Extinction

Giant Ground sloth ----------------------------> Tree Sloth (Brazil)

 The largest ground sloth was the size of an elephant.

 Their claws could reach 50cm in length;; that's the size of a human forearm.

 The Ground Sloth was nothing like any other animal to have roamed the earth, with a
tiny head, slim shoulders and massive hind quarters.

 Despite their huge claws and intimidating appearance, these sloths, like their modern day tree sloth predecessors, were herbivores.

one process of extinction that's occurring over time and space

two type of processes that happen in time and space- have some rate of extinction then you reach equilbrium over time there is a balance between extinction and speciation.

When you think of extinction think there is a rate power-relationship between speciation they are in equilibrium 

Long-­term balance between rates of speciation and extinction.

An equilibrium species richness can also be predicted for large continents based on rates of speciation and extinction among existing species

Geologic time- species that are vulnerable for the extinction process- 

1. A brief history of extinction on Earth

2. Which species are more vulnerable to extinction?

geological time- species which are reallly vulnerable extinction process Earth

Four billion species estimated to have evolved on the Earth over the last 3.5 billion years…….

…….of these, 99% are gone

99% is going to be extinct if you look at the whole geological time- extinction is a process that is inevitable - our geological time is so huge  but this has happened in the past 

-­ Mass extinctions are times when the Earth loses more than three-­ quarters of its species (not families) in a geologically short interval

-­ It has happened only five times in the past 540 million years or so

past had five number of families that have become extinct - one process of max extinction 
Five extinctions Five hungred million years ago.

Outcome : Ordovician event lost an estimated 86% of species. 
Cause:  Onset of alternating glacial and interglacial episodes, changes in atmospheric and ocean chemistry (CO2).

Outcome: Devonian event lost an estimated 75% of species.
Cause: Global cooling (followed by global warming),mayb tied 2the diversification of land plants.

Outcome: Permian event lost an estimated 96% of species.
Cause:Siberian volcanism.Global warming.Ocean acidification. Evidence for a meteor impact still debated.

Outcome: Triassic event lost an estimated 80% of species.
Cause: Elevated atmospheric CO2 levels, which increased global temperatures. Ocean acidification led to a calcification crisis in the world oceans

Outcome: Cretaceous event lost an estimated 76% of species.
Cause: 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.

The causes are the drivers that led to these outcomes. 

what is underlying causing the extinction- global climate change is the main driver of extinction

- for example  the Siberian volcanism changed a lot of the acidification in the ocean- one of the main effects in this period of time.
- climate change is really important and it is really important because we are accelerating the extinction by doing a lot of change in the climate everyday.

Scientists agree that climate change is going to be the cause of mass extinction 

Does Trump give a ****? 

• They only account for 4% of total extinctions (background rate is high)
These extinctions only caused 4% but those events those events have great effects on species extinction- produce massive diversification from our range of species- change in composition. So very important for changing diversification. 

• They disrupt overall development of diversity

• Survivors tend to be generalists and opportunists
Creating species with different characteristics that domnate the world today, problem is that you are changing your atmosphere - many species will become extinct. have about 20,000 of animals and plants which are in the red list

- common species not rare- different characteristics - recurrent selection by giving wheat characteristics of barley - large embryo - high vigour 

• 10my for recovery of biodiversity - 10 millions of years how are these species going to come back? These extinctions were very small just represent 4% but we're going to need 10 millions of years to recover.

IUCN Red List data:

• 20,210 animal & plant species are threatened with extinction

• 1 in 8 birds will be extinct

• 1 in 5 mammals will be extinct

• 1 in 3 amphibians will be extinct

While speciation will occur eventually, this is not in a time-­frame relevant to us

Problem is that you changing the atmosphere and because of that there are a lot of species which are becoming threatened at risk of extinction. '

This is why there are so many people who study amphibians because ONE IS THREE is going to be extinct. If we don't change our behaviour this is what is going to happen. 

Extinction magnitudes of IUCN-­assessed taxa in comparison to the 75% mass-­extinction benchmark. This report is core of the lecture today 

(Barnosky et al.) shows that... 

Traits promoting survival                                                    Traits promoting extinction

i) r-selected traits                                                                    K-selected traits

ii) Large populations                                                               Small populations

iii) Widespread                                                                       Rare

iv) High genetic variability                                                      Low genetic variability

v) Rapid dispersal                                                                  Slow dispersal

vi) Human commensalism                                                     Exploited by humans

Many traits that you can observe, comparing traits that promote survival and promoting extinction. 

R-species selected traits they are going to survive, and K will become extinct.
Large population they are going to survive- straightforward. 
rapid dispersal is a useful technique to stop the extinction.
human interaction will promote extinction and if you do conservation or exploitation humans will be in two parts. 

• r species (“opportunistic pioneers”) have been selected for their ability to reproduce rapidly

example in the forest show the pioneers that grow very fast they are going to survive through all of these events of extinction because they have the ability to reproduce rapidly.

