Think What are the 2 different types of population curve we have seen?

Pair Can you describe one to your partner? Can your partner describe the other?

Share Can you SKETCH and ANNOTATE a graph for the two types of curve as a group

Learning outcomes You should be able to: List examples of density-dependent and density- independent factors Describe the role of density-dependent and density- independent factors in the regulation of populations

Population growth Population numbers in an area / ecosystem are determined by four conditions, what do you think they are? Births Deaths Immigration Emigration

What stops a population from growing exponentially? LIMITING FACTORS

Two types Density-dependent Competition for resources and space Disease Parasitism Predation Density-independent Extremes of weather (drought, fire, hurricanes) Long-term climate change Volcanic eruptions Tsunamis / floods What do you think the difference is? Can you think of any examples? Related to population density. Factors that lower the birth rate or raise the death rate as a population grows in size. Factors which affect a population irrespective of population density, notably environmental change.

Prey increases Predator increases Prey decreases Predator decreases Density-dependent factors Negative feedback mechanisms Where have you seen this diagram before? What real-life examples do you have for this diagram? NOW: Using your answers -explain how predator prey relationships can be considered density- dependent.

Predator / prey relationship

Density-independent Mosquitoes are plentiful in the summer months When autumn sets in the populations crash. Why? Summer Winter Population Time

Review Density –Dependent Disease Predation Food source Territory Mates Density-independent Tsunami Temperature Volcanic eruption Light intensity Forest fire Run to the right side depending on the type of factor Do it outside

Density-dependent factors… can be further divided into… Internal factors Act within a species External factors Act between different species

Internal factors Act within a species fertility (intraspecific competition) size of breeding territory limited food supply

External factors Act between different species and come from outside predation disease

Impact of human activities Cause of population growth Example Increase available resources by farming; nutrient pollution Reduce competitionby poisoning insect pests Reduce pressure from predators by over-hunting large carnivores Introduce animals to new areas game release

Impact of human activities Cause of population decline / extinction Example Change the physical environment and cause habitat disruption by draining a swamp; toxic pollution Change the biological environment by introducing new species rabbits in Australia; rats on islands Overkillbig-game hunting Cause secondary extinctionsloss of food species

Checking outcomes Get out your learning outcomes booklets and complete them… Hand them in so that I can check them for classwork.