C4.1 - population and growth (1d) Flashcards
carrying capacity
maximum population size that an ecosystem can support
- population growth slows and then fluctuates as the carrying capacity of environment is reached
what are examples of limiting factors that can influence carrying capacity for plants and animals?
carrying capacity varies with the abundance of limiting resources
plants - herbivory, water, light, soil salinity
animals - predation, shelter, territory, oxygen
both - temperature, waste build-up, disease
when is carrying capacity exceeded?
what is the immediate consequence of this?
carrying capacity is exceeded when a species produces more offspring than the environment can support
- the immediate consequence of this is competition, a lack of resources, and eventually death
population
an interacting group of organisms of the same species living in an area, who normally interbreed
how are populations distinguished?
there are usually multiple populations within one species, however individuals from different populations cannot interbreed, called reproductive isolation
- these individuals are classified as the same species because interbreeding is functionally possible
what are the three phases of the sigmoidal population growth curve?
- exponential growth phase
- transitional phase
- plateau phase
what is exponential growth?
what conditions are required for exponential growth?
regular doubling of a population size
- natality and immigration are much greater than mortality and emigration
conditions required are:
- ideal environment with unlimited resources
- absence of limiting factors
- little disease and few predators
what are characteristics of the transitional phase?
- growth is slowed as resources become limited
- immigration and natality is still higher then emigration and mortality
- increased competition for resources
- presence of predators and disease
what are the characteristics of the plateau phase?
- growth continues to slow as population size plateaus at carrying capacity
- the rate of natality is equal to the rate of mortality
- population size is not constant but oscillates around the carrying capacity
what are strengths of the wildebeest species in illustrating the population growth curve?
- exponential growth (1958 - 1972)
- plateau phase (1978 - 2003)
- carrying capacity of 1300
what are weaknesses of the wildebeest species in illustrating the population growth curve?
- no clear transitional phase
- decrease in population during plateau phase ( due to density-independent factor)
what is a model?
what organisms can be used for models?
a model is a simplification of complex systems and can be modelled by taking observations of simple organisms such as duckweed or yeast
- duckweed can be counted by eye
- yeast can be counted using a microscope
how can we use duckweed to model the sigmoidal curve?
place duckweed in a cup of water in a warm environment with lots of light and count the number of individual plants over time
how can we use yeast to model the sigmoidal curve?
add yeast and sterile nutrient broth to a sample, cover and shake to remove bubbles, then add methyl blue indicator and view under the microscope over a period of time
what are pros and cons of using duckweed and yeast to model sigmoidal curves?
pros - easy to store and small, low cost, quick
cons - as organisms are grown in closed systems, accumulation of metabolic waste can cause death
