Biodiversity in Plants and Animals
The term biodiversity was coined by Walter
G. Rosen in the year 1986. Biodiversity is the diversity or variability of
living organisms present on earth and other species undergone extinction
million years ago. In other words, it is the Biological diversity which denotes
the total number of different living species, living within a particular region
including the microbes, plants, animals, and ecosystems such as coral reefs,
forests, rainforests, deserts etc. In biodiversity, every single living species
has an equally important role in the ecosystem. It is the totality of genes,
species and ecosystems in a defined area.
According to the Convention of Biological
Diversity (CBD), biological diversity – or biodiversity – means “the
variability among living organisms from all sources including, inter alia,
terrestrial, marine and other aquatic ecosystems and the ecological complexes
of which they are part. This includes diversity within species, between species
and of ecosystems”.
All living organisms can be divided into
five kingdoms, Animals, Plants, Fungi, Protists and Bacteria.
It has been estimated that there are
around 8.7 million species of plants and animals in existence among which only
around 1.2 million species are identified and described so far. Millions of
other organisms remain a complete mystery to us. The various forms of life on the planet
included 7.8 million species of animal, 298,000 species of plant and 611,000
species of mushrooms, mould and other fungi along with 36,400 species of
protozoa, single-celled organisms, and 27,500 species of algae with no estimate
on the number of bacteria.
Plant
Biodiversity
Algae:
More than 40,000 species of algae are known and described and another 360,000
species are believed to exist. Most of these yet to be described and
identified algae are expected to be present in barks, rocks, marine
environment, Polar Regions, etc.
Most
of the green algae are cosmopolitan and are present in marine, brackish, fresh
water and soil environments. They are distributed in about 1040 species
and 170 genera and 8 orders. Cladophoraceae
is the largest family among green algae and this family contains about 300
species.
Brown
algae are mainly present in ocean and there are 265 genera and more than 1500
species in about 14 orders. They are found in maximum
diversity at Japanese region of Pacific and North Atlantic.
Red
algae are the largest group of algae and they are also found mainly in
ocean. There are about 555 genera and they are in maximum diversity at
Japanese region of Pacific and North Atlantic and in South Australia.
The
microalgae such as desmids, diatoms, etc are difficult to be surveyed.
Bryophytes:
More than 14,000 to 16,000 species of bryophytes are known. Among this
8000-9000 species coming under 425 genera are mosses and 6000-7000 are
liverworts. It is expected that about 30,000 more species are yet to be
discovered. Majority of bryophytes are reported from cooler regions
especially in tropical forest and temperate woodlands. The Indo
Australian archipelago and South America are the areas where bryophytes are
richly distributed followed by South Australia, North America, North-east Asia,
Himalayas, East Africa and Europe. The largest genera among bryophytes
are Plagiochila (500 species) and Frullania (400 species).
Pteridophytes:
These are vascular land plants and along with gymnosperms and angiosperms they
dominate the terrestrial environment. There are about 15,000 species of
pteridophytes which are native in tropical forest. It consists of Psilophytales, Lycophytales and Sphenophytales. Psilophytales
contain two genera, Lycophytales have
5 genera and Sphenophytales have 1
genus. These are diverse group and exhibit diverse sizes, from very tiny
to very large tree ferns. 12.5% of the total world fern species are found
in Papua New Guinea.
Gymnosperms:
Gymnosperms are mostly trees and a few are shrubs. There are 500 species of Conifers, 100 species of Cycads
and 71 species of Gnetales
identified. Ginkgo biloba is known as living fossil and is native to
China. Conifers are predominant over
temperate and alpine regions of tropics.
Angiosperms:
These constitute flowering plants. There
are about 235,000 to 300,000 species in this category. Almost 500,000 species are yet to be
discovered. The species of these plants
are grouped in 17,000 genera under 200-600 families. Orchidaceae
(25,000 to 35,000 species) and Leguminosae
(15,000 species) are the largest families.
Angiosperms are the most dominant plant element in earth. The size of plants in this category range in
size from 1 mm (Wolffia) to over 100
meters (Eucalyptus)
Animal Biodiversity
Animals
are the eaters of Earth. They are heterotrophs and depend directly or
indirectly for their nourishment on plants, photosynthetic protists, algae or
autotrophic bacteria. Animals vary diversely in their size. They
range from too small to be observed with naked eye to enormously large whales
and giant squids
Animal
kingdom includes 35 phyla and most of them occur in sea. Fewer phyla occur in
fresh water and very few are present in land. Three phyla such as Arthropoda
(spiders and insects), Mollusca (snails) and Chordata (Vertebrates) dominates
animal world.
