What are the three phases for the usual pattern of growth?
- Slow growth- initially small number of individuals reproduce to slowly build up their numbers.
- A period of rapid growth where the ever increasing number of individuals continue to reproduce.
- A period when the population growth declines until its size remains more or less stable.
What are abiotic factors?
These are concerned with the non-living part of the environment
What are biotic factors?
These are concerned with the activities of living organisms.
What abiotic conditions influence the size of a population?
Temperature
Light
pH
Water and humidity
How does the abiotic factor temperature influence the size of a population?
Each species has a different optimum temperature.
Cold blooded- as temp falls below this enzymes work more slowly and so metabolic rate is reduced.
Above- potential denaturation.
Warm blooded- homestasis (maintaining temp)
However further from optimum = less energy spent on growth trying to maintain temp.
How does the abiotic factor light influence the size of a population?
Ultimate source of energy for ecosystems.
Rate of photosynthesis increases as light intensity increases.
Greater rate of photosynthesis increases growth rate.
How does the abiotic factor pH influence the size of a population?
Affects the action of enzymes.
Optimum levels.
How does the abiotic factor water and humidity influence the size of a population?
Where water is scarce populations are small (only well adapted).
Humidity affects transpiration rates in plants and the evaporation of water from the bodies of animals.
What is intraspecific competition?
Occurs when individuals of the SAME species compete with one another for resources such as food, water, breeding sites, etc.
What is interspecific competition?
Occurs when individuals of DIFFERENT species compete for resources such as food, light, water, etc.
Where populations of two species initially occupy the same niche, one will normally have a competitive advantage over the other.
What is predation?
Predation occurs when one organism if consumed by another.
Summarise the relationship between predators and their prey and its effect on population size.
Predators eat their prey, reducing its population.
Fewer prey- predators are in greater competition with each other for the prey that are left.
Predator population is reduced as some individuals are unable to obtain enough prey for their survival.
Fewer prey eaten.
Prey population increases.
Predator population increases.
What two major and relatively recent events that have led to an explosion in the human population.
The development of agriculture
The development of manufacturing and trade that created the industrial revolution.
Factors affecting the growth and size of the human population.
Birth rate and death rate.
Immigration and emigration.
Population growth =
(births + immigration) - (deaths + emigration)
Percentage population growth rate (in a given period) =
Population change during the period/ population at the start of the period
x 100
Factors affecting birth rates…
- Economic conditions
- Cultural and religious backgrounds
- Social pressures and conditions
- Birth control
- Political factors
Birth rate =
number of births per year/ total population in the same year
x 1000
Factors affecting death rates…
- Age profile
- Life expectancy at birth
- Food supply
- Safe drinking water and effective sanitation
- Medical care
- Natural disasters
- War
Death rate =
Number of deaths per year/ total population in the same year
x 1000
What information is required in order to calculate the growth rate of a population?
Birth rate and death rate
What are the steps in mark release recapture?
- Capture a sample of a species and count them.
- Mark them in a harmless way.
- Release them back into their habitat.
- Wait a week, then take a second sample from the same population.
- Count how many of the second sample are marked.
What is the equation you can use after mark release recapture to estimate population size?
total population size = number caught in 1st sample x number caught in 2nd sample/ number caught in 2nd sample
Suggest why % average life expectancy for males is lower?
Males more risk of CHD, less HDL in blood than females
More men smoke
Men go to war
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Ecology Definitions18
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Respiration25
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Populations27
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The Nitrogen Cycle19
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Energy and ATP12
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Photosynthesis and Light Dependent Reaction20
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Genetics22
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Photosynthesis and Light Independent Reaction16
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Respiration Memory Table8
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Energy transfer and energy loss41
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The Carbon Cycle7
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Succession and Conservation16
