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8.4. Limiting factors and adaptations

Limiting factors

The limiting factors are the environmental or ecological factors that act directly on the living beings of a population, limiting their size, since these factors determine their birth rate, mortality, migrations, etc. They are those that regulate the growth and expansion of a species.

If environmental factors are optimal for the development of a living being, they favor the growth of that organism in that biotope. But if any of these factors prevents the growth of a species, it is called a limiting factor.

Among these physical and chemical factors that determine the biotope are:

  • Abiotic factors (not dependent on population density):
    • Climatic:
      • Light. Only the most superficial organisms access it in water. On land, there is also competition in leafy areas for access.
      • Temperature. Some living things cannot live at the temperature that others live.
      • Water: It is necessary for it to rain or for living beings to be able to access water in order to live. If there is no water, they die.
      • Atmospheric pressure.
    • Non-climatic:
      • Soil factors: The chemical composition of the soil, its pH, salinity, etc. makes some plant species may or may not survive in it.
      • Factors of the aquatic environment: The concentration of O2 , dissolved CO2, the degree of salinity, the existence of currents, etc., limits the development of some organisms.
  • Biotic factors (depend on population density):
    • FoodIf they don't have enough food, the population will have to be smaller.
    • Interspecific relationshipsThe number of predators limits the number of prey, and vice versa.
    • Intraspecific relationships. The relationships that are established between individuals of the same species can also limit their existence.

Biological adaptations

The survival of a species depends on the ability to adapt to changes that occur in the environment in which they live. The adaptation process can be fast or very slow. All living beings evolve adapting to the conditions of the environment.
Some of the biological adaptations can be:

Adaptations to the day or night

Depending on whether the species have adapted to develop their activity during the day or at night, the following are distinguished:

  • Diurnal speciesThey have very good color vision and very sharp. For example, the eagle.
  • Nocturnal species. They have black and white color sensitive night vision, accompanied by a very sensitive ear. For example, the owl.

Búho nival es un buen ejemplo de especie que se ha adaptado al ambiente

The snowy owl or snow owl (Bubo scandiacus) is a species well adapted to the environment of the Arctic Circle. It is nocturnal but when in summer, it does not get dark at the Pole, it has to be a diurnal hunter. Of this species is Hedwig, the white owl from Harry Potter.

Reproduction strategies

Not all species have the same capacity to colonize new places or the same competitive capacity, so they usually follow one of two types of reproductive strategies:

Strategy of the "r"

They are species that have many young but many of them die. They do not take care of their descendants and their life is short. These species are the first to colonize new ecosystems. The size of the population is highly variable, there is no equilibrium.

Some strategic species are bacteria, rodents, insects, etc.

Video: Reproductive strategy "r".

Why are there so many flies?

Each female of Musca domestica can lay about 120 eggs at a time, which will mature in two weeks. Thus, only with the summer months, about seven generations of flies can be produced. That fly would produce billions of flies in a single summer if it weren't for the environment, with its predators and cold winters that don't increase the fly population so much.

Strategy of the "k"

These species have few offspring but care for them until they can fend for themselves. They present little mortality, being their long life. They are characteristics of stable ecosystems.

Examples of strategic k species are large animals, such as humans.

Video: Reproductive strategy "k".

Species specialization

According to the degree of specialization of the species, the following are distinguished:

Generalist species

The generalist species are unspecialized species with very broad ecological niches, being able to use a variety of resources. It can live in a wide range of environmental conditions, so it adapts easily to changes in its environment.

For example, man, rats, flies, seagulls, would be generalist species.

Specialist species

The specialist species can only live in a narrow range of environmental conditions, so its ecological niche is small. They depend on a very specific resource, so if it disappears, their survival is in serious danger.

For example, the panda bear feeds on bamboo leaves and the koala on eucalyptus.

Oso Panda comiendo bambú

Adaptations to the type of medium

Living beings have evolved by adapting to environmental conditions, acquiring characteristics that favor their survival and reproductive success. These adaptations can affect the morphology, the functioning of some organs or the behavior of the individual.

Some of the adaptations to the environment are the following:

Adaptations to the aquatic environment

Plant adaptations to the aquatic environment

Aquatic plants that live completely submerged have other adaptations different from those that have floating leaves, but the following adaptations to the environment can be highlighted:

  • The root in submerged plants is poorly developed, since it does not need to absorb water through it. In floating plants it is more developed.
  • The leaves of the submerged plants are tape-shaped so that they do not break in the water and they do not have stomata. The leaves of floating plants, on the other hand, have a large surface area and have stomata to allow the entry and exit of gases and water.
  • The stems do not have supporting tissues because the water supports them. They do not have conductive vessels because they are surrounded by water and can absorb it.

Adaptations of animals to the aquatic environment

The main adaptations of animals to the aquatic environment are:

  • They have shapes adapted to move in the water, such as fins or fusiform shape.
  • Its density is very similar to that of water, so it is easier to move.
  • Some have a swim bladder to control ascent and descent.
  • Respiratory system through gills or through the skin.

Adaptations to the terrestrial environment

Plant adaptations to the terrestrial environment

  • Root highly developed to support the plant and take in water and nutrients.
  • System of conduction vessels that transport water and nutrients from the root to the rest of the plant.
  • The stomata of the leaves allow the exchange of gases with the atmosphere and the regulation of excess water.
  • Stem with supporting skeleton that allows the plant to stand upright.
  • Sheets prepared to capture the light energy of the Sun.

El cactus es un ejemplo de adaptación al medio árido

Cactus in the Jardín de Cactus de Teguise (Lanzarote).

Adaptations of animals to the terrestrial environment

  • Waterproof external structures that prevent desiccation: chitin in invertebrates and skin in vertebrates.
  • Presence of skeleton that allows to keep the organism upright: chitin exoskeleton in invertebrates and bone endoskeleton in vertebrates.
  • The fertilization is internal to facilitate the union of gametes.
  • They have structures that allow them to move, since they have the need to move to find food.
  • The respiratory systems are internal.
  • Eggs protected with a waterproof shell to prevent desiccation. Mammals have the placenta that feeds the embryo.

Interactive activity: Adaptations of organisms.