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


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.


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



- 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.


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.


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.


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

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

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

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.

Biodiversity

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