Adaptations and Interactions in Aquatic and Terrestrial Environments
To the Availability of Water:
In Desert Areas:
- Plants: Bushes have small leaves and are covered with impermeable substances (in order to avoid losing water). Some plants turn their leaves into spines, while others store water in their stems and leaves.
- Animals: Many desert animals are nocturnal or are only active in the early hours of the morning.
In Tropical Forests: (There is a lot of water)
- Plants: Trees generally have large leaves with sharp, protruding edges for eliminating excess water.
To Temperature:
To resist the low temperatures of cold seasons, plants remain in their seed form or shed their leaves and reduce their activity. Animals hibernate or migrate. The organisms that best adapted to the conditions are endotherms (control their body temperature as birds or mammals). They have insulations (layers of fat, feathers, hair, etc.)
Organisms reactivate their life cycles in warm seasons:
- Plants: Flower and produce fruit.
- Animals: They reproduce. If temperatures are very high, they adopt nocturnal habits; they regulate their temperature by sweating or panting (if they are endotherms).
2.4 Abiotic Factors in Aquatic Environments
Availability of water: Water is never a limiting factor.
Availability of light and temperature: These 2 abiotic factors decrease as solar radiation diminishes, as latitude and depth increase. Consequences of these factors:
- A photic or sunlight zone is generated (at some 200m from the surface) and an aphotic or dark zone (from 200m onwards).
- The temperature on the surface, varies according to latitude; and descends up to 300-400m, where it stabilizes between 0 and 3ºC
2.5 Life in Aquatic Environments
Seas and oceans are enormous masses of water that contain very little life: biodiversity is concentrated where there is light and nutrients for autotrophic organisms. Life is mostly found in coastal areas and in areas of upwelling.
- The coast is where plants and algae can attach to the substrate, according to their capacity to absorb light (first, the plants and green algae; the brown algae and, finally, red algae).
- Upwelling areas are isolated places where marine currents cause nutrient-rich water to rise up.
2.6 Some Adaptations to Aquatic Environments
To life in water: In order to resist the salinity, these organisms have special physiological processes.
- To move, they have fusiform bodies, fins, etc.
- To resist wave movement, they are flexible, or they have mechanisms for attaching themselves to the substrate.
To temperature and the availability of light
- In abyssal zones, organisms have luminescent organs.
- In polar regions, organisms have layers of fat, feathers or hair, and ability to regulate their temperature.
The characteristics of abyssal fish are the large mouth and the luminescent lures in order to trap their prey in the dark.
3. Biotic Factors
Biotic relationships or interactions are those that are established between individuals in a community or biocenosis. They can be intraspecific or interspecific.
3.1 Intraspecific Interactions:
Intraspecific interactions are those which take place in the biocenosis between organisms of the same species. The most common are competition and intraspecific associations.
Intraspecific Competition:
Intrasepecific competition is demonstrated by several different behaviours, such as fighting for territory and hierarchy.
- Fighting for territory: This occurs when individuals challenge each other, and the winner obtains the right to “use” the territory it was fighting for.
- Hierarchies: Here each individual has preference for using resources over others that are further down the dominance scale.
Associations:
- Family associations: Made up of individuals which are related to each other. They can be parental if both parents and the offspring are present, matriarchal formed by the mother and the offspring or filial if only the offspring forms the association.
- Gregarious associations: Formed by individuals that are not related to each other, but that join together with a specific purpose, defending themselves or looking for food.
- Colonial associations: Formed by individuals that reproduce asexually and remain close to their parent their whole life. Like for example polyps which aim is to obtain food more easily.
- State associations: Those where there is a division of tasks. The individuals form a hierarchy and exhibit some anatomical and physiological differences.
3.2 Interspecific Interactions:
Interspecific interactions are those which take place in the biocenosis between organisms of different species.
Interspecific Competition:
- Interspecific competition is produced when two species use the same limited resource.
- Ecological niche is a set of traits that characterise its adaptations, the area in which it can live, it needs and enable it to integrate into the ecosystem, and define its function in that ecosystem.
Non-Competitive Interspecific Interactions:
- Predation (+,-): Interaction where the predator (+), captures and kills the prey (-), for food.
- Parasitism (+,-): Interaction where one species, the parasite (+), lives off another, the host (-), which it feeds off without causing it to die.
- Commensalism (+,0): Interaction where one of the species, the comensal, benefits from any excess food or without affecting it in any way.
- Mutualism (+,+): Two organisms of different species in which both benefit.