It
is difficult to give an exact definition for the life, as the nature of life is
not clear. According to Encarta@ Wodd English Dictionary, definition of living
is:
"Spiritual
existence transcending physical death; the period from birth to death; the
quality that makes living animals and plants different from dead organisms and
inorganic matter. Its functions include the ability to take in food, adapt to
the environment, grow, and reproduce".
The
biological world is viewed as a hierarchy of levels. These levels include
chemicals, organelles, cells, organs, organisms, and ecologies. There are three
conceptions for life: as a loose cluster of properties, a specific set of
properties, and metabolization.
Several
hundred years ago, people thought that there was a vitalism inside life bodies
that keep the body to be a life. The scientific results absolutely denied the
existence of vitalism. The demise of vitalism told us that no super physical
substance or force or spirit to distinguish any life from non-life. For all we
know, all life phenomena obey to all the natural laws (physical and chemical)
that adapted to the non-life world. There is no any extra natural law for the
life world only. Life is no more unified than a collection of overlapping
properties from overlapping disciplines, such as, biophysics, biochemistry,
molecular biology, genetics, evolution, ecology, cytology, microbiology,
physiology, anatomy and heredity, etc.
Farmer and Belin listed eight characteristics of the
life:
- process,
- self-reproduction,
- information
storage of self-representation,
- metabolism,
- functional
interactions with the environment,
- interdependence
of parts,
- stability
under perturbations,
- and
the ability to evolve.
According to Mayr, the process of living could be defined by
a list of the kinds of characteristics by which living organisms differ from
inanimate matter:
- All
levels of living systems have an enormously complex and adaptive
organization.
- Living
organisms are composed of a chemically unique set of macromolecules.
- The
important phenomena in living systems are predominantly qualitative, not
quantitative.
- All
levels of living systems consist of highly variable groups of unique
individuals.
- All
organisms possess historically evolved genetic programs which enable them
to engage in teleonomic processes and activities.
- Classes
of living organisms are defined by historical connections of common
descent.
- Organisms
are the product of natural selection.
- Biological
processes are especially unpredictable.
- Life
is continuum.
- All
life organisms are programmed to death naturally, which is called
apoptosis.
A novel definition of life (Tetz and Tetz, 2019):
“Life
is an organized matter that provides genetic information
metabolism”.
Biodiversity
refers to the variety of living species on Earth, including plants, animals,
bacteria, and fungi. While Earth’s biodiversity is so rich that many species
have yet to be discovered, many species are being threatened with extinction
due to human activities, putting the Earth’s magnificent biodiversity at risk.
Biodiversity
is very important for human beings as it provides many basic needs such as
food, fuel, shelter, and medicine. Further, ecosystems provide crucial services
such as pollination, seed dispersal, climate regulation, water purification,
nutrient cycling, and control of agricultural pests. It also holds value for
potential benefits, such as new medicines and other possible unknown services.
Biodiversity has cultural value to humans as well, for spiritual or religious
reasons for instance. The intrinsic value of biodiversity refers to its
inherent worth, which is independent of its value to anyone or anything else.
Finally, the value of biodiversity can also be understood through the lens of
the relationships we form and strive for with each other and the rest of
nature. We also value biodiversity because it helps in maintaining the
correct balance of nature.
Types of Biodiversity
Biodiversity
further classifies into three major types: 1. Genetic Diversity
2. Species Diversity 3. Ecological Diversity
1. Genetic Diversity
Genetic
diversity is also known as genetic polymorphism. It is basically a type of
dissimilarity expressed at the genetic level by each individual in a
species. No two individuals belonging to the same species are exactly similar.
For example, in the species of human beings, each human shows a lot
of diversity in comparison to another human. This is due to the
difference in DNA sequences, and these differences form the genetic diversity
in species. All organisms have DNA and each individual’s DNA is organized into
genes. These contain the instructions to build our bodies. Small changes in DNA
might change blue eyes to green or straight hair to curly hair. The
combined differences in the DNA of all individuals in a species make up the genetic
diversity. Genes are responsible for the traits exhibited by organisms
and, as populations of species decrease in size or go extinct, unique genetic
variants are lost. Since genes reside within species, why should we consider
genetic diversity as a separate category? Because they hold "genetic
potential." For example, many of the crops that we grow for food are grown
in monocultures of genetically homogeneous individuals. Because all individuals
are the same, a disease, insect pest, or environmental change that can kill one
individual can extirpate an entire crop. Most of our high-yield varieties show
significant reductions in yield within about 5 years, as pests overcome the
crops’ natural defenses. Plant breeders look to wild plant relatives and to locally
grown landraces to find new genetic varieties. They can then introduce these
genes into crops to renew their vigor. Genetic variation allows species to
evolve in response to diseases, predators, parasites, pollution, and climate
change.
