Prepared by Senjuti Saha, Associate Professor, Women's Christian College, Kolkata

1. 2.19 GEO-A-CC-4-10-TH – Soil and Biogeography
Unit II: Biogeography
Topic 7
Concepts of Biosphere, Ecosystem, Biome, Ecotone, Community
and Ecology
Senjuti Saha
Associate Professor
Women’s Christian College
Kolkata

2. • BIOSPHERE
• ECOSYSTEM
• COMMUNITY
• POPULATION
• ORGANISM

3. Biosphere:
The biosphere is the global sum of all ecosystems. The two joined words are
‘bio’ and ‘sphere’. It can also be termed as the zone of life on Earth, a closed
system (apart from solar and cosmic radiation and heat from the interior of the
Earth), and largely self-regulating
By the most general biophysiological definition, the biosphere is the global
ecological system integrating all living beings and their relationships, including
their interaction with the elements of the lithosphere, geosphere, hydrosphere,
and atmosphere
The biosphere is postulated to have evolved, beginning with a process of
biopoesis (life created naturally from non-living matter, such as simple organic
compounds) or biogenesis (life created from living matter), at least some 3.5
billion years ago

4. More recently, in 2015, ‘remains of biotic life’
were found in 4.1 billion-year-old rocks in
Western Australia. According to one of the
researchers, "If life arose relatively quickly on
Earth ... then it could be common in the
universe.“
 In a general sense, biospheres are any closed, self-regulating systems
containing ecosystems. This includes artificial biospheres such as Biosphere 2
and BIOS-3, and potentially ones on other planets or moons
The earliest evidence for life on Earth includes biogenic graphite found in
3.7 billion-year-old metasedimentary rocks from Western Greenland and
microbial mat fossils found in 3.48 billion-year-old sandstone from Western
Australia

5. Ecosystem
• An ecosystem is a community of living organisms in conjunction
with the nonliving components of their environment, interacting
as a system and the concept was first put forward by A.G.Tanley
(1935)
• These biotic and abiotic components are linked together through
nutrient cycles and energy flows
• Energy enters the system through photosysnthesis and is
incorporated into plant tissue. By feeding on plants and on one-
another, animals play an important role in the movement
of matter and energy through the system. They also influence the
quantity of plant and microbial biomass present
• By breaking down dead organic matter, decomposers release
carbon back to the atmosphere and facilitate nutrient cycling by
converting nutrients stored in dead biomass back to a form that
can be readily used by plants and other microbes

8. Ecosystems are controlled by external and internal factors
External factors such as climate, parent material which forms the soil
and topography, control the overall structure of an ecosystem but are
not themselves influenced by the ecosystem
Unlike external factors, internal factors are controlled, for example,
decomposition, root competition, shading, disturbance, succession,
and the types of species present
Ecosystems are dynamic entities—they are subject to periodic
disturbances and are in the process of recovering from some past
disturbance
Ecosystems in similar environments that are located in different parts
of the world can end up doing things very differently simply because
they have different pools of species present

9. Internal factors not only control ecosystem processes but are also
controlled by them and are often subject to feedback loops
Resource inputs are generally controlled by external processes like
climate and parent material. Resource availability within the
ecosystem is controlled by internal factors like decomposition, root
competition or shading
Although humans operate within ecosystems, their cumulative
effects are large enough to influence external factors like climate
Biodiversity affects ecosystem functioning, as do the processes of
disturbance & succession
Ecosystems provide a variety of goods & services upon which
people depend

10. Biome
A biome /ˈbaɪoʊm/ is a community of plants and animals that have common
characteristics for the environment they exist in. They can be found over a range of
continents. Biomes are distinct biological communities that have formed in
response to a shared physical climate
Biome is a broader term than habitat; any biome can comprise a variety of
habitats.While a biome can cover large areas, a microbiome is a mix of organisms
that coexist in a defined space on a much smaller scale. For example, the human
microbiome is the collection of bacteria, viruses, and other microorganisms that are
present on or in a human body
A 'biota' is the total collection of organisms of a geographic region or a time period,
from local geographic scales and instantaneous temporal scales all the way up to
whole-planet and whole-timescale spatiotemporal scales. The biotas of the Earth
make up the Biosphere

