Environmental Factors and Adaptations of Living Things
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Environmental Factors
Characteristics of the environment that affect living things are called environmental factors. They can be abiotic (related to non-living things) or biotic (related to living things).
Biotic and abiotic factors
⦁ Abiotic factors: Physical and chemical conditions that affect living things.
The main abiotic factors are water, light, temperature, soil, pH, humidity, and nutrients found in water and soil. Some abiotic factors are more important than others depending on the location they are in.
- Sunlight is essential for life on Earth to exist.
- The concentration of oxygen in the atmosphere decreases as altitude increases.
- Temperature is a decisive factor in the physiological activity of living things.
- Water is an essential substance that all living things need.
- The concentration of mineral salts is very important in aquatic and terrestrial environments.
⦁ Biotic factors: Are the organisms that share the same natural environment. Living things have complex relationships that can be of two different types:
- Intraspecific relationships: those between individuals of the same species
- Interspecific relationship: those between individuals of different species.
Limiting factors
Limiting factors determine the extreme values after which an organism cannot develop properly. Therefore, they can limit the growth of a population.
Example: A particular environment has enough food for its population of birds to increase, but there are only enough nesting areas for the individuals who already live there. The population will not increase, and the limiting factor would be space.
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.
Endemic species: there are species that have adapted themselves to very specific conditions that only exist in some areas. They are very vulnerable and sensitive to minimum changes usually.
Adaptations to water scarcity
PLANTS | ANIMALS |
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Adaptation to temperature changes
ANIMALS (TO COLD) | PLANTS (TO COLD) |
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(TO HEAT) | (TO HEAT) |
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2.3. Adaptations to sunlight
Animals
Eyes adapted to see in very low conditions such as nocturnal birds.
Bioluminescence is the light some nocturnal animals emit such as some jellies.
Plants
In most cases, plants have adapted to make the most use of sunlight radiation.
Epiphytes: Need sunlight to live and they can climb over the other plants.
Regarding aquatic environments, when sunlight goes through 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 wavelength at particular depths:
Green algae (they only have chlorophyll and they have to live near the surface), brown algae (they have another pigment as well as the chlorophyll, that allows them to live in slightly deeper waters) and red algae (have a red pigment that allows them to live in deeper areas)
Adaptations to lack of oxygen
High altitudes
There are very few animals that live in these areas because the environmental conditions are very harsh due to low temperatures and lack of food. 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
Aquatic mammals have to keep the correct oxygen concentration in their blood when they dive into water. They have developed the following adaptations to do so:
- They reduce their heart rate when they are underwater.
- Cetaceans have 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 varying salt concentration
It controls the amount of water that goes in and out of the organism through a process called osmosis.
If the environment has a high concentration of salt, too much water leaves the organism, causing it to die.
If the concentration of salt is very low, too much water enters the organism and it cannot survive.
Organisms have adapted in different ways in order to regulate osmosis:
PLANTS | MARINE INVERTEBRATES |
Halophytes are one of the species that can live in soil with a high concentration of salt because they secrete excess of salt and select just the salts they need. | Their cells have the same concentration of salt as the external environment, so there is no excess of water entering or exiting their organisms. |
FRESHWATER FISH | SALTWATER FISH |
To compensate for the water going into them, they don't drink water and expel large amounts of urine that has a low salt content. |
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MARINE BIRDS |
They expel salty solutions through their salt glands, which are connected to their nostrils. This is why they can drink seawater. |
Adaptations to a 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.