AGE 101 LECTURE SERIES
Types of species distribution
Clumped distribution
This is the most common type of dispersion found in nature. In clumped distribution, the distance
between neighbouring individuals is minimized. Clumped distribution of species occurs because of
the following reasons: (i) Scarce resources, this type of distribution is found in environments that are
characterized by patchy resources. Animals need certain resources to survive and when these
resources become scarce during certain parts of the year animals tend to “clump” together around
these crucial resources; (ii) Social factors, individuals might be clustered together in an area due to
social factors such as selfish herds and family groups, for example wolves in packs. Clumped
distribution in species acts as a mechanism against predation as well as an efficient mechanism to
trap or corner prey. African wild dogs use the technique of communal hunting to increase their
success rate at catching prey. (iii) Inability of offspring to independently move from their habitat. This
is seen in juvenile animals that are immobile and strongly dependent upon parental care.
Even distribution/ uniform distribution
Uniform distribution, also known as even distribution, is evenly spaced. It is less common than
clumped distribution. Uniform distributions are found in populations in which the distance between
neighbouring individuals is maximized. The need to maximize the space between individuals
generally arises from competition for a resource such as moisture or nutrients, or as a result of direct
social interactions between individuals within the population, such as territoriality. For
example, penguins often exhibit uniform spacing by aggressively defending their territory
among their neighbours. Farming and agricultural practices often create uniform
distribution in areas where it would not previously exist, for example, orange trees growing
in rows on a plantation.
Random distribution
Random distribution, also referred to as unpredictable spacing, is the least common form of
distribution in nature and occurs when the members of a given species are found in
homogeneous environments in which the position of each individual is independent of the
11
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other individuals: they neither attract nor repel one another. Random distribution is rare in
nature as biotic factors, such as the interactions with neighbouring individuals, and abiotic
factors, such as climate or soil conditions, generally cause organisms to be either clustered
or spread apart. Random distribution usually occurs in habitats where environmental
conditions and resources are consistent. This pattern of dispersion is characterized by the
lack of any strong social interactions between species. For example; when dandelion seeds
are dispersed by wind, random distribution will often occur as the seedlings land in random
places determined by uncontrollable factors.
Factors affecting species distribution
The distribution of species into clumped, uniform, or random depends on different abiotic
and biotic factors. Any non-living chemical or physical factor in the environment is
considered an abiotic factor. There are three main types of abiotic factors: climatic factors
consist of sunlight, atmosphere, humidity, temperature, and salinity; edaphic factors are
abiotic factors regarding soil, such as the coarseness of soil, local geology, soil pH, and
aeration; and social factors include land use and water availability.
An example of the effects of abiotic factors on species distribution can be seen in drier areas,
where most individuals of a species will gather around water sources, forming a clumped
distribution.
Biotic factors, such as predation, disease, and competition for resources such as food, water,
and mates, can also affect how a species is distributed. A biotic factor is any behavior of an
organism that affects another organism, such as a predator consuming its prey. For example,
biotic factors in a quail’s environment would include their prey (insects and seeds),
competition from other quail, and their predators, such as the coyote.
ENVIRONMENTAL CHANGE
CONCEPTS IN POPULATION GEOGRAPHY
Population geography is the study of the ways in which spatial variations in the distribution,
composition, migration, and growth of populations are related to the nature of places.
12
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Types of species distribution
Clumped distribution
This is the most common type of dispersion found in nature. In clumped distribution, the distance
between neighbouring individuals is minimized. Clumped distribution of species occurs because of
the following reasons: (i) Scarce resources, this type of distribution is found in environments that are
characterized by patchy resources. Animals need certain resources to survive and when these
resources become scarce during certain parts of the year animals tend to “clump” together around
these crucial resources; (ii) Social factors, individuals might be clustered together in an area due to
social factors such as selfish herds and family groups, for example wolves in packs. Clumped
distribution in species acts as a mechanism against predation as well as an efficient mechanism to
trap or corner prey. African wild dogs use the technique of communal hunting to increase their
success rate at catching prey. (iii) Inability of offspring to independently move from their habitat. This
is seen in juvenile animals that are immobile and strongly dependent upon parental care.
Even distribution/ uniform distribution
Uniform distribution, also known as even distribution, is evenly spaced. It is less common than
clumped distribution. Uniform distributions are found in populations in which the distance between
neighbouring individuals is maximized. The need to maximize the space between individuals
generally arises from competition for a resource such as moisture or nutrients, or as a result of direct
social interactions between individuals within the population, such as territoriality. For
example, penguins often exhibit uniform spacing by aggressively defending their territory
among their neighbours. Farming and agricultural practices often create uniform
distribution in areas where it would not previously exist, for example, orange trees growing
in rows on a plantation.
Random distribution
Random distribution, also referred to as unpredictable spacing, is the least common form of
distribution in nature and occurs when the members of a given species are found in
homogeneous environments in which the position of each individual is independent of the
11
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, AGE 101 LECTURE SERIES
other individuals: they neither attract nor repel one another. Random distribution is rare in
nature as biotic factors, such as the interactions with neighbouring individuals, and abiotic
factors, such as climate or soil conditions, generally cause organisms to be either clustered
or spread apart. Random distribution usually occurs in habitats where environmental
conditions and resources are consistent. This pattern of dispersion is characterized by the
lack of any strong social interactions between species. For example; when dandelion seeds
are dispersed by wind, random distribution will often occur as the seedlings land in random
places determined by uncontrollable factors.
Factors affecting species distribution
The distribution of species into clumped, uniform, or random depends on different abiotic
and biotic factors. Any non-living chemical or physical factor in the environment is
considered an abiotic factor. There are three main types of abiotic factors: climatic factors
consist of sunlight, atmosphere, humidity, temperature, and salinity; edaphic factors are
abiotic factors regarding soil, such as the coarseness of soil, local geology, soil pH, and
aeration; and social factors include land use and water availability.
An example of the effects of abiotic factors on species distribution can be seen in drier areas,
where most individuals of a species will gather around water sources, forming a clumped
distribution.
Biotic factors, such as predation, disease, and competition for resources such as food, water,
and mates, can also affect how a species is distributed. A biotic factor is any behavior of an
organism that affects another organism, such as a predator consuming its prey. For example,
biotic factors in a quail’s environment would include their prey (insects and seeds),
competition from other quail, and their predators, such as the coyote.
ENVIRONMENTAL CHANGE
CONCEPTS IN POPULATION GEOGRAPHY
Population geography is the study of the ways in which spatial variations in the distribution,
composition, migration, and growth of populations are related to the nature of places.
12
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