Biodiversity

Question 1

What were Alexander von Humboldt’s greatest discoveries?

Answer 1

> mapping out climatic zones of the earth

> the latitudinal diversity gradient

Question 2

What is the latitudinal diversity gradient?

Answer 2

The nearer to the tropics

= the greater increase in variety of structure, grace of form, mixture of colours & species

Question 3

What are the other patterns/gradients?

Answer 3

> altitudinal gradient
= more species at lower altitudes

> depth gradient
= fewer species at greater depths

Question 4

How does area affect diversity?

Answer 4

Larger islands have more species

= positive correlation

Question 5

How can we measure diversity?

Answer 5

> alpha diversity 
> beta diversity 
> gamma diversity 
> evenness
> functional diversity 
> sampling

Question 6

What is alpha diversity?

Answer 6

Total no. of species in a habitat

=species richness

Question 7

What is beta diversity?

Answer 7

Difference of a habitat from other habitats

= Ratio between regional and local species diversity

Question 8

What is gamma diversity?

Answer 8

Total species diversity in a region

Question 9

What is evenness?

Answer 9

Relative abundance of species in a habitat

= how much 1 species dominates

Question 10

What is functional diversity?

Answer 10

What a species does

Question 11

Explain the shape of the asymptotic graph of species against time when sampling

Answer 11

Curve rises quickly as you find the common species
Discovery then slows as it gets harder to find the rarer species
When curve levels out = found all species

Question 12

What does a lower Simpson’s index indicate?

So, what is normally done to make more sense?

Answer 12

Higher diversity

Take the inverse

Question 13

What is beta diversity inversely proportional to?

What does a high beta mean?

Answer 13

Shared species

Few shared species

Question 14

What does beta diversity increase with?

Answer 14

Distance

- move farther away, beta goes up

Question 15

What is the equation for calculating beta diversity?

Answer 15

Jaccard Similarity Index:

J = C / (C+U1+U2)

C: common species
U1: species unique to habitat 1
U2: species unique to habitat 2

Question 16

What does the latitudinal gradient in beta diversity show?

Answer 16

There are fewer shared species at low latitudes

e.g. more shared in Eastern Canada + Alaska
than Florida + California

Question 17

What are the possible explanations for explaining higher diversity in the tropics?

Answer 17

> habitat heterogeneity
> environmental disturbance
> species-area affects
> primary productivity 
> temp

Question 18

What is habitat heterogeneity?

Answer 18

Different habitats support different species
- more habitats = more species

Tropics have higher heterogeneity? - hypothetical but never proven

Question 19

What is the intermediate disturbance hypothesis?

Answer 19

Too much disturbance (drought fire, flood etc) prevents species from becoming established

Too little means a few species can crowd all other species out

Question 20

What is the ideal situation in the intermediate disturbance hypothesis?

Answer 20

Disturbance is low enough to let many species get established

BUT high enough that dominants get killed off frequently - preventing them from taking over

Question 21

What are the historical effects that could lead to higher diversity in the tropics?

Answer 21

Predicted affects of climate change worst at higher latitudes

Milankovitch cycles every 26,000 years cause poles to freeze & heat up again
BUT lesser effect on tropics

Question 22

How could species-area effects cause greater diversity in the tropics?

Answer 22

Greater surface area in the tropics than at the poles

PROBLEM - Russia & Siberia should have many species

Question 23

What is the mid-domain effect?

Answer 23

If you have lots of species w/ varying latitudinal ranges & randomly arrange them, the widely-distributed species will include the tropics

PROBLEM: assumes tropics have species w/ large geographic ranges (actually have small range = high beta diversity)

Question 24

What is the relationship between primary productivity & diversity?

Answer 24

Low productivity ecosystems have few species

Some high productivity environments have lots of species, some don’t

U-shaped = diversity increases w/ productivity up to a point & then decreases

Question 25

What is the relationship between diversity & temp?

Answer 25

As temp increases, diversity increases

Question 26

Where do many groups originate?

Answer 26

Low latitudes & then spread to high latitudes

Question 27

How are evolutionary dynamics different in the tropics?

Answer 27

High speciation rate

Low extinction rate