19 Competition and Predation

• Intraspecific competition is between individuals of the same species
• Compete for food, water, mates etc
• The availability of resources determines the size of the population
• Limpets compete for algae as this is their main source of food, more algae reults in a bigger population
• Oak trees compete for light and water from the soil. Over tie, there will be just a few large, dominant oak trees
• Robins compete for breeding territory as females are only attracted to males with established territories as this will hold space for food and a suitable nest

• Interspecific competition is between individuals of different species
• Compete for the same resources, other than mates
• One species normally has a competitive advantage over the other species which will increase this species' poluation whilst decreasing the other
• If conditions remain constant the less competitive species will become extinct
• This is the competitive exclusion principle
• 'The one that uses the resources the most effectively will ultimately eliminate the other'
• No two species can operate within the same niche
• Birth rate and death rate need to be linked to look at how polualtions change over time. This can be affected by a change in food supply or a new predator can impact the biirth and death rates of a species
• This effect may take long periods of time to see a change in population

• When predator prey relationships are investigated in labs, the prey is usually exterminated quite quickly due to the range of the habitat being limited by the lab conditions
• In nature the variety of environments is much larger so prey can adapt and use their surroundings more to their advantage
• Therefore, prey populations are varely rarely completeley diminished
• Often hard to obtain accurate predation data as habitats are endless and it can be hard to calculate numbers
• Sizes can only be estimated by sampling

• Preators eat prey reducing the number of prey
• With fewer prey, the predators are left in greater competition with eachother
• Predator population is reduced as there isn't enough food for some to survive and reproduce
• With fewer predators, more prey can survive and reproduce
• This increases the population of prey
• With more prey, more predators can survive and reproduce
• This increases the popualtion of predators

This causes the population of predators to lag behind te popualtion of prey on a population graph

• Disease and climatic factors also play a part in chnaging the fluctuations on a graphy of a predator-prey cycle
• This creates selection pressure as at each cycle only the best adapted are going to survive and reproduce accelerating natural selection