4.6 BIODIVERSITY WITHIN A COMMUNITY

COMMUNITY?

All populations of different species that live in an area.

SPECIES RICHNESS?

HOW TO DETERMINE?

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

• Quadrats.

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?

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;