Advances
in genetic engineering have allowed scientists to introduce beneficial genes
from one species to another. For example, diabetics used to depend on insulin
from human cadavers, or from cows or pigs. Human insulin was expensive, and
non-human insulin could cause allergic reactions. Now we can isolate the gene
that codes for human insulin, insert it into bacterial cells, and let the
bacteria produce large quantities of human insulin. Other notable feats in
genetic engineering include the introduction of genes that enhance the
nutritive value of food, create crop resistance to insect pests, induce sheep
to produce a protein for treating cystic fibrosis disease, and alter bacteria
so that they can clean up toxic mine wastes through their metabolic
activities.
2. Species Diversity
Species is agroup of organisms genetically so similar, that they can
interbreed and produce fertile offspring is called a species.
Species
diversity stands for the number and distribution of
species. The number of species in a region varies widely depending upon the
varied environmental conditions. For example, it is usually observed that
civilizations residing beside water bodies show more species than the one
compared to the areas away from water bodies. The species diversity is
usually measured in terms of the total number of species within discrete
geographical boundaries. Species are distinct units of diversity each playing a
specific role in the ecosystem. In nature, the number and kind of species, as
well as the number of individuals per species vary, leading to greater
diversity.
3. Ecological Diversity
Ecological
or ecosystem diversity defines the diversity observed among the ecosystems in a
particular region. Ecosystems include all the species, plus all the
abiotic factors characteristic of a region. For example, a desert ecosystem has
soil, temperature, rainfall patterns, and solar radiation that affect not only
what species occur there, but the morphology, behavior, and the interactions
among those species. When ecosystems are intact, biological processes are
preserved. These processes include nutrient and water cycling, harvesting light
through photosynthesis, energy flow through the food web, and patterns of plant
succession over time. A conservation focus on preserving ecosystems not only
saves large numbers of species but also preserves the support systems that
maintain life. Diversity at the level of community and ecosystem exists
along 3 levels:
- It
could be within-community diversity (alpha diversity), Alpha
Diversity is usually expressed by the number of species (i.e., species
richness) in that ecosystem,
- between-communities
diversity (beta diversity) that is a comparison of diversity between
ecosystems, usually measured as the amount of species change between the
ecosystems and
- diversity
of the habitats over the total landscape or geographical area (gamma
diversity), it is a measure of the overall diversity within a large
region.
Threats to Biodiversity
Currently
the planet is inhabited by several million species in about 100 different
phyla. About 1.8 million have been described by scientists, but conservative
estimates suggest that there are 5–15 million species alive today, since many
groups of organisms remain poorly studied. Over 15,000 new species are
described each year. However, modern extinction rates are high, at 100 to 1000
times greater than background extinction rates calculated over the eras. The
last great mass extinction was 65 million years ago, at the end of the
Cretaceous, when the dinosaurs went extinct. The International Union for the
Conservation of Nature estimates that 22% of known mammals, 32% of amphibians,
14% of birds, and 32% of gymnosperms are threatened with extinction. Over
the last century, humans have come to dominate the planet, causing rapid ecosystem
change and massive loss of biodiversity across the planet. Major direct threats
to biodiversity include habitat loss and fragmentation, unsustainable resource
use, invasive species, pollution, and global climate change. The other main
causes include growing human population and overconsumption of natural
resources. The loss of biodiversity could adversely affect our environment
as the balance is lost and the natural food web is disturbed. We still have not
identified all the species living on the earth but of all the ones identified
till now, many have already been marked as extinct. Thus, due to its major role
in our survival, conservation of biodiversity has now become a matter of
high priority.
Causes of biodiversity loss
The
main causes of biodiversity loss include land-use changes, changing levels of
atmospheric carbon dioxide, changing climate, biological invasion and nitrogen
deposition.
