UNIT III: LIVING THINGS AND THEIR ENVIRONMENT If a population’s density is very high, that means there are
h, that means there are lot of
organisms crowded into a certain area. If a population’s density is
Module 4 : Ecosystem: Biodiversity low, that means there are very few organisms in an area.
BIODIVERSITY AND STABILITY FACTORS AFFECTING POPULATION
Biodiversity is a term that describes how varied living 1. DENSITY- INDEPENDENT LIMITING FACTOR
things are in a specific area. - factors that can stop a population from growing can be
Organisms are part of biodiversity and may be such things as natural diseases, temperature, sunlight and
economically and ecologically value. the activities of human in the environment.
Their products are source of food, medicine, clothing, - Natural disasters such as tropical cyclones, floods,
shelter and energy. earthquakes and fires will stop a population from growing
They are important in maintaining balance in the no matter how many organisms are living in certain area.
ecosystem as they perform a specific roles. - The same goes for the temperature of an area and the
Some species maintain the quality of natural bodies of amount of sunlight it receives.
water; prevent soil erosion and floods, cycle minerals - Human activities that will alter the environment will also
in the soil and absorb pollutants. decrease the number of organisms in a population,
Some species feed on insects and pests which control regardless of the size of the population.
the population of organisms in certain environment, 2. DENSITY- DEPENDENT LIMITING FACTOR
thus making the ecosystem balance and stable. - factor that regulates a growth and influenced by
population density, come into play when a population
The values of species can be divided into various categories;
reaches a certain number of organisms.
1. DIRECT ECONOMIC VALUE - For example, when a population reaches a certain size,
Species are considered to have direct economic there won`t be enough resources (food, shelter, water) for
value if their products are sources of food, medicine, all the organisms.
clothing, shelter and energy. For example, some medicines
POPULATION`S CARRYING CAPACITY- maximum number of
being used nowadays have formulations extracted from
organisms that can be supported or “carried” by the environment.
plants and animals.
2. INDIRECT ECONOMIC VALUE EXPONENTIAL POPULATION GROWTH- a population experience
Species have indirect economic value if there are this growth before they reaches its carrying capacity. During this
benefits produced by the organism without using them. period, there are plenty of resources available for all organisms, so
For example, certain species maintain the chemical quality more births are recorded than death in organisms.
of natural bodies of water, prevent soil erosion and flood,
cycle materials in the soil and absorb pollutants. Limiting Factors that
3. AESTHETIC VALUE Depend on Population
A lot of species provides visual or artistic Density
enjoyment, like a forested landscape and the calming
beauty of a natural park; or they may be used in spiritual 1. Disease and
Parasites
meditation like in Prayer Mountains.
2. Competition for
resources-
Biodiversity is important because it sustains
organisms with better adaptations to obtain (food) resources
through the flow of energy the food web on
will be able to reproduce more often and its population will
Earth and contributes to environment stability.
grow.
Stability of an ecosystem can be described as
3. Predation- plenty of prey are available, predators will be able
the resilience to withstand changes that may
to eat sufficiently, thus have energy to reproduce much and
occur in the environment.
increase their numbers.
The Ups and Down of Population Growth 4. Emigration- emigration occurs when as a population
approaches its carrying capacity, and individual organisms leave
A population is a group of organisms of the same species and go to a new area where they can find enough resources for
that live in a certain area. survival and reproduction.
Ecologists regularly monitor the number of organisms in
many populations. ENVIRONMENTAL PROBLEMS AND ISSUES
The Philippines is considered as one of the biologically
Populations that are growing or diminishing can be a strong richest country in the world because of its high biodiversity at
indicator of potential problems in the organism’s environment and various levels. We have all these rich natural biological
such condition alarm the ecologists if something is going wrong. But resources but we have not truly protected them. We are losing
it is not enough to simply know if the number of organisms in an this global heritage due to habitat destruction, overuse and
area is increasing or decreasing; ecologists need to know why the population. As our forests are destroyed at a fast rate, the
number of organisms is decreasing. natural habitats such as dwelling places of plant and animal
species are also lost.
Any population, whether it be that of humans, animals, the
Our coral reefs, where the fishes lay eggs, are badly
mold growing on bread or bacteria living in your intestines, will grow
damaged by destructive fishing methods such as muro- ami,
if more organisms are being developed ( Genetically modified
dynamite and fine nets in fishing.
organisms) or born, than dying. In addition, people hunt animals, collect plants, and sell
corals and exotic animals for livelihood and other activities that
BIRTH RATE ( natality) – number of births in a population cause the population of these organisms to decrease at faster
DEATH RATE ( mortality) – number of organisms that are rate.
dying in a population The rate of development in some part of the country is
extraordinary. The natural landscape has been changed by tall
Thus, if the birth rate is greater than the death rate, a population buildings, establishments, house projects, expressways, railway
will grow. If death rate is greater than the birth rate, then the systems and overpasses. Other reclaimed areas have been
population will decrease. converted into industrial structures and technoparks.
POPULATION DENSITY- refers to the number of organisms
per unit area.
