Ecosystems and Biodiversity

Ecosystems and Biodiversity - Key QS Definitions:

• Habitat - The place where an organism lives

• Community - All the organisms that live together in an ecosystem

• Population - The number of organisms of one species in an ecosystem

• Ecosystem - A natural biological unit made up of living and non-living parts, ie the community and the habitat. 

• Biodiversity - The variety that exists among living things

• Species - A group of organisms that can interbreed to produce fertile offspring

• Biotic - A living feature of an ecosystem, such as food supply, disease, predation

• Abiotic - A non-living feature of an ecosystem, such as light intensity, precipitation, temperature, wind speed, wind direction

• Adaptation - Any feature that makes an organism well suited to living in its environment

• Competition - A negative interaction that occurs between organisms whenever there is demand for a limited resource

Ecology

Ecology is the study of the relationships between living organisms, including humans, and their physical environment; it seeks to understand the vital connections between plants and animals and the world around them. 

The video below shows a summary of what exactly Ecology is:-

Ecology also provides information about the benefits of ecosystems and how we can use Earth’s resources in ways that leave the environment healthy for future generations. 

In order to understand how living organisms interact in the environment, first we need to understand how scientists describe living systems at increasingly smaller scales:-

Biotic and Abiotic factors

Factors which influence where plants and animals live can be classed as either biotic or abiotic. 

Biotic factors are living conditions, such as the other species living in the area, risks of predation, competition for food, etc., whereas abiotic factors are non-living conditions, such as the presence of sufficient water or correct temperature, etc.

Adaption

Not all species can survive in a particular ecosystem, for instance a Polar Bear would quickly die in a Desert ecosystem.

Charles Darwin’s theory of evolution describes how living organisms have changed over time in order to be better suited to their environment. This provides them with a greater chance of survival. These changes are known as adaptations. 

Adaptations differ depending on the type of environment an organism lives in and can be behavioural or structural. 

• Behavioural Adaptions : Adaptions in how the organism acts which improves survivability; for example living in herds for protection, only being active at night etc. 

• Structural Adaptions : Adaption in the physical shape of the organism which improves survivability; for example fur in cold climates, claws for digging etc. 

The video below shows how Cacti are adapted to survive the Desert Ecosystem:-

Competition

Ecological competition are the negative interactions between organisms for the same resources within an ecosystem. Resources are the parts of the ecosystem required for survival and reproduction such as food, water, shelter, light, territory, soil nutrients etc. Members of the same species may also compete for mates. 

There are two types of Competition:- 

• Intra-specific competition : Competition within a species for resources, for example male Red Deer competing for territory and mates. 

• Inter-specific competition : Competition between different species for resources, for example Lions and Cheetahs both preying on Gazelle. 

Competition Case Study : Red and Grey Squirrel 

The introduction of grey squirrel from America between 1876 and 1929 as an ornamental species in country estates has led to a huge impact on the native Red Squirrel population. 

Grey Squirrel are larger than the Red Squirrel and live in denser groups, so when introduced into a new area the Grey Squirrels will quickly outcompete the Red Squirrels  for food and resources.  

The Grey Squirrel also is a carrier (a carrier of a disease can spread it without showing symptoms themselves) for the disease 'Squirrel Pox' which is alomost always fatal to Red Squirrels. 

The maps below show how the range of the Red Squirrel has reduced over the last 75 years:-

Shuttleworth C. RSST Where to find red squirrels - Link 

In order to protect native Red Squirrel populations and reduce the damage to the wider ecosystem, Defra (The UK Government Department for Environment, Food & Rural Affairs) has begun to control the population of Grey Squirrels though the use of contraceptive-laced food:-

Biodiversity

Biodiversity is a measure of the variety of living organisms in an ecosystem. Biodiversity is greater in ecosystems that provide a bigger range of different habitats and are home to larger populations of a variety of organisms, with the most biodiverse ecosystems being tropical rainforests.

Ecosystems with high levels of biodiversity help to provide the resources needed to sustain life, including human life. For example, novel medicines such as new antibiotics can be discovered in areas of high biodiversity.

The Biodiversity Intactness Index (BII) is a measure created to estimate the biodiversity loss across an area using a combination of land use, other human pressures and species abundance data to give a simple figure for biodiversity ‘intactness’  (how much nature is left from a pristine state). 

This analysis has been performed on 240 countries worldwide, with the countries ranked from highest BII to lowest. Scotland is ranked in the lowest 12% of 'biodiversity intactness' globally, with a value of 56%. This means that Scotland has lost nearly half of its original biodiversity as a result of human actions:-

Biodiversity Case Study (Terrestrial) : Cloud Forests

Cloud Forests are areas of incredibly high biodiversity, with Cloud Forests globally occupying only 0.4% of the land surface but containing about 15% of global diversity of birds, mammals, amphibians and tree ferns.

Cloud forests take their name due to the near continual fog and low-hanging clouds that hover around the upper canopy of the forest before condensing onto the leaves of trees and dripping onto the plants below. This causes a slower rate of evaporation and provides the plants with continuous supply of moisture, without the need for soil.

