Populations, Communities, and Species Interaction

1. Populations, Communities,and Species Interaction Chapter 3

2. Outline: • Critical Factors and Tolerance Limits • Adaptation and Natural Selection • Speciation • Taxonomy • Ecological Niche • Species Interaction • Population Growth • Community Properties and Structure • Succession

3. Population,Communities & Species Interaction • Why, where and How? • Why a particular organism lives in a particular area? Where he lives and how it interacts with its environment? • How he deals with environmental stresses? • Why one species is dominant over the other? • How species interact with each other in a community to survive?

4. Critical Factors and Tolerance Limits • Environmental factors should be within tolerable limit for organims to survive • Critical Factor - Single factor in shortest supply relative to demand is a critical determinant in species distribution. • Tolerance Limits refer to minimum and maximum levels beyond which a particular species cannot survive or reproduce. • Many species exhibit tolerance limits that are more critical for young than adults.

5. Tolerance Limits

6. Adaptation • Adaptation - Process where species acquire traits that allow them to survive in their environments. • Limited range of physiological modifications. • E.g transferring an indoor winter plant outside to outside during spring . • Inheritance of specific genetic traits allowing a species to live in a particular environment. Is explained by the theory of Evolution (Charles Darwin).

7. Natural Selection • Natural Selection - Describes process where better competitors survive and reproduce more successfully. • Small, spontaneous, random mutations occur in every population creating genetic diversity& one trait could be better than other, means of survival. • Limited resources or environmental conditions may exert selective pressure on a population (influence fertility or survivorship in nature).

8. Factors Exerting Selective Pressure • Physiological stress due to in appropriate levels of a critical environmental factor. • Moisture, Light, pH, temperature • Predation includes • Parasitism, Disease • Competition: Some organisms when they move to new habitat, may be just lucky to survive than better suited.

9. Speciation • Given enough time, mutations may collectively allow a species to become better suited to new environmental conditions. • Evolution sometimes creates entirely new species, physically distinct from their ancestors. • DivergentEvolution- Separation of one species into new species even though they occupy the same territory. Compare the Cheetahs with House cat. • Convergent Evolution- Unrelated organisms evolve to look and act alike. E.g Fruit eating Galapagos finch looks and behave like the parrots but they are genetically different.

10. Taxonomic Naming System • Binomial - based on Latin. • Taxonomic classification of Corn: • Kingdom - Plantae • Phylum-Anthophyta • Class-Monocotyledons • Order-Commenales • Family-Poaceae • Genus -Zea • Species-Zea Mays • Refer pg 54 Table 3.1 for Humans .

11. Ecological Niche • Habitat - Set of environmental conditions in which a particular organism lives. • Ecological Niche is described as either • A description of role played by a species in a biological community or • A total set of environmental factors that determines species distribution. • Generalists –A broad niche eg Racoons have a wide range of habitat. • Specialists – A narrow niche e.g Panda occupy a specific habitat.

12. Resource Partitioning

13. Ecological Niche • Resource Partitioning - Alter behavior or physiology to minimize competition ( Move to other areas, or become extinct). • Partition then allows several species to utilize different parts of the same resource and co exists within a single habitat).

14. Ecological Niche of Wood Warblers

15. Weedy Species • Opportunistic Species - Quickly appear when opportunities arise. • Many weeds e.g the Dandelions • Pioneer Species – The opportunistics can quickly colonize open, disturbed, or bare ground.They can be useful in minimising soil erosion or a nuisnance.

16. SPECIES INTERACTION • Predation • Any organism that feeds directly on another living organism is termed a predator. • Predation influences population balance of communities involving: • All stages of life cycles of predator and prey. • Specialized food-obtaining mechanisms. • Specific predator-prey adaptations. • Predation can exert selective pressures which is called co-evolution (both predator and prey adapt to suit the situation, both adapt to new situation and allow the sps to survive and evolve.

17. Competition • Intraspecific - Competition among members of the same species e.g Within a patch of grass,,some are tall, some dwarf,some, sickly looking….all plants of the same sps absorb the same nutrients for growth. • To survive they are aided by: • Dispersal ( e.g seed dispersal by wind, air , Rain • Territoriality :Defending resource-rich area, primarily against members of own species • Resource Partitioning (to reduce intraspecies competition, sps move away from area) • Interspecific - Competition between members of different species for the same nutrients. E.g Different sps of birds feeding for the same plot of corn.

18. Symbiosis • Symbiosis - Intimate living together of members of two or more species for mutual benefits. Types: • Commensalism - One member benefits while other is neither benefited nor harmed. • Cattle and Cattle Egrets • Mutualism - Both members benefit. • Lichens (Fungus and cyanobacterium) • Parasitism - One member benefits at the expense of other. • Humans and Tapeworms

19. Defensive Mechanisms • Batesian Mimicry(H.W Bates,1857)- Harmless species evolve characteristics that mimic unpalatable or poisonous species.E.g the Wasp & the longhorn beetle (Pg 60) • Mullerian Mimicry (F. Miller,1878) - Two unpalatable or dangerous species evolve to look alike.E.g several species of mushrooms looks alike and produce fungal toxin which may be deadly.

20. POPULATION DYNAMICS • Population Growth • Exponential Growth - Growth as a percentage of the whole :dN/dt=rN • dN= change in numbers of individual • Dt= change in time • R= rate of growth • N= no. of individuals in a population • Biotic Potential - Potential of a population to grow in the absence of expansion limitations (if nothing was limiting its expansion).

21. Limiting Factors • Population growth is regulated by internal ( Maturity , body size, hormones) & external factors (Food, habitat, interaction). • Environmental Resistance (factors which reduce pop growth rates) • Density-Dependent Factors - Mortality rates increase as the density of the population increases. Pop density is dependent on: E.g: Disease, Stress, Predation • Density-Independent Factors - Effect on mortality rate is independent of population density. • Abiotic conditions eg drought, frost may kill mosquito pop.immaterials of the number with which they started the pop.

22. Abundance -Total number of organisms in a community. • Diversity - Number of different species, ecological niches, or genetic variation • Complexity - Number of species at each trophic level, and the number of trophic levels, in a community.

24. Resilience and Stability • Constancy (Lack of fluctuation) • Inertia (Resistance to pertubation) • Renewal (Ability to repair damage)

25. Community Structure • Randomly Arranged • Individuals live wherever resources are available. • Clumped • Individuals cluster together for protection, assistance, or resource access. • Regularly Arranged

26. Community Structure

27. COMMUNITIES IN TRANSITION • Ecological Succession • Primary Succession - A community begins to develop on a site previously unoccupied by living organisms. • Pioneer Species • Secondary Succession - An existing community is disrupted and a new one subsequently develops at the site. • Ecological Development

28. Primary Succession

29. Ecological Succession • Climax Community - Community that develops and seemingly resists further change. • Individualistic Community - Species become established according to their ability to colonize and reproduce in a given area.