Population Wcology Flashcards
population
a group of organisms of the same species living in a defined area where they may interbreed freely
what are factors affecting the size of a population called
population parameters
4 types of population parameters
- immigration
- mortality
- emigration
- natality
2 population parameters that increase the population size
- natality
2. immigration
2 population parameters decreasing population size
- mortality
2. emigration
survivorship curves
show that different populations have differing abilities to survive.
growth form
patterns of population increases
2 types of growth firms
- geometric(j-shaped) growth form
2. logistic(s-shaped) growth form
why would a population stop increasing
because there might be lack of food sources or there might be unfavourable conditions where the population is not able to adapt quick enough
phase where the population dies off suddenly
extinction phase
carrying capacity
maximum number of organisms of a specific species that a specific habitat can support/accommodate
lag phase
- there’s a slow increase
- individuals become(begin to adapt to environment) sexually matured
- organisms find mates and start producing offspring
accelerating phase
- there’s a rapid increase
- there is no environmental resistance(because they’re adapting to the environment)
- birth rate is higher than the death rate
decelerating phase
- increase rate is slower
2. there’s increased environmental resistance
equilibrium phase
- numbers(resources provided become limited) reaches a more or less constant level known as carrying capacity
environmental resistance
- all the factors that stop population growth
2. they lower the birth rate or increases the death rate
factors that stop population growth
- competition for food
- crowded living conditions
- disease
- predation(predators vs prey)
methods to determine the size if the population
- direct method
2. indirect method(mark-recapture method)
direct method
involves conducting a census, by counting all the individuals. it can only be used for stationary, slow moving or large individuals
(in a closed population mostly)
types of indirect methods
- mark-recapture method
mark-recapture method
- individuals are captured, counted, marked and released
- after allowing time for mixing another group is caught and the marked individuals in it are counted
- the total population is estimated by using the formula[p=(m×c)÷r]
precautions for using mark-recapture method
- the parking must not damage or affect the movement of the individuals
- allow time for mixing and prevent emigration and immigration
quadrat method
count the individuals in several
what is the size of a population regulated by
- density independent factors
2. density dependent factors
density independent factors
affect the population regardless of its size and these factors can always be recognized on a graph by a sudden drop on population numbers
examples of density independent factors
- climate(severe storms)
2. disasters(floods, earthquakes, fires)
density dependent factors
control the size of the population if its numbers are high
examples of density dependent factors
- lack of food
- water
- space and shelter
- parasitism and disease
why does population also decrease
because the environment can no longer sustain them and if it continues to decrease it can lead to species extinction
competition
when two or more individuals compete for the same resources that are jb short supply like food, shelter, nesting sites and mates
interspecific competition
is between two individuals of different species
intraspecific competition
is between two individuals of the same species
predation
is a process whereby animals of one species kill and feed directly on animals of another species
advantages of predation
the fitness and number of the prey population is controlled. mainly the old, sick and very young are killed
characteristics of a graph that shows relationship between predator and prey
- there are always two wavy lines
- the prey line peaks first and is at its highest, its always higher than the predator line
- with a decline in predators there is an increase in prey
energy flow
is the transfer of energy, originating from the sun, through all the trophic(feeding) levels in the food chain
1st trophic levels
consists of producers, and is where energy is lost as heat(respiration)
2nd trophic level
consists of primary consumers(herbivores) and energy is lost as heat, urine and faeces
3rd trophic level
consists of secondary consumers(carnivores) and energy is lost as heat(R), urine(U) and faces(F)
what happens when energy is lost at each level
less and less enrgy is passed on to successive levels
energy budget
shows what amount of energy eaten(C-consumed) goes into the tissues(P) and what happens to the rest(R,U,F)
C=P+R+U+F
what is a population pyramid(age-sex pyramid)
it’s a bar graph that shows the composition, by age and sex, of a nation’s population at the time of a census and it’s a convenient way to show, visually, give a national population is made up.
3 major age/sex groups a population contains
- pre-reproductive
- reproductive
- post-reproductive
what is the age structure of a population determined by
what proportion of the population falls into each of these age groups
age structure
the relative numbers of individuals of each age ina population
how is a graph constructed
- top of the pyramid shows the older population; bottomed of the pyramid shows the younger population
- number(%) of males is shown on the left and females is shown on the right in 5 year age groups. and there tend to be more females than males in older age groups
different types of population pyramids
- rapidly growing population
- stable population
- declining population
what does a rapidly growing population depict
- high birth rate
- rapid fall in each upward age group due to high death rates
- short life expectancy as found in LCD’s(due to lack of medical care, basic needs and income)
what does a stable population depict
- declining birth rate
- low death rate
- more people living to old age as found in MDC’s
(this is because these countries have more contraceptives and less kids cause they are focused on economic growth)
what does a declining population depict
- low birth rate
- low death rate
- higher depender ratio
- longer life expectancy as found in affluent countries
what happens if the pre-reproductive age group is the largest
- population will increase
what happens if the pre-reproductive age group is the smallest
population will decrease
population with more old non-reproductive individuals
it will grow more slowly than a population either a larger percentage of your individuals of reproductive age
purpose of population graphs
- provide a quick way to asses how rapidly or slowly a nation’s population is growing
- show if a country is more developed or less developed
- show history of a nation’s growth
- be useful in determining the number of economic dependents being supported like those under 1 years/over 65 years of age
forms a economically dependent group
0-15 year olds
represent the productive working group that forms the labour force of a country
15-65 year olds
represents senior citizens who are also dependent on the countries work force
65+ year olds
factors causing the make up of a population to change
- HIV/AIDS causing deaths of many secually active young women and men particularly in developing countries
- high proportions of young immigrants being rapidly absorbed, or losses due to emigration of able-bodied young adults
- losses due to able-bodied men fighting wars
- reduced birth rates during times of economic crisis
