Basic Principles of Ecological Science

Evolution

Darwin’s Theory is a scientific theory laying out a reasoning for evolution, not only that it does occur but also why. The theory itself says basically, that through natural process certain species and individuals within a species will survive over others due to their ability to adapt or to be more suited to their environment.

If a genetic characteristic within a species allows it to survive and produce more offspring, that characteristic will then be carried on to a grater number of the species. The members of the species who do not have the characteristic will not survive to reproduce so well, and over time tend to be eliminated. This is known as Natural selection.

Classification
The scientific system of classification is a means of organisation for plants and animals so that you can identify and understand how they relate to other plants and animals. It allows you to see the relationships between species and what common attributes the may have. There are seven main levels to this and some sub-divisions occur. The classification is arranged from the largest to smallest groups, with smaller groups becoming closer in relation to each other.

The classes are as follows,
Kingdom, Phylum, Class, Order, Family, Genus and Species.


Habitat
Habitat is an area/environment that supports an organism or an ecosystem. There are plenty of different types of habitats but these can often fall under the four major habitat types.

Terrestrial – Relating to the earth and generally composed on land/ ground.

Freshwater – Aquias habitat, relating to water that is not salty or contains minimal salts.

Estuarine – A habitat where the seas salt water meets and mixes with freshwater.

Saltwater – Habitat occurring in sea or saltwater.


Population Ecology
This is the study of populations, their patterns, influences, effects and interactions. It also works to use these statistics to try to predict survival and reproduction in management of natural populations.

Populations are limited by numerous factors, space, food supply, disease, competition, predation. For a species to survive it must have adequate room to live, in a certain areas their may be limited nesting spaces, a lack of space can also lead to a lack of food and species numbers would be effected. Competition between species for food and space will affect population levels. A disease within a species could kill off and limit survival rates.

Behaviour between individuals within a species (intra-specific) has a direct effect on their population rates. All species need to survive and reproduce, and to do so successfully will result in population growth. How a species interact affect its survival and reproduction. Their mating habits, feeding habits and how territorial they might be are all factors to consider, along with social behaviour and family units. Some species can be fiercely territorial and will attack and kill each other, some eat their own young, some can have complicated and difficult mating habits. This will all have a direct effect on population rates.

Behaviour between different species (inter-specific) can have a massive influence on individual species populations. If two different species are competing for the same space and food one will generally be more dominant or aggressive than the other, resulting in a growth in the dominant species and decline in the other. When a new species is introduced into an environment it can upset the already existing balance of that ecosystem. Competition then grows for food and space and other species may loose out, these introduced species can lead to a loss of native species, e.g. Grey vs. Red squirrels, it all depends on the individual species involved and their ability to adapt.

Ecosystem ecology
Ecosystem is the word used to describe a community of organisms in an environment and how they all functions as a unit. There are two components to this unit, abiotic, which is everything that is ‘non living’ such as soil, climate, water, atmosphere. The second component is the biotic, which refers to the ‘living’ organisms; plants, animals, insects, fungi and bacteria are all part of this.

The abiotic factors will produce the initial environment and cannot be controlled, however the biotic part of the ecosystem will influence their non-living habitat in how they populate, feed and interact with other species as well as their environment.

All components of an ecosystem rely on each other for future survival and must exist as a whole.



Community
A community is the term given to a group of species living in an area under similar environmental conditions that interact with each other in various ways. These include competition (for food, space), predation and the different types of symbiosis. All the organisms living in the community are dependant on each other for survival, be it directly or indirectly.

Communities have an organised system or structure, through which energy flows and nutrients and water are cycled. Because species in community have similar reactions to the environment, you tend to find a characteristic set of species in that area. For example on heathland you will find heather, bilberry, lichen and birch scrub, this is because they all require very similar conditions and react in similar ways to the properties of the environment they are found in. This helps you to recognise communities with relative ease.

Ecological Succession
This is the term applied to a predictable sequence of changes that occur in a community over time if left unmanaged. If an area is left to it’s own devices it will go through various stages, each stage making more suitable conditions for the next. Succession takes place because the impact that organisms have on an environment changes its structure. Changes in environment (soils, moisture, nutrients, light) means that species will adapt, these adaptations will affect the environment and thus the cycle begins again. This means that no area ever stays the same and will be continually changing.

