Ecosystems and Biodiversity

Glossary

Characteristics and Benefits of a Diverse Ecosystem

Characteristics

A diverse ecosystem possesses several key characteristics that contribute to its richness and complexity. Here are some of the characteristics of a diverse ecosystem:

High species richness

• A diverse ecosystem is characterised by a high number of different species coexisting within it. This includes a variety of plants, animals, microorganisms, and other organisms.

Genetic diversity within species

• Diverse ecosystems exhibit a wide range of genetic variation within species. This genetic diversity allows species to adapt and respond to environmental changes and increases the resilience of the ecosystem as a whole.

Presence of a variety of habitats

• Diverse ecosystems contain a variety of habitats, such as forests, grasslands, wetlands, coral reefs, and more. These different habitats support distinct species and ecological processes, contributing to overall ecosystem diversity.

Complex ecological interactions

• A diverse ecosystem is characterised by intricate ecological interactions between species. This includes relationships such as predation, mutualism, competition, and symbiosis, which contribute to the stability and functioning of the ecosystem.

Various trophic levels and food webs

• Diverse ecosystems have a range of trophic levels, representing the different feeding positions within the food web. This includes producers (plants and algae), consumers (herbivores, carnivores, omnivores), and decomposers (bacteria, fungi), allowing for the flow of energy and nutrients through the ecosystem.

Different ecological functions performed by species

• Diverse ecosystems possess a variety of ecological functions performed by different species. Each species has a unique role in processes such as pollination, seed dispersal, nutrient cycling, and decomposition, contributing to the overall functioning and services provided by the ecosystem.

Spatial heterogeneity in species distribution

• Diverse ecosystems exhibit spatial heterogeneity, meaning that the distribution and arrangement of different species and habitats are varied across the landscape. This spatial complexity further enhances the diversity of the ecosystem.

Temporal variability and dynamic nature

• Diverse ecosystems also exhibit temporal variability, with changes occurring over time due to seasonal fluctuations, ecological successions, and disturbances. This temporal variation contributes to the dynamic nature of the ecosystem.
  

These characteristics highlight the importance of biodiversity and its role in maintaining the health, stability, and functioning of ecosystems. They also emphasise the value of conserving and protecting diverse ecosystems to sustain their ecological services and ensure the well-being of both humans and other organisms.

Benefits

A biodiverse ecosystem provides numerous benefits that are essential for the well-being of both nature and humans. Here are the key benefits of a biodiverse ecosystem:

Ecosystem services

• Biodiverse ecosystems deliver a wide range of ecosystem services that support human livelihoods and well-being. These services include clean air and water, pollination of crops, regulation of climate, soil fertility, natural pest control, and the provision of food, medicine, and raw materials.

Resilience and stability

• Biodiverse ecosystems are more resilient and resistant to environmental changes and disturbances. They can better withstand threats such as climate change, invasive species, and diseases. The presence of diverse species and genetic variation ensures that even if some species are affected, others may step in to maintain ecosystem functions.

Increased productivity

• Biodiversity enhances ecosystem productivity. Different species have unique roles in nutrient cycling, photosynthesis, and biomass production. Greater species diversity often leads to increased productivity, supporting the growth and abundance of plants, animals, and other organisms within the ecosystem.

Nutrient cycling and ecosystem functioning

• Biodiverse ecosystems are crucial for the cycling and availability of nutrients. Each species contributes to the decomposition, recycling, and distribution of nutrients, promoting healthy soil, water quality, and overall ecosystem functioning.

Economic value and livelihoods

• Biodiversity provides significant economic value and livelihood opportunities. Industries such as tourism, agriculture, forestry, and pharmaceuticals depend on diverse ecosystems for their operations. Additionally, many local communities rely on ecosystem services for food, clean water, and cultural practices.

Aesthetic and cultural value

• Biodiverse ecosystems are aesthetically pleasing and culturally significant. They provide opportunities for recreation, inspiration, and spiritual connections with nature. Many indigenous cultures depend on biodiversity for their cultural practices, knowledge, and identity.

Climate regulation

• Biodiverse ecosystems play a crucial role in regulating the Earth's climate. Forests, wetlands, and other biodiverse habitats act as carbon sinks, absorbing and storing carbon dioxide, a greenhouse gas responsible for climate change. Conserving biodiversity helps mitigate climate change by preserving these carbon storage systems.
  

