Population Ecology Flashcards
group of individuals belonging to the same species living in the same habitat or interbreeding and sharing genetic information
population
has a unique physical distribution in time and space
population
contains members of different ages and its size or density is likely to change over time, increasing or decreasing according to the reproductive success of its members
population
understanding this is important for interpreting census or survey data for population control
population dynamics
four primary ecological events that influence population are:
natality
mortality
immigration
emigration
mathematically, this relationship can be expressed in the following simple equation
change in pop. density = (natality+immigration) - (deaths+emigration)
factors, both biotic and abiotic, affecting the births, deaths, immigration or emigration, producing an impact to population density
secondary ecological events
may also affect the frequency, extent, magnitude, or duration of a primary ecological event
secondary ecological evnts
act as population regulating factors, and are also regarded as environmental resistance whenever the limit a population from its maximum reproductive potential
secondary ecological events
secondary ecological events can be divided into two broad categories
independent factors
density-dependent factors
could result to increased mortality decreasing population density
natural calamities
might result to prey natality allowing its population to grow
inactivity of predators
include events or conditions that are usually weather- or climate-related
density independent factors
affects all members of the population in similar ways, regardless of its size or density
density independent factors
Factors whose effects on the population is constant regardless of the number of individuals preset
density independent factors
example include unusual weather patterns, strong tropical cyclones or super typhoons such as typhoon Yolanda, natural disasters (hurricanes, volcanic eruptions, earthquakes), seasonal cycles (flood and droughts), and even certain
human activities such as construction of dams and deforestation, extreme temperature, photoperiod
density independent factofs
➢
have negative effect on population density just as much as favorable climatic conditions can have a positive effect
density independent factors
operate only when the population density reaches a certain level, operate proportionately to the size of population
density dependent factors
factors operate mostly when a population is large and dense while they do not greatly affect small and scattered populations
density dependent factors
examples include parasitism, disease, predation, competition, dispersal and immigration, pathogens causing infectious diseases
density dependent factors
example of density-dependent factors that are susceptible to spread of contagious disease caused by parasites than a small and sparse population
parasitism
example of density-dependent factors which includes predators migrating to areas with high density of prey populations or a behavioral response, predators will focus their attention primarily on the
most abundant prey species
predation
for limited resources is also density dependent, when population become crowded, organisms compete for food, water, space, light and other requirements for life
competition
members may face competition mostly from individuals of other species who need the same resources
interspecific competition
members of one population may compete with other members of the same population
intraspecific competition
may weaken survival and reproduction
competition
density-dependent factor that refers to the physical trait or behavioral adaptation that reduces or eliminates competition is likely to be favored by natural selection leading to evolutionary change
behavioral response
– determines where a population lives
ecological niche
occurs whenever the niche parameters of two (or more) different species overlap
interspecific competition
the more the overlap, the greater the competition
interspecific competition
interspecific competition may lead to (3) outcomes
competitive exclusion
range restriction
competitive displacement
wherein one species is competitively superior driving other species into extinction
competitive exclusion
wherein each species is confined to a particular habitat outcompeting the other species
range restriction
wherein two species evolve in divergent direction, able to adapt to different resources allowing them to co-exist in the same habitat with little competition or without direct competition at all
competitive displacement
pattern of population growth
exponential growth or logistic growth
s-shaped curved, limited resources, population growth slows, stable
logistic growth
(J-shaped curve), unrestricted growth
exponential growth
regulate exponential growth, aligned with the law of tolerance
limiting factors
states that the abundance of organism can be can be controlled by certain limiting factors where levels of these exceed maximum or minimum limits of tolerance of that organism
law of tolerance
law of tolerance is also known as
shelford’s law
the abundance or distribution of an organism can be controlled by certain factors (climatic, topographic, and biological requirements) where levels of these exceed maximum or minimum limits
of tolerance of that organism
what law
law of tolerance
may be contest or scramble competition depending on the availability of resources
intraspecific competition
will take place if the resources are stable over time; individuals will establish a territory and will defend it from intruders
contest competition
each territory generally provides enough resources for the owner’s survival and reproduction
contest competition
individual who fail to establish a territory can be a competitive disadvantage
contest competition
strongest individuals are likely to hold a territory, they have the best chance to survive and reproduced, passing their g enes to the next generation
contest competition
occurs in situations where resources are temporary
scramble competition
individuals that compete for these resources scramble for access in a first-come-first-served basis
scramble competition
first arrivals get the best conditions for survival and reproduction, those who come late will encounter a depleted resource that may no longer support growth and development.
