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Biodiversity
Definition:
Biodiversity or biological diversity simply means the variety of life
The more formal definition is “the the variability among living organisms from all sources including inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and ecosystems.”
Three Elements of Biodiversity
Biodiversity
Genetic Diversity Organismal Diversity Ecological Diversity
Organismal Diversity
The elements of organismal diversity are based in human constructs used to classify organisms based on their evolutionary traits and features.
Kingdom
Phyla
Family
Genera
Species
Subspecies
Populations
Individuals
Genetic Diversity
Genetic diversity revolves around the components of the genetic material that makes up organisms and the variations in the genetic construct between individuals of a certain population and between populations .
Populations
Individuals
Chromosomes
Genes
Nucleotides
Ecological Diversity
The elements show the different and varying scales of ecological differences.
Biomes
Bioregions
Landscapes
Ecosystems
Habitats
Niches
Populations
There have many studies regarding how to measure biodiversity in nature. But even today, no sufficient and accurate result has been found.
There are two elements of “measuring biodiversity.”
1. The number of entities
2. Degree of difference between those entities
Measuring Biodiversity
Methods for Measuring Biodiversity
Because of the lack of a proper consensus regarding the definition
of biodiversity, there is no concise way of measuring biodiversity.
Currently, there are two methods that scientists resort to, to measure
biodiversity.
1. Genetic Coding – catalogue variations in the genes of different
species to study their differences.
2. Counting of species present in a certain area – the global standard
for biodiversity.
Studying Past Biodiversity
Studying Past Biodiversity
There are two ways how scientists study past biodiversity.
1. Molecular Evidence
2. Fossil Record
1. Molecular Evidence
- The comparison of molecular data of different organisms that enables the generation of evolution trees.
Studying Past Biodiversity
2. Fossil Record
Fossils – remains left behind by past organisms
Disadvantages:
- The number of species that left behind fossils are small
compared to the total number of species who dwelt on Earth.
- Only a tiny percentage of remains of a complete fossil have
been recovered so there is none or rarely a complete fossil set of a
certain species.
- Fossils recorded are more inclined to the more abundant,
prevalent, and longer lived species.
History of Biodiversity
1. All species came from a single ancestor and its
evolution was a slow process.
2. The arrival of multicellular organisms produce a great
effect in the diversification of organisms.
3. The growth of varying biodiversity came from the
developments or mutation of certain genes which gave a
significant change to organisms.
4. A massive explosion of varying organisms came which
resulted in many species diversifying.
Process of Biodiversity
Biodiversity is a process that involves three steps
1. Diversification – a period on increase in the number of
species
2. Stabilization – a period of stasis in the number of
species
3. Extinction – a period decrease in the number of
species
These pattern produces an S-shaped graph
involving a small increase, a rapid increase, then an
approach to an asymptote.
Process of Biodiversity
Another important factor in biodiversity is the number of
families present in any given area.
The general pattern is that throughout all the ages the number
of families present increases and when plotted yields an
exponential graph that approaches an asymptote.
There is no general pattern for biodiversity and no general explanation but rather many internal and external mechanisms which drive it.
1. In any given era, there is a dominating species which is more diverse than the other species.
2. The number of species present result from the relationship of the rates of speciation (adding species) and rates of extinction.
3. Extinctions are a general part of biodiversity. Mass extinctions or massive phenomena that kills many species changes the biodiversity and the emerging biodiversity will be different from the previous biodiversity.
Due to the fact the biodiversity is measured by counting the number of species present in a certain area, there are five main methods used by scientists to measure biodiversity.
1. Estimation of the overall numbers of species based on the opinions of experts.
2. Patterns of species description
3. Proportion of undescribed species
4. Well-studied areas
5. Well-studied groups
** These are all just assumptions so an accurate answer is impossible.**
Quantifying Biodiversity
“Biodiversity is not distributed evenly across the Earth. Rather, species numbers form a richly textured surface of highs and lows, and species composition (the particular set of species) changes in spatially complex ways. (Biodiversity)”
- Species diversity depends on spatial scales.
1. Species – Area relationships
2. Local – Regional Area Relationships
Quantifying Biodiversity
Quantifying Biodiversity
- As the area increases, the species number also increases. The
relationship for this is:
S = cAZ
Log S = Log c + Z Log A
where S is the number of species, A is the area, and Z and c
are constants and known as the Arrenhius relationship.
Quantifying Biodiversity
There are 4 reasons why such a relationship exists.
1. More species are documented from larger areas because typically more individuals live there.
2. Larger areas have more diverse habitats thus allowing more varied species to exist.
3. The number of species in an area forms a balance between those species that colonized the area and those that have gone extinct.
Quantifying Biodiversity
4. The larger the area, the higher the potential geographic range of the species existing there which means that if a certain species has a high rate of speciating due to geographic boundaries they also tend to have lower extinction rates due to their numbers which helps the species thrive.
- Although this relationship covers most aspects it doesn’t mean it’s always true if other factors are considered.
Quantifying Biodiversity
The species richness of a local area is not independent
of the region where it can be found. There are 2
possible relationships.
1. “Local richness may be directly proportional to but
less than, regional richness.”
