19 Populations in ecosystems Flashcards
Ecology
The study of the inter-relationships between organisms and their environment.
What is an ecosystem made up of?
All the interacting biotic and abiotic features in an area.
What are the two main processes in an ecosystem?
The flow of energy through the system and cycling of elements within a system.
Population
A group of interbreeding organisms of one species in a habitat.
Community
All the populations of different organisms living and interacting in a particular place at the same time.
Habitat
A place where a community of organisms live. (Within one ecosystem, there are many habitats)
Microhabitats
Smaller units within a habitat
Niche
Describes how an organism fits into the environment.
What could never happen between two species?
Occupying exactly the same niche.
What would happen at the start of the population growth curve?
Slow growth - because small number of individuals reproduce slowly to build up numbers.
What would happen at the middle of the population growth curve?
Ever increasing number of individuals continue to reproduce (exponential growth)
What would happen at the end of the population growth curve?
Stable state - only cycling fluctuations, due to food supply or predator numbers.
Carrying capacity
The certain size that each population can be sustained over a long period of time.
Limiting factors
Determines the carrying capacity of any population.
E.g. of abiotic factors
Light, water, pH and temperature
E.g. of biotic factors
activities of living organisms - competition and predation
How does each abiotic factors affect population size?
Temperature: Optimum temperature for different species. Enzymes activity etc.
Light: Photosynthesis, affects food chain.
pH: action of enzymes.
Water & humidity: essential to growth and living. Humidity affects rate of transpiration.
Reasons causing human population explosion.
- Development of agriculture
- Development of manufacturing and trade created by the industrial revolution.
- Medicine, increases life expectancy.
Factors affecting the growth and size of human populations
Basic factors: birth rate and growth rate
Individual populations: immigration and emigration
Equation for population growth.
(births + immigration) - (deaths + emigration)
Equation for %population growth rate (in a given period)
Population change during the period/ population at the start of the period x100
Factors affecting birth rates
- Economic conditions
- Cultural and religious backgrounds
- Social pressures and conditions
- Birth control
- Political factors
Equation for Birth rate
number of births per year/ total population in the same year x100
Factors affecting death rates
- age profile (general age of the population)
- life expectancy at birth
- food supply
- safe drinking water and effective sanitation
- medicinal care
- natural disasters
- war