scramble competition
may also give populations a favorable advantage, allowing them to reduce mortality, use resources more efficiently, or accomplish tasks that could not be performed by solitary individuals
cooperative interaction
best exemplified by social insects, such as ants, bees, wasps and termites. They were able to outnumber all other animals in many terrestrial habitats and, despite their small size, they usually play dominant roles in community ecology, both as consumers and as decomposers
cooperative interaction
may also be between different species in the form of symbiotic relationships, i.e. mutualism and commensalism
cooperative interaction
world’s population grew very slowly until this
1750
a long period of this happened until 1000 BCE (before common era), when the world’s population was approximately 300 million; this was followed by a period of slow growth from 1000 BCE to approximately 1750
stationary growth
did not become exponential until around 1750 due to high mortality counterbalancing the high fertility
population growth
function of several factors, including poor nutrition, which led directly to deaths through starvation and indirectly through increasing susceptibility to disease; epidemics; and, quite possibly, infanticide and geronticide, especially during times of food shortage
high mortality
Decline in deaths starting in the middle of 18th century occurred because of
➢
Improvement in food availability
➢
Housing
➢
Water cleanliness
➢
Personal hygiene
➢
Public sanitation
reason of lowered mortality in the 20th century
medical advances
civilization where theories about population growth first appeared
ancient greece
English clergyman and economist that was considered to be the pioneering theorist of modern age
thomas malthus
Formulated a principle that held that unchecked population grows more quickly than the mans of subsistence (food and resources) to sustain it
thomas malthus
Became notorious for his principle of population “increment in population’ and ‘decrement in food supply
thomas malths
Published his views on the effect of population on food supply on 1798
thomas malthus
Population grows at a ___ rate (1, 2, 4, 16, 32) and food production increases at an ___rate (1,2,3,4,etc.)
geometric
arithmetic
Population growth will/will not always exceed the amount of food supply
will
will be controlled either by preventive checks or positive checks
population
checks that include lowering the number of births, particularly by postponement of marriage age
preventive checks
include increasing deaths by means of famines, plagues,
natural disasters, war
positive checks
is morally based preference so family planning and contraception was supported by later followers of Malthus (neo-Malthusians)
preventive checks
Negative effects of population growth:
war
violence
environmental degradation
unchecked population grows more quickly than the means of subsistence (food and resources to sustaine it)
principle of population
directly opposed Malthus’ views on population wherein he disagreed with the Malthusian idea of a universal principle of population that applied to all societies
karl marx
For him, population growth depended upon the economic base of society thus capitalist society is characterized by its own population principle called “Law of Relative Population Surplus”
Karl Marx
what population principle did Karl Marx propose
Law of Relative Population Surplus
He argued that capitalism creates overpopulation (i.e. a surplus of people relative to jobs), leading to increased unemployment, cheap labor, and poverty
Karl Marx
requires unemployment in order to ensure a docile, low-paid class of laborers
capitalism
He envisioned that overpopulation would not occur in post-capitalist, communist society
KArl Marx
in the middle of the 20th century, this became the dominant theory of population growth
demographic transition theory
Based on observed trends in Western European societies, it argues that populations go through three stages in their transition to a modern pattern
demographic transition theory
three stages of demographic transition theory
pre-transition
stage of transition
post transition
characterized by low or no growth, and high fertility is counterbalanced by high mortality
what stage
pre-transition
mortality rates begin to decline, and the population grows at a rapid pace. By the end of this stage, fertility has begun to decline as well. However, because mortality decline had a head start, the death rate remains lower than the birth rate, and the population continues to experience a high rate of growth.
what transition
stage of transition
the movement to low fertility and mortality rates is complete, producing once again a no
-growth situation.
post transition
explains these three stages in terms of economic development namely industrialization and urbanization
theory of demographic transition
Since 1980, this theory has been criticized for its failure to consider cultural variables and its hypothesized relationship between population growth and economic development
theory of demographic transition
is the maximum number of individuals of a given species that an area’s resources can sustain indefinitely without significantly depleting or degrading those resources
carrying capacity
expanded to include not degrading our cultural and social environments and not harming the physical environment in ways that would adversely affect future generations
human carrying capacity
cannot continue indefinitely in a resource-limited environment.
