Notes and summary on Population Ecology - IEB Matric bio/life Science
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Life Sciences
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12th Grade
Notes and summary on Population Ecology + Diversity of reproductive strategies. Covers strictly what you need to know for all tests and assessments (as dictated by the SAGS guidelines). Includes annotated diagrams and images to illustrate points mentioned, as well as additional research, helpful wh...
POLULATION COMMUNITY
A population consists of all the organisms of Communities are made up of all the
a given species that live in a particular area populations of different species in a given
at one time. Population ecologists study the area at one time
size + density + structure of populations (interactions between populations)
+ change over time.
= different SPIECES + same PLACE + same
= same SPIECE + same PLACE + same TIME
TIME
SPECIES ECOSYSTEM
A species, is a group of individuals with Groups of organisms (biotic factors = living)
similar characteristics which are capable of that interact with each other and with the
breeding and producing fertile offspring. environment (abiotic factors = non-living) in
different ways constitute an ecosystem.
HABITAT ECOLOGICAL NICHE
A habitat is an environment where an An ecological niche is the functional role the
organism lives and reproduces. organism plays in its community.
, BIOTIC ABIOTIC
Living, or once living, factor in an ecosystem Non-living factor in an ecosystem
LEVELS OF ECOLOGY
Ecosystems are influenced by both biotic
Ecologists often work at five broad levels,
and abiotic factors.
sometimes discretely and sometimes with
Biotic factors =animals, plants.
overlap: organism, population, community,
Abiotic factors = water, soil, air, sunlight,
ecosystem, and biosphere.
temperature, and minerals.
ECOSYSTEMS + DEPTH
An ecosystem consists of all the biotic and abiotic factors that influence that community.
Ecosystem ecologists often focus on flow of energy and recycling of nutrients.
POPULATION PARAMETERS
Factors that affect changes in population size are called POPULATION PARAMETERS.
These four ecological events influence the size (density) of a population.
CHANGE IN POPULATION DENSITY = (BIRTHS + IMMIGRATION) – (DEATHS + EMIGRATION)
INCREASE POPULATION DECREASE POPULATION
natality Immigration (IN) mortality Emigration (EXIT)
birth rate in animals individuals entering this is the number of individuals leaving
and the production an area from deaths per 1000 an area. This occurs
of seeds in plants. It another area. This individuals per year especially when an
is the percentage occurs especially i.e., Death rate area becomes
increase of the when a population overpopulated,
population per unit ENTER a favorable resulting in a lack of
time new habitat. food or space.
CLOSE POPULATION OPEN POPULATION
In a closed population (no immigration or Individuals can enter the population or
emigration) the only factors affecting leave the population. These factors that
population size are the birth rate (natality) affect population size are called immigration
and the death rate (mortality). or emigration respectively
POPULATION ECOLOGY
The ecological study of how biotic (living) and abiotic (non-living) factors influence the
density, dispersion, and size of a population
CARRYING CAPACITY
The maximum
population size that can
be supported by the
available resources in an
environment, resource-
limited environment. a
can population becomes
so large that it runs out
of free space, outgrows
its food supply, or
exhausts other assets.
, POPULATION GROWTH PATTERNS
Characteristic patterns of growth are dependent on reproduction rate and limiting
environmental factors.
EXPONENTIAL GROWTH - GEOMETRIC LOGISTIC GROWTH
this model shows the growth of a the population experiences a levelling off of
population in an ideal environment with exponential growth due to limiting
unlimited resources. This can be depicted as resources. In turn, the shape of the
a J-shaped curve on a graph that models graph, S-shaped curve on a graph that
population growth. models population growth.
POPULATION REGULATING FACTORS
Populations would continue to grow if there weren’t any factors that limit or regulate their
sizes. These factors include: competition, drought, disease, predation & climate-related
changes.These factors prevent a population from reaching its maximum reproductive
growth rate and are collectively called environmental resistance.
Carrying capacity is the maximum number Every ecosystem has different carrying
of individuals of a certain species that an capacities. If the organism exceeds the
environment can support indefinitely carrying capacity the environment cant
without depleting the resources. sustain it and the resources will become
depleted.
DENSITY DEPENDENT DENSITY INDEPENDENT
Referring to any characteristic that changes Referring to any characteristic that changes
population size because it is affected by population size because it is not affected by
population density; for example, population density; for example, natural
competition disasters like an earthquake
AVALIBILITY OF REASOURCES
FOOD SPACE DISEASES SHELTER
population increases, Overcrowding can lead In dense populations, Low availability of
the rate at which the to hormonal diseases can spread shelter results in high
food is used up also disturbance more rapidly and may mortality as the
increases, resulting in Aggression and killing cause a decrease in predators find prey
less food, and of young may occur population size more easily
mortality from under overcrowded Low. Population sizes
starvation conditions. have more shelter
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