an insect whereas broad spectrum pesticides are applicable to a wider range of organisms and still have the same effect for each.
Chitin Inhibitors can be given as an example of narrow-spectrum pesticides and the second generation pesticides in the answer can be given as an example of broad-spectrum pesticides.
I hope this answer helps.
Answer: The correct option is A (chromosome Number is reduced from diploid to haploid)
Explanation:
In sexual reproduction, offspring are produced by fusion of two different sex cells which usually come from two different parents. These sex cells are know as gametes.
Meiosis is a type of cell division that gives rise to gametes in which the chromosome number is halved. Thus, the gamete cell is said to contain a haploid number (n) of chromosomes.
A diploid cell has two sets of chromosomes: one from the male parent and the other from the female parent. When a diploid cell undergoes meiosis the following occurs:
--> the chromosomes replicate once and
--> the nucleus and cell duplicate ( divide equally) twice.
As a result, the diploid parent cell gives rise to four haploid gamete cells. Therefore the statement "chromosome Number is reduced from diploid to haploid ' is true concerning meiosis I.
Answer:
Carbohydrates, particularly glycoproteins act as ligands for cell surface receptors.
Explanation:
Glycoproteins
- Glyproteins are conjugate molecules comprising of carbohydrates conjugated with proteins.
- Glycoproteins play a vital role in cell-cell recognition, pathogen recognition and and cell adhesion.
- Glycoproteins on the surface of pathogens act as prominent antigens for the immune system.
Glycoproteins in Fertilization:
Several glycoproteins are attached to the surface of the zona pellucida, the envelope of the oocyte. In humans, these have been termed as ZP1-4.
Glycoprotein-sperm interaction is one of the most crucial steps in fertilization. This receptor-ligand interaction ensures the entry of the sperm into the zona pellucida, the extracellular coat, covered in glycoproteins that surrounds the oocyte or egg.
Carbohydrate binding proteins present on the surface of the sperm recognize the glycoproteins on the zona pellucida (ZP). This enables them to adhere to the surface of the ZP and also to gain access to the oocyte.
Answer:
The force that holds the gases in the sun. The force that causes a ball you throw in the air to come down again. The force that causes a car to coast downhill even when you aren't stepping on the gas. The force that causes a glass you drop to fall to the floor.
