Chapter 5 Biodiversity, Species Interactions and Population Control - PowerPoint PPT Presentation

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Chapter 5 Biodiversity, Species Interactions and Population Control


Chapter 5 Biodiversity, Species Interactions and Population Control Prevent premature extinction how ? Status of natural populations, species in danger of extinction ... – PowerPoint PPT presentation

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Title: Chapter 5 Biodiversity, Species Interactions and Population Control

Chapter 5Biodiversity, Species Interactions and
Population Control
Species Interact in major ways
  • Interspecific competition 2 or more species
    interact to gain access to limited resources
  • Predation prey/predator
  • parasitism - parasite/host
  • Mutualism benefits both species
  • Commensalism benefits one species , no effect
    on the other

Role of predation
  • Cyclic changes sharp increases in number
    followed by seemingly periodic crashes
  • Wolves controlling deer and moose populations
  • Sheep and rabbits controlling plant growth

Competition for resources
  • the greater the overlap the more intense the
  • Resource partitioning specialized traits allow
    species to use shared resources at different
  • Competitive exclusion intense copetition
    between 2 equal species, both suffer (one more
    than the other) by having reduced access to

Population Dynamics
  • characteristics of populations change in response
    to environmental conditions
  • Size number of individuals
  • Density number of individuals in a certain
  • Distribution spatial pattern clumping,uniform
  • random dispersion
  • Age distribution structure - percentage of
    individuals in each age group

What limits population growth?
  • Birth, death, immigration, emigration

Population change
  • (birth immigration) - (death emigration)
  • dependent on resource availability or other
    environmental changes

Intrinsic rate of increase
  • rate at which a population could grow if it has
    unlimited resources
  • always limits - light, water, space, nutrients
  • High r reproduce early in life, short
    generation ie. reproduce many times many
    offspring house fly

Carrying capacity - capacity for growth
  • number of individuals of a given species that can
    be sustained indefinitely in a given area (K)
  • determined by interaction between biotic
    potential and environmental resistance (factors
    that act jointly to limit a population)

Population Dynamics and Carrying Capacity
  • Basic Concept Over a long period of time,
    populations of species in an ecosystem are
    usually in a state of equilibrium (balance
    between births and deaths)
  • There is a dynamic balance between biotic
    potential and environmental resistance

Carrying Capacity (K)
  • Exponential curve is not realistic due to
    carrying capacity of area
  • Carrying capacity is maximum number of
    individuals a habitat can support over a given
    period of time due to environmental resistance

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Biotic Potential
  • Ability of populations of a given species to
    increase in size
  • Abiotic Contributing Factors
  • Favorable light
  • Favorable Temperatures
  • Favorable chemical environment - nutrients
  • Biotic Contributing Factors
  • Reproductive rate
  • Generalized niche
  • Ability to migrate or disperse
  • Adequate defense mechanisms
  • Ability to cope with adverse conditions

Environmental Resistance
  • Ability of populations of a given species to
    increase in size
  • Abiotic Contributing Factors
  • Unfavorable light
  • Unfavorable Temperatures
  • Unfavorable chemical environment - nutrients
  • Biotic Contributing Factors
  • Low reproductive rate
  • Specialized niche
  • Inability to migrate or disperse
  • Inadequate defense mechanisms
  • Inability to cope with adverse conditions

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Population Density
  • Population Density (or ecological population
    density) is the amount of individuals in a
    population per unit habitat area
  • Some species exist in high densities - Mice
  • Some species exist in low densities - Mountain
  • Density depends upon
  • social/population structure
  • mating relationships
  • time of year

Reproductive Strategies
  • Goal of every species is to produce as many
    offspring as possible
  • Each individual has a limited amount of energy to
    put towards life and reproduction
  • This leads to a trade-off of long life or high
    reproductive rate
  • Natural Selection has lead to two strategies for
    species r - strategists and K - strategists

r - Strategists
  • Spend most of their time in exponential growth
  • Maximize reproductive life
  • Minimum life

R Strategists
  • Many small offspring
  • Little or no parental care and protection of
  • Early reproductive age
  • Most offspring die before reaching reproductive
  • Small adults
  • Adapted to unstable climate and environmental
  • High population growth rate (r)
  • Population size fluctuates wildly above and below
    carrying capacity (K)
  • Generalist niche
  • Low ability to compete
  • Early successional species

K - Strategists
  • Maintain population at carrying capacity (K)
  • Maximize lifespan

