UNDERSTANDING BIOLOGICAL COMMUNITIES AND SPECIES INTERACTIONS

community, in biology, an interacting group of various species in a common location. For example, a forest of trees and undergrowth plants, inhabited by animals and rooted in soil containing bacteria and fungi, constitutes a biological community.

1. Understanding
Biological
Communities and
Species Interactions

2. Physiological
Stress
Temperature
Moisture Levels
Nutrient Supply
Competition
resource limitations .
Predation
role of predators
Factors:
Chance
random relocation events

3. Concept: The single factor in shortest
supply relative to demand is the critical
determinant of species distribution.
Liebig’s Principle of Limiting
Factors

4. 1
Maximum
and
minimum
tolerance
limit.
2
Zones of
intolerance
leading to
extinctio.
3
Role of
indicator
species in
assessing
habitat
health.
Shelford’s Law of Tolerance:

5. Generalists ( e.g.,
rats — broad niche )
Specialists ( e.g.,
pandas — narrow
niche )
Ecological Niche
An ecological niche is a species' role in
its ecosystem, including its habitat,
food sources, interactions, and
adaptations.
Types:
Fundamental Niche – The full range of
conditions a species could occupy.
Realized Niche – The actual conditions
a species does occupy due to
competition.
Types of species
based on niche
breadth:

6. Predation, Parasitism, and Disease
Acclimation ( temporary adaptation )
species adaptation mechanisms:
Genetic Adaptation (evolutionary change )
Luck ( random relocation )

7. Law of Competitive Exclusion
No two species can occupy the same niche
independently.
Resource Partitioning as a solution.
Example: Owls and hawks hunting at different
times.

8. TYPES OF SPECIATION:
Allopatric Speciation ( geographic
isolation )
Sympatric Speciation ( behavioral
isolatio )
Speciation

9. Directional
Selection ( one trait
favored )
Stabilizing Selection
( eliminating
extremes )
Disruptive
Selection ( favoring
extreme traits )
Types of Natural Selection

10. Interspecific
Competition
( between different
species )
Intraspecific
Competition
( within the
same species )
Competition

11. TYPES:
Predators hunt and consume other
organisms, playing a vital role in
ecosystems by controlling prey
populations, maintaining biodiversity,
and driving natural selection.
Key Roles:
Regulate prey to prevent overpopulation.
Maintain biodiversity by balancing
species interactions.
Encourage adaptation through natural
selection.
Predation
Herbivores,
Carnivores,
Omnivores
( predators )
Scavengers and
Decomposers
( not predators )

12. Symbiosis — Species Living
Together
Commensalism ( one benefits, other unaffected )
Mutualism ( both benefit )
Parasitism ( one benefits, one harmed )

13. A species or group of species
whose impact on its
community is much larger and
more influential than would be
expected from mere
abundance
Without keystone species, the
ecosystem would be
dramatically different or cease
to exist altogether
Can be plant and animals;
can be top predators and
Herbivores
Keystone
Species:

14. Keystone Species:
Sea Stars
Hummingbirds
Prairie Dogs
Mountain Lion
Sea Otters
Sugar
Maple

15. Keystone Species:
Elephants on African
Savannas

16. Productivity — rate at which energy is converted into biomass.
Abundance & Diversity — number of species and individuals in
an ecosystem.
Structure — spatial arrangement of organisms in community.
Complexity — number of species interactions within the
ecosystem.
Resilience — ability to recover from disturbances.
Stability & Resilience — How well a community maintains
balance overtime.
Fundamental Properties of
Biological Communities

17. Primary Productivity— Energy in
Ecosystems
Photosynthesis powers ecosystems
by converting sunlight into energy,
supporting food chains, producing
oxygen, and regulating carbon levels.
It sustains biodiversity and
ecosystem stability.
Factors affecting
productivity:
light
temperature
nutrients
High Productivity occurs
under ideal conditions
IMPOTANCE OF PHOTOSYNTHESIS

18. Abundanc: Total number of organisms
Diversity: Variety of species
Inverse Relationship:
High Diversity = Low Abundance
High Abundance = Low Diversity
Abundance vs. Diversity

19. RANDOM
TYPES OF SPECIES
DISTRIBUTION:
Ecological
Structure —
Species
Distribution
Patterns
UNIFORM
CLUMPED

20. Stable Ecosystems resist disturbances
Stability and Succession
TYPES OF SUCCESS:
Primary Succession ( new land colonization ).
Secondary Succession ( ecosystem recovery
after disturbance ).

21. Species interactions maintain ecosystem
balance.
Understanding these relationships aids in
conservation efforts.
Conclusion