Overall, the benefits of a biodiverse ecosystem extend to ecological, economic, cultural, and climate-related aspects, highlighting the importance of preserving and protecting biodiversity for a sustainable future.

Characteristics and Consequences of Ecosystem Degradation

Characterisation

A degrading ecosystem exhibits several characteristics that indicate a decline in its health, resilience, and functioning. Here are some common characteristics of a degrading ecosystem:

Loss of biodiversity

• A degrading ecosystem experiences a reduction in species richness and abundance. This loss of biodiversity can occur through habitat destruction, pollution, invasive species, overexploitation, and other human activities.

Decreased ecosystem services

• As an ecosystem degrades, the capacity to provide essential ecosystem services declines. This may include reduced water quality, diminished soil fertility, decreased pollination and seed dispersal, and weakened regulation of climate and natural disasters.

Altered species composition

• Degrading ecosystems often undergo changes in species composition. Some species may decline or disappear, while others may become dominant. These shifts can disrupt ecological interactions and affect the overall functioning of the ecosystem.

Habitat degradation

• Degrading ecosystems experience physical and structural changes to their habitats. This can involve deforestation, urbanisation, fragmentation, degradation of coral reefs, and pollution of water bodies. Such habitat degradation limits the availability of suitable habitats for different species.

Disruptions in nutrient cycling

• In a degrading ecosystem, nutrient cycles may be disrupted, leading to imbalances and nutrient deficiencies or excesses. This can occur due to factors like soil erosion, pollution, or changes in land use practices.

Increased susceptibility to disturbances

• Degrading ecosystems become more vulnerable to disturbances, such as wildfires, disease outbreaks, or extreme weather events. Weakened resilience and reduced biodiversity make it challenging for the ecosystem to recover from such disturbances.

Declining productivity

• Productivity within a degrading ecosystem often declines. This can result from reduced photosynthetic capacity, diminished nutrient availability, or disrupted food webs, leading to lower biomass production and energy flow.

Loss of cultural and aesthetic value

• A degrading ecosystem may lose its cultural and aesthetic value. This can manifest as the disappearance of traditional practices, loss of culturally significant species, reduced opportunities for recreation, and diminished inspiration from nature.

It is crucial to identify and address these characteristics of ecosystem degradation to promote conservation, restoration, and sustainable management of ecosystems and their valuable services.

Consequences

The consequences of a degrading ecosystem can have far-reaching impacts on both the environment and human well-being. Here are some key consequences of ecosystem degradation:

Loss of biodiversity

• Ecosystem degradation often leads to a loss of biodiversity, including the decline or extinction of plant and animal species. This loss of biodiversity reduces ecosystem resilience, disrupts ecological interactions, and can have cascading effects on the entire food web.

Decline in ecosystem services

• Ecosystem degradation diminishes the ability of ecosystems to provide essential services. This can result in reduced availability of clean water, decreased agricultural productivity, impaired soil quality, weakened regulation of climate, and a decline in natural pest control, among other services.

Impacts on human health

• Degraded ecosystems can have negative impacts on human health. For example, deforestation and habitat degradation can increase the risk of infectious diseases by altering wildlife habitats and facilitating the transmission of diseases between animals and humans (zoonotic diseases). Air and water pollution resulting from ecosystem degradation can also directly affect human health.

Economic losses

• Ecosystem degradation can lead to economic losses through reduced productivity in agriculture, fisheries, and forestry. Additionally, the loss of ecosystem services can result in increased costs for water treatment, flood control, and other human interventions that ecosystems usually provide for free.

Disruption of livelihoods

• Many communities depend on ecosystems for their livelihoods, such as farming, fishing, and tourism. Ecosystem degradation can disrupt these livelihoods through the loss of natural resources, reduced availability of food and income, and increased vulnerability to environmental risks.

Increased vulnerability to natural disasters

• Degraded ecosystems are more vulnerable to natural disasters such as floods, landslides, and droughts. The loss of vegetation cover and destruction of natural buffers in degraded ecosystems can amplify the impacts of such events, leading to increased risks for nearby communities.

Climate change impacts

• Ecosystem degradation contributes to climate change through the release of greenhouse gases, reduced carbon sequestration, and altered land surface characteristics. Conversely, climate change can also exacerbate ecosystem degradation by intensifying droughts, storms, and other climatic factors.

It is crucial to address ecosystem degradation through conservation, restoration, and sustainable management practices to mitigate these consequences and ensure the long-term health and well-being of both ecosystems and human societies.