Almost
all animals (98%) are invertebrates, that is they lack back bone. Only 2%
animals are vertebrates, that is having back bone.
The
invertebrates are divided into seven phyla. The invertebrate phyla are Molluscs
(snails and octopuses), Arthropods (insects, spiders and crabs), Echinoderms (sea
urchins and starfish), Cnidaria (jellyfish), Porifera (sponges), Annelids
(segmented worms) and Platyhelminthes (flatworms).
Vertebrates
belong to the phylum Chordata. Vertebrates are subdivided into five classes,
Fish, Amphibians, Reptiles, Birds and Mammals.
The largest group in vertebrates are bony fish. Amphibians are animals that include
salamanders, newts, caecilians, frogs and toads. Most reptiles live on land while some, like crocodiles and turtles, and
some snakes survive in water. Birds come
under two categories, either flightless birds or flying birds. All mammals breathe using lungs, and therefore
live on land and mammals that live in water, like whales and dolphins, come to
the surface of the water to breathe.
Invertebrates
Invertebrates lack a backbone, have an
external skeleton for protection and as a supporting structure. Approximately
95% of all animal species are invertebrates such as insects.
Zooplankton
Mollusks - snails, clams, squid, and octopuses
Crustaceans - crabs, lobsters, and shrimp
Echinoderms - sea stars, brittle stars, sea urchins,
sand dollars, and sea cucumbers
Arthropods - insects, beetles; moths
and butter flies; wasps, ants, and bees; flies and mosquitoes; grasshoppers and
crickets; and cockroaches.
The
insects possess enormous evolutionary success due to their small size, high
reproductive rate and ability to adapt rapidly to environmental changes. These inhabit
nearly every ecosystem except the polar regions and the oceans.
Vertebrates
Vertebrates have skeletal support and are
relatively large. Most have two pairs of appendages: fins, limbs, or wings.
Fish, amphibians, and reptiles are ectotherms, with body temperatures the
same as the surrounding environment. Birds
and mammals are endotherms, able to keep their body temperatures nearly
constant, independent of the temperature of their surroundings.
There are 50,000 species of vertebrates in
seven classes:
·
Agnatha,
Chondrichthyes, Osteichthyes (fish): These are ectothermic, aquatic vertebrates
with gills, usually fins, and an elongated body covered with scales.
·
Amphibia
(amphibian): Ectothermic vertebrates with aquatic larvae; adults live in land
or water; includes frogs, toads, newts, salamanders, and caecilians
·
Reptilia
(reptiles): Egg laying ectothermic vertebrates with scaly, dry skin.
·
Aves (birds):
Endothermic, egg laying vertebrates with feathers for insulation, most can fly
·
Mammalia
(mammals): Endothermic vertebrates are covered with hair or fur for insulation,
nourish their young with milk from the mammary glands, and mostly give live birth
to young.
Fish
Fish
live in fresh or salt water of all depths and all temperatures and breathe
through gills.
Cartilaginous
fish (class Chondrichthyes), consisting of sharks, are extremely diverse and
successful; they have remained nearly unchanged for 70 million years.
Bony
fish (class Osteichthyes) are more diverse. Stream lined fish, such as tuna and
mackerel, Flatfish, including sole and halibut, Elongate fish, such as eels, are
examples.
Amphibians
Amphibians
need to live in or near water. Members of the order Caudata (salamanders and
newts) have long tails and equal sized front and rear legs, similar to lizards.
Members
of the order Anura (frogs and toads) have large, muscular hind legs for
jumping, webbed feet for swimming, and no tail. Frogs absorb oxygen dissolved
in water when they are in wet places and breathe through lungs when they are in
land. Toads have stouter bodies and thicker skins, allowing them to live
farther from water.
Reptiles
Reptiles
are scaly, dry skinned, air breathers. Their lungs, water proof skin, and
shelled eggs allow them to live away from water. The reptiles include
Crocodilia (crocodiles, caimans, and alligators), Squamata (lizards and
snakes), and Testudines (turtles).
Lizards
have low bodies, long tails, and legs that extend outward from the sides of
their bodies. Snakes (and legless lizards) have no limbs.
Turtles
have a shell for protection. Dinosaurs (superorder Dinosauria), the most famous
reptiles, have been extinct for 65 million years.
Birds
Birds
are endotherms with feathers for insulation and hard shelled eggs and they can
live in a wide range of environments.
They are the most diverse class of terrestrial vertebrates. Species
range in size from tiny hummingbirds (order Trochiliformes) to enormous
ostriches (order Struthioniformes).
