L10 - Species Interactions and Community Dynamics

Question 1

Conditions

Answer 1

physical or chemical characteristics of the environment; not consumed by the organism

Question 2

Resources

Answer 2

availability regulated by the environment; consumed by the organism,
E.g. mineral nutrients, light, water

Question 3

Liebig’s Law of the minimum

Answer 3

the limiting resource determines maximum growth
If one essential nutrient is deficient, plant growth will be poor even when other nutrients are abundant.

Question 4

What determines fundamental niche?

Answer 4

Species have an optimum and tolerance range for conditions and resource availability. The combination of these determines where a species can exist.

Question 5

Populations

Answer 5

group of individuals of the same species occupying a space at the same time (n)

Question 6

What are populations characterised by?

Answer 6

Density, age structure (distribution of individuals over age classes), birth rate and death rate.

Question 7

What does population growth (r) depend on?

Answer 7

Age distribution, survivorship and fertility per age class. Would be exponential J shaped if no limiting resources and competition (is S shaped instead).

Question 8

Carrying capacity (K)

Answer 8

refers to the number of individuals that can be supported in a given area within natural resource limits and sustainably (i.e. without degrading the natural, social, cultural and economic environment)
Not fixed for a given area

Question 9

Intraspecific competition

Answer 9

competition within a species

Question 10

interspecific competition

Answer 10

competition between species

Question 11

Competition coefficient

Answer 11

the ratio between the competitive effects of both species (1/10 = 0.1)

Question 12

Total competitive effect

Answer 12

= (competition coefficient)(total population size)

Question 13

How is growth determined without competition?

Answer 13

By the fraction of the carrying capacity that is used by the population

Question 14

Dominant competition

Answer 14

if a species can deplete the resource beyond K of the other species, without surpassing its own K

Question 15

Multiple outcomes

Answer 15

if each species can reduce the resource beyond the other species K, without affecting its own growth

Question 16

Coexistence

Answer 16

if neither species can exclude the other by reducing the resource beyond K

Question 17

Gause’s law

Answer 17

species with identical ecological requirements cannot coexist in the same environment

Question 18

Competitive exclusion rarely occurs in nature because?

Answer 18

• Variability in resource availability
• Competition for multiple resources at the same time
• Diffuse competition (multiple species)
• Resource partitioning and adaptation - niche differentiation

Question 19

Diffuse competition

Answer 19

the total (weak) competitive effects of several interspecific competitors

Question 20

Niche differentiation

Answer 20

process by which competing species or individuals adjust their resource use or behaviour to minimise direct competition

Question 21

How do species change in response to competition?

Answer 21

Change behaviour or morphological characteristics (e.g. plants can change height, stem diameter etc)

Question 22

Why do populations fluctuate around K?

Answer 22

Time lags

Question 23

Exploitative (or scramble) competition

Answer 23

organisms only react to the resource, not each other. Shared resources are overused and depleted due (tragedy of the commons)

Question 24

Contest (or interreference) competition

Answer 24

organisms actively compete with each other over the resource. There are winners and losers.

Question 25

What is the most probable shaped curve for population growth?

Answer 25

S curve, this reflects how growth is not exponential due to limiting factors. Instead it levels off at carrying capacity

Question 26

What causes niche differentiation?

Answer 26

Niche shifts = determined by the replacement of niche space between species (i.e. change location)
Niche contraction/expansion = species reduces/increased its niche breadth (i.e. behaviour)