Abiotic Factors

Abiotic factors are nonliving components of an ecosystem that influence the organisms and their interactions within a particular biome. These factors can vary across different biomes and play a crucial role in shaping the distribution and adaptation of organisms. Here are six examples of abiotic factors and their importance in different biomes:

• Temperature

• Temperature is a critical abiotic factor that greatly influences the types of organisms found in a biome. Extreme temperatures can limit the range of species that can survive, while more moderate temperatures can support a wider variety of life. For example, the temperature range in the desert biome can be quite extreme, with scorching heat during the day and drastic temperature drops at night.

• Precipitation

• Precipitation, including rainfall and snowfall, is vital for determining the availability of water in a particular biome. It directly affects the type of vegetation and the distribution and abundance of organisms. Biomes such as rainforests receive high amounts of precipitation, supporting lush vegetation and diverse animal life.

• Sunlight

• Sunlight availability is crucial for photosynthesis and energy production in plants. The amount and intensity of sunlight vary across different biomes, influencing the types of plants and organisms that can thrive. Forest biomes, for example, have a dense canopy that filters sunlight, creating a unique microclimate on the forest floor.

• Soil Composition

• Soil composition, including factors such as mineral content, pH levels, and organic matter, has a significant impact on plant growth and nutrient availability. Different biomes have distinct soil characteristics. For example, the nutrient-rich soil in temperate deciduous forests supports the growth of a diverse range of plants.

• Water Availability

• The availability of water is crucial for the survival of organisms in any ecosystem. In aquatic biomes, such as oceans, lakes, and rivers, water is abundant and serves as a habitat for a wide variety of organisms. However, even in terrestrial biomes, the availability of water, such as in wetlands or near rivers, greatly influences the types of organisms that can thrive.

• Altitude/Elevation

• Altitude or elevation plays a significant role in determining the abiotic conditions in a biome. Higher elevations generally have cooler temperatures and reduced atmospheric pressure, which can limit the types of organisms that can survive. Mountainous biomes, such as alpine tundra, are characterised by harsh environmental conditions due to high elevations.

These six examples highlight some important abiotic factors and their significance in different biomes. It is important to recognise that the importance of abiotic factors may vary within and across biomes, and the complexity of their interactions greatly influences the distribution and adaptations of life forms.

Notes

• Temperature

• Determines the range of organisms that can survive in a biome

• Extreme temperatures can limit species diversity

• Moderate temperatures support a wider variety of life

• Precipitation

• Influences the availability of water in a biome

• Determines the types of vegetation and the distribution of organisms

• High precipitation supports lush vegetation and diverse animal life

• Sunlight

• Essential for photosynthesis and energy production in plants

• Varies in intensity and availability across biomes

• Influences the types of plants and organisms that can thrive

• Soil Composition

• Determines nutrient availability and pH levels for plant growth

• Varies in mineral content and organic matter across biomes

• Soil characteristics impact the types of plants that can flourish

• Water Availability

• Crucial for the survival of organisms in any ecosystem

• Varies in abundance and availability across biomes

• Aquatic biomes provide habitats for a wide range of organisms

• Altitude/Elevation

• Altitude affects abiotic conditions in a biome

• Higher elevations often have cooler temperatures and reduced air pressure

• Limitations at higher elevations impact the types of organisms that can survive

These abiotic factors interact with one another and influence the distribution, adaptations, and diversity of organisms within different biomes.

Abiotic Factors in Biomes

Abiotic factors are non-living components of an ecosystem that shape its environment and impact the organisms living there. Examples of abiotic factors in different biomes:

Rainforest: Desert:

• High rainfall     -   Low rainfall

• Mild seasonal changes     -   Extreme temperature changes

• Warm temperatures     -   Sandy soil

• Latitude (near the equator)     -   Clear skies 

• Sunlight     -   Low moisture

Grasslands: Mountains:

• High winds     -   High elevation

• Near neutral pH soil     -   Snow

• Cliffs     -   Boulders

• Storms     -   Strong winds

• Soil texture     -   Low oxygen levels

Ocean: Forests:

• Higher salinity     -   Peaking sunlight

• Ocean currents     -   Rocks

• Water depth     -   Humidity 

• Pollution     -   Soil fertility

• Rocks     -   Moisture

These abiotic factors have varying levels of importance for the organisms living in each biome. For example, water availability is crucial in arid desert biomes, while sunlight availability is important for photosynthesis in rainforests. Temperature variations can significantly impact organisms in mountain ecosystems, and ocean currents play a vital role in marine ecosystems.

