Understanding Environmental Factors and Adaptations
Environmental Factors
The characteristics of the environment that affect living things are called environmental factors. They can be biotic or abiotic.
Biotic/Abiotic Factors
Abiotic factors are the physical and chemical conditions that affect living things: water, temperature, light, soil, pH, humidity, and nutrients found in soil or water.
Biotic factors are the organisms that share the same natural environment.
Intraspecific Relationships
Those between individuals of the same species.
Interspecific Relationships
Those between individuals of different species.
Limiting Factors
Limiting factors determine the extreme values after which an organism cannot develop properly. For terrestrial plants, the most frequent factors are water, followed by temperature, light, and some chemical elements. The limiting factors for aquatic plants are temperature, density, and light. In the 19th century, Justus Liebig formulated his law of the minimum: a plant’s growth is controlled by the least abundant nutrients. A species’ reaction to a limiting factor is represented through a tolerance range curve, in which the highest point is the most favorable condition for the growth of the species. The two endpoints are the maximum and minimum tolerance limits, and between these is the tolerance interval.
Adaptations of Living Things to the Environment
Adaptation is the evolution of organisms so that they are able to survive in a specific environment. Adaptations can be morphological, physiological, or behavioral.
There are species that have adapted themselves to very specific conditions that only exist in some areas. These species are referred to as endemic species. They are usually very vulnerable species that we must protect, and many of them are in danger. Spain is a country rich in endemic species due to its wide range of habitats.
Plants
Annual plants complete their life cycle in the season that favors their development.
- Hard, leathery small leaves to reduce water loss.
- Deep widespread roots.
- Leaves with few stomata (pores) that open only at night to reduce water loss.
- Drought-resistant seeds.
- Water is stored in special tissues.
Animals
Desiccation-resistant structures.
Insulated bodies.
Excretion products that have very little water.
Water is produced inside the organism by metabolic reactions.
Nocturnal.
Adaptations to Cold
- Skin insulation (fat and hair).
- Metabolic rate slows down during winter (hibernation).
- Individuals come together to increase the temperature around them.
Adaptations to Sunlight
Animals
Eyes adapted to see in very low light conditions. This is the case of nocturnal birds, such as the boreal owl. Bioluminescence is the light some nocturnal animals emit, such as fireflies, or some animals that live in the deep sea, such as comb jellies.
Plants
Sunlight conditions are different in aquatic environments. When sunlight goes through the water, some wavelengths, which plants use for photosynthesis, are absorbed. The area that receives sunlight is referred to as the photic zone. Algae have special pigments that allow them to use the wavelengths at particular depths:
- Green algae only have chlorophyll and have to live near the surface.
- Brown algae have another pigment (as well as chlorophyll) that allows them to live in slightly deeper waters.
- Red algae have a red pigment that allows them to live in even deeper areas.
The area where there is little or no sunlight is called the aphotic zone.
Adaptations to Lack of Oxygen
High Altitude
- Animals that live in these areas have developed the following adaptations in order to obtain the necessary oxygen:
- An increase in red blood cells, which are smaller too.
- An increase in lung capacity.
Aquatic Environments
- They reduce their heart rate when they are underwater.
- Cetaceans have a higher percentage of blood than other mammals.
- Their blood has a higher number of red blood cells.
- They accumulate oxygen in their muscles and blood.
- Blood flow to organs is reduced (except to the heart and brain).
Adaptations to Lack of Food
Mammals
Some mammals hibernate, so they reduce their metabolism as much as possible when food is scarce. Their heart rate and respiratory rate slow down, and their body temperature decreases. During the months before winter, some mammals accumulate a layer of fat under their skin. They then use the fat reserve when they hibernate. Some mammals adapt their behavior: they store food in secret places (this is common in areas with very cold winters, as food is scarce).
Reptiles
Reptiles living in environments that have noticeable differences between seasons spend the cold months in a lethargic state. Just like hibernating animals, they reduce their metabolism and use the reserves of nutrients that they stored in their bodies during the warmer seasons when food is more abundant.
How Living Things Change Their Environment
Plant roots break rocks and turn and air the soil, which makes it easier for erosion to occur. Lichens help in the formation of soil by breaking rocks. Foraminifera, which are protoctist microorganisms, have been found in sedimentary rocks that occupy large areas of land. Some animals, such as earthworms, move and air the soil: this process makes soil more fertile, although it also favors erosion.
- The accumulation of large numbers of coral skeletons can lead to the formation of islands and coral reefs.
- Vegetation has a direct influence on climate, as it creates special conditions that can be very different from the environments nearby. The evaporation of water from their leaves creates a humid microclimate that modifies the environment considerably. Trees also help create these microclimates, as they prevent sunlight from passing through.
- Some plants have deep roots and can live near sand. They obstruct the movement of sand dunes.
- Humans are the living things that modify the environment the most: sometimes these modifications can lead to irreversible, devastating consequences.
Population
A population is a group of organisms of the same species that live in the same territory and can reproduce together. Being part of a population gives a series of advantages to the individuals that form it. Some of the advantages are: reproduction is easy, protection against adverse environmental conditions, defense is easier, and so on. However, sometimes it can have negative effects.
The relationships established between the individuals of a population are referred to as intraspecific relationships. The purpose of these relationships is to facilitate reproduction and to make finding food easier, improve protection, divide labor, and favor migrations.
Cooperative Intraspecific Relationships
In these relationships, individuals group in order to make their life easier. Some of these relationships are permanent, and others are just temporary. These relationships can be colonies, families, caste systems, and social.
- Colonies: individuals join intimately and are a result of asexual reproduction. This means that all of the individuals are genetically the same.
- Families: they are relationships between parents and their offspring, so the parents can look after the offspring. They can be temporary or permanent. The duration of the relationship varies according to the time the offspring need to be raised by their parents: the longer they stay with their parents, the more they learn. Most family relationships last as long as it takes to raise the offspring, though there are some species, such as swans and orcas, where the parents stay together after their offspring leave. Families can be classified according to the individuals that form them and the number of parents they have.
- Caste Systems: all the individuals are organized in a hierarchical way and are descendants of a particular female. They tend to be individuals that have anatomical and physiological differences. This allows them to divide communal work. Termites, bees, and ants are examples of caste systems.
- Social: individuals live together to help each other mutually. They tend to happen for a specific period of time in order to search for food, defend themselves from predators, migrate long distances (as in the case of herds and flocks) or to reproduce (as in the case of monkeys).
Competitive Intraspecific Relationships
These relationships are established when individuals have to compete for a limited resource. Limited resources could be sunlight, food, space, or even individuals for mating. This type of competition controls populations. Intraspecific relationships by passive transport: The mechanical action of some agents, such as wind and water, makes individuals of the same species group together. Mosquitoes, and other insects, are grouped by the effect of air currents.