1. Habitat Loss
Habitat
refers to the area where species seek food, get shelter and reproduce. The
greatest threat to wild plant and animal species is due to destruction or
alteration of their habitat. If an animal’s habitat is destroyed or disrupted,
it must adapt to the new changes, move elsewhere or die. When it is forced out
of its territory, and if it finds a suitable habitat there is a possibility
that the habitat is already in use. Consequently, it must compete with the
local population of the same species as well as other animals. The other option
is that it must migrate into a marginal habitat where it may succumb to
predation, starvation or disease. Some organisms such as pigeon, house
sparrows, rodents and deer flourish in the modified habitats provided by human
activities but many others do not.
2. Habitat destruction
Habitat
destruction is recognised today as the most significant threat to global
biodiversity and bears responsibility for much of the species loss worldwide.
This includes: felling of forests for land use (e.g. clear felling for
development and agriculture), large scale logging and small scale patchwork
agriculture. Shifting cultivation alone is believed to be responsible for 70%
of deforestation in Africa, 50% of deforestation in Asia, and 35% of forest
loss in the America. When habitats are not completely destroyed, they are
fragmented into smaller patches, creating islands of habitats in a sea of
development. Fragmentation exposes species to more light, wind and temperature
effects than are natural, thus affecting the species survival as food and water
sources are lost and few mates remain. In fragmented landscapes many species
soon become isolated from others of their own kind resulting in inbreeding,
loss of genetic diversity and local extinction. More than three quarters of the
species that are in danger of extinction today are due to the destruction of
their forest habitats. A large number of these species are from the tropics,
where human population growth has been most explosive and habitats have been
destroyed most rapidly. Tropical rain forests cover a mere 7 per cent of the
earth’s surface, yet they house about three quarters of the total species.
Today these forests are being destroyed at an alarming rate.
3. Industrial wastes and pesticides
Industrial
wastes and pesticides also cause severe impact, particularly on the aquatic habitats.
For example, during the 1950s and 1960s, insecticides particularly chlorinated
hydrocarbons (such as DDT), reduced the population levels of several birds such
as the bald eagle and brown pelican. Pesticides harm insect pollinators,
including managed honeybee populations, which can in turn reduce crop yields.
Runoff seeping into rivers, lakes and coastal environments can produce negative
impacts on entire aquatic ecosystems. These substances mimic or interface with
normal hormones in living organisms.
4. Selective Destruction of Species
The
selective destruction of one species of an existing fauna can produce equally
unfortunate results. For example, the Passenger pigeon (Ectopistes migratorius)
was probably most abundant bird on earth as recently as the middle of the
nineteenth century. Their flocks darkened the sky during migration, and one
such flock alone was 400 km long and had no less than two billion birds. So
huge was their numbers that the branches of trees would break under the weight
of the perching birds. It took hours for the flocks to pass through a place.
There used to be as many as 90 nests per tree throughout a stretch of forest of
about 5 km width and 67 km length. In 1871, an estimated 136 million passenger
pigeons nested in a 2,200 sq. km area of central Wisconsin, USA. An immense
tonnage of droppings fertilised the forests where passenger pigeons roosted.
Today there is not even a single passenger pigeon on the earth. This happened
because millions of passenger pigeons were killed for food every year.
5. Domestication of Selective Species
Humans
have taken care of the living beings which are useful to them through extensive
breeding programmes, to derive maximum benefit of their products. During the
process, the species have lost certain useful characteristics so much so that
these forms cannot survive on their own in nature. A very good example is corn,
which is pampered so much by human that if it is left on its own, it cannot
survive. Today human has large herds of domestic animals. These animals can
also play a significant part in the reduction of animal populations by
overgrazing the land, thus destroying the vegetation on which both they and the
wild animals depend. The native wildlife of a particular area is capable of
utilising the native plant life much more efficiently than introduced domestic
cattle, and is thus much less likely to convert fertile areas into deserts. The
other important parameter is that the domestic cattle are carriers of several
diseases which they can transmit to wild animals. For example, the steady
rehabilitation of the Great Indian Rhinoceros was seriously hampered by the
rinderpest disease which they contracted from the local domestic cattle.
6. Global Climate Change
Substantial
evidence demonstrates that people are contributing to measurable changes in the
global climate, threatening life. By burning fossil fuels such as oil, natural
gas and coal and by burning trees, we have dramatically increased the amount of
CO2 in the atmosphere. While scientists do not know the exact effects of
increased CO2, they predict that it will lead to higher overall global
temperatures, increasing sea levels, and changes in climate patterns. The
changed atmospheric conditions that result from global warming could create greater
numbers of intense storms and prolonged droughts. On the other hand, the
expected speed of climate changes coupled with direct loss of natural habitat
may prevent some species from adapting quickly enough. They are likely to
become extinct, locally or more broadly, and their roles in natural systems
will be lost forever.
