Ecosystems

• Ecosystems CAPE U1 Environmental Science syllabus Module 1 Objective 9-18 Page 7 https://media.cntraveler.com/photos/589218b36ce0e5bb7a6ec534/master/pass/Trinidad-and-Tobago-GettyImages-174774690.jpg
• Objectives


  • Understand & discuss the following:
  • Calculate species diversity ( Pg 7 Objective 10 )
  • The relationship between species diversity and ecosystem ( Pg 7 Objective 11)
  • Factors affecting population growth in a natural ecosystem ( Pg 7 Objective 12)
  • The concept of carrying capacity ( Pg 7 Objective 13)
  • Human interactions within natural ecosystems ( Pg 7 Objective 14)
• Objectives


  • Understand & discuss the following:
  • At least two ecosystems in territory ( Pg 7 Objective 15 )
  • Measure environmental parameters in a habitat ( Pg 8 Objective 16)
  • Apply scientific method to experimental design and analysis ( Pg 8 Objective 17)
  • Present and interpret data using appropriate charts, table and graphs ( Pg 8 Objective 18)
• Ecosystems and diversity II

  • Analyze the relationship between species diversity, community and ecosystem stability
  • Diversity between species
  • Diversity of species in an ecosystem helps to protect it from threats. Natural selection causes populations to adapt to their environment and to differentiate from one another. Species differ form each other in their resource requirements and their interactions with other species. Therefore species composition and interactions have a major influence on ecosystem functions and stability
• Ecologists test stability of Maine ecosystem over two decades - Science Nation - YouTube
• Resilience and stability


  • Some biological communities tend to stay relatively stable and constant over time
  • The species diversity index is sometimes taken as an indicator of ecological stability
  • The assumption is that the greater the calculated value for species diversity the more stable will be the ecosystem
• Ecosystem resistance


  The ability of an ecosystem to resist change after a disturbance
• Ecosystem resilience


  The ability of an ecosystem to return to its original state after experiencing some change
• Local ecological stability


  The tendency of a biological community to return to its original state after a small or local disturbance
• Global ecological stability


  The tendency of a biological community to return to its original state after a major disturbance
• Resilience - YouTube
• The Basics of Biology DVD Series Population Biotic potential, environmental resistance - YouTube
• Ecosystem Stability: The Jellyfish - YouTube
• • While each of these types of stability is related to species diversity, this is not always the case
  • It is now generally accepted that the relationship between species diversity and ecosystem stability probably varies with the environment
  • Therefore healthy and simple biological communities in environments with very demanding abiotic conditions are likely to be more stable and less prone to human disturbance than biological communities that are fragile and complex but are found in environments with less demanding abiotic conditions
• Species diversity


  • A measure of the diversity within an ecosystem
  • This is really the number of different species in a particular area, the species richness weighted by some measure of abundance such as number of individuals or biomass
  • Another measure of species diversity is the relative abundance with which each species is represented in a given area- the species evenness
• Population size


  The number of individuals in a population
• Population density


  The number of individuals per unit area
• Population growth


  A change in the number of individuals in a population. Population growth is positive when the overall number of individuals in population increase and negative when the overall number of individuals in a population decrease
• Population growth rate


  The change in number of individuals in a population per unit time. This could be positive or negative
• Population Limiting Factors | Biology - YouTube
• Density-dependent factors


  Factors that are usually biotic and include food availability, level of predation and ability to resist disease
• Density-independent factors


  Factors that are usually abiotic and affect the same proportion of the population irrespective of the population size or density. Density-independent factors include weather events and natural disasters that affect populations
• Biotic potential


  The maximum rate at which a population can increase when resources are unlimited and when environmental conditions are ideal
• Factors affecting biotic potential

  • Age of reproductive maturity
  • 'litter size'; the number of offspring produced at each reproductive event
  • Number of reproductive events that occur in an individual's lifetimes
  • 'survival rate of the species', how many offspring survive to reach reproductive age
• Environmental resistance


