Terrestrial life refers to life on land. Life did not originate on land and it was not until the Silurian period, which began about 444 million years ago, that terrestrial ecosystems began to develop. It was during this period that early vascular plants appeared. Rhyniopsida was one of these early vascular plants, although it is now extinct, which was composed of simple vascular tissue.
Life on land is extremely diverse since climate and topography vary across the globe. For instance, organisms can reside in alpine environments, glacial environments and Tropical climates, to name a fraction of the possible habitats which are present on land. The concept of biomes is a method for segregating this array of diverse environments. Biomes represent different geographic regions around the globe separated in terms of their climate, the organisms which reside there and soil variation.
Additionally, terrestrial life presents a variation of stressors for organisms which are not faced by organisms living in water. Some stressors are a huge concern in some environments and of little concern in other environments. These stressors include:
- Dehydration: Organisms on land need to maintain enough water in their bodies since the dry air causes constant evaporation. Adaptions, such as the waxy cuticle possessed by plants to reduce water loss, is an adaptation to this stressor.
- Freezing: The water inside organisms can start to freeze at low temperatures and even destroy their cells if the water inside them turns to ice and punctures the living cells. For example, coniferous trees have needle-like leaves to minimize the surface area for absorbing water.
- Overheating: At extremely high temperatures overheating can result and cause proteins to become denatured.
- Gravity: Unlike in the water, there is no buoyancy effect on land and thus, organisms need to possess structures to keep them rooted. For example, trees have large root systems to keep them from toppling over.
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