B. CHANGES IN POPULATION SIZE

1. 1. Population growth models B. CHANGES IN POPULATION SIZE

2. a. geometricgrowth for populations with fixed breeding times eg. one breeding cycle per year All of the penguins come ashore at the same time to breed. As some babies die, the population falls again until next breeding season

3. b. exponential growth for populations that are constantly growing eg. Yeast They do not have a breeding season they just divide when conditions are right. However, this can’t go on for ever and so we get the next slide.

4. c. logisticgrowth rate growth that levels off as the population grows towards its carrying capacity carrying capacity – the maximum number of organisms that can be sustained by the available resources over a period of time

5. carrying capacity exceedingphase pop size stationaryphase log phase lag phase time

6. lag phase – slow growth at start as get established logphase – rapid growth when population is settled in new area stationary phase – long term pattern fluctuates, but always below carrying capacity exceeding phase – pass carrying capacity, damage environment and so pop is reduced

7. 2. affecting population change births, deaths, emigration &immigration 3. Types of populations a. open population – all 4 factors affect population b. closed population – no emigration or immigration to change the population

8. 4. percentage population change % population change = [(births + immigration) – (deaths + emigration)] x 100 initial population size pg 670 # 7 a and #5 a,b,c

9. Gulls & Terns pg 6