  The total effect of all the limiting factors, biotic/abiotic that act together to prevent the maximum reproductive potential from being achieved
• Environmental resistance factors


  • Temperature
  • Climate
  • Predators
  • Disease organisms
  • Space
  • Parasites
  • Food
  • Suitable habitat
• Populations Biotic Potential | Biology | Ecology - YouTube
• • Environmental resistance may result in a decrease in the rate of a population in several ways:
  • Some species have high reproductive rates that will allow them to reach large numbers very quickly, given unlimited resources and no limiting factors
  • Environmental resistance factors will decrease the reproductive rates and survival of offspring
  • The maximum reproductive rate is the biotic potential. Environmental resistance reduces biotic potential
• • As populations reach the maximum carrying capacity of a habitat or ecosystem, environmental resistance increases to cause a decline in the growth rate
  • Eventually the reproductive success rate is reduced to a level that the ecosystem can sustain
• Carrying capacity


  The maximum population size that can be sustained by a particular environment over a relatively long period of time
• • If there is overpopulation there can be many implications for the environment
  • Carrying capacity may be considered to be the theoretical equilibrium population size at which a given population will stabilize in a particular environment when its resources remain constant
  • It is the maximum sustainable population size that can be supported indefinitely without degrading the habitat and limiting resources for future members of the population and for future generations
• Ecological Carrying Capacity - YouTube
• • There are instances when population increases are rapid during the exponential growth phase, resulting in an overshooting of the carrying capacity
  • Under such conditions the environment will be unable to support the growing population
  • Populations that show such growth curves are called boom-and-bust populations. In such instances, overpopulation can harm the environment and lead to a lower carrying capacity
• Species overpopulation - YouTube
• • Expanding populations always reach a size limit imposed by certain factors such as water, space and nutrients or by prevailing adverse conditions such as extreme weather events (drought, floods and temperature extremes)
  • Environmental resistance together with biotic potential keeps a population in balance and prevents it from overshooting the environmental carrying capacity
• Ester Boserup


  • It is generally acknowledged that carrying capacity for humans is a function of population size as well as differing levels of consumption, and types of technologies used in production and consumption
  • It should be noted that technologies that impact overall consumption also impact carrying capacity
  • This school of thought is based on the work of Ester Boserup , a Danish agricultural economist who suggested that, as populations increased, we would, out of necessity develop technological solutions to increase our resource base, for example developing artificial fertilizers to grow more crops
  • Therefore we do not reach carrying capacity because the resource base has been developed
• Thomas Robert Malthus


  • Thomas Robert Malthus was known for his theories about change populations
  • According to his theory, human population exhibits a J-shaped curve and is accelerating
  • Malthus argued that population increases exponentially, but resources increase linearly and so eventually we exceed carrying capacity
• • An examination of this diagram and an understanding of the concept of carrying capacity according to Malthus would tell us that such growth cannot continue because resource limitations and/or environmental degradation will cause human population growth curves to approach an upper limit, the carrying capacity
  • The carrying capacity for humans is acknowledged to be more complex and the definition is usually expanded to include not degrading out cultural and social environments and also not harming the physical environment in ways that will adversely affect future generations. This implies and links with the concept of sustainability and sustainable development
• Joel Cohen: ''Carrying capacity is determined jointly by human choices and natural constraints. Consequently, the question, how many people can the Earth support, does not have a single numerical answer, now or ever. Human choices about the Earth's human carrying capacity are constrained by facts of nature which we understand poorly. So any estimates of human carrying are only conditional on future human choices and natural events.''
• • For a given area, the carrying capacity is the maximum number of individuals of a given species that could be supported be the resources present without significantly degrading or depleting the resources
  • The carrying capacity may be lowered by resource destruction and degradation during overshoot events or extended through technological and social changes
  • It is important to note that most resources that humas use are finite and we are constrained as are all other organisms
  • It is logical that human carrying capacity is dependent on our lifestyles and quality of life
  • Human carrying capacity must also be though of in cultural terms (cultural carrying capacity)