Abiotic factors create the environmental conditions that shape the distribution, abundance, and interactions of living organisms in different biomes. Understanding these factors is essential for studying and conserving diverse ecosystems.

Food Chains and Food Webs

In a food chain, each organism occupies a specific trophic level, which represents its feeding position in the chain. Here is an overview of trophic levels and their names:

1. Producers

• Producers, also known as autotrophs, make up the first trophic level. They are capable of producing their own food through processes like photosynthesis or chemosynthesis. Examples include plants, algae, and some types of bacteria.

2. Primary Consumers

• Primary consumers, also known as herbivores, occupy the second trophic level. They feed directly on producers. Examples include animals such as rabbits, deer, and insects that consume plants or algae.

3. Secondary Consumers

• Secondary consumers occupy the third trophic level. They are carnivores that feed on primary consumers. Examples include predators like snakes, birds of prey, and some fish that consume herbivorous animals.

4. Tertiary Consumers

• Tertiary consumers occupy the fourth trophic level. They are carnivores that feed on other carnivores or secondary consumers. Examples include apex predators like lions, sharks, and owls.

There can be additional trophic levels beyond these, depending on the complexity of the ecosystem and the number of feeding interactions. It is important to note that not all organisms fit neatly into a specific trophic level, as some may feed on multiple levels or exhibit omnivorous behaviour.

Creating a food chain or food web with multiple trophic levels:

Here's an example of a simplified food web with multiple trophic levels in a forest ecosystem:

1. Producers: 

• Trees, grasses, and other photosynthetic plants

2. Primary Consumers

• Rabbits, deer, insects

3. Secondary Consumers

• Snakes, hawks, foxes

4. Tertiary Consumers

• Coyotes, bobcats

5. Apex Predators

• Mountain lions, bears

This example demonstrates the flow of energy and nutrients from producers to primary consumers, secondary consumers, and up the trophic levels. Each organism plays a crucial role in balancing the ecosystem and maintaining energy flow.

• The 10% Rule and the Efficiency of Energy Transfer:

• The 10% rule states that only about 10% of the energy from one trophic level is transferred to the next trophic level. The majority of energy is lost in the form of heat during metabolic processes or is used for the organism's own growth and maintenance.

This rule explains why a plant-based diet tends to be more efficient in terms of energy transfer. When humans consume plants directly, they obtain energy from the producers, bypassing the inefficiency of energy transfer that occurs when energy flows through multiple trophic levels. By consuming plant-based foods, humans can obtain a higher proportion of available energy compared to consuming meat or animal products. This is because energy is lost at each step as it moves up the food chain.

In a plant-based diet, humans can gain energy more directly from the sun through plant photosynthesis, rather than relying on the energy stored in animals that have consumed plants. This approach is more efficient and sustainable, as it reduces the loss of energy through each trophic level and minimises the environmental impact associated with higher trophic levels.

By adopting a plant-based diet, humans can contribute to more efficient energy usage and contribute to a more sustainable food system.

Classification

Biological classification is hierarchical and indicates the relationship between organisms based on their physical structures and the similarities in shared molecular sequences.

Classification is the process of sorting a variety of different things into manageable groups. The study of biological classification is dilled taxonomy or systematics. Classification allows scientists to identify, study, and share information about a biological species. A universally accepted system of classification is important as it allows scientists to identify a species based on shared characteristics. One of the simplest approaches to sorting organisms into groups is called artificial classification.

Artificial classification

Artificial classification sorts organisms into groups based on similar identifiable characteristics.

• Organisms are organised into groups based on a limited number of similar characteristics such as the presence of wings or an exoskeleton.

• Figure 4.10 shows nine different animal species.

Artificial classification can be used to group these animal species by their similar characteristics.

• The dolphin, turtle, fish, platypus, crab, and duck are all aquatic organisms.

• The ladybug, hawk (bird), and duck are all capable of winged flight.

• The ladybug and the crab both have an exoskeleton.

• The hawk, ladybug, crab, turtle, platypus, and duck lay fertilised eggs.

Artificial classification is the basis for the creation of dichotomous keys.

Natural classification

A natural classification system considers the degree of evolutionary relationship among organisms. Natural classification organises species into groups of organisms that share characteristics that have been inherited from a common ancestor (called homologous characteristics).

• Homologous characteristics have an underlying similarity of structure and position regardless of function.

