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Genetic adaptations to the local conditions differentiate these species. Ecosystem Diversity This speaks about the variety of habitats in a region. Example is San Francisco Bay-Delta ecosystem constituted of wetlands, estuaries, grasslands, fresh and salt water, rivers". Methods to Measure Biodiversity and Relative Strengths and Weaknesses Ecologists measure diversity in three different scales. Alpha diversity is measured by counting the number of species within the ecosystem. Beta diversity measures diversity between two ecosystems – comparing species that are unique for each ecosystem.

Gamma diversity measures overall diversity for several ecosystems within a specific region. Various methods have been created to measure biodiversity empirically. Whittaker (1972) specified three metrics to measure biodiversity that encompasses species richness. Species Richness It is simply a count of species; however, it does not take into account its abundance and their relative distributions. Against this, species diversity will count on species richness and its evenness. Simpson Index This is a good statistical method used quantify the biodiversity of a specie.

It measures number of species and abundance of each species. It also measures total numbers in each species. Species diversity is derived from the mathematical formulae that give highest values to ecosystems. It requires huge number of workers, skill and resources. Shannon-Wiener Index This method quantifies the uncertainty associated with the prediction. The index gives how the species is distributed in an ecosystem. This is the most widely used index as far as community ecology is concerned.

The average uncertainty goes up as the number of species increases and the distribution becomes even. Answer 2. Insects have their body structure made of head, thorax and abdomen. The head part consists of eyes, that could be simple or compound, and antennae to provide smell sense. The thorax is made of fused segments with a pair of legs. The two other fused segments have a pair of wings with variations as per the groups. The abdomen part contains digestion, production and excretion organs. The primary adaptation to life on land was possible through the development of internal tubes for breathing.

The internal tubes are connected to the trachea delivering air to the tissues. The tubes get open to the outer area through spiracles to allow air to enter through the trachea and tracheoles. The ends of tracheoles penetrate cells to provide oxygen and eschew carbon dioxide. Each of the three thoracic parts in all insects consists of a pair of legs and the hind legs possess a pair of wings. That is how six legs and four wings are found in most of the insects. Paleoptera is defined as most primitive winged insects.

That means all paleopterans will have a specific physical characteristics or wings as a common feature. This does not mean that it includes all winged insects; it just includes primitive ones. Paleoptera and Neoptera differ to each other in their wing articulation. The subclass Pterygota has two further divisions called the Exopterygota and the Endopterygota. Exopterygota insects have life cycles that pass through three stages – egg, nymph and adult. A larger number of insects such as Roaches and Mantids; Dragonflies and Damselflies; Crickets, Grasshoppers and Locusts; True Bugs are part of Exopterygota division.

In contrast, Endopterygota have life cycles