Ecosystems & Populations

Ecosystem

Combination of the community of organisms living in a habitat and their interactions with each other and the physical environment

Abiotic Factors

Not due to living things e.g rainfall and temperature

Biotic Factors

Living things in the habitat, part of the environment due to living things e.g disease.

Community

Interacting populations in the same area at the same time e.g trees and undergrowth plants.

Habitat

Where an organism lives

Competition

Relationships between organisms for resources in the same area at the same time

Environment

Combination of physical, chemical and biological factors that act upon an organism.

population

group of organisms of the same species in a defined area

Density Dependant Factor

Factors that increase as population increases

Density Independent Factor

Factors that decrease the population

Ecological Niche

The role, activities and location of an organism within a habitat. No two organisms occupy the same niche.

Rate of Growth =

Birth Rate - Death Rate +/- Net Migration

Biotic Potential

Organisms feed and breed and produce offspring

Lag Phase

'Population becoming established

Exponential phase

Births>Deaths

Stationary Phase

Population is at carrying capacity

Why does Biomass and energy decrease?

Energy is lost to the environment, not all energy is absorbed, carnivores only eat a portion of their food.

Photosynthetic Efficiency

Measure of how well a plant is able to capture light energy

GPP

Rate of production of chemical energy in organic chemicals by photosynthesis.

GPP=

NPP + Respiration

NPP=

GPP- Respiration

Population Density

Total Number in all quadrats sampled / no of quadrates x area of a quadrat

Lincoln Index

n1 x n2 / Nm

Succession

The change in structure and species composition of a community over time

Primary Succession

No previous vegetation and then development begins as plants move in

Secondary Succession

Colonisation of an area where organisms are already present