populations and population growth

Question 1

survivorship curves

Answer 1

• type 1: most organisms die late in life e.g. humans
• type 2: uniform rate in decline e.g. birds
• type 3: high mortality rate in young organisms e.g. fish

Question 2

population growth

Answer 2

• exponential when environment is favourable and resources not limiting
• large animals tend to grow logistically so resources are not limiting

Question 2

autumn moth

Answer 2

• exponential growth
• large population of moths harms vegetation
• population crash the next year as food becomes limiting factor, the environment can now sustain fewer individuals

Question 3

carrying capacity

Answer 3

the maximum population of a given organism that a particular environment can sustain

Question 4

idealised s-shaped curve of population growth

Answer 4

• logistical growth, population stays at carrying capacity
• large mammals have strategies to prevent population overshoot
• e.g. when a badger population reaches a certain size, subordinate females don’t reproduce but instead support the offspring of the dominant female

Question 5

overshoot and dieback population growth

Answer 5

• rapidly expanding population temporarily overshoots carrying capacity of the environment, reducing future carrying capacity and causing population dieback to new carrying capacity

Question 6

survivorship strategies, r selected species or ‘spenders’

Answer 6

• density independent, catastrophes happen often
• variable population that never stabilises and ignores carrying capacity
• survivorship curve type 3 (lots of young, high early mortality)
• usually lax competition

Question 7

survivorship strategies, K selected species or ‘savers’

Answer 7

• more predictable
• density dependent sustainable populations
• population constant, at equilibrium near carrying capacity
• survivorship type 1 and 2

Question 8

optimum conditions for population growth, time lags e.g. Dapnia

Answer 8

• 18C = slow steady population growth at start then stable large population
• 25C, rapid population growth, then population booms and busts, stored oil droplets for food are overused

Question 9

Reindeer populations in the Arctic

Answer 9

• solitary in N. Arctic
• in groups subArctic
• introduced to 2 islands in Alaska in 1911
• St George island population maintained possibly as closer to mainland, so population was managed through culling
• boom and bust in St Paul island as carrying capacity destroyed from rapid growth