Biodiversity and how we assess it?
BIODIVERSITY at its most basic level includes the full range of species on the planet from the simplest structures that contain DNA, the viruses through to organisms with possess nucleuses, it includes single-celled organisms through to multi-cellular organisms which include plants, animals and fungi. This can be considered SPECIES DIVERSITY.
At a different level, biodiversity would include the genetic variation within a single population or between several populations, the genetic variation within a variety or subspecies or species. This can be considered GENETIC DIVERSITY.
At its widest level it can include variations in the biological communities in which species live, the ecosystems in which the communities occur in and the interactions among these levels. This can be considered COMMUNITY-LEVEL DIVERSITY.
GENETIC DIVERSITY is needed by any species in order to maintain reproductive vitality, resistance to disease, and the ability to adapt to changing conditions. Genetic diversity within domestic plants and animals is of particular value in the breeding programme necessary to maintain them.
SPECIES DIVERSITY represents the range of evolutionary and ecological adaptations of species. The variety of species can be considered a resource and maintaining such variety gives the option of it being used as an alternative. For example the diversity of tropical rain forest species is particularly important in finding new pharmaceutical products.
COMMUNITY-LEVEL DIVERSITY represents how species coexist in specific habitats and the relationships between species in ecosystems. The maintenance of proper ecosystem functionality is one of the main tasks that has to be undertaken by Nature Conservation Agencies.
Species are generally defined from a morphologically, physiologically or biochemically distinct (taxonomists use this)and are a group of individuals that can potentially breed among themselves (ecologist use this)
Nomenclature of Species
Hierarchical organisation (Kingdom, Phylum, Class, Order, Family, Genus, Species)
PROBLEMS WITH THE SPECIES CONCEPT
Species versus varieties (e.g. dogs)
Identification (species-rich communities)
ORIGIN OF SPECIES
Biological organisms evolved 3.5 billion years ago
Conceptualization of the species concept:- Darwin and Wallace
Based on more offspring produced than survive
Differences in genetic material will enable some individuals to grow, survive and reproduce better than other individuals.
When a population is sufficiently changed genetically than it can no longer interbreed with the original species call it PHYLETIC EVOLUTION.
SPECIATION is particularly rapid on islands Galapagos (Darwin’s finches) and Hawaii (Honey creepers) and is termed ADAPTIVE RADIATION
TWO TYPES OF SPECIATION
Allopatric speciation created through geographical separation
Sympatric speciation occurs without geographical separation
RATES OF SPECIATION
Generally a slow process
Fast speciation achieved through unequal division of chromosomes which arise to polyploids (plants and even animals e.g. Gila monster)
Speciation rates currently much slower than extinction rates.
(National parks generally too small to support speciation process)
Important concept is the population defined as a group of individuals that mate with one another and produce offspring, a species may include one or more populations.
Individuals within a population are usually genetically different from one another and this is reflected in their genes.
Genes are units of a chromosome that code for a specific protein.
Alleles are alternative forms of genes coding for the same trait.
GENETIC VARIATION is achieved via recombinations of genes
GENE POOL is the total array of genes and alleles in a population
GENOTYPE combination of alleles possessed within an individual
PHENOTYPE morphological, physiological, anatomical and biochemical characterization of the individuals
GENETIC VARIABILITY IN A POPULATION
Determined by the number of genes that have more than one allele (= polymorphic genes) and the number of alleles for each polymorphic gene
For a population to be heterozygous for a gene it must receive two different alleles of the gene from their two parents
Heterozygous individuals tend to grow , survive and reproduce more successfully (=fitter) and is referred to as HYBRID VIGOR
ARTIFICIAL SELECTION is often the reverse of hybrid vigor.
COMMUNITIES AND ECOSYSTEMS
Species interactions within biological communities come about through processes such as
Species occupy distinct trophic or feeding levels within communities and reflect their way in which they obtain energy. Individual species often have specific feeding relationships with other species that can be represented as a food chain or food web.
Certain keystone species appear to be important in determining the ability of other species to persist in a community. These keystone species are often top carnivores but can be other species (including a fruiting tree species for a suite of frugivores). The loss of a keystone species from a community can result in a cascade of extinctions of other species.
LEOPARD or CROWNED EAGLE (REDUCED)
BIRDS (REDUCED DUE TO PREDATION)
FOREST TREES (REDUCED POLINATION/SEED DISPERSAL PROCESSES UPSET)
Certain keystone resources, such as water holes and salt licks may occupy small fractions of a habitat, but may be crucial to the persistence of many species in an area.
MEASURING BIOLOGICAL DIVERSITY
Mathematical indices of biological diversity have been developed to examine and compare patterns of species distribution at local and regional levels. Such mathematical indices are chiefly useful for examining particular groups of species rather than the full range of species and interactions founds in nature.
Many of these measures examine the evenness of species occurrence in relation to the number of species. Differing techniques have different biases with some being strongly affected by sampling size and others by species rarity.
ALPHA DIVERSITY: The number of species in a single community
BETA DIVERSITY: degree to which species composition changes along environmental gradients and the effects looks at species turnover.
GAMMA DIVERSITY: applies to larger geographical scales and looks at the rate at which additional species are encountered as geographical replacements within a habitat type occur in different localities.