Transcript
Geographic distribution/ range Population density Population dispersion Immigration Emigration Logistic growth
Exponential growth Biotic potential Environmental resistance Carrying capacity Density-dependent factors Density independent factors
1. Geographic distribution2. Density3. Dispersion4. Growth rate5. Age structure
What is a population?What is a population?A population is a group of individuals of the same species occupying the same general area.
- geographical range of a species or a group of species
- the suitability of habitats influences the distribution of a species (each species is adapted to a rather limited range of abiotic and biotic conditions)
Population densityPopulation density
- the number of individuals per unit area or volume
- pattern of spacing among individuals in a habitat
Types of dispersion:RANDOM
- habitat conditions are uniform / resource availability is steady- individuals neither attract nor avoid each other- rare in nature
UNIFORM- individuals are evenly spaced in a habitat- due to competition or territorial behavior
CLUMPED- species are aggregated in patches- most common in nature because:
cluster around patchy resources live in social groups species has limited dispersal powers
- increase in the size of a population of organisms
population size the number of individuals that contribute to a population’s gene pool
For mobile animals Individuals are captured and marked in some way,
then the marked animals are released. Later, animals are captured and checked for marks. In the later sample, the proportion of marked
individuals should be representative of the proportion marked in the whole population.
- increase in the size of a population of organisms
population size the number of individuals that contribute to a population’s gene pool
Factors that affect population size:1. Number of births (natality)2. Number of deaths (mortality)3. Immigration/Emigration
Immigration – the arrival of new residents from other areasEmigration - individuals permanently move out of the
population
–no overall increase or decrease during a specified interval; population size is stabilized (assuming that immigration and emigration balance each other number of births = number of deaths)
04/10/23Free PowerPoint Template from
www.brainybetty.com 12
Individuals in population have constant rate of reproduction
Over time, becomes infinitely large Under ideal conditions with unlimited
resources, population will grow exponentially Ideal condition- abundant space, food,
protection against predator and disease
Does not continue naturally for a long time
04/10/23Free PowerPoint Template from
www.brainybetty.com 15
Carrying capacity
Due to decrease in resources that lead to decrease in population growth
Decrease in pop growth maybe caused by decrease in death rate, increase in death rate or the occurrence of both at the same time at the same rate Is also true for emigration and immigration
Recall: limiting factors determine the primary productivity of an area
In population, a limiting factor causes population growth to decrease
Pop size
competition
predation
Parasitism and disease
Drought and other climate extremes
Human disturbances
Depends on the population size Is due to population density
Major force of evolution Competition should be decreased Evolution will lead separation of niches
No same species can occupy the same niche at any given place and time
One of the best population control Characterized by fluctuations of the prey and
predator populations
Limiting factor that affects the population regardless of its size Characterized by a CRASH in the population
size
biotic potential/reproduction potentialmaximum rate of growth of a population
conditions are optimal / idealhigh reproduction, low mortality
environmental resistancefactors that limit population growth
limiting factors: food, space, O2, shelter, accumulation of wastes
carrying capacity maximum number of individuals in a population (or
species) that a given environment can support indefinitely
in the steady state (of logistic growth) size oscillates around this number
Age structure the number of individuals in each of several
age categories:1. prereproductive age – have the potential to
produce offspring when they mature2. reproductive age – actual reproducing
members3. postreproductive age 1 & 2 make up the population’s
reproductive base
The biotic potential of an ecosystem is affected by environmental resistance, thus resulting in a maximum carrying capacity
Understanding patterns in human population growth is important in addressing population problems around the world.
top related