Populations and Ecosystems Flashcards
What is the biosphere?
The life supporting layer of land, air and water that surrounds the Earth.
What is an Ecosystem
A specific area made of interacting biotic and abiotic features. There are two main processes: the flow of energy through the system and the cycling of elements within the system.
What is a population?
A group of interbreeding organisms of one species in a habitat.
What is a community?
All the populations of different organisms living and interacting in a particular place at the same time.
What is a habitat?
Where a community of organisms live.
What is an ecological niche?
How an organism fits into the environment.
Investigating populations things
Quadrats Random Sampling Systematic sampling Measuring Abundance Mark-release-recapture techniques
Quadrats: what do we need to consider when using them?
Size of quadrat depends on size of subject organism
Number of sample quadrats to record within the area
Position of each quadrat within the area
Random sampling
Avoids bias
Random numer generator to get coordinates
Count frequency of species or organisms within the quadrat
Systematic sampling
Use transects
Used to investigate transitions
e.g: to measure the abundance of grass from the trunk of the oak tree on the field to the middle of the field.
Measuring abundance: what does it measure?
Frequency
Percentage cover
Mark-release-recapture
Estimated population size =
(total individuals in 1st sample x total individuals in 2nd sample) / number marked individuals recaptured
Mark-release-recapture only works under which assumptions?
The proportions marked and unmarked in the 2nd sample is the same as the marked and unmarked in the total population.
Marked individuals spread evenly throughout the population.
Closed system: no immigration or emigration.
No deaths or births
Marking provides no disadvantage (e.g: doesn’t makes individual more conspicuous)
Marks not rubbed off, or lost.
Population growth curves have which stages
Slow growth
Rapid growth
Plateau with fluctuations
Abiotic factors
Temperature
Light intensity
pH
Water and humidity
Biotic factors
Availability of food
Presence of predators
Disease
What is infraspecific competition?
Individuals of the same species compete for resources like food, water and breeding sites
What is interspecific competition?
Individuals of different species compete for resources like food, light, and water
What is a predator?
A predator is an organism that feeds on another organism known as their prey
Predator prey relationship
Predators eat their prey –> reducing prey population
Less prey –> more competition between each other
Decrease in predator population as some can’t eat enough
Less predators –> few prey eaten
Increase in prey population –> more to eat for predators
Predator population increases
Factors affecting growth and size of human populations
Immigration
Emigration
Birth rate
Death rate
Factors affecting birth rate
Economic conditions –>generally LEDCs = high BR
Religious backgrounds –> some religions oppose birth control and encourage larger families
Social pressures –> large families = higher social standing
Birth control –> availability of contraception and abortion
Political factors –> education and tax policies
Factors affecting death rate
AGE PROFILE –> ageing = more elderly = more deaths
LIFE EXPECTANCY a birth
Availability of FOOD and a balanced diet
SAFE DRINKING WATER and effective sanitation –> less water-borne diseases e.g: cholera
MEDICAL CARE
NATURAL DISASTER frequency: drought, famine, disease or tectonic or meteorological = high death rate
WAR