This moisture helps to promote a huge amount of biodiversity, particularly within the type of plants known as epiphytes. These are plants which grow on other plants without damaging them, collecting their moisture and nutrients from the air, rain, and debris that surround them. 

The Monteverde Cloud Forest in Costa Rica, for example, only covers an area of 105 km² (half the size of Glasgow) but is home to 3,200 species of plants, including 700 species of trees and 500 species of orchids, approximately 425 species of birds, 120 species of mammals, 60 species of amphibians and 101 species of reptiles. 

Biodiversity Case Study (Aquatic) : Coral Reefs

Coral Reefs have the highest biodiversity of any ecosystem on the planet. Coral Reefs cover less than 1% of the ocean floor, but contain more than 25% of all marine life.

Coral reefs are built by coral polyps as they create layers of calcium carbonate beneath their bodies to anchor them to the rock. The calcium carbonate that is created by hard corals provides a foundation for baby corals to settle upon, causing the reef to grow slowly in size. 

Coral reefs are found all around the globe, and are split into two groups:-

• Warm Water (Tropical) Reefs : These are found in warm oceans (growing best between 23–29°C) such as the waters off the coast of Australia. 

• Cold Water Reefs: These are found in much colder oceans (they are able to survive temperatures below -10°C) such as the Northern Atlantic around Scotland. 

You would study ocean animals, plants and ecosystems to increase our knowledge and understanding of the environment, genetics, and animal or plant biology. You could work on research projects to observe and better understand ocean animals, plants and ecosystems, projects to protect and conserve sealife or to develop and manage marine resources. 

You could choose to study microscopic organisms such as plankton or huge cetaceans - whales. Marine life includes fish, mammals, birds, reptiles and invertebrates that rely on the ocean to survive. Or you could focus on studying the ocean’s plants, algae, fungi or coral. 

Depending on your area of research you might work in a laboratory or at sea; many roles will involve a mixture of both. You would write up and publish the findings from your research. You might also present your findings at conferences or teach at a university.

Sampling Techniques (Living Organisms)

When a habitat is studied it is almost impossible to count every individual that lives there. Small samples are taken which represent the whole habitat. Then the abundance of a particular species can then be estimated (how many individuals there are). 

Sampling techniques include:-

• Quadrat

• Transect (line)

• Nets

• Traps (pitfall, camera + mammal) 

• Capture – mark – recapture 

Quadrat Sampling

Quadrats are used to sample plants and rarely, slow moving organisms such as slugs. The quadrat should be applied randomly and then the organisms within identified and counted. 

Sometimes, an organism may be partially inside the quadrat, making accurate counting awkward.  A general rule is made that if more than 50% of the organism is in the quadrat, it is counted:-

The above quadrat sample result would be 6 clams in the same area (5 fully within, 1 mostly in).

There are several ways to measure organisms within a Quadrat:- 

• Number of an individual species - The total number of individuals of one species (eg daisies) is recorded.

• Species richness - The number of different plant or animal species is recorded but not the number of individuals within a species.

• Proportional cover - The number of segments of the quadrat's area that a species is present within, as a fraction or percentage of the total area. Proportional cover is used when it is difficult to identify individual plants, such as grasses or moss.

Quadrat Case Study : Garden lawn

Transect (Line) Sampling

Quadrats are also used in a more systematic way, using a Transect. A transect involves using the quadrat along a straight line across an area, and is used to investigate how species changes across an area. Abiotic factors (such as moisture level or temperature) influence the species that are present in a particular location.

Net Sampling

Quadrats and Transects work well for stationary organisms such as plants or barnacles, but they do not work for moving organisms. In order to sample moving organisms, Net sampling can be used. In net sampling, a net is swept through an area being sampled to collect small organisms (usually invertebrates or fish), allowing their abundance to be recorded. 

Nets can be used in streams to sample invertbrates living in the sediment through a method known as 'Kick Sampling' :

Traps (Pitfall, Camera + Mammal) 

Traps are another method that can be used to sample a population. By temporarily trapping or imaging  organisms, their presence in an area can be determined. 

A Pitfall Trap is a simple device used to catch usually ground dwelling invertebrates - such as beetles . A Pitfall Trap consists of a container buried so that its top is level with the surface of the ground, with a covering to prevent birds eating the trapped invertebrates, as well as preventing rainwater from filling the trap. Once, counted, the invertebrates are released back into the environment.

Camera Traps are composed of a digital camera connected to an infrared sensor to detect animals moving past the camera. When an animal moves past the sensor it causes the camera to trigger, recording an image or video to a memory card for later retrieval. 

Camera traps provide data on species location, population sizes and how species are interacting. They also allow observation of species without direct human interaction.

Mammal Traps are humane traps used to temporarily capture small mammals (such as mice) in order to calculate their abundance in the ecosystem. The traps have a one way entrance; once the mammal enters it cannot escape. Once counted, the mammals are again released unharmed back into the environment. 

