3.5 Population size and ecosystems 1 Flashcards
What is an ecosystem?
A balanced biological system made up of biotic and abiotic elements
What is a habitat?
A particular area occupied by a population
What is a community?
The different populations of species that live in a habitat
What is a niche?
An organism’s role in the ecosystem
What is ecology?
A branch of Biology that studies the relationship between living organisms and their environment
What is an environment?
The complex of physical, chemical, and biotic factors that act upon an organism or an ecological community and ultimately determines its form and survival
What is a population?
The number of organisms of the same species in a certain place, at a certain time, which can reproduce
Which factors increase a population?
Immigration and birth rate/ rate of cellular division
Which factors decrease a population?
Emigration and death rate/ rate of cellular death
What is the equation for a stable population?
Immigration + birth rate = Emigration + death rate
What is the equation for a growing population?
Immigration + birth rate> Emigration + death rate
What is the equation for a decreasing population?
Immigration + birth rate < Emigration + death rate
What are the two strategies for population growth?
- Fugitive species (r)
-Equilibrium species (k)
Describe a fugitive species (r)
-Rapid reproduction rate and dispersal
-Can invade new habitats rapidly
-Can’t tolerate competition
-i.e. sea palm and dandelion
Describe an equilibrium species (k)
-Balance population numbers with competition in a stable habitat
-Growth pattern is sigmoidal (one-step growth)
-i.e. elephant and fox
Describe the log phase of a population growth curve
-Numbers increase rapidly
-More individuals are available for reproduction
-Lack of environmental resistance
- Cell division>Cell death
Describe the lag phase of a population growth curve
-Little or no cell growth
-Organisms adapt and prepare for growth
- Enzyme/ protein synthesis
Describe the stationary phase of a population growth curve
-Birth rate=death rate
-Some limiting factors
-Population reaches maximum (carrying capacity)
Describe the death phase of a population growth curve
-Death rate>Birth rate
-Could be environmental resistance/food source/ toxin build-up (ethanol)
What is the carrying capacity?
The maximum number of individuals of a species that the habitat can support indefinitely (without threatening other species in the habitat)
What is a population crash?
A sudden drop in population due to population significantly exceeding carrying capacity. Following carrying capacity is lower due to habitat damage
What are environmental factors that may limit population growth?
-Predators
-Disease
-Shortage of requirements for survival (food, water, shelter, light)
What is the competitive exclusion principle?
When two species occupy the same niche, there will be competition and one species will outcompete the other
Why is intraspecific competition more significant?
Members of the same species have the same niche and compete for the exact same resources. It tends to be stabilising influence of population size
What are examples of abiotic factors?
-Light
-Humidity
-Topography
-Pollution
What is a density-dependent factor?
The effect of these factors increase with population size
What is a density-independent factor?
The effect of these factors are independent of population size
What does PANDA stand for?
Predators
Availability of resources
Nutrient supply
Disease
Accumulation of wastes
What does PAW stand for?
Phenomena
Abiotic factors
Weather conditions
