8.2 - Biodiversity

Concept of Biodiversity

Biodiversity comprises genetic diversity, species diversity and ecosystem diversity.

Genetic diversity:
- variation of genes among individuals within a population and between populations of the same species;
- differences arise from isolation and individual adaptation to different environments;
- no two individuals of the same species are identical;
- different gene combinations produce genetic variation, for example the many cultivated rice varieties worldwide.
Species diversity:
- variation and variability of organisms on Earth;
- includes the total number of species in a community (species richness) and their distribution in a community (species evenness);
- tropical rainforests have high species diversity, with 5–10 million insect species and more than two million flowering-plant species.
Ecosystem diversity:
- variety of habitats, biotic communities and ecological processes in terrestrial, marine and other aquatic environments;
- biodiversity-rich ecosystems occur in oceans, deserts and swamps.

Phylogeny: evolutionary history of a species or a group of genetically linked organisms.
Phylogenetic classification: a system showing the evolutionary relationships and history of organisms; used in many modern classification systems.
Classification is based on homologous structures.
Homologous structures: body parts or anatomical structures shared by organisms with a common ancestor, although their functions differ.
The forelimbs of humans, cats, whales and bats share the same bone structures but differ in size, length and function, indicating a common ancestor.

A phylogenetic tree is a diagram representing hypotheses about evolutionary relationships among a group of organisms.
Its branches show how species or groups diverge from the same ancestor.
Phylogenetic sequence of land plants:
- green algae (common ancestor) → non-vascular plants such as mosses;
- seedless vascular plants such as ferns;
- seed vascular plants: gymnosperms such as conifers and angiosperms or flowering plants.
Angiosperms have seeds enclosed within fruits, which ensures species survival.

Provides sources of food, medicine and education.
Maintains the balance of nature.
Supports recreation and scientific research.
Individuals, organisations and governments share responsibility for preserving and conserving biodiversity.
In situ conservation: maintains species in their natural habitats, such as national parks and permanent forest reserves.
Ex situ conservation: conserves species outside their natural habitats, such as in zoos and botanical gardens.