Ecological succession occurs in two ways. Primary succession takes place where no soils were present before, new substrate can be deposited (e.g. from lava flow or glacial melts), pioneer plants such as mosses and lichen (known as primary colonisers) start to create more suitable conditions for plant growth. Plants are found at specific stages of succession, firstly grasses then shrubs followed by trees. The species of animals found depends on the vegetation present. The final stage is known as the climax and in many cases this final stage is dominated by mixed deciduous woodland.

Secondary succession occurs in areas that already support life but have been unable to develop to the climax stage through damage/destruction either by natural disaster or human intervention. In many cases secondary succession occurs much faster than primary, this is because there is already an existing seed bank in the soil and roots that may have been undisturbed. The reduced competition would mean than more competitive or adapted species would dominate quickly. The final result is the same though and all although it may have taken a different route the climatic stage will still eventually occur if left to do so.

Once the climax stage has occurred the area still continues to develop through the regeneration cycle. If a tree falls, it leaves an open space in the canopy; eventually this space will be filled by another tree. In the beginning many plants will attempt to succeed this space, but a mini succession will occur with similar stages but on a much smaller scale. This will be continually occurring as the vegetation in the community is of various ages and stages.


Nutrient cycles

Carbon Cycle
Carbon dioxide is taken in by plants and used to produce carbohydrates for growth. Some is put back into the atmosphere through respiration. When animals eat plants they take on the carbon, which is then passed up the food chain. When the organism dies, the carbon in the tissue is broken down by bacteria and fungi (with the aid of oxygen) and converted into carbon dioxide. This is then released back into the atmosphere.

In areas of water, cooler temperatures allow for more carbon dioxide to be dissolved, the water circulates and warmer waters allow the carbon to be released back into the atmosphere.

Nitrogen cycle
Nitrogen in the atmosphere becomes fixed in the soil by nitrifying bacteria, which convert it into nitrogen compounds (nitrite, nitrate, ammonium), which allows plants to absorb and utilise the nitrogen. It is then stored in the plant, when animals eat the plants they take on the nitrogen and again it is released back into the cycle via decomposition by bacteria and fungi, this process is known as mineralization.

Phosphorous cycle
This cycle differs from many, as the cycle doesn’t have a gaseous stage, the largest source of phosphorous is found in sedimentary rock.
Rain causes weathering of rock, exposing and distributing of the phosphates throughout soils and water. Plants take up the phosphate ions and they are stored in organic tissue. The phosphate is passed on through the food chain, it is returned through excretion of urine and faeces and by decomposition of dead organic matter.

Phosphates that runoff into water, settle on the bed and can take along time to return to the cycle if not circulated in the water to be taken in by aquatic plants and passed through the food chain.

Energy Flow
Energy is what allows everything to survive; it cannot be created only transferred. This applies to all life on the planet, everything needs energy and as it cannot be made it must be obtained from outer sources. Nearly all life on the planet is dependant on the energy from the sun.

Solar energy radiates down onto the earths surface, photosynthesis transfers this light energy into chemical energy, which is then passed on through the food chain to sustain other organisms. These are known as trophic levels.

Only a minute percentage of all the sun’s energy reaches the earth’s surface, most of the light and heat energy is lost on passage through the atmosphere. From this energy only1-5% is used in photosynthesis. These organisms are the first trophic level or primary producers. The energy is stored in the plant until it is consumed by another organism; this energy is then passed into the consumer. These are usually herbivores also known as the primary consumers. The energy is passed on to creatures that prey on the herbivore and thus continue through the food chain.

During this process of energy transfer, losses occur along the way, this is because of energy used for heat, respiration, growth, movement etc. This means that at each trophic level the total amount of energy declines from one transfer to another, limiting the total number of trophic levels (usually to about 5). This is known as transfer efficiency. Transfer efficiency varies from one organism to another and also in different types of food chain. Because carnivores use more energy than herbivores when obtaining new energy, the total energy gain is less; it reduces the further up the chain you go. Energy is also transferred to bacteria and fungi when an organic organism decomposes.

Because of this flow of energy, it is unrealistic to think in terms of food chains, very few species rely on one species for food (it would be highly inefficient) and if changes were to occur to one species in a chain, it would directly effect all the other organisms in that chain. This is why food webs give a better understanding of the way that organisms transfer and gain their energy needs. Secondary consumers (carnivores) tend to have a varied diet, creating more complex webs. These webs are more stable then simple ones, allowing for a bigger range of energy sources.