4.6 BIODIVERSITY WITHIN A COMMUNITY

COMMUNITY?

All populations of different species that live in an area.

SPECIES RICHNESS?

• A measure of the number of different species in a community.

METHOD TO DETERMINE SPECIES RICHNESS?

1. A method of selecting sampling sites at random;

2. Use of quadrat;

3. Count number of (different plant) species (at site / in each quadrat);

WHAT DOES AN INDEX OF DIVERSITY DO?

Describes the relationship between:

1. The number of species in a community (species richness).

2. The number of individuals in each species (population size).

WHY IS INDEX OF DIVERSITY BETTER THAN SPECIES RICHNESS? (2)

1. Measures abundance / number / population (size) of each species;

2. (So useful because) may be many of some species OR (So useful because) may be few of other species.

HOW CAN INDEX OF DIVERSITY VALUES BE INTERPRETED?

• HIGH: Stable and ancient site, many species which are evenly represented.

• LOW: Habitat dominated by few/one species.

MONOCULTURE WHAT AND WHY?

• Remove existing vegetation and grow one crop species.

• Aims to provide ideal conditions for the crop to grow and supply a high yield.

HOW DO SOME FARMING TECHNIQUES REDUCE BIODIVERSITY?

\WHY DOES BIODIVERSITY DECREASE IN LARGER FIELDS?

(Larger fields have relatively)

More centre OR

Less edge OR

Less hedge OR

Fewer species;

WHY IS CONSERVATION NEEDED?

BALANCE BETWEEN CONSERVATION AND FARMING?

ADVANTAGES AND DISADVANTAGES OF REPLANTING HEDGES?

Advantage -

• Greater (bio)diversity so increase in predators of pests

  ::: less damage to crops

• Increase in pollinators so more yield/income

Disadvantage -

• Reduced land area for crop growth/income.

• Greater (bio)diversity so increase pest population.

• Increase pest population so less yield/less income/(more) need

• for pesticides/(more) damage to crops.

• Increased (interspecific) competition so less yield/income.

• More difficult to farm so less income;