20. The answer is 1 (Precambrian)
21. The answer is 4 (Pennsylvanian)
22. The answer is 2 (Bony Fishes, Dinosaurs, and Mammals)
23. The answer is 2 (Reptiles)
Answer:
Humans cannot occupy the lowest levels.
Explanation:
Answer:
a) R= allele for red colored flower
I= Allele for ivory flowers
b) Genotype of pink flowered plant: RI
c) Incomplete dominance
d) 100%
Explanation:
When the dominant allele is not able to fully mask the expression of the recessive allele in the heterozygous state, it is said to be incomplete dominance. The R and I alleles impart red and ivory color respectively to the flowers of the snapdragon plant. The heterozygous genotype "RI" imparts a pink color to the flowers and therefore, the alleles are said to exhibit incomplete dominance.
The genotype of red-flowered snapdragon plant = RR. The genotype of ivory flowered snapdragon plant= II. When a red-flowered snapdragon plant is crossed with an ivory flowered snapdragon plant, the progeny is heterozygous in nature with the "RI" genotype. The phenotype of the progeny is "Pink flower" since the R allele is incompletely dominant over the allele I.