2. “As regional richness increases, local richness might
attain a ceiling above which it does not rise despite
continued increases in regional richness.”
- The majority of areas exhibit the first
relationship.
Categorization of Areas
There are many ways by which areas of the world are
categorized based on their biodiversity.
1.Oceans and Lands
Categorization of Lands
-Eight Biogeographic Regions
» Fourteen Habitats or Biomes
» 867 Ecoregions
Categorization of Oceans
- Four Major Biomes
Hotspots
There are 25 certain areas that contain a disproportionate amount of species compared to other areas. These areas having mega-diversity are called hotspots. Some countries having such diversity are:
Hotspots
1. Brazil 2. Indonesia 3. Colombia 4. Mexico 5. Australia 6. Madagascar
7. China
8. Philippines
9. India
10. Peru
11. Papua New Guinea
12. Ecuador
13. USA
14. Venezuela
15. Malaysia
16. South Africa
17. Democratic Republic of Congo
Endemism
A species is endemic to a certain area if it exists nowhere else in the planet. There are two types of endemism.
1. Neoendemics – species which evolved newly
2. Palaeoendemics – evolutionary relicts
Factors that affect endemism:
1. Area – as area increases, the number of endemic species also increases
2. Latitude – Endemism increases towards the equator
3. Species Richness – Species number and endemism often have opposite values.
Endemism
Reasons for Endemism:
1. Unusual Environment Conditions - local species
evolve more differently to survive their habitats
2. Isolation - the separation of a certain species due to
barriers may cause them to evolve differently
3. Historical - varying environmental conditions can
limit certain species to a specific area
Biodiversity Gradients
Certain factors that affect biodiversity:1. Latitude2. Altitude3. Depth4. Shapes of Landmass
Latitude:1. Biodiversity increases from the polar areas to the
equator.2. The peak of biodiversity is in the 20-30°N.3. The gradient increases rapidly from the north to the
equator then declines slowly to the south.
In the oceans, the pattern increases from the north, then a sudden increase in the temperate zone after which the pattern return to normal.
Reasons for latitude gradients:
1. Area effects – the tropics have a large surface area thus increased rates of speciation
2. The availability of energy – there are more food available in the tropics
3. Time – the equator is less likely to be affected by large scale phenomena like ice age giving the organisms more time to evolve.
Biodiversity Gradients
Altitude
The Earth is three dimensional so altitude is a key player in biodiversity. Temperature change due to altitude change also affects biodiversity.
As elevation increases, biodiversity decreases:
Two graphs:
1. Simple Linear Decline Graph
2. Hump Shaped Graph - an increase from low to mid height followed by a decrease from mid to high height.
Altitude
Factors of Biodiversity
1. Area
2. Energy Availability
3. Isolation
4. Zonation
Depth
- Depth plays a huge part in the biodiversity of marine systems.- As depth increases, temperature decrease, pressure increases, and light and nutrients decline.Two possible graphs:1. Simple Linear Decline Graph2. Hump – Shaped Graph – the majority of organisms in the
oceans follow this pattern
Depth
Factors of Biodiversity:
1. Area
2. Energy Availability
3. Isolation
4. Zonation
5. Sediment Characteristics
Shapes of Land Masses
The shapes of land mass also affects biodiversity. An example of this is the shape of peninsulas and bays.
Species richness declines towards the tip of the peninsulas (the peninsula effect).
Marine species richness in bays “declines across bays with distance from the open sea (the bay effect).
Importance of Biodiversity
I. Direct-Use Values
II. Indirect-Use Values
III. Non-Use Values
Direct-Use Values
Direct-Use Values
Food
Food
Medicine
Medicine
Biological Control
Biological Control
Industrial Materials
Industrial Materials
Recreational Harvesting
Recreational Harvesting
Ecotourism
Ecotourism
Indirect-Use Values
Indirect-Use Values
Indirect-Use Values
Indirect-Use Values
Non-Use Values
Non-Use Values
Non-Use Values
Non-Use Values
Human Impacts on Biodiversity
Extinctions of Species
Extinctions of Species
Overexploitation
Overexploitation
Habitat Loss and Degradation
Habitat Loss and Degradation
Habitat Loss and Degradation
Habitat Loss and Degradation
Introduced Species
Introduced Species
Extinction Cascades
Extinction Cascades
Size and Growth of Human Population
Size and Growth of Human Population
Maintaining Biodiversity
Convention on Biological Diversity
Convention on Biological Diversity
Convention on Biological Diversity
Convention on Biological Diversity
Convention on Biological Diversity
Convention on Biological Diversity
Convention on Biological Diversity
Convention on Biological Diversity
Summary
Biodiversity has played a fundamental part in the history of
our world. It plays a key role in the sustenance of every life on
Earth. But because of human activities, biodiversity has come
under fire, and its collapse will also lead to our demise. Such
is the importance of biodiversity and the role that humans
have for protecting it. Human beings with their technology
should strive to protect biodiversity because it is not just the
key to their survival but also for their future
Reference
Gaston, Kevin, and John Spicer. Biodiversity:
An Introduction. 2nd ed. Oxford: Blackwell
Publishing, 2004.