Capture - Mark - Recapture

A variation on Trapping can be the Capture - Mark - Release method. In this method, the organism is captured in some way, they are counted and then marked or tagged in some way that is harmless to them. They are then released back into the environment.

At a later date, traps are again used and the number of marked and unmarked organisms are counted. An estimate of the total population can then be estimated using the following equation:-

Measuring Abiotic Factors

Organisms all have requirements for life that mean they are suited to their habitats, this is known as adaptions. For example, an Arctic Seal has a thick layer of blubber to keep it warm in the cold arctic water. If you took that same animal to a tropical ocean it would quickly overheat and die. 

These environmental factors that affect an organism's ability to live in an area are known as 'Abiotic Factors'. 

Investigating Abiotic Factors : Choice Chamber

The impact of abiotic factors on an organism can be investigated using a device such as a "Choice Chamber". This is a circular set of chambers, each with a different set of conditions.

The conditions within the choice chamber are controlled by : 

• Using water and drying agents to control moisture level 

• Covering sections to control light level 

When organisms such as woodlice, are introduced into the choice chamber, the organisms will tend to move to the areas which have the most favourable conditions for them :  

Investigating Abiotic Factors : Soil Moisture (Crucible & Oven Method)

In the field, a soil moisture probe can be used to measure the soil's moisture level, giving a fairly reliable result. A more accurate way of measuring the soil's moisture, known as the 'Crucible & Oven' method, requires samples to be collected and then returned to the lab.  

The collected samples are weighed whilst wet, heated in an oven overnight to dry, and then re-weighed. The difference between the two measurements will give the mass of water in the original sample. 

For example :  

Limitations of Sampling Techniques

In Science, it is of huge importance that the results gained are 'reliable'. The reliability of results is to what extent an experiment, test or other measuring procedure yields the same results on repeated trials.

Sampling techniques provide good information about the frequency and distribution of organisms in an area, but there will always be limitations within the procedures which can cause errors in the overall analysis, making the data less reliable. 

Limitations can include :- 

• Identifying organisms incorrectly when recording 

• The 'sample size' being too small 

• 'Random sampling' not actually being random 

• Errors in equipment set-up or use

Identification Errors

The data gathered in all field work is only valid if all organisms are correctly identified. In some cases this is easy to do (for example, a daisy and a buttercup look very different) but it is not always so easy. Similar species will look very similar, and can cause huge errors in data if organisms are misidentified. 

Misidentifying organisms can also come with health risks too. Every year in Scotland, people are poisoned after eating wild Fungi they thought were safe to eat, because they thought they were a different species. This is why it is not recommended to eat any Fungi found in the wild, unless it has been checked by an expert (and these can also make mistakes!).  

The example below shows how easy it is to make mistakes when identifying Fungi:-

A way to reduce identification errors is to use paired-statement keys to aid identification. Paired-statement keys use paired questions with branching pathways to identify an organism:-

Sample Size Issues

The size of a sample taken should be as large as is practically possible to do as, the larger the sample size, the more accurate the results will be, giving a better representation of the sampled population. The larger the population size, the smaller the 'margin of error' in the data will be. The smaller the margin of error, the more likely the data reflects the full population. 

The graph below shows how increasing the 'sample size' affects the 'margin of error':-

Taking many repeat measurements or having a large sample size will also make it easier to spot anomalous result. Anomalous results (a result that doesn’t fit in with the pattern of the other results) can be easily spotted in the data and discarded, leading to a more accurate calculation of the mean. 

'Random Sampling' Issues

A sample is only truly random if every individual in a population has an equal chance of being selected.

Humans are very susceptible to thinking something is random when it is not. For example, when using a quadrat to 'randomly' sample an area, one method would be to simply throw the quadrat and use it where it lands. However, this is not really random as the person decides where and how hard to throw etc, bringing in the risk of unconsciously throwing it into a 'good' location.

In order to ensure randomness a better method would be to split the area to be sampled into quadrat sized tiles and then use a random number generator to pick the tiles to sample.

Equipment Issues

Equipment can only provide good data if it is in good working order, is calibrated and is used correctly. 

The images below show pieces of equipment that are not in good working order, using any of these would result in inaccurate results:-

Calibrating a piece of scientific equipment is the process in which a piece of equipment is checked against a reference to ensure the accuracy of the results given. 

The image below shows the accuracy of a Vernier Caliper being checked against reference blocks of known size:-

Using equipment correctly is again of vital importance to gathering accurate data. Following all instructions for a piece of equipment is the easiest way to prevent inaccuracies. 

For example, A thermometer will show very different air temperatures if it is in direct sunlight compared to when it is in the shade, due to the direct warming from the Sun. In order to gain a correct reading of the air temperature, a thermometer should always be used in the shade:-

Some piece of equipment are only accurate when used under certain conditions. Using the equipment outside of these conditions will give inaccurate results.

For example, as metal will expand or contract when heated or cooled, a Steel Rule will only be accurate when used at the temperature specified on it. The diagram below shows the difference in measurement of a bar with a Steel Rule at different temperatures:-