Temperature, Tropism, Taxis, and Food Webs in Ecosystems
Temperature: Definition and Significance
Temperature is a physical quantity that expresses the degree of hotness or coldness of a substance. Generally, a hotter object will have a higher temperature. Physically, it is a scalar quantity related to the internal energy of a thermodynamic system. More specifically, it is directly related to the internal energy known as “sensitive energy,” which is the energy associated with the movement of particles in the system, whether in a translational, rotational, or vibrational sense. As a system exhibits more sensitive energy, it becomes “hotter,” meaning its temperature is higher.
In the case of a solid, these movements manifest as vibrations of the particles around their fixed positions within the solid. In a monatomic ideal gas, it is the translational motion of particles (for multiatomic gases, rotational and vibrational movements should also be considered).
That said, temperature can be defined as the quantification of the molecular activity of matter.
The development of techniques for measuring temperature has undergone a long historical process, as it requires assigning a numerical value to an intuitive concept like hot or cold.
Many physicochemical properties of materials or substances vary with temperature, such as their state (solid, liquid, gas, plasma), volume, solubility, vapor pressure, color, or electrical conductivity. Temperature also influences the rate at which chemical reactions occur.
Tropism: Plant Responses to External Stimuli
Tropism is a directional growth response produced by a plant hormone in reaction to an external stimulus.
Plants lack sense organs. They can move to adapt to changes in their environment. Similar to animals, plants can detect environmental changes and respond accordingly.
The most common response in plants is slow growth in a specific direction determined by the stimulus. These responses can be:
- Positive: When the plant grows toward the stimulus.
- Negative: When the growth direction is opposite to the stimulus.
Types of Tropism
- Phototropism: Change in growth direction due to variations in light.
- Geotropism or Gravitropism: A response to the gravitational force of bodies.
- Heliotropism: Orientation of leaves and flowers toward the Sun.
- Hydrotropism: Movement of the plant toward humid areas where water is present.
- Chemotropism: Caused by the presence of chemical substances like dissolved salts, oxygen, etc.
- Thigmotropism: Oriented growth movement in response to physical contact.
Taxis: Directed Movement in Response to Stimuli
Taxis is the directed movement of an organism in response to a stimulus. When discussing taxis, we refer only to movement.
- Positive Taxis: If the organism moves toward the stimulus, it is called positive taxis.
- Negative Taxis: If the organism moves away from the stimulus, it is called negative taxis.
Food Webs: Interconnected Food Chains in Ecosystems
Food webs, also known as trophic webs, represent the entirety of food chains within an ecosystem, where each link is connected to another by arrows indicating “is eaten by” or “eats.” A food chain or food web begins with a producer (plants). Then, consumers feed on producers, and decomposers feed on any decomposing organic matter, including primary, secondary, tertiary consumers, etc. The process is cyclical, with producers ultimately feeding on the decomposed remains, thus restarting the cycle.
In a [biocenosis], a population of herbivores feeds on different populations of producers, and different populations of consumers feed on different populations of herbivores.
Trophic relationships are more complex than a simple “chain.” In reality, multiple interconnected food chains within a community form a food web or trophic network.
A food web is a set of interconnected food chains within an ecosystem.