3.2 Origins of Biodiversity Flashcards
natural selection mechanism
within a population of one species there is genetic diversity, which is called variation -> some individuals are fitter than others -> advantage -> reproduce more successfully -> offspring inherit advantagous genes -> survive -> pass genes on
define speciation
the formation of new species when populations of a species become isolated and evolve differently
geographical isolation
a physical barrier that leads to populations becoming separated, eventually leading to speciation
causes include plate activity, the formation of mountains, seas, lakes, rivers and deserts
plate tectonics
the movement of eight major and several minor internally rigid plates of the Earths lithosphere in relation to each other and to the partially mobile asthenosphere below.
list 3 physical factors that might separate populations
- mountain ranges
- bodies of water
- natural events
temporal isolation
species that live lives during different times of day, and therefore dont interbreed
behavioural isolation
courtship rituals between two species vary
constructive plate margins
plates move apart
destructive plate margins
plates move together
collision plate margins
plates collide
collision of plates can lead to:
- uplift and mountain formation → form physical barrier which isolates populations
- spread of species through the creation of land bridges → mixing of gene pools and possible hybridisation
plate activity can:
- create new islands usually through volcanic activity
→ can lead to adaptations to fill new habitats/niches - move plates through different climatic conditions→ evolutionary changes, for example the northward movement of the Australian plate -> drying much of continent -> evolution of drought-tolerant species
mass extinction definition
a period in which at least 75% of the total number of species on the Earth at the time are wiped out.
how many mass extinctions have there been
5
why is the Sixth Extinction different?
caused by a single species (humans)/biotic factors:
- climate change
- development of agriculture
- clearance of native species
- pollution
- over-exploitation
2 phases of the Sixth Extinction
1: began when the first modern humans began to disperse to different parts of the world about 100000 years ago
2: about 10000 years ago when humans turned to agriculture to grow food
(development of agriculture and clearance of native ecosystems accelerated pace of extinction)
possible causes of mass extinctions
- asteriod impact
- volcanic activity leading to climate change
- extreme temperature changes
- sea level change due to glacier formation
