Question

1. Describe and state the assumptions and disadvantages of the mark-recapture technique used to quantify population size and density.

2. What are the causes of habitat fragmentation?

3. What factors impact the diversity and density of life-forms in fragmented habit patches?

4. Define each of the 4 different types of meta-populations.

5. Shooting the grey wolves was advocated in the 1930s as a way of increasing the numbers of Dall mountain sheeps in Denali National Park, Alaska. Explain the ecological data that lead to stopping the indiscriminate killing of the grey wolves in the 1950s.

6. In the construction of life tables, vital statistics of a population of life-forms is studied. What art the vital statistics analyzed in order to determine the health status of living populations of animals in nature?

7. Environmentally our earth has changed, is changing and not necessarily for the better. What anthropogenic activities have been involved in bring about global change?

Answer 1

1) Mark recapture technique - This is a study that is used to estimate the population size of a species in a particular habitat. The assumptions of the technique are:

• There must be no emigration or immigration within the populations.
• The organsims that were initally marked should be mixed perfectly with the rest of the existing population.
• The life span must not cross the sampling time
• No harming of organisms done and hence equal number of organisms must be marked.

The disadvantages are :

• Time consuming process and is costly
• To reduce behavioural disturbances, the marking must be minimum

2) There can be many numerous causes for the loss and fragmentation of the habitat. Some of them are :

• the geological processes that alter the environment
• Human activities like urbanization, deforestation, transportation, agriculture etc.

3) The factors determining the diversity and density of the life forms are the limitation of resources, the human interference, the environmental changes like lack of trees of areas to live.

4) There are four different types of metapopulations. They are:

• Classical metapopulation model - Migration is a necessary factor for the stability of the population. There is a steady extinction rate and there are even preoccupied patches of the habitat.
• Patchy metapopulation model - The subpopulations are dependant on each other and they function as a single population. Extinction does not affect the entire population .
• Non equilibrium metapopulation model - The subpopulations are independent and they function as individual populations. The size is small and isolated and there are distinct patches of separation between the populations.
• Mainland-island metapopulation model - Located near a larger mainland and the extinction rates are much lower and has lesser impact.