K- Strategist
  • Fewer, larger offspring
  • High parental care and protection of offspring
  • Later reproductive age
  • Most offspring survive to reproductive age
  • Larger adults
  • Adapted to stable climate and environmental
  • Lower population growth rate (r)
  • Population size fairly stable and usually close
    to carrying capacity (K)
  • Specialist niche
  • High ability to compete
  • Late successional species

Survivorship Curves
  • Late Loss K-strategists that produce few young
    and care for them until they reach reproductive
    age thus reducing juvenile mortality
  • Constant Loss typically intermediate
    reproductive strategies with fairly constant
    mortality throughout all age classes
  • Early Loss r-strategists with many offspring,
    high infant mortality and high survivorship once
    a certain size and age

Survivorship curves
  • proportion of survivors of a particular species
    in a particular age group
  • a)late loss type I - elephant
  • b) early loss type II songbirds
  • c) constant loss - intermediate reproductive
    strategies- starfish

Population growth
  • J-shaped - exponential growth curve, growth
    starts slowly then speeds up
  • S - shaped curve- logistic growth curve - slow
    start, rapid exponential growth, levels off when
    K is reached

Population cycles in nature
  • relatively stable - slight fluctuation above and
    below carrying capacity, tropical rain forest
  • erupt - high peak, crash - raccoons
  • cyclic - boom and bust

Effect of population density on population growth?
  • Density Independent floods, drought, hurricane,
    habitat destruction, pesticide spraying
  • Density dependent competition for resources,
    predation, disease infectious diseases plague
    in Europe

Communities and ecosystems respond to
environmental change
  • Primary succession- gradual establishment of
    biotic communities in life less areas where there
    is no soil in a terrestrial ecosystem or nobottom
    sediment in an aquatic ecosystem
  • Secondary succession series of comunities or
    ecosystems with different species develop in
    places containing soil or bottom sediment

Primary succession
  • bare rock subject to weathering crumbles into
    particles, releasing nutrients
  • Pioneer or early successional species (lichens or
    mosses)attach to rock and start the process of
    rock formation by secreting mild acids
  • Mid successional plants grasses, herbs, small
  • Late successional species trees that can tolerate

Secondary succession
  • ecosystem has been disturbed , removed or
    destroyed, some soil or bottom sediment remains
  • abandoned farmland, burned or cut forests,heavily
    polluted streams, flooded lands

Living systems are sustained through constant
  • complex system of positive and negative feedback
    loops that interact to provide stability
  • Inertia or persistence ability of a living
    system such as grassland or forest to survive
    moderate disturbances
  • Resilence ability of a living system to be
    restored through secondary succession after a
    moderate disturbance

Conservation Biology
  • Investigate human impacts on biodiversity
  • Develop practical approaches to maintaining
  • endangered species management, wildlife reserves,
    ecological restoration, environmental ethics

Prevent premature extinction how ?
  • Status of natural populations, species in danger
    of extinction
  • Status of the functioning of ecosystems
  • Measures taken to maintain habitat quality which
    will support wild species population

Understand status of natural populations
  • Measure current population size
  • Determine how size will change with time
  • Determine whether populations are sustainable

Anthropogenic impact
  • Fragmenting or degrading habitat, simplifying
    natural ecosystems, strengthening genetic
    resistance to pesticides, eliminating predators,
    introduce alien species, over harvesting,
    interfering with nutrient cycles

Working with Nature
  • Learn six features of living systems
  • Interdependence
  • Diversity
  • Resilience
  • Adaptability
  • Unpredictability
  • Limits

Basic Ecological Lessons
  1. Sunlight is primary source of energy
  2. Nutrients are replenished and wastes are disposed
    of by recycling materials
  3. Soil, water, air, plants and animals are renewed
    through natural processes
  4. Energy is always required to produce or maintain
    an energy flow or to recycle chemicals

Basic Ecological Lessons
  1. Biodiversity takes many forms because it has
    evolved over billions of years under different
  2. Complex networks of and feedback loops exist
  3. Population size and growth rate are controlled by
    interactions with other species and with abiotic
  4. Organisms generally only use what they need

Four Principles for Sustainable
  1. We are part of, not apart from, the earths
    dynamic web of life.
  2. Our lives, lifestyles, and economies are totally
    dependent on the sun and the earth.
  3. We can never do merely one thing (first law of
    human ecology Garret Hardin).
  4. Everything is connected to everything else we
    are all in it together.
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