11. World Biome Types

12. Biome Types
TERRSTRIAL AQUATIC
RAIN FOREST
TROPICAL OR
TEMPERATE
TUNDRA
TAIGA
DESERT
TEMPERATE
DECIDUOUS
GRASSLAND
MARINE FRESHWATER
OCEANS
CORAL REEFS
ESTUARIES
RIVERS & STREAMS
PONDS & LAKES
WETLANDS

13. ECOTONE & EDGE EFFECT
An ecotone is a transition area between two biomes, where two
communities meet and integrate. It may be narrow or wide, local (the zone
between a field and forest) or regional (the transition between forest and
grassland ecosystems. It may appear on the ground as a gradual blending of
the two communities across a broad area, or it may manifest itself as a
sharp boundary line

14. The word ecotone was coined from a combination
of ecology plus -tone, from the Greek tonos or tension –
in other words, a place where ecologies are in tension
Edge Effects are changes in population or community
structures that occur at the boundary of two or
more habitats. Areas with small habitat
fragments exhibit especially pronounced edge effects
that may extend throughout the range. As the edge
effects increase, the boundary habitat allows for
greater biodiversity
Ecotone is the
cause
&
Edge Effect is the
result

15. COMMUNITY
In ecology, a Community is a group or association of populations of
two or more different species occupying the same geographical area
at the same time, also known as a biocoenosis. The term community
has a variety of uses. In its simplest form it refers to groups of
organisms in a specific place or time, for example, "the fish
community of Lake Ontario before industrialization"
Community Ecology or Synecology is the study of the interactions
between species in communities on many spatial and temporal
scales, including the distribution, structure, abundance, demography,
and interactions between coexisting populations. The primary focus
of community ecology is on the interactions between populations as
determined by specific genotypic and phenotypic characteristics

16. Community ecology also takes into account abiotic factors e.g. annual temperature or soil
pH. These non-living factors can influence the way species interact with each
other. Abiotic factors filter the species that are present in the community, and therefore
community structure. For example, the difference in plants present in the desert
compared to the tropical rainforest is dictated by the annual precipitation. These non-
living factors also influence the way species interact with each other. Humans can also
have an effect on community structure through habitat disturbance, such as introduction
of invasive species.
Community ecology has its origin in European plant sociology. It examines processes such
as predator–prey population dynamics or succession
Community Ecology examines patterns such as variation in:
Species richness
Species evenness
Biodiversity
Productivity (ecology)
Food web
Community structure

17. Ecology Ecology (from Greek: οἶκος, "house", or
"environment"; -λογία, "study of") is a branch
of biology concerning interactions
among organisms and their biophysical
environment, which includes
both biotic and abiotic components. Topics of
interest include the biodiversity,
distribution, biomass, and populations of
organisms, as well as cooperation and
competition within and between species
Ecology is not synonymous with environmentalism, natural
history, or environmental science. It overlaps with the closely
related sciences of evolutionary biology, genetics, and ethology.
An important focus for ecologists is to improve the
understanding of how biodiversity affects ecological function
STUDY OF ECOLOGY
ENVIRONMENT
Biotic
Abiotic
Factors
HABITAT
ECOSYSTEM

18. Ecologists seek to explain:
Life processes, interactions, and adaptations
The movement of materials and energy through living
communities
The successional development of ecosystems
The abundance and distribution of organisms and
biodiversity in the context of the environment
The word "ecology" ("Ökologie") was coined in 1866 by the German
scientist Ernst Haeckel. Ecological thought is derivative of established currents
in philosophy, particularly from ethics and politics. Ancient Greek philosophers
such as Hippocrates and Aristotle laid the foundations of ecology in their studies
on natural history. Modern ecology became a much more rigorous science in
the late 19th century. Evolutionary concepts relating to adaptation and natural
selection became the cornerstones of modern ecological theory

