Transcript Understanding Our Environment

Populations, Communities,
and Species Interaction
Chapter 3
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Outline:
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Critical Factors and Tolerance Limits
Adaptation and Natural Selection
Speciation
Taxonomy
Ecological Niche
Species Interaction
Population Growth
Community Properties and Structure
Succession
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Population,Communities & Species Interaction
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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?
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Critical Factors and Tolerance Limits
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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.
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Tolerance Limits
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Adaptation
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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).
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Natural Selection
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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).
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Factors Exerting Selective Pressure
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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.
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Speciation
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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.
 Divergent Evolution- 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.
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Taxonomic Naming System
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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 .
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Ecological Niche
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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.
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Resource Partitioning
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Ecological Niche
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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).
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Ecological Niche of Wood Warblers
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Weedy Species
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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.
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SPECIES INTERACTION
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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.
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Competition
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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 17
Symbiosis
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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
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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.
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POPULATION DYNAMICS
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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).
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Limiting Factors
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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.
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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.
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Resilience and Stability
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Constancy (Lack of fluctuation)
Inertia (Resistance to pertubation)
Renewal (Ability to repair damage)
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Community Structure
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Randomly Arranged
 Individuals live wherever resources are
available.
Clumped
 Individuals cluster together for protection,
assistance, or resource access.
Regularly Arranged
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Community Structure
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COMMUNITIES IN TRANSITION
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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
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Primary Succession
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Ecological Succession
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Climax Community - Community that
develops and seemingly resists further
change.
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Individualistic Community - Species become
established according to their ability to
colonize and reproduce in a given area.
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