Populations and Ecosystems

Resources and exponential growth

• A population: a group of organisms of one species that lives in the same place and the same time and can successfully reproduce.

• Growth occurs at a rate higher than what is needed to replace individuals that have left or died.

• Exponential growth in populations:– Typically short term, in new habitat with lots of

resources, or when pressures are removed such as species protection

Exponential Growth

. protection

                              

Exponential Growth and re-introduction

• Cases where habitat has been destroyed in the past can deplete a species. Ex. Deforestation

• When the habitat is reinstated it is possible to reintroduce the species and as long as the resources remain available exponential growth will occur.

• Ex. Wild turkeys went from 4400 to 70,000 in 20 years.

Limiting Factors

• Exponential growth cannot be sustained naturally

• As the population increases the individuals have access to fewer resources

• Abiotic factors also play a huge role

Carrying Capacity

• Carrying capacity is the size of the population that can be supported indefinitely but the available resources and services of an ecosystem.

• When a population is maintained at carrying capacity it is at an equilibrium (Balanced)

• When a resource is being used at a rate that exceeds carrying capacity the population will drop in relation.

• This resource could be food, but may also be abiotic.

Human Activity and Carrying Capacity

• Urban Sprawl-the spreading of city area across natural habitats results in habitat loss. This affects the carrying capacity of many species.

• Intensification, building up as opposed to out is one solution to prevent habitat loss.

Interactions Among Species

• Ecological Niche– The way that an organism occupies a position in an

ecosystem, including all the necessary biotic and abiotic factors.

– Ex. Biotic niche of brown bat• Insects it eats • Competitors (common Nighthawk)• Predators

– Abiotic niche of brown bat• Places for roosting and hibernation• Time of night it hunts• Airspace it flies• Temperature range it can tolerate