Extinction Flashcards
Define extinction
Then end of a species or group of taxa
what is the difference between background extinction and mass extinction
Background = a continual, natural process
Mass = an accelerated rate of extinction that sharply reduces the Earth’s biodiversity
Define extinct in the wild
When individuals of a species only exist in captivity
Define locally extinct
When a species/ taxon is no longer present in an area previously inhabited
Define ecologically extinct
Species found in low numbers in a community so that they now have little impact on the ecology of a habitat
Define extirpation
the disappearance of a particular population, but not the entire species globally
What is the average rate of background extinction
Between 2-10 million years (average = 4)
When is extinction classed as mass extinction
at times when the earth loses more than ¾ of its species in a geologically short interval
How many mass extinctions has there been?
5
Name the 5 mass extinctions
Ordovician Devonian Permian Triassic Cretaceous
Which was the most famous mass extinction and why
Cretaceous - the extinction of the dinosaurs
Which extinction was the biggest?
Permian - over 95% of marine and 50% of all families globally were extinct
What likely caused the Permian extinction?
A massive perturbation (disturbance)
Name 3 types of species more likely to go extinct
Any from: Higher tropic levels Endemic species Specialists Migratory species Poor dispersers Smaller populations Species with complex lifecycles
Why are endemic species more at risk of extinction
Because they have limited/ restrictive distributions and geographic ranges meaning they are vulnerable to disturbance of those areas
Why are smaller populations more vulnerable to extinction?
Because they have less genetic variation in gene pools Leads to inbreeding Extinction vortex (pop. gets smaller = less genetic variation = smaller population)
What is an extinction vortex
the forces affecting small populations that cause them to spiral into a vortex of increasingly smaller populations and endanger their long-term survival
Which particular type of species has the most damaging affect on an ecosystem if lost
Key stone species
Name 3 extinct species
Stellas sea cow (1768) Great Auk (1844) Tasmanian Tiger (1933) Baji river dolphin (2006) Moa (1642) Dodo (1681) Passenger pigeon (1914)
What happened to the passenger pigeon?
There was 3-5 billion in mid 1800s (abundant)
Hunted to extinction
Extinct by 1914
Why were the passenger pigeons vulnerable to extinction?
They had complex lifecycles - needed to rest and raise chicks around lots of other pigeons – when numbers began to decline, they could no longer breed properly
What 2 main reasons cause species to go extinct
Disturbances
Small populations die out
Name 5 human causes of extinction
Habitat destruction and fragmentation Climate change Pollution Over exploitation Introduced/ alien species
Which anagram can help remember the human causes of extinction?
HIPPO
Habitat destruction Introduced species Pollution Population Overexploitation
