Week 14

Question 1

Meaning of ecology, population ecology, community ecology and ecosystem ecology.

Answer 1

• Ecology: Study of interactions among organisms and their environment
• Population Ecology: How populations change over time
• Community Ecology: How population/species interact with each other
• Ecosystem Ecology: Study of interactions in a defined area, including living and non-living components

Question 2

{Population Ecology}

Describe characteristics of populations

Answer 2

A)Size: Number of individuals

• Birth rate: # of births/population size
• Death rate: # of deaths/ population size

B)Density: Number of individuals in a certain space
-Relative density = # x species/total

C)Dispersion: How individuals are spaced out across the range

• Uniform: Evenly spaced
• Random: Position of an individual is independent of that another individuals
• Clumped: The habitat may be patchy (all together)

Question 3

{Population Ecology}

Describe limiting factors to population growth

Answer 3

• Abiotic (non-living) and Biotic (living)
• Density-Independent: Birth and death rates don’t depend on the number of individuals in a population (e.g. fires, natural disasters, tornadoes, etc)
• Density-dependent: Birth and death rates altered due to the number of individuals in a population (competition, predation, disease, parasitism, behaviour, etc)

Question 4

{Population Ecology}

Define Carrying Capacity

Answer 4

Maximum population size of a species that can be substained in a specific environment. It is determined by density-dependent limiting factors.

Question 5

{Population Ecology}

Compare Exponential and Logistic Growth models

Answer 5

Exponential Growth: Characteristics of populations without limiting factors
-dN/dt = rN
dt = difference of time
r = rate of growth of the population

The equation represents the change in population size from one generation (time=t) to the next generation (time=t+1)

The exponential growth is not realistic, because it does not include the environmental limits (density, food abondance, etc) !!

Logistic Growth: It includes a limit to population size —> carrying capacity
-dN/dt = rN(K-N/K)
K = carrying capacity
-N(t+1) = N(t) + rN(t)(K-N(t))/K

The logistic growth model is realistic!

Question 6

{Population Ecology}

Consequences of exceeding carrying capacity

Answer 6

A)If the population overshoot the carrying capacity, the environment is damaged therefore there will be a crash and the population will die out

B)If the population respects the carrying capacity there will be low damage, resources will recover and the population will fluctuate (raise and fall repetitively)

C)If the population respects the reduced carrying capacity there will be high damage

Question 7

{Population Ecology}

Describe how natural selection and trade-offs shape life history

Answer 7

Life History = Pattern of energy investment used for survival and reproduction events typical of a species

Natural selection shapes organisms to optimize their survival and reproduction in the face of ecological challenges posed by the environment.

Trade-offs are that maximizing one life history trait will come at cost to another.

Question 8

{Population Ecology}

Determine between R-selected and K-selected strategies

Answer 8

K-Selected: Population grows slowly until carrying capacity is reached.

• Density Dependent
• Mature later
• Greater longevity
• Increased competition
• Fewer offspring
• Larger offspring
• Types I and II strategies

R-Selected: High intrinsic growth rate; reproduce early/often

• Density independent
• Mature early
• Lower longevity
• Decreased competition
• More offspring
• Smaller offspring
• Type III strategy

Question 9

{Community Ecology}

Define ecological niche and determine between fundamental and realized niche

Answer 9

Ecological niche is a position/role of an organism in the ecosystem, in relation to: habitat, activity patterns (period of time during it is active), resources and interactions.

There is two variable that determine a species’s niche: biotic factors (food, ressources, etc) or abiotic factors (pH, temperature, moisture, etc)

Fundamental niche: Conditions which a species can exist in the absence of competitors (no limiting factors) (large size)

Realized niche: Conditions under which a species is found with the interactions with other species (a lot of limiting factors) (small size)

Realized niche is always smaller than fundamental niche because there is an overlap.

⭐️Two species CANNOT occupy the same niche, because of competitive exclusion principle!