Populations Communities and Species Interaction Chapter 3 1

Populations, Communities, and Species Interaction Chapter 3 1

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

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? 3

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. v 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. 4

Tolerance Limits 5

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

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

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

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. v Divergent Evolution- Separation of one species into new species even though they occupy the same territory. Compare the Cheetahs with House cat. v 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. 9

Taxonomic Naming System • • Binomial - based on Latin. Taxonomic classification of Corn: v Kingdom - Plantae v Phylum-Anthophyta v Class-Monocotyledons v Order-Commenales v Family-Poaceae v Genus -Zea v Species-Zea Mays v Refer pg 54 Table 3. 1 for Humans. 10

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

Resource Partitioning 12

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

Ecological Niche of Wood Warblers 14

Weedy Species • • Opportunistic Species - Quickly appear when opportunities arise. v 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. 15

SPECIES INTERACTION • Predation v Any organism that feeds directly on another living organism is termed a predator. v Predation influences population balance of communities involving: - All stages of life cycles of predator and prey. - Specialized food-obtaining mechanisms. - Specific predator-prey adaptations. v 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. 16

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: v Dispersal ( e. g seed dispersal by wind, air , Rain v Territoriality : Defending resource-rich area, primarily against members of own species v 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 17

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

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) v 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. v 19

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

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) v Density-Dependent Factors - Mortality rates increase as the density of the population increases. Pop density is dependent on: E. g: Disease, Stress, Predation v 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. 21

• • • 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. 22

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

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

Community Structure 26

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

Primary Succession 28

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. 29

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