Two genes (A and B) are located on each of two pairs of homologous chromosomes. In a tetrad, one sister chromatid contains alleles ab, while the other sister chromatid contains alleles AB (upper and lower case indicate different alleles of the same gene). Which genetic combinations are possible in the four gametes that are produced from a single chiasma between these chromosome pairs

i think it is true in my reasonment ..

spiders belong to a group of arachnids.

arachnids have the following traits :

they have two body parts.

they have eight legs unlike insects which have 6 legs.

they have no wings.

these traits distinguish them from insects.

the information that antonio is doubting us the statement that spiders differences are as a result of being first to evolve.

this is because the evolution of one species is independent of the other species.

the nitrogen cycle provides nitrogen to the ecosystem from the atmosphere, ground and oceans. nitrogen is an important component of complex molecules such as amino acids and nucleotides, which lead to the creation of proteins and dna, the building blocks of all life. plants absorb nitrogen in the form of ammonium, nitrate ion and, on rare occasions, as amino acids. animals receive nitrogen necessary for biological processes from feeding on living or dead organic matter.