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Theme A: Unity and Diversity Level of organization: Ecosystem
Define Biodiversity
The biological or living diversity per unit area
[The measure of the number of species and their relative abundance in an area]
Ecosystem diversity concept
The range of different habitats or ecological niches per unit area
Species diversity concept
The variety of species per unit area [includes species richness (the number of species) and species evenness (relative abundance)
Genetic diversity concept
The range of genetic material present in a gene pool or in the population of a species
What is Simpson’s reciprocal index? What is it used for?
Diversity indices, that is used to describe and compare communities, as well as assess whether the impact of human development is sustainable or not.
What are the points to consider when comparing communities?
Low diversity could indicate pollution, eutrophication or recent colonization of a site.
The species richness of an area is often indicative of general patterns of biodiversity.
Comparisons must be made between areas containing the same type of organism in the same ecosystem.
High D value= stable and ancient site; all species have similar abundance.
Low D value= disturbance; pollution, recent colonization or agriculture management, where one species dominate.
What does fossil evidence suggest about the comparison between current no.of species on earth and past levels of biodiversity?
Through fossil evidence and radiometric dating:
The sequence in which the groups of species involved.
Timing of the appearance of major phyla.
Conclusion: There are currently more species alive on earth than any other time in the past.
Case Study: North Island Giant Moa [important points]
One of the 3 extinct moa in the genus Dinornis.
A group of flightless birds.
The second tallest among the 9 moa species.
-2 meter tall from the ground upto their backs, 3 meter tall including their neck.
Showed sexual dimorphism
adult females were much larger than adult males.
Lived on New-Zealand’s north island
An example of the terrestrial megafauna.
Extinct by 1500 in New Zealand
Stable population for 40,000 years until humans came in.
Causes: Hunting; Farming; Deforestation
Through Ancient DNA studies, radiocarbon dating and stable dietary isotope analysis.
-Significant climate and environmental changes had no major impact on their population.
-Adapted by tracking their preferred habitat when their previous one is altered.
Played a major role in shaping the structure and composition of vegetation communities.
-Altered vegetation composition and structure.
-Regeneration patterns.
-Fire frequencies.
Case study: The Caribbean Monk seals [important points]
Declared extinct in 2008
The species had a widespread distribution across the Caribbean sea.
Part of a group called Pinnipedia; only one of these species to go extinct due to human causes.
Causes:
1. Hunting for fur, meat and oil from it’s blubber.
2. Captured for displays in museums and zoo’s.
3. Overfishing activities.
4. Non-aggressive and tame behavior made them easy to kill.
Their extinction had a huge effect across the Caribbean’s food web:
- Top predator, feeding on a variety of fish and vertebrates.
- Caused some species of fish to expand and therefore alter biodiversity.
Case study: Falkland Island Wolf [important notes]
The only Native land mammal of the Falkland islands.
Said to have lived in burrows.
Diet probably consisted of: Ground-nesting birds, grubs, insects and seashore scavenging.
Cause: settlers of the island, considered them as a threat to their sheep; carried out a huge-scale operation of poisoning and shooting them.
It was possible due to lack of forests and their tameness.
They weren’t particularly threatening nor was it a significant predator.
Characteristics of Tropical rain forests
- Found close to the equator.
- Warm and stable climate.
- Temperature: 20 - 35 degree Celcius.
- Hugh rainfall [2500 mm/year].
- Grow on nutrient poor soils that are thin and easily eroded.
Consequences of the characteristics
High levels of photosynthesis and high productivity.
High productivity = High amounts of biological matter and food.
Which leads to ecosystem complexity, abundant resources and niche diversity.
Abundant niches= High species richness and biodiversity.
Which makes them vulnerable to disturbance.
Nutrient poor soils= Use of fertilizers.
Use of fertilizers= negative impacts
Causes of ecosystem loss using the example of Dipterocarp Forests
Description:
-Main hardwood species in the tropical rainforests of south east Asia.
- Dominate the 3rd largest island in the world; Borneo.
- Borneo has high species diversity.
