Populations and Sustainability Flashcards
Draw, label, and annotate with explanations, a generalised growth curve for natural populations.
- Phase 1/ lag phase/ slow growth - Small numbers of individuals that are initially present reproduce increasing the total population. Birth rate> death rate.
- Phase 2/ exponential phase/ rapid growth- Number of breeding individuals increases, the total population multiplies exponentially. No constraints. birth rate»death rate.
- Phase 3/ stationary phase/ stable state- further population growth is prevented by external constraints. Population size fluctuates, but overall its size remains relatively stable. Birth rates= death rates. Slight changes- fluctuations in limiting factors e.g prey
Define abiotic factor
Non-living conditions in a habitat
Define biotic factor
The living components of an ecosystem.
Define limiting factor
An environmental resource or constraint that limits population growth
Define carrying capacity
The maximum population size that an environment can support
Give 3 examples of limiting factors for population size and explain how each affects population size.
- Competition between the organisms for resources
- Build-up of the toxic by-products of metabolism
- Disease
Define Density dependent factors
- Any factor limiting the size of a population whose effect is dependent on the number of individuals in the population.
- For example, disease will have a greater effect in limiting the growth of a large population, since overcrowding facilitates its spread.
- Other examples- competition, predation, grazing
Define Density independent factors
- Factors that have an effect on the whole population regardless of its size
- e.g. Natural disasters- fires, earthquakes, volcanic eruptions and storms
Define migration
Seasonal movement of animals from one region to another.
Define immigration
The movement if individual organisms into a particular area increases population size.
Define emigration
The movement of individual organisms away from a particular area decreases population size
Define intraspecific competition
Competition between organisms of the same species
Define interspecific competition
Competition between organisms of different species
Give 4 examples of what organisms might compete for.
- Food
- Shelter
- Space
- Light
Describe and explain the “competitive exclusion principle”.
- Two species competing for the same resources cannot co-exist. (If they compete for all the same resources)
- If two species are competing for the same food source, but one is better adapted, the less well adapted species is likely to be out-competed
- If conditions remain the same, the less well adapted species will decline in number until it can no longer exist in the habitat alongside the better adapted species.
Give an example of interspecific competition in the UK
- Red and grey squirrels
- In 1870s grey squirrel was introduced to UK
- Its population quickly increased and resulted in red squirrel disappearing from many areas
- Grey squirrel can eat a wider range of food than the red squirrel and as it is larger can store more fat
- This increases its chances of survival and therefore ability to reproduce thus increasing its population.
- An increasing population of grey squirrels further reduces the food supply available to the red squirrels- reducing their ability to survive and reproduce.
Explain why intraspecific competition is an example of a density dependent biotic factor,
- The availability of the resource they are competing for determines the population size.
- The greater the availability the larger the population that can be supported.
- This results in fluctuations in the number of organisms present in a particular population over time
Describe how intraspecific competition effects population size over time
- Wavey graph- up then down
- Step 1- When a resource is plentiful in a habitat, all organisms have enough of the resource to survive and reproduce- increase in population size
- Step 2- As a result of the increased population, there are many more individuals that share the food or space available. Resources are now limited; not enough is available for all organisms to survive. Population size will decrease.
- Step 3- Less competition exists as the smaller population means less organism are competing for the same resources. This means more organisms survive and reproduce, resulting in population growth.
- Repeating cycle
Define predator
- Organisms that kill and eat another organism
- Predators have evolved to become highly efficient at capturing prey e.g. sudden bursts of speed, stealth and fast reactions
Define prey
- Organisms that are killed and eaten by other organisms
2. Prey have evolved to avoid capture- camouflage, mimicry or defence mechanisms (spines).
Define predation
- The capturing of prey in order to sustain life
- A biotic factor
- A type of interspecific competition
Describe and explain the general pattern shown in predator-prey relationships.
- Peaks and troughs in the size of prey population are mirrored by peaks and troughs of predator population after a time delay.
- Stage 1- An increase in prey populatio provides more food for predators, allowing more to survive and reproduce- increase in predator population
- Stage 2- Increased predator poplation eats more prey organisms, causing a deline in prey population Death rate of prey> birth rate
- Stage 3- Reduced prey population can no longer support the large predator population. Intraspecific competition for food increases , resulting in decrease in size of predator population.
- Stage 4- Reduced predator numbers result in less of the prey population being killed. More prey organisms survive and reproduce, increasing prey population.
- Cycle continues
Define the terms “conservation” and “preservation”, and explain the difference between the
- Conservation = the maintenance of biodiversity through human action or management.
- Preservation = the protection of an area by restricting or banning human interference.
- Preservation is when humans try to leave an area alone whereas conservation is when humans actively do things to support the biodiversity of an area.
Define reclamation
A form of conservation in which ecosystems which have been damaged or destroyed are restored.