A3.1, A3.2, A4.1, A4.2

Biological Species Concept (BSC)

A species is a group of organisms that can interbreed and produce viable, fertile offspring.

Reproductive Isolation Mechanisms

Barriers that prevent different species from interbreeding.

Prezygotic Barriers

Reproductive barriers that occur before fertilization.

Postzygotic Barriers

Reproductive barriers that occur after fertilization.

Hybrid Inviability

Offspring fail to develop or survive.

Allopatric Speciation

The formation of new species due to a geographical barrier separating populations.

Sympatric Speciation

The formation of new species without geographical isolation, often due to genetic differences.

Clade

A group of organisms that includes a common ancestor and all its descendants.

Cladogram

A branching diagram showing evolutionary relationships.

Natural Selection

The process where favorable traits increase in a population.

Homologous Structures

Similar structures due to shared ancestry.

Analogous Structures

Structures with similar functions but different evolutionary origins.

Adaptive Radiation

Rapid evolution of diverse species from a common ancestor.

In situ conservation

Protecting species in their natural habitat.

Ex situ conservation

Protecting species outside their natural habitat.

Anthropogenic Threats

Human-induced factors threatening species: habitat destruction, invasive species, pollution, global climate change

Evidence for Evolution

Includes fossil record, comparative anatomy, embryology, molecular biology, and biogeography.

Pentadactyl Limb

A limb structure found in various vertebrates suggesting a common ancestor.

Hybridization

Interbreeding of two species that can lead to new species formation.

Adaptive Radiation Example

Darwin’s finches developing different beak shapes to exploit food sources.

Describe the impact of adaptive radiation and hybridization on biodiversity.

adaptive radiation as the process by which members of a species diverge rapidly to occupy available niches, hybridization can increase diversity BECAUSE it can lead to the formation of a new species (if fertile)

Discuss the current biodiversity crisis.

biodiversity includes species, genetic and ecosystem diversity, other causes of the current biological crisis e.g. overhunting, selection of evolutionarily distinct and globally endangered species for conservation prioritisation in the EDGE of Existence programme

sympatric reproductive isolation example

temporal: different breeding times, behavioral: different mating rituals

polyploidy

whole-genome duplication, chromosomes duplicated but cell doesn’t divide resulting in increased chromosome number.

allotetraploid

four sets of chromosomes from two different species, can only breed with each other

convergent evolution

explanation of analogous structures, where unrelated species evolve similar traits due to similar environmental pressures.

differential selection

traits of populations gradually become more different, causes: climate, predation, competition

caribbean monk seal extinction

hunted, overfishing

giant moa extinction

resulted from hunting and habitat loss.

mixed dipterocarp forest of southeast asia

logging, land conversion, global warming

loss of the aral sea

water management, two feed rivers diverted

EDGE of existence

evolutionarily distinct: few/no close relatives, globally endangered: likely to become extinct, higher sore = more prioritized