Week 24 Flashcards
(42 cards)
What are characteristics of the giant ground sloth?
- Holocene Era (10,000yrs ago)
- Size of an elephant
- Claws reach 50cm long
- Tiny head, slim shoulders, massive hind quarters
- Herbivores
How can speciation and extinction rate be predicted for large continents?
An equilibrium species richness can also be predicted for large continents based on rates of speciation and extinction among existing species
What are mass extinctions?
Times when the Earth loses more than three-quarters of its species in a geologically short interval
(Happened only 5 times in the past 540million years)
What was the main cause of Ordovician extinction event?
Ordovician event lost an estimated 86% of species.
Onset of alternating glacial and interglacial episodes, changes in atmospheric and ocean chemistry (CO2).
What was the main cause of Devonian extinction event?
Devonian event lost an estimated 75% of species.
Global cooling (followed by global warming), possibly tied to the diversification of land plants.
What was the main cause of Permian extinction event?
Permian event lost an estimated 96% of species.
Siberian volcanism. Global warming. Ocean acidification. Evidence for a meteor impact still debated.
What was the main cause of Triassic extinction event?
Triassic event lost an estimated 80% of species.
Elevated atmospheric CO2 levels, which increased global temperatures. Ocean acidification led to a calcification crisis in the world oceans.
What was the main cause of Cretaceous extinction event?
Cretaceous event lost an estimated 76% of species.
A meteor impact in the Yucatán is thought to have led to a global cataclysm and caused rapid cooling. Preceding the impact, biota may have been declining anyway due to climate change.
What percentage of total extinctions does mass extinction account for?
4%
However, they disrupt overall development of diversity and it takes 10my for recovery of biodiversity
What do survivors of mass extinctions tend to be?
Generalists and opportunists
Why may some question if the Earth’s sixth mass extinction already arrived?
IUCN Red List data:
27,000 animal & plant species are threatened with extinction
14% birds
25% mammals
40% amphibians
What traits promote survival compared to traits that increase vulnerability to extinction?
Survival: r-selected traits such as:
- Large populations
- Widespread
- High genetic variability
- Rapid dispersal
- Human commensalism
Vulnerability: k-selected trains such as:
- Small populations
- Rare
- Low genetic variability
- Slow dispersal
- Exploited by humans
Example of r-species (opportunistic pioneers) and k-species (specialists) in terms of extinction?
r-species have been selected for their rapid ability to reproduce such as the brown rat
k-species have features that favour populations remaining close to the habitats carrying capacity such as African Elephant
What are features of r-species habitat, population, body size, growth and mature time?
habitat = unstable, unpredictable
population = fluctuate widely
body size = small
growth = rapid
mature time = short
What are features of k-species habitat, population, body size, growth and mature time?
habitat = stable, predictable
population = close to carrying capacity
body size = large
growth = slow
mature time = long
True or false: initial population size defines likelihood of extinction for both mammals and birds?
True!
Why are small and isolated populations so vulnerable to extinction?
Demographic reasons:
- unequal sex ratio
- low chance of locating reproductive partner
- low fecundity due to age, illness
- low cooperative interaction in food acquisition, predator detection
Genetic reasons:
- low genetic diversity
- inbreeding depression
Low Dispersal ability
How do relationships with humans either benefit or disadvantage organisms in terms of extinction?
Benefit:
- Commensal species derive food / other benefits from another organism without hunting
Disadvantage:
- Antagonistic relationships with humans
- Most likely explanation for global extinction of megafauna in Pleistocene
What are some predispositions organisms may have to extinction?
- Rarity (small range, small populations)
- Large, slow-growing and long-lived
- Large area requirements
- Top of food web/conflict with humans
What are predispositions of the Eurasian Wolf to extinction?
Rarity (small range, small populations)
large, slow-growing & long-lived
large area requirements
top of food web/conflict with humans
specialised needs
adapted to core habitats
Poor dispersal/insular
The extinction vortex explains factors which may lead to extinction. What are directional factors?
Habitat loss, pollution, over exploitation, exotic species
Leading to small, fragmented, isolated populations
The extinction vortex explains factors which may lead to extinction. What are genetic problems?
Due to small, fragmented, isolated populations as a result of directional factors. This leads to genetic problems which causes inbreeding and loss of genetic diversity
This therefore causes reduced adaptability, survival and reproduction.
Further reducing the species
The extinction vortex explains factors which may lead to extinction. What are stochastic factors?
Demographic stochasticity, environmental variation and catastrophes further reduce species populations (causing small, fragmented, isolated populations) in already reduced species due to directional factors and genetic problems.
Why do we monitor biodiversity conservation?
Understanding baseline patterns (e.g. migration, phenology)
Changes over time in response to stressors (e.g., climate change, land-use change)
Responses to specific interventions (e.g. wildlife management)
Recovery of a species (e.g., species reintroduction)
Biodiversity net gain – ensuring development (over)compensates
