The figure illustrates the soil zinc tolerance of the grass species Anthoxanthum along a transect from inside a mine to the middle of a pasture outside the mine.
Which one or more of the following processes explain(s) the observed pattern of zinc tolerance in this grass species?
The question focuses on understanding the observed pattern of zinc tolerance in the grass species Anthoxanthum across a transect from inside a mine to a pasture. The given graph shows the variation in zinc tolerance.
The correct answer is Local adaptation. Let's explain why this is the case and rule out the other options:
- Local adaptation: This is the evolutionary process where a population evolves specific traits that confer advantages in their local environment. In the graph, grass species inside the mine have higher zinc tolerance compared to those in the pasture. This pattern suggests adaptation to the high-zinc environment near the mine. Hence, local adaptation is a reasonable explanation for the observed pattern.
- Genetic drift: It is a random process that can cause changes in the frequency of traits in a small population. However, genetic drift does not explain the specific pattern of tolerance related to a distinct environmental gradient observed here.
- Coevolution: This process involves two or more species affecting each other's evolution. The pattern shown in the graph does not indicate interactions between species influencing each other's evolution, so coevolution is not applicable.
- Introgression: Introgression refers to the incorporation of genes from one species into the gene pool of another through hybridization and backcrossing. This process does not explain the specific adaptation to zinc within a single species as observed in the graph.
Therefore, the most plausible explanation for the observed pattern is Local adaptation.
Important Questions from Natural selection
- Which one or more of the following is/are NOT essential for evolution by natural selection to take place in a population?
- Two bacterial variants are growing together in the same flask. At any relative frequency of the two variants, the population growth rate of the rarer variant is higher. The above is an example of ________.
There are two species, X and Y, with abundances $x$ and $y$, respectively. Species X has growth rate $\alpha$, and species Y has growth rate $\beta$. Assume that the sum of the species abundances is constant over time, i.e., $x + y = 1$. Let $x$ and $y$ follow the rate equations:
$$\frac{dx}{dt} = \alpha x - \varphi x,$$
$$\frac{dy}{dt} = \beta y - \varphi y,$$ where $\varphi$ is the average species fitness.
Which one of the following options correctly represents the expression for $\varphi$?From an original population \(P\) of a butterfly species, two experimental populations \(X\) and \(Y\) were established. In \(X\), males and females were maintained in standard conditions, and females were allowed to mate and lay eggs. Only eggs from females laying small clutches (i.e., \(S\) eggs or fewer) were allowed to hatch and the rest were not utilized. In \(Y\), males and females were maintained in standard conditions and females were allowed to mate and lay eggs. From each female, \(S\) eggs were randomly selected and allowed to hatch, and the rest were not utilized. After 20 generations of these experimental conditions, relative to the original population \(P\), and assuming that clutch size is under genetic control, we expect clutch size to be ______________________in \(X\) and ___________________ in \(Y\).
- In which of the following four plots, showing reproductive fitness versus a trait, is the strength of selection MAXIMUM?
