7.1.1 Communities

Competition

Organisms within a community often compete for the same resources.

• Intraspecific competition: Competition within the same species.

• Interspecific competition: Competition between different species. Plants may compete for:

• Light: Needed for photosynthesis.

• Space: To grow and spread out.

• Water: Essential for all biological processes.

• Mineral ions: Needed for growth, like nitrates for making proteins. Animals may compete for:

• Space (territory): To live and raise offspring.

• Food: Necessary for energy and growth.

• Water: Vital for survival.

• Mates: To reproduce and pass on genes.

Interdependence

Interdependence is the way in which organisms in a community depend on each other for survival.

• Vital Services:
  • Food: Some species are food for others.
  • Shelter: Some organisms provide shelter or protection for others.
  • Reproduction: Involves processes like pollination and seed dispersal. For example, bees pollinate flowers, while birds may help in spreading seeds. The removal or addition of a species can greatly impact the entire community. For example, changing the number of predators can alter the population sizes of prey species, leading to a ripple effect throughout the community.

Stable Communities

A stable community is one where all biotic (living) and abiotic (non-living) factors are in balance, resulting in population sizes that remain relatively constant over time. Stable communities are often hard to replace once lost.

Examples of stable communities:

• Tropical rainforests
• Oak woodlands
• Coral reefs