exponential growth
Eventually a population becomes so large that it runs out of free space, outgrows its food supply, or exhausts other assets
exponential growth
As population density approaches the carrying capacity, competition becomes more intense, mortality _____ , the birth rate ___, and any one of the following alternatives
is possible
increases
drops
logistic or sigmoid curve/ boom or bust
population leveling out and stabilize below carrying capacity
logistic or sigmoid
the population may briefly overshoot the carrying capacity and then crash, resulting into depletion of natural capital and ecosystem collapse
boom or bust
provide greater information on population status, the effects of ecological and anthropogenic activities
population density
describe the relationship between area, population, and density
D = P/A
arrangement of individuals within a habitat at a particular point in time, and broad categories of patterns used to describe them
dispersion pattern
organisms are clustered together in groups, may reflect a patchy distribution of resources in the environment
climped
most common pattern of population dispersion
climped
organisms have an unpredictable distribution, typical of species in which individuals do not interact strongly
random
organisms are evenly spaced over the area they occupy, typical of species in which individuals compete for a scarce environmental resource, such as water in a desert
uniform
a population contains three age groups: prereproductive (0-14), reproductive (15-44), and postreproductive (45 and older)
age structure
prereproductive age groups includes
0-14
reproductive group includes
15-44
postreproductive grop includes
45 and older
number of individuals who are born alive; measured as crude birth rate (number of live births/1,000 mid year total
population)
natality
number of individuals who die; measured as crude death rate (number of deaths per 1,000 mid-year total population)
mortality
number of individuals that enters a population
immigration
number of individuals that move out of a population
emigration
– the variability of the population size determines the population growth rate (birth rate + immigration) – (death rate + emigration)
population size
group of individuals of the same species occupying a particular area at a given time
population
level where group of individuals of the same species live together in a certain ecosystem (biome)
population
population characteristics
read
➢size
➢density
➢patterns of dispersion; distribution
➢demographics (age structure, sex ratios)
➢rates of growth (or decline)
➢limits on population growth
number of individuals in a given area
population size
factors that affect population size
natality
mortality
migration
production of new individuals per unit or time under a particular set of ecological conditions, expressed as a rate
natality
expressed as a number of individuals born per 1,000 individuals per unit of time
human population birth rate
crude birth rate formula
number of births / midyear total population x 1000
number of individuals dying per unit of time
mortality
determined by physiological longevity and/or unfavorable environmental conditions, by diseases, by predators, competition
mortality
crude death rate formula
number of death / midyear total pop x 100
movement of individuals from one place to another
migration
act of individual moving out from their original place
emigration
movement is coming into or joining a population
immigration
maximum number of individuals that the population can support
carrying capacity
– refers to the way individuals are spaced within their area
population dispersion
refers to the number of percentage of males and females in young, middle, and older groups
age structure
Philippines Gender ratio of men to women
101:100 (1.01)
refers to changes that are predicted to occur in the members of the population over time, includes 4 variables:
population dynamics
population dynamics invlude 4 variables
density
dispersion pattern
age structure
size of population
How are populations measured:
➢Population density – number of individuals in a given area or volume
➢Count all the individual in a population
➢Estimate by sampling
population coping mechanism on envi pressure to control population
R vs K strategists
species or populations that respond quickly to favorable conditions, usually low, the population increases exponentially when environmental conditions becomes favorable
R strategists
populations whose numbers are maintained close to saturation level or carrying capacity (K)
K strategists
difference in numbers between a population over time
absolute growth
1997 = 5,910,566,295 vs 2017 =
7,550,262,101 (growth of
1,639,695,806)
absolute or relative?
absolute
____ growth expressed in crude
rate
relative
2000 = crude growth rate –
1.4% for every 1,000 people, 14
individuals are added per
year
absolute or relative
relative
anything that
drives a population’s size and slow
or stops it from growing
limiting factors
is the population
within an area that the environment
can support sustainably and
maintain stable equilibrium.
carrying capacity
few offspring, low
infant mortality, parental care
of young, most survive until
old age, large mammals
including humans
survivorship curve?
type I
equal chance of
living or dying throughout the
lifetime, birds, reptiles, small
mammals
survivorship curve
type II
high infant mortality
rate, many offspring, no
parental care, invertebrates,
fish, amphibians, and plants
survivorship curve
type III
degradation of this include loss of cropland, forest, wetlands, wildlife habitats
land and biodiversity
degradation of this include use of surface water, increased runoff and flooding, pollution, natural sewage treatment
water
