The impact of anthropogenic climate change on terrestrial organisms is often exp

Question

The impact of anthropogenic climate change on terrestrial organisms is often expected to increase with latitude, as the greatest increases in temperature are expected to happen at high latitudes. However, the biological impact of rising temperatures also depends on the physiological sensitivity of organisms to temperature variation. Researchers calculated fitness curves as a function of environmental temperature for representative insect taxa from temperate (A) and tropical (B) locations; the critical thermal minimum (CTmin), optimal environmental temperature (Topt), and critical thermal maximum (CTmax) are indicated on both curves. They then (C) predicted the change in fitness in response to climate warming for all insect species studied, as a function of latitude.

What are the potential mechanisms by which organisms can respond to changing climate conditions?

Based on these results, which group of insects (temperate or tropical) is most physiologically tolerant to high temperature stress under current conditions?

Do these data support the idea that high latitude species are most likely to be negatively affected by thermal stress in the future? Explain.

Explanation / Answer

Climate can play a major role in affecting the behavior of organisms on earth. In response to changing climate, including temparature and precipitation, these organisms can bring about a modification in their phenotype and thermal tolerance. An increase in temperature leads to an decrease in the water content of the organism, leading to increase in salt content in the various organelles. These increased salinity helps in protecting the denaturation of DNA (DNA denatures at 70 degrees), thus protecting the organism in turn. Furthermore to fight against increased temperatures, organisms have the following adaptations:

1. Presence of waterproofing hydrocarbons on body surface that can prevent the evaporation of water

2. Excretion of concentrated feces and urine, to prevent loss of water

3. Reducing the amount of water vapor lost through breaths

4. Plants have a lower leaf surface, along with thickened leaves to prevent evaporation

5. Thick hair on the body surface of animals helps protect them from overheating and sweating

Insects that are more tolerant to higher temperature stress belong to the temperate region rather than the tropical region. The tropical region has more uniform climate as compared to the temperate regions, making the insects from the tropical region more sensitive to any climatic change.

The impact of anthropogenic climate change on terrestrial organisms is predicted to increase with latitude. Yet the biological impact of rising temperatures also depends on the physiological sensitivity of organisms to temperature change. The results show that warming in the tropics, although relatively small in magnitude, is likely to have the most deleterious consequences because tropical insects are relatively sensitive to temperature change and are currently living very close to their optimal temperature. In contrast, species at higher latitudes have broader thermal tolerance and are living in climates that are currently cooler than their physiological optima, so that warming may even enhance their fitness. Tropical insects will approach near-lethal temperatures much faster than will insects from temperate climates, even though the rate of warming in the tropics is predicted to be half that of high latitudes

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