Overview of Ecology

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Chapter 18
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Overview of Ecology

• Ecology scientific study of the interactions
  between organisms and their environment
• 2 components of environment
• Biotic living factors
• All other organisms in the environment
• Abiotic nonliving chemical and physical
• temperature, light, water, minerals, air

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Ecology as Scientific Study

• Process of observing and describing organisms or
  systems in natural habitat
• Experiments done in field and lab, descriptive
  complemented by simulations
• Always uses the scientific process

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Hierarchy of Interactions

• Organismal ecology
• Population ecology
• Community ecology
• Ecosystem ecology

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Organismal Ecology

• Looks at evolutionary adaptations that allow
  individual to survive in their abiotic
  environment
• e.g. distribution, equipment

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Population Ecology

• Group of individuals of same species living in a
  certain area
• Factors that affect population density and growth

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Community Ecology

• All organisms that live in a certain area
• An assemblage of populations of different species
• How population interactions affect community
  structure
• Predation, competition, etc

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Ecosystem Ecology

• All abiotic factors and also the community of
  species in a certain area
• e.g. energy flow and chemical cycling among
  biotic and abiotic factors

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Biosphere

• Global ecosystem, sum of all ecosystems
• Far into the atmosphere deep down under the ocean

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Ecology and Environmentalism

• Important to know relationships between organisms
  and environments
• 1950s technology increased ag. productivity and
  decreased pests
• BUT, late 1950s problems were noticed
• DDT (predatory birds, human milk)
• Rachel Carson Silent Spring

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Abiotic factors of the Biosphere

• Sunlight
• Water
• Temperature
• Wind
• Rocks and soil
• Periodic disturbances

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Patchy biosphere

• Distribution patterns in aquatic and terrestrial
  reflect region differences and abiotic factors
• Habitats environmental situations in which
  organisms live
• Each has certain organisms based on abiotic
  factors

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Sunlight

• Energy to all ecosystems
• Limit in aquatic environments impacts growth and
  distribution
• Competition for sunlight in aquatic and
  terrestrial (forests)

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Water

• No lack for aquatic org., but concentration can
  be a problem
• Terrestrial org. have adaptations
• Plants have waxy coating
• Mammals have dead layer of skin
• Kidneys help concentrate waste so we loose little
  water

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Temperature

• Important because of effect on metabolism
• Critical temps
• 0C (32F) AND 50C (122F)
• Some exceptions
• Some NA turtles and frogs can freeze
• There are prokaryotes that are heat-loving and
  live in hot springs

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Wind

• Brings food to certain organisms
• Disperses pollen and seeds
• Creates openings in ecosystems
• Increases water loss in organisms
• Change growth pattern

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Rocks and Soil

• Limits distribution of plants and animals
• Soil variation contributes to patchiness
• Substrate composition
• Ocean impacts attachment and burrowing
• Lake, river, stream impact water chemistry and
  in turn plants and animals

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Periodic Disturbances

• Fires, tornados, hurricanes, volcanoes
• Repopulated by survivors or recolonized
• Plants have adaptations to fire, and some depend
  on fire to maintain them

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Evolutionary Adaptations

• By natural selection from interaction of
  organisms and environment
• Hawk eats mice, mice that reproduce are better
  camouflaged
• 3 adaptations
• Physiological
• Anatomical
• Behavioral

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Physiological Responses

• Cats, birds fluffing up humansgoose bumps
• Acclimation longer term physiological response
  that is still reversible
• low elevation to high (increase RBC to carry O2)
• Birds and mammals tolerate temp extremes because
  they are endotherms
• Reptiles ectotherms to NOT tolerate temp
  extremes

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Anatomical Responses

• Heavier coat of fur or feathers
• Coat color changes seasonally
• Plants are usually more anatomically plastic
  compared to animals (e.g. trees)

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Behavioral Responses

• Animals can change location
• local sun to shade
• Distances (migrating)
• seasons birds, monarchs
• Humans anywhere, anytime
• Examples

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Population Ecology ?

• Looks at what factors influence population
• Size (number of individuals)
• Growth rate (rate of change in population size)
• Density (number of individuals per unit area or
  volume)
• Population structure (including relative numbers
  of individuals of different ages)

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• Population a group of individuals of the same
  species living in a given area at a given time
• What is deemed to be a population depends upon
  the research question being asked.

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Population Density

• of individuals of a species per unit area or
  volume
• Ways to determine
• Do an actual count
• Count random sample plots (more better est.)
• Count nests or burrows
• Mark-recapture method

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Patterns of Dispersion

• How individuals are spaced within the
  populations geographic range
• Uniform
• Random
• Clumped

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Uniform

• typically results from interactions among
  individuals
• plants that compete for water and nutrients
• animals and social interaction
• large amounts of birds nesting in small area

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Random

• Only occurs in absence of strong attraction or
  repulsion
• e.g. not breeding season and resources are
  plentiful
• Rare because of environmental conditions and
  social interactions

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Clumped

• Individuals in patches (most common)
• Unequal distribution of resources
• Trees lining a river or stream
• Animals
• Food distribution
• Mating
• Social behavior

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Population Growth Models

• The Exponential Growth Model
• Ideal of an unlimited environment
• The Logistic Growth Model
• Reality of a limited environment

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Exponential Growth Model

• Population multiplies by constant factor during
  constant time
• Growth rate depends on individuals already in the
  population
• Bigger the population faster it increases
• Generally short lived because conditions are not
  always ideal

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Logistic Growth Model

• Population-limiting factors factors that
  restrict population growth
• Idealized population growth slowed by limiting
  factors

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• Carrying capacity number of individuals in
  population that environment can maintain with no
  net increase or decrease

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Regulation of Population Growth

• Two categories of population-limiting factors
  that contribute to carrying capacity
• Density Dependent Factors
• Density Independent Factors

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Density-Dependent Factor

• Population limiting factor whose effects
  intensify as the population increases
• OR
• Affect greater of population as number of
  individuals increases
• e.g. limited food supply, build up of poisonous
  wastes

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• Deer populations grow with abundant food supply,
  then increased deer population impact food
  quality and abundance and deer population
  deceases again
• Food is density-dependent factor

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Density-Independent Factors

• Population-limiting factor whose intensity is
  unrelated to population density
• First freeze of the winter
• These often impact population before
  density-dependent factors do

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