Topic 7 C Populations in ecosystems Flashcards
What is an ecosystem
All the organisms living in a community plus all the abiotic conditions in the area where they live
What is a habitat
The place where an organism lives in an ecosystem
What is a niche
The role of a species within its habitat
Includes its biotic interactions and abiotic interactions
What is intraspecific competition
Occurs when individuals of the same species compete with one another for resources such as food, water, light or breeding sites
What is interspecific competition
Occurs when individuals of different species compete for resources
When populations of two species are in competition one will normally have a competitive advantage over the other. The population of this species will gradually increase while the other gradually diminishes. If conditions remain the same this will lead to the removal of one species – the competitive exclusion principle. To show how a factor influences population size, it’s necessary to link it to death and birth rate.
Predation
Occurs when one organism is consumed by another.
Effect of predator-prey relationships on population size:
Predators eat the prey, reducing the population of prey
With fewer pray available, the predators are in greater competition with each other
The predator population is reduced as some individuals are unable to obtain enough prey for survival and reproduction
With fewer predators, more prey are able to survive and reproduces so their population replenishes
With more prey available for food, the predator population increases
What is abundance
Abundance is the number of individuals of a species within a given area. Abundance can be measured by:
Frequency which gives an idea of the species present and their general distribution, however doesn’t provide information on their density and detailed distribution
Percentage cover - It’s useful when a species is abundant or difficult to count. The data can be collected rapidly and individuals don’t need to be counted. It’s less useful when organisms occur in overlapping layers (plants)
Mark release recapture method
Capture
Mark in a way that is non-harmful and doesn’t impact survival
Release back into habitat and allow time to disperse
Recaptured and number of marked individuals recorded
Estimating population size: total in 1st sample x total in 2nd sample / number of marked individuals recaptured
What does mark, release, recapture rely on
The proportion of marked to unmarked individuals in the second sample being the same as the proportion of marked to unmarked individuals in the population as a whole
The marked individuals from the first sample being distributed evenly
The population has a definite boundary to avoid immigration or emigration
Few deaths or births
What is succession?
The process by which an ecosystem changes over time
At each stage, the plant and animal communities slowly change the environmental conditions
Primary succession
Pioneer species changes environment
Environmental conditions become more favourable
Climax community eventually reached
What is secondary succession
Happens on land that’s been cleared of all plants but soil remains
E.g. after fire or deforestation
Similar to primary succession though starts at a later stage and the pioneer species are larger plants
What is conservation
The protection and management of species and habitats (ecosystems) in a sustainable way
Examples of conservation methods
Management of succession
Seed banks
Captive breeding
Fishing quotas
Protected areas
Percentage change
final value - original value / original value x100