Most
birds can fly, although a few have lost the ability and have developed other
adaptations such as running (ostriches) or swimming (penguins). Flying birds
are lightweight, with a bony bill and hollow bony skeletons. Seabirds have
webbed feet for swimming; long legs for
wading;
fat deposits, light bones, and air sacs for buoyancy; an oily secretion for
waterproofing feathers and providing insulation; highly developed eyesight for
locating fish in the water; and a salt gland over the eye to eliminate excess
salt.
Mammals
Mammals
are air breathing endotherms with hair or fur for insulation that allows them
to live in nearly all environments. Most
species are terrestrial, a few are aquatic. The majority of mammals are
placental. Mammals are born from their
mother’s body and fed mother’s milk when they are young.
Roughly
half of all mammal species are in the order Rodentia, examples rats, Capybara
Bats
(order Chiroptera) are the only true flying mammals.
Members
of the order Carnivora include species of flesh eating mammals, such as cats,
dogs, mongooses, bears, seals, and walrus.
Order
Insectivora includes small animals such as shrews and moles.
The
two orders of hoofed mammals are the odd toed Perissodactyla, which includes
the horse and rhinoceros, and the even toed Artiodactyla, which includes the
deer, antelope, camel, pig, and cow.
Whales,
dolphins, and porpoises (order Cetacea) are marine mammals
Humans,
monkeys, apes, and lemurs belong to the order Primates
With intelligence as an adaptive strategy, humans have colonized nearly every habitat on the land, from the coldest polar regions to the tropical jungles.
Importance of plant and animal biodiversity
Biodiversity have a key role in human
nutrition. It safeguards the sustainable
productivity of soil and provide the genetic resources for all crops and
livestock species that we utilize as food. The diversity of plant and animal
resources forms the basis for the wellbeing of society and serves as an
important source of food and income. Plants and animals provide medicine,
timber, biomass, energy, fertilizer, transport, etc so that our livelihoods and
welfare are dependent on them.
Pants are an important resource for food,
shelter, and agriculture and include bushes, grasses, herbs, shrubs, trees,
vines, ferns, and mosses. They are the primary producers and provide us with
the oxygen and carbohydrate.
There are several animal species which are
trained, domesticated and used for food production, agriculture, livestock, etc.
They play a vital role in food safety.
Contribution
to economies: Agriculture, including livestock and
fishery, contribute to national economies.
Wild foods of both plant and animal origin are of considerable economic
value and they also provide important ecosystem services that contribute
significantly to national and global economies. Example, the herbal medicine,
crop pollination by insects, etc.
Contribution
to human nutrition and health: Plant and animal
biodiversity provides nutritionally diverse food products in diverse food
chains. This nutritional diversity is mainly observed at species level even
though variety/cultivar/breed-level differences also exist. Biodiversity provides support for drug
discovery and the availability of medicinal resources. about 80% of the world population depends on
medicines from nature for primary healthcare.
Biodiversity loss is associated with
global health implications where changes in biodiversity such as changes in
populations and distribution of disease vectors, scarcity of fresh water,
impacts on agricultural biodiversity and food resources etc increases
infectious disease transmission.
Contributions
to livelihoods of rural populations: Income and livelihoods,
especially of poor people, are highly dependent on biodiversity, on wild or
uncultivated natural ecosystems.
Livestock provide nutritional supplements
to staple plant-based diets and provide manure for soil fertilization, fibre
for clothes and serve as financial instruments and enhance social status.
Ecosystem
services and functions: Ecosystem services are essential for human
life as they provide provisioning services, regulating services, supporting
services and cultural services. Ecosystem provide food and clean water (provisioning
services), regulate floods, drought, land degradation and diseases (regulating
services), support soil formation, nutrient cycling and pollination of crops (supporting
services), and provide recreational, spiritual and cultural benefits (cultural
services).
Both crop and livestock productions are
interdependent with ecosystem services and thus biodiversity, resulting in both
positive and negative impacts. On one hand, agricultural landscapes that
contain significant areas of semi-natural lands are important for wildlife,
such as breeding sites for birds and on the other hand, pesticides and habitat
loss, degradation and fragmentation threaten natural pollinators.
References
- Textbook of Biodiversity, K V Krishnamurthy, Science Publishers
- Biology, 4th Edition, Raven and Johnson, WCB Publishers
- https://www.nationalgeographic.org/encyclopedia
- https://www.theguardian.com/environment/2011/aug/23/species-earth-estimate-scientists
- https://www.siyavula.com/read/science/grade-7/biodiversity/02-biodiversity?id=toc-id-6
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