19. Ecological Niche
In ecology, a niche is the match of a species to a specific
environmental condition. It describes how an organism or
population responds to the distribution of resources and competitors
(for example, by growing when resources are abundant, and
when predators, parasites and pathogens are scarce) and how it in
turn alters those same factors (for example, limiting access to
resources by other organisms, acting as a food source for predators
and a consumer of prey). "The type and number of variables
comprising the dimensions of an environmental niche vary from one
species to another [and] the relative importance of particular
environmental variables for a species may vary according to the
geographic and biotic contexts

21. The Grinnellian niche concept embodies the idea that the niche of a
species is determined by the habitat in which it lives and its
accompanying behavioral adaptations. In other words, the niche is the
sum of the habitat requirements and behaviors that allow a species to
persist and produce offspring. For example, the behavior of
the California thrasher is consistent with the chaparral habitat it lives
in—it breeds and feeds in the underbrush and escapes from its
predators by shuffling from underbrush to underbrush. Its 'niche' is
defined by the felicitous complementing of the thrasher's behavior
and physical traits (camouflaging color, short wings, strong legs) with
this habitat

22. Conceptually, the Eltonian niche introduces the idea of a
species' response to and effect on the environment. Unlike other niche
concepts, it emphasizes that a species not only grows in and responds to an
environment based on available resources, predators, and climatic
conditions, but also changes the availability and behavior of those factors as
it grows. In an extreme example, beavers require certain resources in order
to survive and reproduce, but also construct dams that alter water flow in
the river where the beaver lives. Thus, the beaver affects the biotic and
abiotic conditions of other species that live in and near the watershed. In a
more subtle case, competitors that consume resources at different rates can
lead to cycles in resource density that differ between species. Not only do
species grow differently with respect to resource density, but their own
population growth can affect resource density over time

23. The Hutchinsonian niche is an "n-dimensional hypervolume", where the
dimensions are environmental conditions and resources, that define the
requirements of an individual or a species to practice "its" way of life, more
particularly, for its population to persist. The "hypervolume" defines the multi-
dimensional space of resources (e.g., light, nutrients, structure, etc.) available to
(and specifically used by) organisms, and "all species other than those under
consideration are regarded as part of the coordinate system."
The niche concept was popularized by the zoologist G. Evelyn Hutchinson in
1957. Hutchinson inquired into the question of why there are so many types of
organisms in any one habitat. His work inspired many others to develop models to
explain how many and how similar coexisting species could be within a given
community, and led to the concepts of 'niche breadth' (the variety of resources or
habitats used by a given species), 'niche partitioning' (resource differentiation by
coexisting species), and 'niche overlap' (overlap of resource use by different species)

24. An organism free of interference from other species could use the full range of conditions
(biotic and abiotic) and resources in which it could survive and reproduce which is called
its fundamental niche. However, as a result of pressure from, and interactions with, other
organisms (i.e. inter-specific competition) species are usually forced to occupy a niche that
is narrower than this, and to which they are mostly highly adapted; this is termed
the realized niche
Hutchinson used the idea of competition for resources as the primary mechanism driving
ecology, but overemphasis upon a species' dependence upon resources has led to too little
emphasis upon the effects of organisms on their environment, for instance, colonization and
invasions.
The term "adaptive zone" was coined by the paleontologist George Gaylor Simpson to
explain how a population could jump from one niche to another that suited it, jump to an
'adaptive zone', made available by virtue of some modification, or possibly a change in
the food chain, that made the adaptive zone available to it without a discontinuity in its way
of life because the group was 'pre-adapted' to the new ecological opportunity.
As a hemi-parasitic plant, the mistletoe in this tree exploits its host for nutrients and as a
place to grow.
Hutchinson's "niche" (a description of the ecological space occupied by a species) is subtly
different from the "niche" as defined by Grinnell (an ecological role, that may or may not be
actually filled by a species

25. THANK YOU