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.
• 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.

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/dtrN
• 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.

23
(No Transcript)
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.

30
(No Transcript)