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Life Science 142 > Ecology 4 - > Flashcards

Ecology 4 - Flashcards

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Biology 101 flashcards
1
Q

Explain shortage of food and populations

A
  • Limited resources
  • Shortages of fod and shelter,increased competition between individuals and disease outbreaks, will eventually cause growth to slow down
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2
Q

Explain logistic growth

A
  • Results when the environment restricts growth
  • Usually occurs in organisms with continuous breeding
  • Produces an S-shaped or sigmoidal curve
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3
Q

Explain the four phases of logistic growth

A
  1. Lagphase - Growth is slow as the population is still small ( bottom )
  2. Exponential growth phase – Growth increases as more individuals are added
  3. Deceleration phase–Growth slows down
  4. Stable equilibrium phase–Very little growth ( top )
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4
Q

Explain carrying capacity

A
  • ” K “ of a population is the maximum number of individuals that can be supported by the environment
  • Population growth cannot increase indefinitely because resources are limited
  • When a population reaches carrying capacity, it stops growing – the death rate matches the birth rate
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5
Q

What happens at the carrying capacity

A

The population will usually fluctuate around the carrying capacity

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6
Q

Explaing logistic growth formula with carrying capacity

A
  • Calculate logistic population growth

The formula becomes:

G = rmaxN ((K-N) / K)

  • G = change in population size
  • rmax = maximum net reproduction per individual
  • N = population size
  • K = carrying capacity
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7
Q

Explain logistic growth fully

A
  • (K-N) / K represents the effect of carrying capacity on population growth
  • If N is small, the term (K-N) / K is close to one and has little effect on population growth
  • If N is approaching K, the term (K-N) / K is close to zero and has a strong effect on population growth
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8
Q

Explain population regulation and its factors

A
  • Population regulation is the control of population size
  • Population regulating factors (limiting factors) limit the size of a population
  • Prevent a population from increasing exponentially
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9
Q

What factors play a role in regulating population size

A

Both biotic and abiotic factors

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10
Q

What are the factors of population size regulation

A
  1. Density-independent factors (abiotic)
  2. Density-dependent factors (biotic)
  3. Intrinsic factors (biotic)
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11
Q

For competition to take place what ,ust there be

A
  1. Resources in limited supply
  2. Incr in density ( leading to reduction in fitness )
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12
Q

Explain density independent factors

A
  • A population regulating factor which is not influenced by the population size
  • The intensity of the effect does not increase with increased population size

Examples: severe weather conditions, fires, natural disasters

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13
Q

Explain density dependent factors

A
  • A population regulating factor which is influenced by population size
  • The percentage of the population affected does increase as the density increases

Examples: predation, competition, disease, parasites

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14
Q

Explain competition

A
  • When individuals compete for resources (e.g. food, light, space) that are in limited supply
  • As a result, some members of the population may be unable to survive, grow, or reproduce
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15
Q

Explain intraspecific competition

A

Individuals of the same species compete with each other

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16
Q

Explain interspecific competition

A

Individuals of one species compete with individuals of another species

17
Q

Explain intrinsic factors

A
  • Factors based on anatomy, physiology, behaviour) may also help to regulate population size
  • Density-independent and some density- dependent factors are extrinsic

eg ) Territoriality and Dominance hierarchies

18
Q

What are examples of intrinsic factors

A
  • Dispersal – leaving the population
  • Social behaviour – co-operation and sharing of resources
  • Physical characteristics – adaptations to the environment
19
Q

Explain strategies for survival

A
  • Evolution acts on organisms to increase their individual genetic contributions to future generations
  • To grow, survive, reproduce and thus contribute genetically to future generations, organisms must allocate their limited energy supply for maximum benefit
20
Q

Explain life history

A
  • Concerns lifelong patterns of growth and reproduction and includes particulars such as:
  1. Number of births per reproduction
  2. Age at reproduction
  3. Life span
  4. Probability of living the entire lifespan
  • Natural selection shapes the life history of a species to suit its environment
21
Q

Explain the two life history strategies

A
  1. r-selection
    - In unpredictable environments, density- independent factors keep populations in the lag or exponential phase of growth
  2. K-selection
    - Stable environments allow populations to approach the carrying capacity
22
Q

Explain r-selection fully

A
  • Organisms live in unstable, unpredictable environments
  • They are subject to density-independent factors
  • They need to reproduce quickly, before the environment changes
  • Produce many “cheap” offspring
  • r-Selected organisms are called r-strategists
23
Q

What are characteristics of r-strategiests

A
  • Low population density
  • Produce large numbers of offspring
  • Small body size
  • Early maturity
  • Short-lived
  • No parental care
  • Controlled by density-independent factors  Good dispersers and colonizers
24
Q

Explain k-selection fully

A
  • Organisms live in stable, predictable environments
  • The population is at or near the carrying capacity
  • Organisms are subject to density-dependent factors
  • Produce few “expensive” offspring
  • K-selected organisms are called K-strategists
25
Q

What are characteristics of k-strategists

A
  • High population density
  • Produce small numbers of offspring
  • Large body size
  • Late maturity
  • Long-lived
  • Significant parental care
  • Controlled by density-dependent factors
  • Specialists

Life Science 142 (16 decks)

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