Mechanisms of Evolution and Speciation
The cumulative change in allele frequencies in a population over generations.
Evolution
This type of reproductive barrier prevents fertilisation from occurring between populations, often through differences in mating behaviour, timing, or habitat location.
Pre-zygotic Isolation
Automatic movement of an animal toward or away from a stimulus.
Taxis
Plants that flower only when nights are shorter than a specific length.
Long-day plants or Short-night plants
Hierarchical groups where rank determines access to resources, mates, and breeding opportunities.
Dominance Hierarchies
Random changes in DNA that introduce new genetic variation in a population.
Mutations
This post-zygotic reproductive barrier occurs when the offspring of two different species are viable but cannot produce their own fertile gametes.
Hybrid Sterility
Internal physiological cycles that persist without external cues but can be entrained by them.
Endogenous Rhythm
The environmental cue plants measure to determine the correct flowering time.
Photoperiod
Interaction in which one organism benefits while the other is unaffected, such as epiphytes growing on trees.
Commensalism
Random change in allele frequencies in small populations due to chance events.
Genetic Drift
Mating occurs, but zygotes fail to develop or embryos die early.
Hybrid Inviability
A social system where subordinate animals help rear the offspring of dominant individuals.
Cooperative Breeding
This plant response involves growth or movement toward a directional stimulus, such as light or gravity.
Tropism
Competition within a species that can lead to reduced survival or reproductive success for some individuals.
Intraspecific Competition
This process occurs when a single ancestral species rapidly evolves into multiple species, each adapted to exploit different ecological niches.
Adaptive Radiation
This evolutionary process favours traits that increase an individual’s chances of mating, either through attracting mates or outcompeting rivals.
Sexual Selection
This term refers to the behavioural and physiological tactics used by individuals to maximise reproductive success, such as monogamy, polygyny, or polyandry.
Mating Systems
The cellular pigment that switches forms under red and far-red light, allowing plants to track night length.
Phytochrome
Social systems in which multiple individuals cooperate to rear offspring, forage, or defend territory, without strict hierarchy.
Cooperative Social Groups
This type of evolution occurs when two or more species influence the evolution of one another.
Co-evolution
This term describes differences in appearance or behaviour between males and females of the same species.
Sexual Dimorphism
These groups form temporarily or loosely, with minimal hierarchy or defined roles, often assembling for foraging or protection rather than cooperative breeding.
Unstructured Social Groups
When plants drop their leaves during unfavourable conditions to preserve energy
Senescence
A type of mating system in which males gather in a specific area and display competitively to attract females, who visit the site solely to choose a mate.
Lek