Reptile Sex Determination and Climate Change
This question concerns how temperature-dependent sex determination in reptiles like crocodiles and turtles is affected by climate change, specifically rising temperatures, and the impact on population growth in small populations.
Temperature-Dependent Sex Determination (TSD)
- Turtles: Lower temperatures produce males, while higher temperatures produce females.
- Crocodiles: The pattern is opposite to turtles. Therefore, higher temperatures produce males, and lower temperatures produce females.
Impact of Rising Temperatures
Climate change causes an increase in global temperatures.
- Turtles: Increased temperatures lead to a higher proportion of females being produced.
- Crocodiles: Increased temperatures lead to a higher proportion of males being produced.
Effect on Population Growth in Small Populations
- For turtles, a shift towards more females might impact the sex ratio, but reproduction can still occur if males are sufficiently available.
- For crocodiles, a significant increase in males and a corresponding decrease in females, especially within a small population, severely limits reproductive success. The availability of females becomes a critical bottleneck, likely leading to a more substantial negative impact on population growth compared to the effect on turtles.
Therefore, the demographic change caused by rising temperatures is likely to negatively impact the population growth of crocodiles more than turtles.
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)?
