In seedcracker finches from Cameroon, small- and large-billed birds specialize in cracking soft and hard seeds, respectively. If long-term climatic change resulted in all seeds becoming hard, what type of selection would then operate on the finch population?
a. disruptive selectionb. directional selection
c. stabilizing selection
d. No selection would operate because the population is in Hardy-Weinberg equilibrium.

B. directional selection

Explanation:

Directional selection was first described by Charles Darwin. Directional selection, or positive selection is a mode of natural selection in which an extreme phenotype is favored over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype. Under directional selection, the advantageous allele increases as a consequence of differences in survival and reproduction among different phenotypes. The increases are independent of the dominance of the allele, and even if the allele is recessive, it will eventually become fixed.

An example of directional selection is fossil records that show that the size of the black bears in Europe decreased during interglacial periods of the ice ages, but increased during each glacial period.

B. Directional selection

Explanation:

Directional selection: Individuals that display a more extreme form of a trait have greater fitness than those with an average form of the trait i-e one extreme is favoured.

For example : the surrounding woody environment may provide better camouflage for darker mice, thus most of the lighter colour mice may be easily hunted.

As in the above mentioned scenario, if long-term climatic change resulted in all seeds becoming hard, directional selection would then operate on the finch population

enzyme active site and substrate specificity

enzymes bind with chemical reactants called substrates. there may be one or more substrates for each type of enzyme, depending on the particular chemical reaction. in some reactions, a single-reactant substrate is broken down into multiple products

which

what is a measurement of the earth’s history divided into time periods?

> fossil record <

sedimentary rock

> geologic time scale <

radioactive elements