Human Threats and their consequences:
- Rainforests logged commercially for export market.
- Deforestation [2000-5, 3.9% per annum].
- Removal of trees in large numbers during logging operations.
- Conventional logging methods cause damage to the forest, which leads to an increase in light-loving and riverine species.
-Changes in the forest structure= reduced biodiversity.
- Oil palm plantations are monoculture with low species diversity; Fragment rainforests, block migration routes and remove habitats for animals.
- Insecticides and herbicides [used to control insect pests and weed]: reduce biodiversity.
- Animals that stray into the plantations— illegally killed.
- Loss of forest = reduced transpiration from leaves— affects local weather patterns= drier areas= more prone to fire.
- No forest cover= eroded soil= impossible/difficult for the original vegetation to regrow.
- The role of the rainforests as an economic resource has been reduced.
Causes of ecosystem loss using the example of The Great Barrier Reef
Description:
- The world’s largest coral reef ecosystem.
- Located in the coral sea off the northeast Australia.
- One of the richest and most complex natural ecosystems on the planet.
Human threats and their consequences:
- Fragile coral easily damaged by divers’ fines and boat anchors.
- Tourists break off bits of the coral pieces as souveniers. [though it’s illegal]
- Overfishing disrupts the balance of species int eh food chain.
Accidental damage from anchors and pollution from boat.
- Seafloor trawling— unintentional capture of the other species and destruction of the seafloor.
- Change in land use [large-scale farming, low-level subsistence agriculture] require plantations to have heavy inputs of fertilizers and pesticides: inorganic nitrogen pollution increase by 3000 %
- Algal bloom due to excessive nutrients from sewage and pollution.
- Sedimentation increased by 800% due to deforestation: available habitats damaged.
- Climate change: reduction in population numbers.
- Mass coral bleaching events caused due to increased sea temperatures due to climate change: loss in biodiversity and ecological value.
Where can the evidence for a biodiversity crisis be drawn from?
IPBES [Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services]
IUCN [International Union for Conservation of Nature’s Red List]
IPBES
Found in 2012 to strengthen the link between scientific information and policy decisions relating to conservation and sustainable use of biodiversity, long-term human well-being, and sustainable development.
To establish current levels of biodiversity and estimates of species extinction, results from reliable surveys of biodiversity in a wide range of habitats around the world are required.
Provides significant and reliable scientific guidance for policymakers.
Data obtained is sampled regularly to identify trends.
IUCN
Established in 1964
Most comprehensive and trusted sources of info on the extinction status of organisms
Each assessed species is rated on a scale indicating it’s ecological health.
Each entry to the list contains the details of the research papers used to make the assessment.
What are the causes for the exponential growth of human population
Increased access to energy
Better healthcare
More nutritious food
Clearer water
Better sanitation
Anthropogenic causes for the current biodiversity crisis
Hunting and other forms of overexploitation
Urbanization
Deforestation and clearance of land for agriculture
Pollution and spread of disease
Alien invasive species due to global transport
Describe how Hunting and other forms of overexploitation causes the current biodiversity crises
Overharvesting and hunting has caused a significant reduction in population size of many species.
Animals are hunted for food, medicine, fashion, souvenirs and to supply exotic pet trade.
Describe how Urbanization causes the current biodiversity crises
Urbanization is the increase in the proportion of people living on towns and cities.
Land is cleared to build towns and cities, which results in natural ecosystems being lost.
Describe how Deforestation and clearance of land for agriculture causes the current biodiversity crises
Deforestation is a major cause for biodiversity loss.
High demand for food has lead to clearance of more land for agriculture, the natural ecosystems are replaced with monocultures.
Mining activities such as mining Coltan to obtain Tantalum, results in habitat destruction.
Describe how Pollution and spread of disease causes the current biodiversity crises
Pollution is the addition of a substance to the environment by human activity at a rate that is greater than which can be considered harmless to the environment.
It damages habitats and kills animals and plants leading to the loss of life and reduction in population numbers of species.