Biodiversity conservation
Needs of Conservation of Biodiversity
Biodiversity
conservation is the protection and management of biodiversity to obtain
resources for sustainable development. It is considered as key
component for administration of natural assets. Main objective of
biodiversity conservation is to preserve the diversity of species and
sustainable utilization of species and ecosystem.
It
is very important to conserve biodiversity because it provides us with various
resources including food, medicine, fibers, wood products, and more. Most of
the human population depends on plants for food and medicines. Actually, plants
are the only source of food for the world population and other food sources
like animals depend upon the plants for their survival. Similarly, many of our
medicines are chemicals produced by pharmaceutical companies, but the original
formulas were often derived from plants. For example, opiate pain relievers are
derived from poppies, aspirin is derived from willows, quinine for treating
malaria comes from the Chinchona tree. The rosy periwinkle (Vinca
rosea) and Pacific yew (Taxa brevifolia) both provide substances
used in chemotherapy to inhibit the cell division of cancerous cells.
Fibers
for clothing, ropes, sacking, webbing, netting, and other materials are
provided by a large number of plants, including cotton plants, flax plants
(linen), hemp (cordage and sail canvas), Agave plants
(sisal), Corchorus plants (jute), bamboo and palms. Trees
provide the wood products used in making homes, furniture, and paper
products. Ecosystem also provides us other services include the
decomposition of waste, pollination, water purification, moderation of floods,
and renewal of soil fertility. These services are often overlooked, and are not
generally valued as part of the economy until they cease to function. When
economic value is assigned to these services, it is often startlingly high. For
example, insect pollinators help produce many commercially important fruits
such as almonds, melons, blueberries, and apples. The global economic value of
pollination services performed by insects has been valued at $217 billion per
year. Travel, which provides great pleasure to many people, is motivated
by the desire to see this combination of cultural, landscape and biological
diversity. Ecotourism is travel with the desire to view, sustain, and support
natural ecosystems and local cultures. Support from ecotourism can reduce habitat
destruction, preserve species that suffer from poaching and illegal trade in
the pet market, plus provide jobs for the local economy.
Conservation
needs different strategies, they can be species based or habitat based or
ecosystem based. Some species are given importance at national level while some
need treatment at international levels. Most of the conservation is done at in
situ and ex situ conditions.
Ex-situ conservation
Ex-situ
conservation means, literally “off-site conservation”. It is the process of
protecting population of an endangered species of plant or animal by removing
it from an unsafe or threatened habitat and placing it, or part of it, under
the care of humans. While ex-situ conservation is comprised of some of the
oldest and best known conservation methods known to human, it also involves
newer, sometimes controversial laboratory methods. Ex-situ conservation, while
helpful in human’s efforts to sustain and protect our environment, is rarely
enough to save a species from extinction. It is to be used as a last resort or
as a supplement to in-situ conservation because it cannot recreate the habitat
as a whole: the entire genetic variation of a species, its symbiotic
counterparts, or those elements which, over time, might help a species adapt to
its changing surroundings. Further more, ex-situ conservation techniques are
often costly. Plants and animals living in ex-situ breeding grounds have no
natural defense to the diseases and pests new to the species.
In-situ conservation
In-situ
conservation means “on-site conservation”. It is the process of protecting an
endangered plant or animal species in its natural habitat, either by protecting
or cleaning up the habitat itself, or by defending the species from predators.
The benefit to in-situ conservation is that it maintains recovering populations
in the surroundings where they have developed their distinctive properties.
Wildlife conservation is mostly based on in-situ conservation. This involves
the protection of wildlife habitats. Also, sufficiently large reserves are
maintained to enable the target species to exist in large numbers. The
population size must be sufficient to enable the necessary genetic diversity to
survive within the population. In-situ Conservation is believed to be the best way to maintain the
earth’s biological diversity. It also allows natural evolutionary processes to
continue and for species to keep on adapting to their surroundings. However,
this needs good management practices and controlled land use to ensure the successes
of conservation objectives. Thus Protected Areas play a very important role in
in-situ conservation of species, particularly threatened species, by ensuring
conservation of their habitat.