Lecture 26

Question 1

What is a niche?

Answer 1

the range of a species being representative in the environmental range

the species range is a subset of the environmental range

the axes represent the axes of the niche

niche is defined by different variables (e.g. temperature vs algal food size)

Question 2

2 factors that influence distribution

Answer 2

1) conditions - aspects of the environment that aren’t influenced by consumption e.g. temp or amount of light

2) resources - the aspects of the environment that become less abundant as they become consumed

Question 3

How did Hutchinson define niche?

Answer 3

• a multidimensional hyperspace, containing conditions and resources that allow the species to survive

= fundamental niche

Question 4

What is the realized niche?

Answer 4

• it is smaller than the fundamental niche due to:

competition
dispersal limitations
disturbances
stochasticity (chance events)

Question 5

environmental gradients e.g.

Answer 5

• cover
• aspect
• solar radiation
• temperature

Question 6

What are some environmental variables for terrestrial settings?

Answer 6

climate
soil type
humidity

Question 7

What are some environmental variables for freshwater settings?

Answer 7

temperature
water quality
flow magnitude and variability

Question 8

What are some environmental variables for marine settings?

Answer 8

depth
temperature
salinity
currents
dissolved oxygen

Question 9

What is competitive exclusion?

Answer 9

if 2 species compete for the same limited resource, one will dominate in the long term

Question 10

What is resource partitioning?

Answer 10

species change morphology (size and shape) to reduce competition

this is known as character displacement

it can also occur through changes in BEHAVIOUR

e.g. changing from nocturnal to diurnal

Question 11

Spatial and temporal variability allows co-existence

Answer 11

• different moisture levels across an area
• temp changes at dif times

Question 12

How can community patterns be measured in space?

Answer 12

• structure e.g. height of vegetation + density
• environmental relationships

Question 13

What are some of the objective methods used to measure community patterns?

Answer 13

• look at abundance of a species at each set of sites and then classify that vegetation on the basis of that
• looking at associations b/w different species - which ones occur most frequently together
• cluster analysis (cladogram sort of thing)
• ordination (graph) - similarity b/w animals is based on how close they are in the graph

map the distribution of species - what’s the relationship b/w community and environment?
model then map
2 steps: classify first, then predict

also possible to classify and predict in one