• K species (“specialists”) have features that favour populations remaining close to the habitat’s carrying capacity

K species cannot survive in different capacities  going to be threatened by extinction process. this is one example of a life strategy that is promoting or helping extinction.

r-­selected species

Brown rat
c. 6 rats per pregnancy
c. 6 generations a year
going to have 2 trillion rats if you don't have mortality rates happening 

K-selected species

African elephant
1 calf per female 
every 5 years

10 years have 2 elephants. every 5 years they have one baby. 

Rats vs Elephants – potential growth of the female population over a 10 year period (no mortality)

5 years –
c.15,000 female rats,
c. 1.5 female elephants

10 years –
c.>2 trillion female rats
c. 2.4 female elephants

Doesn't take into natural measures, such as, mortality rates- likelihoods of diseases or human interaction - pest control. 

This is a wrong number because you are not considering mortality, mortality because of predators competition within themselves - the increase of rats would be smaller because of this process. just one typical example of two species. 

                                 r species                                                        K species 

Habitat             unstable, unpredictable                                    stable, predictable

Populations      fluctuate widely in nos.                               close to carrying capacity 

Body size                  small                                                               large 

Growth                       rapid                                                               slow

Time to                       short                                                               long 
mature 

A little overview that they have these characteristics to survive, have this natural theory link it with other theories to explain biodiversity.

                                               r species                                               K species 

Reproductive period               short                                                       long

Offspring                            many, small                                                 few, large 

Parental care                     little or none                                                  high 

Adult mortality                      high                                                            low

Dispersal                               high                                                            low
ability 

Offspring r focus more on reproductivity than biomass  - this is the main characteristic which is very common no matter what taxa you are looking at. 

Initial population size defines likelihood of extinction for both mammals and birds

a lot of nesting extinction rate low, just one nest- extinction rate really high (graph shows this)
- Hunter & Gibbs 2007 

size of the population is a good predictor in how vulnerable this species is to extinction- size- main driver

• Small geographic ranges (species endemic to islands)

Primack 2008

Dodo these species became extinct because they lived in a small area. 

Why are small and isolated populations so vulnerable: demographic reasons

• Unequal sex ratio

• low chance of locating a reproductive partner
- so rare it will be hard to find female or male

• low fecundity due to age, illness - fertility - fecundity 

• low cooperative interaction in food acquisition, predator detection
  need to work together 

Why are small and isolated populations so vulnerable -demographic reasons

• Unequal sex ratio

Skewed sex ratio 

Selecting hunting of males in elephant seals leads to skewed sex ratio

this is one of things that will promote extinction

Small populations = low genetic diversity 

Low genetic diversity limits the ability to respond to new conditions (disease) as this graph shows 

Billington 1991 

Low variability = Inbreeding depression

how many seeds you can produce over time- small population = produce less seeds  
reducing the number of individuals causes inbreeding 

Ipomopsis aggregata - Scarlet Gilla 

Inbreeding leads to higher offspring mortality

The relationship between dispersal ability and local extinction, corrected for national range size of the Orthoptera species of Germany.

if dispersal ability is very low local- specialists not really generalist- extinction rate high
very high ability to disperse in the landscape = low extinction rate

dispersal capability in the landscape- high - low extinction, low- high extinction

• Some species benefit from humans (commensal species derive food or other benefits from another organism without hurting or helping it)

cockroach - take food benefits from humans - this is increasing over the years- taking the benefits of living with humans -

• Many species have antagonistic relationships with humans….

shark fin soup - this is a typical antagonistic relationship 
the humans are going to increase because of other species, they are threatened by humans.

contemporary contentious example 

• Humans most likely explanation for global extinction of megafauna in Pleistocene…

megafauna - large/giant animals - little bit prehistoric 

Megafauna are really present in Africa, in South America we killed megafauna that were there but hunted by humans. Africa is one of the biggest continents where you had the biggest megafauna- typical example of the human interaction.

 summary of everything been said 

• Rarity (small range, small populations)

• large, slow-­growing & long-­lived

• large area requirements - size of area

• top of food web/conflict with humans

• Rarity (small range, small populations)

• large, slow-­growing & long-­lived

• large area requirements - size of area

• top of food web/conflict with humans

is an example of this 

• 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- Island 

Need a special area that cannot be promoted by conservation

e.g. the forest specialist ant

• Extinction is a natural process. There have been 5 mass extinctions so far, but we may be entering the 6th...

in the past five extinctions now we're in another process of extinction - SIX- we're accelerating this process 

• Rare species (small range & small populations) are more likely to go extinct. This is because small and isolated populations suffer from demographic & genetic problems.

can predict who gonna survive - factors  can predict who is going to die by the size of species

• Predisposition to extinction is also related to life strategies, habitat requirements and a species relationship with humans.

related to life - who is adapted by the key characteristics.