• The forelimbs of mammals are homologous because they are all modifications of the same structure.

• The front flipper of the whale has a different function to the front leg of a horse, but the two structures have similar positions in the body (Figure 4.13).

• The species shown in Figure 4. 13 are grouped together in a natural classification system as they have an identifiable evolutionary relationship.

Dichotomous keys

Keys are used in biology to categorise and identify organisms.

• A dichotomous key is a series of statements consisting of two choices that describe the characteristics of the unidentified organism.

• Further statements are made using a different characteristic until all organisms have been placed into a subgroup.

• Figure 4.11 shows six arthropod species.

Artificial classification is limited in the sense that characteristics are chosen on the basis of similarities in function (analogous characteristics). No consideration is given to evolutionary relationships between two species. For example, a bird and a winged insect are grouped together on the basis that both organisms have wings and use those wings to fly (Figure 4.12). However, winged insects and birds do not share a recent common ancestor and have vastly different genes.

Biodiversity and Ecosystem Dynamics: Populations at Risk Succession

Impacts of the arrival of Europeans in Australia:

• Introduced European agricultural practices to a fragile landscape

• Extensively cleared native vegetation

• Replaced deep-rooted native vegetation with crops

• Introduced hard-hoofed ungulates (e.g. cows and goats) and other herbivores (e.g. rabbits)

• Introduced new predators (e.g. cats and foxes) and persecuted native predators (e.g. dingo and thylacine)

• Dammed waterways and extracted water

• Changed fire regimes

• Increased erosion and added nutrients into the water supply

Processes that threaten ecosystems in Australia:

• Land clearance

• European red fox

• Feral cats

• Cane toads

• Invasive weeds

• Chytrid fungus

• Root-rot fungus

• Marine debris

• Long line fishing
  

Land clearance is a major issue across Australia, around the coast where most of the population lives. This has recently become an issue with NSW and QLD has removed legislation and large-scale land clearance has recommenced.

What does clearing vegetation do?

• Loss of biodiversity

• Habitat destruction eliminates living space and resources necessary for many species, leading to population decline or extinction

• Disruption of ecosystem functions

• Critical processes such as pollination, seed dispersal and nutrient recycling are interrupted and reduce the resilience of an ecosystem

• Increased edge effects

• Fragmentation of habitats creates more ‘edge’ areas which can expose species to predators and invasive species

• Reduced genetic diversity

• As populations decrease, genetic diversity also decreases. Small, isolated populations are vulnerable to inbreeding 

Low genetic diversity and extinction risk

• Limited adaptability

• Species with low genetic diversity have a reduced ability to adapt to changing environmental conditions such as climate change, new diseases or shifts in predator/prey dynamics

• Increases susceptibility to diseases

• Individuals within a population may have similar immune responses, making entire populations vulnerable to certain diseases

• Inbreeding

• Results in expression of harmful recessive traits, which can lead to reduced fitness, lower reproductive success and higher mortality rates

• Having more genetic variation is like having more tools to survive and thrive in different conditions

Genetic bottlenecks

• A sharp reduction in the size and genetic diversity of a population due to an environmental event (e.g. famines, earthquakes, floods, fires, tornadoes, disease, droughts) or human activities (e.g. hunting)

• A small population with small genetic diversity survives to pass on genes to future generations, genetic diversity remains low until genetic mutations take place (which takes a very long time)

Cheetahs

• Cheetah populations have experienced several genetic bottlenecks, mainly due to habitat loss, conflict with humans and hunting

• Around 10,000 years ago cheetahs went through a severe bottleneck (between 7 and 12 individuals remaining)

• Modern cheetahs have remarkably low genetic diversity compared to other big cats

• Conservation efforts and breeding programs carefully manage breeding pairs

How do ecosystems rebound from disturbances?

Primary succession

• Occurs on a newly formed substrate (e.g. sand dunes, moraines, lava flows)

• Generally unfavourable

• Species that disperse easily and tolerate harsh conditions act as pioneers

Secondary succession

• Occurs after catastrophic destruction of existing system (tornadoes, fire, agriculture)

Traditional practice

• Indigenous fire management has been conducted in Australia for between 40,000 and 60,000 years

• The general principles can be summarised as follows;

• Cultural knowledge and practice

• Seasonal burning

• Mosaic burning

• Biodiversity conservation

• Land and resource management

• Collaboration and knowledge

• Adaptive and responsive

• Connection to culture and country