Population size Flashcards
A group of organisms with similar characteristics, which produce fertile offspring
What is a population?
a group of the same species that are found in a particular area and can crossbreed freely
What is a community?
a group of populations occuring in a particular area
What is a ecosystem?
a unit of plant and animal communities in interaction with eachother aswell as with non-biotic factors
What is an enviroment?
The external factors, living and no-living surrounding an organism and influencing its development and surival
What is a habitat?
The specific enviroment in which a plant of animal species normally occurs
What is a population size?
a populaion size refers to the total number of individuals in a population
What is a populaion density?
The population density is the number of indivduals of a population per unit area. e.g. 10 sheep per hectare
what are the four factors known as parameters, that effect the population size?
- Natality
- mortality
- immigration
- emigration
What is the direct technigues used to determen a population size?
- cencus
- counting
- aerial photographs
What are the indirect techniques used to determen a population size?
- mark-recapture technique
- quadrats
Explain the mark-recapture technique.
- a specific are is demarcated
- a number of individuals are caught, counted and marked and they are known as the 1st sample
- the marked individuals are released into the environment
- sufficient time must be allowed for marked individuals to mix with the rest of the population
- another group of indivduals is caught and counted and they are known as the 2nd sample
- the number of marked individuals in the 2nd sample are counted
- the formula P=(m x s) / t is then used to determin the population size
p= estimated population size
m=total number of 1st sample marked
s= total number of animals captuerd in 2nd sample
t= number of marked inidviduals in 2nd sample
explain the quadrats technique.
- a quadrat is usually a square frame of metal, wood or plastic and a known size
- an area where organisms must be counted is demecrated and the surface area is determind
- the quadrat is placed on the ground in the demecrated area and the organisms concerned are counted inside the frame
- this is the number of indaviduals per unit area
- this process is repeated a few times in diffrent areas of the demarcated area by placing the quadrat randomly on the ground
- the average number of individuals per quadrat is caculated
- the total number of individuals in the population is determend using the following formula
population size= average number of individuals per quadrat x surface area of the area / surface area of the quadrate
What are the two basic growth forms in a population?
- Geometric j-shaped
- Logistic s-shaped
Explain the Geometrical growth form.
It is a growth form where the conditions for reproduction is ideal and can result in maximum possible growth rate as the population increases rapidly
What are some characteristics of the geometric growth form?
- has a distinctive j-shape
- initially the increase in numbers is slow
- in time there is a sharp increase in individuals
- a sudden standstill often occurs
Explain the logistical growth form.
It is a growth form where there is suffecient food, water, space and a litle predation
what are the phases in a logistical growth form?
- lag phase
- geometric growth phase
- decelerating growth phase
- equalibruim phas
What is a stable population?
It is a population where the numbers fluctuate around the carrying capacity
What is an unstable population?
it is a population where the numbers far exceed the carrying capacity, this cause the enviroment to be damaged, causeing an decrease in teh carrying capacity of the enviroment
What are the density depended factors?
also known as limiting factore, these factors increase or take an effect when the population numbers increase
an increase in population numbers result in:
* a greater demand for food and water, causing increased compition, which limits the reproduction
* a decrease in living space
* a shortage in shelter
* an increase in predators
What are the density independed factors?
Density independed factors are limiting factors that are more natural occuring such as natrual disasters and extreme changes in tempreture
