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
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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
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Improvement in food availability
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Housing
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Water cleanliness
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Personal hygiene
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Public sanitation