Understanding Veronica Growth Forms
The study observed that Veronica plants exhibit different growth forms in their natural habitats: creeping in rocky sites and upright in grasslands. However, when grown under uniform greenhouse conditions, all plants displayed an upright stem.
Analyzing Greenhouse Results
The critical observation is that the difference in growth forms seen in nature disappeared when environmental conditions were standardized. All plants, regardless of their origin (rocky or grassland habitat), grew upright in the greenhouse.
Explanation: Phenotypic Plasticity
This outcome strongly supports the concept of phenotypic plasticity. Phenotypic plasticity is the ability of a single genotype to produce different phenotypes in response to different environmental conditions.
- In the rocky, open sites, the environment likely triggers a creeping growth form, possibly for protection or resource acquisition in that specific niche.
- In grasslands, the environment promotes an upright growth form.
- The greenhouse, representing uniform conditions, revealed the underlying genetic potential, which favors the upright form. The creeping form was an environmentally induced adaptation, not a fixed genetic difference between the populations.
Evaluating Other Explanations
- Inbreeding depression typically reduces fitness and might affect growth, but it doesn't directly explain the switch between distinct forms based on habitat and the reversion to a uniform form in the greenhouse.
- High gene flow might homogenize populations, but the observed difference *in nature* suggests some level of local adaptation or environmental response is occurring. The uniform result in the greenhouse points away from gene flow being the primary explanation for the *observed differences*.
- While growth form can be polygenic, this genetic aspect doesn't explain why the trait *changes* based on the environment and reverts under uniform conditions. Plasticity is the direct explanation for this environmental responsiveness.
Therefore, phenotypic plasticity best explains why the same species shows different morphologies in different habitats but appears uniform under controlled conditions.
Important Questions from Abiotic factors
The table below lists potential environmental conditions in future climates, related to atmospheric carbon dioxide concentrations ($CO_2$) and mean annual temperature (MAT).
The table also lists potential outcomes with respect to whether conditions will favour grasses with C3 or C4 photosynthetic pathways.
Assuming no other changes in environmental conditions, match the options in the two columns.Environmental conditions Outcomes (P) Increased $CO_2$, no change in MAT (i) C3 performs better than C4 (Q) No change in $CO_2$, increased MAT (ii) C4 performs better than C3 (iii) C3 and C4 perform equally - Mean global temperature since pre-industrial times has increased approximately by
- Terrestrial plants conduct gas exchange through stomata. Having only few stomata on the leaf surface is a common adaptation to which one of the following conditions?
- Some air-breathing marine vertebrates such as whales, seals and marine turtles possess adaptations for long, deep dives. Which one or more of the following is/are examples of such adaptations?
- Which one or more of the following is/are greenhouse gas(es)?
