Reproductive Strategies
The strategy an organism uses to reproduce has profound consequences for genetic variation. This section explores the trade-offs between asexual efficiency and sexual diversity.
Adaptations: The Products of Evolution
Genetic variation provides the raw material for adaptations—heritable traits that enhance survival and reproduction. Explore the types of adaptations with specific Australian examples.
Structural
Physical features of an organism’s body that help it survive.
Physiological
Internal processes and functions that help an organism survive.
Behavioural
Inherited actions an organism performs to increase survival.
Patterns of Natural Selection
Natural selection is the non-random process where traits become more or less common based on survival and reproduction. It can alter the distribution of traits in three main ways.
Other Mechanisms of Evolution
While natural selection drives adaptation, other random mechanisms can also change allele frequencies in a population’s gene pool, especially in small populations.
Genetic Drift
Random fluctuations in allele frequencies due to chance events. It is non-adaptive and has the strongest effect in small populations.
Bottleneck Effect
A sharp reduction in population size due to a random event (e.g., fire, flood) leaves a small, unrepresentative sample of the original gene pool.
Founder Effect
A new population is established by a few individuals, whose gene pool differs by chance from the source population.
Gene Flow
The transfer of alleles between populations through the migration of fertile individuals or their gametes.
Effect on Diversity
Can introduce new alleles to a population, increasing its genetic diversity. However, high rates of gene flow can also reduce the genetic differences between populations, counteracting local adaptation.
Ecosystem Dynamics & Perspectives
Species do not exist in isolation. This section explores the complex web of interactions that structure entire communities, and incorporates the deep ecological knowledge of Aboriginal and Torres Strait Islander peoples.
Keystone Species & Predators
Some species have a disproportionately large effect on their ecosystem. Their removal can cause a “trophic cascade,” leading to dramatic changes throughout the food web.
Example: The Dingo
As an apex predator, the dingo controls herbivore populations, preventing overgrazing and maintaining habitat for smaller native animals.
Example: The Southern Cassowary
As a “gardener” of rainforests, it is one of the only species capable of dispersing the large seeds of many rainforest trees, defining the forest structure.
Aboriginal & Torres Strait Islander Knowledge
Australia’s First Peoples have developed deep, holistic knowledge systems based on managing ‘Country’ for millennia.
Example: ‘Fire-stick Farming’
Controlled burns are used to promote the growth of food plants, clear undergrowth, and prevent large-scale bushfires, showing a deep understanding of species’ fire adaptations.
Example: Ecological Indicators
Using events like a plant flowering to signal the time to hunt a specific animal reflects a multi-generational understanding of species interdependencies.