Small populations are prone to disease; When there is a reduction in the population size, the gene pool is reduced therefore making the species more prone to disease and inbreeding.
Describe how Alien invasive species due to global transport causes the current biodiversity crises
Global trading involves removal of many species from their native habitats and transported huge distances to a new environment.
These alien species become invasive and affect the native species by competing with them and therefore reducing their population size.
Case study: Lion Fish
Venemous and aggressive fish
Characterized by red, white and black strips and elaborate pectoral and dorsin fins which makes them inedible to predators.
They are native to the indo-pacific ocean, but now are increasing abundantly in the carrabian and atlantic oceans.
They expanded in number due to lack of competition, predators and abundant food supply.
Case Study: Water Hyacinth
Introduced as an ornamental plant to the USA from south america.
These plants grew rapidly forming dense mats that spread across water surfaces.
Which lead to the reduction of naive algae and plankton; food for the native species.
Resulting in reduced population size of the native species.
Conservation biology
The scientific study of earth’s biodiversity with the aim of protecting habitats and ecosystems from man-made disturbances.
In situ conservation
Conservation of species in their natural habitat
Ex situ conservation
Preservation of species outside their natural habitat
What are the active requirements of nature reserves for In situ conservation
Active cleaning of overgrowth
Limiting predators
Controlling poaching
Controlling access
Reintroducing locally extinct species
Removing alien species
Receive adequate funding and resources
Protected by legislation
Policing and guarding policies
Provide vital habitat for indigenous species [Provide habitat and food for migrating species]
Biogeographic factors affects..
Species Diversity
Island Biogeography theory
Smaller islands contains fewer species than larger islands
Ideal features of nature reserves for conservation
They’re large
-Support a large range of habitats and therefore greater species diversity.
-High population numbers of each species.
-Greater productivity at each trophic level therefore, longer food chains and greater stability.
-Can maintain top carnivores and large mammals.
They have low perimeter to area ratio to reduce edge effects -Edge conditions very different to interior habitats, therefore, interior specialist species can’t survive.
- The best shape is a circle; lowest edge to areas ratio.
Have corridors to join fragments
-Gene flow between fragmented areas is maintained
-Movement of large mammals and top carnivores is maintained.
What is Rewilding
A form of environmental conservation that seeks to reinstate natural processes and where appropriate, missing species, allowing the complex interactions that exist to be reinstated
3 main principles of rewilding
Core habitat that support biodiversity are established
Connectivity: corridors of habitats connect to core areas, allowing movement of biodiversity between parts of landscape
Carnivores: Top predators needed to maintain the ecological balance of communities
Benefits of rewilding
— Increasing storage of carbon, from the atmosphere
— Helps wildlife to adapt to climate change [Connection between wildlife reserves allow animals to move and habitats to adapt to climate change; has the potential to save a significant no.of species from climate-driven decline/extinction]
— Allows reversal of biodiversity decline/ extinction.
— Supporting economic opportunities for local people [Communities grow and thrive through, nature-based enterprises, production and employment opportunities]
—Improving health and well-being
Reclaimed and restored areas provide:
-Clean water
-Healthy soils
-Flood defenses
-Food and unpolluted air
How does Ex situ conservation usually take place in zoos
Small population obtained from the wild or other zoos
Enclosures for animals are made as similar to their natural environment as possible
Breeding assisted through artificial insemination
Role of botanical gardens in ex situ conservation of plants
Living collection and banks are used to store genetic diversity
Germplasm as a method for ex situ conservation
Cells that are capable of/ are produced by cell division or fertilization [sperm, pollen, seeds]
Represents a live information source for all the genes in a species of plant which can be conserved for long periods and regenerated whenever required
Case study: Golden lion tamarin
Found in the tropical rainforests of brazil
90% of their natural habitat cut down; small fragmented areas left
Probably also carried human diseases such as yellow fever and malaria
Hunted to near extinction
Loss: affected the population of other species [population of species consumed increased, while the species that consume them decreased]
Food chains became shorter producing changes in other trophic levels as well as imbalances in the forests food web
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