Community structure

Question 1

Predictability

Answer 1

When studying anything you want some control

So how predictable are communities

Question 2

Clements

Answer 2

climax community, time = stability, predictable developmental changes, disturbance leads to the same community

Question 3

Gleason

Answer 3

communities are unstable, any interactions that occur are due to proximity, chance if similar relationships develop twice, what juveniles and seeds happen to be present after a disturbance determines new community

Question 4

Are communities predictable?

Answer 4

Based on history and chance so you need to account for both

Question 5

Current and past species distributions

Answer 5

If communities are predictable then the same species should always be found together
However species go not link themselves with one another
Exp : fossil records of pollen show the movement of trees to and from communities the trees do not go in groups
Gleason is closer to being right

Question 6

Keystone species

Answer 6

An organism that has a strong influence on the structure and abundance of the organisms surrounding it
Removing the organism can cause drastic problems in the ecosystem

Question 7

When the keystone changes in abundance then

Answer 7

the entire community is affected

Question 8

disturbance

Answer 8

An event that removes biomass from a community
Exp: fires, floods, fall of a large tree
when it happens, then the community changes
The impact changes according to:

• The type of disturbance
• Its frequency
• severity

can be a part of a pattern
Exp: forest fires
The recovery of it can be predicted in this case
To study this scientists give a community a disturbance regime

Question 9

Disturbance regimes

Answer 9

Is determined by a short term analysis of any disturbances in the area and extrapolating long term data
Exp: 1% boreal forest burns every year
So every piece of boreal forest has a 1/100 chance of burning every year
So the average time between fires in one location is every 100 years

Question 10

Why are regimes important

Answer 10

allow for some disturbance
This can increase biodiversity due to empty niches
Some plants and animals are evolved to use the disturbance to their advantage
The maintain healthy communities then the regime must be maintained

Question 11

After disturbances

Answer 11

surccession

primary

secondary

Question 12

After disturbances

primary

Answer 12

removes soil, and organisms in and on the soil

Question 13

After disturbances

succession

Answer 13

the pattern of organism growth in a community after a disturbance

Question 14

After disturbances

secondary

Answer 14

removes organism but soil is intact

Question 15

The species at each stage is determined by

Answer 15

the traits, interactions and historical/environmental circumstances

Question 16

Pioneering species

Answer 16

Weeds are adapted for disturbed soil
Good dispersal species
Short lived and small species
Little competitive ability
High fecundity
Can tolerate severe abiotic conditions

Question 17

Species interactions

Answer 17

Colonization has occurred now what
The species that exist will affect what other species move in

facilitation

tolerance

inhibition

Question 18

Facilitation

Answer 18

a species make the environment more suitable for living

Question 19

Tolerance

Answer 19

existing species do not hinder other species movement into the territory

Question 20

Inhibition

Answer 20

one species inhibits the other’s growth

Question 21

Succession

Answer 21

can be predictable

Question 22

Species richness

Answer 22

count of the number of species

Question 23

Species diversity

Answer 23

species abundance as well as it’s presence

Question 24

Island biogeography

Answer 24

Island have less species than areas of similar size on the main land

The theory was that speciation takes so long so much of the species richness comes from immigration and extinction

Question 25

what happens with Immigration

Answer 25

slows as the number of species increases, because the chances are higher that anything immigrating is already there,
also competition should increase decreasing immigrates chances of establishing a population

Question 26

what happens with extinction

Answer 26

should increase with richness because of niche overlap and competition is more intense

when it increases species and competition decrease

when species increase, competition and this increase

Question 27

larger the island

Answer 27

higher the immigration

Question 28

closer the island

Answer 28

land the higher the immigration

Question 29

further away and smaller the island

Answer 29

more extinction

Question 30

Question 31

Measuring species diversity

Answer 31

Counting
But that doesn’t take into account abundance
Evenness: a similar abundance of all species present
For this equations have been made to calculate evenness, and number

Question 32

Shannon index

just need to know how to define the equation

Answer 32

Pi : proportion of individuals of species i
H = the species diversity
H = - ∑pi ln pi

Question 33

Global patterns

Answer 33

Latitudinal gradient
Not true for all but for most

Question 34

to be able to affect diversity

Answer 34

The factor must affect immigration, emigration, speciation, and extinction

Abiotic(non living): earths shape,
sunlight, temperature

Question 35

High productivity hypothesis

Answer 35

= high diversity
Increase biomass increases herbivores increases carnivores etc
However: estuaries and experiments show that high productivity does not mean high diversity

Question 36

Energy hypothesis

Answer 36

High temperatures increase productivity and the likelihood that animals can tolerate the physical conditions of the region
new and not well studied
But gastropods diversity increases with temperature

Question 37

Area and age hypothesis

Answer 37

No ice disturbance
However there was drying in the ice age so there is a possibility that the rain forest are younger than some polar habitats

Question 38

Intermediate disturbance hypothesis

Answer 38

Mid successional
With some disturbance all the time pioneering species don’t die increasing species diversity
However no study shows that disturbances happen more in the tropics

Always 3 sections
Disturbance effects the biomass and everything else

High diversity - high disturbance

Tree fall, more place for plants to grown